206 files changed, 9717 insertions, 6391 deletions

diff --git a/crates/base_db/src/fixture.rs b/crates/base_db/src/fixture.rs
index 8d4641355..0132565e4 100644
--- a/crates/base_db/src/fixture.rs
+++ b/crates/base_db/src/fixture.rs
@@ -1,62 +1,4 @@
-//! Fixtures are strings containing rust source code with optional metadata.
-//! A fixture without metadata is parsed into a single source file.
-//! Use this to test functionality local to one file.
-//!
-//! Simple Example:
-//! ```
-//! r#"
-//! fn main() {
-//!     println!("Hello World")
-//! }
-//! "#
-//! ```
-//!
-//! Metadata can be added to a fixture after a `//-` comment.
-//! The basic form is specifying filenames,
-//! which is also how to define multiple files in a single test fixture
-//!
-//! Example using two files in the same crate:
-//! ```
-//! "
-//! //- /main.rs
-//! mod foo;
-//! fn main() {
-//!     foo::bar();
-//! }
-//!
-//! //- /foo.rs
-//! pub fn bar() {}
-//! "
-//! ```
-//!
-//! Example using two crates with one file each, with one crate depending on the other:
-//! ```
-//! r#"
-//! //- /main.rs crate:a deps:b
-//! fn main() {
-//!     b::foo();
-//! }
-//! //- /lib.rs crate:b
-//! pub fn b() {
-//!     println!("Hello World")
-//! }
-//! "#
-//! ```
-//!
-//! Metadata allows specifying all settings and variables
-//! that are available in a real rust project:
-//! - crate names via `crate:cratename`
-//! - dependencies via `deps:dep1,dep2`
-//! - configuration settings via `cfg:dbg=false,opt_level=2`
-//! - environment variables via `env:PATH=/bin,RUST_LOG=debug`
-//!
-//! Example using all available metadata:
-//! ```
-//! "
-//! //- /lib.rs crate:foo deps:bar,baz cfg:foo=a,bar=b env:OUTDIR=path/to,OTHER=foo
-//! fn insert_source_code_here() {}
-//! "
-//! ```
+//! A set of high-level utility fixture methods to use in tests.
 use std::{mem, str::FromStr, sync::Arc};
 
 use cfg::CfgOptions;
@@ -93,7 +35,7 @@ pub trait WithFixture: Default + SourceDatabaseExt + 'static {
     fn with_position(ra_fixture: &str) -> (Self, FilePosition) {
         let (db, file_id, range_or_offset) = Self::with_range_or_offset(ra_fixture);
         let offset = match range_or_offset {
-            RangeOrOffset::Range(_) => panic!(),
+            RangeOrOffset::Range(_) => panic!("Expected a cursor position, got a range instead"),
             RangeOrOffset::Offset(it) => it,
         };
         (db, FilePosition { file_id, offset })
@@ -103,7 +45,7 @@ pub trait WithFixture: Default + SourceDatabaseExt + 'static {
         let (db, file_id, range_or_offset) = Self::with_range_or_offset(ra_fixture);
         let range = match range_or_offset {
             RangeOrOffset::Range(it) => it,
-            RangeOrOffset::Offset(_) => panic!(),
+            RangeOrOffset::Offset(_) => panic!("Expected a cursor range, got a position instead"),
         };
         (db, FileRange { file_id, range })
     }
@@ -112,7 +54,9 @@ pub trait WithFixture: Default + SourceDatabaseExt + 'static {
         let fixture = ChangeFixture::parse(ra_fixture);
         let mut db = Self::default();
         fixture.change.apply(&mut db);
-        let (file_id, range_or_offset) = fixture.file_position.unwrap();
+        let (file_id, range_or_offset) = fixture
+            .file_position
+            .expect("Could not find file position in fixture. Did you forget to add an `$0`?");
         (db, file_id, range_or_offset)
     }
 
diff --git a/crates/base_db/src/lib.rs b/crates/base_db/src/lib.rs
index 5f77a0b1f..980a0ed98 100644
--- a/crates/base_db/src/lib.rs
+++ b/crates/base_db/src/lib.rs
@@ -59,6 +59,8 @@ pub trait CheckCanceled {
         Self: Sized + panic::RefUnwindSafe,
         F: FnOnce(&Self) -> T + panic::UnwindSafe,
     {
+        // Uncomment to debug missing cancellations.
+        // let _span = profile::heartbeat_span();
         panic::catch_unwind(|| f(self)).map_err(|err| match err.downcast::<Canceled>() {
             Ok(canceled) => *canceled,
             Err(payload) => panic::resume_unwind(payload),
@@ -68,6 +70,7 @@ pub trait CheckCanceled {
 
 impl<T: salsa::Database> CheckCanceled for T {
     fn check_canceled(&self) {
+        // profile::heartbeat();
         if self.salsa_runtime().is_current_revision_canceled() {
             Canceled::throw()
         }
diff --git a/crates/cfg/src/tests.rs b/crates/cfg/src/tests.rs
index bd0f9ec48..d8736c893 100644
--- a/crates/cfg/src/tests.rs
+++ b/crates/cfg/src/tests.rs
@@ -8,7 +8,7 @@ fn assert_parse_result(input: &str, expected: CfgExpr) {
     let (tt, _) = {
         let source_file = ast::SourceFile::parse(input).ok().unwrap();
         let tt = source_file.syntax().descendants().find_map(ast::TokenTree::cast).unwrap();
-        ast_to_token_tree(&tt).unwrap()
+        ast_to_token_tree(&tt)
     };
     let cfg = CfgExpr::parse(&tt);
     assert_eq!(cfg, expected);
@@ -18,7 +18,7 @@ fn check_dnf(input: &str, expect: Expect) {
     let (tt, _) = {
         let source_file = ast::SourceFile::parse(input).ok().unwrap();
         let tt = source_file.syntax().descendants().find_map(ast::TokenTree::cast).unwrap();
-        ast_to_token_tree(&tt).unwrap()
+        ast_to_token_tree(&tt)
     };
     let cfg = CfgExpr::parse(&tt);
     let actual = format!("#![cfg({})]", DnfExpr::new(cfg));
@@ -29,7 +29,7 @@ fn check_why_inactive(input: &str, opts: &CfgOptions, expect: Expect) {
     let (tt, _) = {
         let source_file = ast::SourceFile::parse(input).ok().unwrap();
         let tt = source_file.syntax().descendants().find_map(ast::TokenTree::cast).unwrap();
-        ast_to_token_tree(&tt).unwrap()
+        ast_to_token_tree(&tt)
     };
     let cfg = CfgExpr::parse(&tt);
     let dnf = DnfExpr::new(cfg);
@@ -42,7 +42,7 @@ fn check_enable_hints(input: &str, opts: &CfgOptions, expected_hints: &[&str]) {
     let (tt, _) = {
         let source_file = ast::SourceFile::parse(input).ok().unwrap();
         let tt = source_file.syntax().descendants().find_map(ast::TokenTree::cast).unwrap();
-        ast_to_token_tree(&tt).unwrap()
+        ast_to_token_tree(&tt)
     };
     let cfg = CfgExpr::parse(&tt);
     let dnf = DnfExpr::new(cfg);
diff --git a/crates/hir/Cargo.toml b/crates/hir/Cargo.toml
index 2ef5bcbc9..9e329656f 100644
--- a/crates/hir/Cargo.toml
+++ b/crates/hir/Cargo.toml
@@ -13,7 +13,7 @@ doctest = false
 log = "0.4.8"
 rustc-hash = "1.1.0"
 either = "1.5.3"
-arrayvec = "0.6"
+arrayvec = "0.7"
 itertools = "0.10.0"
 smallvec = "1.4.0"
 
diff --git a/crates/hir/src/db.rs b/crates/hir/src/db.rs
index 1902a8d16..df5758342 100644
--- a/crates/hir/src/db.rs
+++ b/crates/hir/src/db.rs
@@ -1,14 +1,6 @@
 //! FIXME: write short doc here
 
-pub use hir_def::db::{
-    AttrsQuery, BlockDefMapQuery, BodyQuery, BodyWithSourceMapQuery, ConstDataQuery,
-    CrateDefMapQueryQuery, CrateLangItemsQuery, DefDatabase, DefDatabaseStorage, EnumDataQuery,
-    ExprScopesQuery, FileItemTreeQuery, FunctionDataQuery, GenericParamsQuery, ImplDataQuery,
-    ImportMapQuery, InternConstQuery, InternDatabase, InternDatabaseStorage, InternEnumQuery,
-    InternFunctionQuery, InternImplQuery, InternStaticQuery, InternStructQuery, InternTraitQuery,
-    InternTypeAliasQuery, InternUnionQuery, LangItemQuery, StaticDataQuery, StructDataQuery,
-    TraitDataQuery, TypeAliasDataQuery, UnionDataQuery,
-};
+pub use hir_def::db::*;
 pub use hir_expand::db::{
     AstDatabase, AstDatabaseStorage, AstIdMapQuery, HygieneFrameQuery, InternEagerExpansionQuery,
     InternMacroQuery, MacroArgTextQuery, MacroDefQuery, MacroExpandQuery, ParseMacroExpansionQuery,
diff --git a/crates/hir/src/display.rs b/crates/hir/src/display.rs
index 97a78ca25..01a4d205f 100644
--- a/crates/hir/src/display.rs
+++ b/crates/hir/src/display.rs
@@ -9,33 +9,33 @@ use hir_ty::display::{
     write_bounds_like_dyn_trait_with_prefix, write_visibility, HirDisplay, HirDisplayError,
     HirFormatter,
 };
+use hir_ty::Interner;
 use syntax::ast::{self, NameOwner};
 
 use crate::{
     Adt, Const, ConstParam, Enum, Field, Function, GenericParam, HasVisibility, LifetimeParam,
-    Module, Static, Struct, Substitution, Trait, Type, TypeAlias, TypeParam, Union, Variant,
+    Module, Static, Struct, Trait, TyBuilder, Type, TypeAlias, TypeParam, Union, Variant,
 };
 
 impl HirDisplay for Function {
     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
         let data = f.db.function_data(self.id);
         write_visibility(self.module(f.db).id, self.visibility(f.db), f)?;
-        let qual = &data.qualifier;
-        if qual.is_default {
+        if data.is_default() {
             write!(f, "default ")?;
         }
-        if qual.is_const {
+        if data.is_const() {
             write!(f, "const ")?;
         }
-        if qual.is_async {
+        if data.is_async() {
             write!(f, "async ")?;
         }
-        if qual.is_unsafe {
+        if data.is_unsafe() {
             write!(f, "unsafe ")?;
         }
-        if let Some(abi) = &qual.abi {
+        if let Some(abi) = &data.abi {
             // FIXME: String escape?
-            write!(f, "extern \"{}\" ", abi)?;
+            write!(f, "extern \"{}\" ", &**abi)?;
         }
         write!(f, "fn {}", data.name)?;
 
@@ -68,7 +68,7 @@ impl HirDisplay for Function {
                 write!(f, ", ")?;
             } else {
                 first = false;
-                if data.has_self_param {
+                if data.has_self_param() {
                     write_self_param(type_ref, f)?;
                     continue;
                 }
@@ -88,10 +88,10 @@ impl HirDisplay for Function {
         // `FunctionData::ret_type` will be `::core::future::Future<Output = ...>` for async fns.
         // Use ugly pattern match to strip the Future trait.
         // Better way?
-        let ret_type = if !qual.is_async {
+        let ret_type = if !data.is_async() {
             &data.ret_type
         } else {
-            match &data.ret_type {
+            match &*data.ret_type {
                 TypeRef::ImplTrait(bounds) => match &bounds[0] {
                     TypeBound::Path(path) => {
                         path.segments().iter().last().unwrap().args_and_bindings.unwrap().bindings
@@ -235,8 +235,9 @@ impl HirDisplay for TypeParam {
     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
         write!(f, "{}", self.name(f.db))?;
         let bounds = f.db.generic_predicates_for_param(self.id);
-        let substs = Substitution::type_params(f.db, self.id.parent);
-        let predicates = bounds.iter().cloned().map(|b| b.subst(&substs)).collect::<Vec<_>>();
+        let substs = TyBuilder::type_params_subst(f.db, self.id.parent);
+        let predicates =
+            bounds.iter().cloned().map(|b| b.substitute(&Interner, &substs)).collect::<Vec<_>>();
         if !(predicates.is_empty() || f.omit_verbose_types()) {
             write_bounds_like_dyn_trait_with_prefix(":", &predicates, f)?;
         }
diff --git a/crates/hir/src/lib.rs b/crates/hir/src/lib.rs
index 4ee08ef21..0acfa582a 100644
--- a/crates/hir/src/lib.rs
+++ b/crates/hir/src/lib.rs
@@ -44,6 +44,7 @@ use hir_def::{
     per_ns::PerNs,
     resolver::{HasResolver, Resolver},
     src::HasSource as _,
+    type_ref::TraitRef,
     AdtId, AssocContainerId, AssocItemId, AssocItemLoc, AttrDefId, ConstId, ConstParamId,
     DefWithBodyId, EnumId, FunctionId, GenericDefId, HasModule, ImplId, LifetimeParamId,
     LocalEnumVariantId, LocalFieldId, Lookup, ModuleId, StaticId, StructId, TraitId, TypeAliasId,
@@ -52,13 +53,14 @@ use hir_def::{
 use hir_expand::{diagnostics::DiagnosticSink, name::name, MacroDefKind};
 use hir_ty::{
     autoderef, could_unify,
-    method_resolution::{self, TyFingerprint},
+    method_resolution::{self, def_crates, TyFingerprint},
     primitive::UintTy,
-    to_assoc_type_id,
-    traits::{FnTrait, Solution, SolutionVariables},
+    subst_prefix,
+    traits::FnTrait,
     AliasEq, AliasTy, BoundVar, CallableDefId, CallableSig, Canonical, CanonicalVarKinds, Cast,
-    DebruijnIndex, InEnvironment, Interner, ProjectionTy, QuantifiedWhereClause, Scalar,
-    Substitution, TraitEnvironment, Ty, TyDefId, TyKind, TyVariableKind, WhereClause,
+    DebruijnIndex, InEnvironment, Interner, QuantifiedWhereClause, Scalar, Solution, Substitution,
+    TraitEnvironment, TraitRefExt, Ty, TyBuilder, TyDefId, TyExt, TyKind, TyVariableKind,
+    WhereClause,
 };
 use itertools::Itertools;
 use rustc_hash::FxHashSet;
@@ -514,8 +516,8 @@ impl Field {
             VariantDef::Union(it) => it.id.into(),
             VariantDef::Variant(it) => it.parent.id.into(),
         };
-        let substs = Substitution::type_params(db, generic_def_id);
-        let ty = db.field_types(var_id)[self.id].clone().subst(&substs);
+        let substs = TyBuilder::type_params_subst(db, generic_def_id);
+        let ty = db.field_types(var_id)[self.id].clone().substitute(&Interner, &substs);
         Type::new(db, self.parent.module(db).id.krate(), var_id, ty)
     }
 
@@ -701,7 +703,7 @@ impl_from!(Struct, Union, Enum for Adt);
 impl Adt {
     pub fn has_non_default_type_params(self, db: &dyn HirDatabase) -> bool {
         let subst = db.generic_defaults(self.into());
-        subst.iter().any(|ty| ty.value.is_unknown())
+        subst.iter().any(|ty| ty.skip_binders().is_unknown())
     }
 
     /// Turns this ADT into a type. Any type parameters of the ADT will be
@@ -831,7 +833,7 @@ impl Function {
     }
 
     pub fn self_param(self, db: &dyn HirDatabase) -> Option<SelfParam> {
-        if !db.function_data(self.id).has_self_param {
+        if !db.function_data(self.id).has_self_param() {
             return None;
         }
         Some(SelfParam { func: self.id })
@@ -863,7 +865,7 @@ impl Function {
     }
 
     pub fn is_unsafe(self, db: &dyn HirDatabase) -> bool {
-        db.function_data(self.id).qualifier.is_unsafe
+        db.function_data(self.id).is_unsafe()
     }
 
     pub fn diagnostics(self, db: &dyn HirDatabase, sink: &mut DiagnosticSink) {
@@ -877,7 +879,7 @@ impl Function {
     ///
     /// This is false in the case of required (not provided) trait methods.
     pub fn has_body(self, db: &dyn HirDatabase) -> bool {
-        db.function_data(self.id).has_body
+        db.function_data(self.id).has_body()
     }
 
     /// A textual representation of the HIR of this function for debugging purposes.
@@ -956,7 +958,7 @@ impl SelfParam {
         func_data
             .params
             .first()
-            .map(|param| match *param {
+            .map(|param| match &**param {
                 TypeRef::Reference(.., mutability) => match mutability {
                     hir_def::type_ref::Mutability::Shared => Access::Shared,
                     hir_def::type_ref::Mutability::Mut => Access::Exclusive,
@@ -1010,7 +1012,7 @@ impl Const {
     }
 
     pub fn type_ref(self, db: &dyn HirDatabase) -> TypeRef {
-        db.const_data(self.id).type_ref.clone()
+        db.const_data(self.id).type_ref.as_ref().clone()
     }
 }
 
@@ -1088,7 +1090,7 @@ pub struct TypeAlias {
 impl TypeAlias {
     pub fn has_non_default_type_params(self, db: &dyn HirDatabase) -> bool {
         let subst = db.generic_defaults(self.id.into());
-        subst.iter().any(|ty| ty.value.is_unknown())
+        subst.iter().any(|ty| ty.skip_binders().is_unknown())
     }
 
     pub fn module(self, db: &dyn HirDatabase) -> Module {
@@ -1100,7 +1102,7 @@ impl TypeAlias {
     }
 
     pub fn type_ref(self, db: &dyn HirDatabase) -> Option<TypeRef> {
-        db.type_alias_data(self.id).type_ref.clone()
+        db.type_alias_data(self.id).type_ref.as_deref().cloned()
     }
 
     pub fn ty(self, db: &dyn HirDatabase) -> Type {
@@ -1128,7 +1130,7 @@ pub struct BuiltinType {
 impl BuiltinType {
     pub fn ty(self, db: &dyn HirDatabase, module: Module) -> Type {
         let resolver = module.id.resolver(db.upcast());
-        Type::new_with_resolver(db, &resolver, Ty::builtin(self.inner))
+        Type::new_with_resolver(db, &resolver, TyBuilder::builtin(self.inner))
             .expect("crate not present in resolver")
     }
 
@@ -1501,8 +1503,8 @@ impl TypeParam {
         let resolver = self.id.parent.resolver(db.upcast());
         let krate = self.id.parent.module(db.upcast()).krate();
         let ty = params.get(local_idx)?.clone();
-        let subst = Substitution::type_params(db, self.id.parent);
-        let ty = ty.subst(&subst.prefix(local_idx));
+        let subst = TyBuilder::type_params_subst(db, self.id.parent);
+        let ty = ty.substitute(&Interner, &subst_prefix(&subst, local_idx));
         Some(Type::new_with_resolver_inner(db, krate, &resolver, ty))
     }
 }
@@ -1567,22 +1569,35 @@ impl Impl {
     }
 
     pub fn all_for_type(db: &dyn HirDatabase, Type { krate, ty, .. }: Type) -> Vec<Impl> {
-        let def_crates = match ty.def_crates(db, krate) {
+        let def_crates = match def_crates(db, &ty, krate) {
             Some(def_crates) => def_crates,
             None => return Vec::new(),
         };
 
         let filter = |impl_def: &Impl| {
-            let target_ty = impl_def.target_ty(db);
-            let rref = target_ty.remove_ref();
-            ty.equals_ctor(rref.as_ref().map_or(&target_ty.ty, |it| &it.ty))
+            let self_ty = impl_def.self_ty(db);
+            let rref = self_ty.remove_ref();
+            ty.equals_ctor(rref.as_ref().map_or(&self_ty.ty, |it| &it.ty))
+        };
+
+        let fp = TyFingerprint::for_inherent_impl(&ty);
+        let fp = if let Some(fp) = fp {
+            fp
+        } else {
+            return Vec::new();
         };
 
         let mut all = Vec::new();
         def_crates.iter().for_each(|&id| {
-            all.extend(db.inherent_impls_in_crate(id).all_impls().map(Self::from).filter(filter))
+            all.extend(
+                db.inherent_impls_in_crate(id)
+                    .for_self_ty(&ty)
+                    .into_iter()
+                    .cloned()
+                    .map(Self::from)
+                    .filter(filter),
+            )
         });
-        let fp = TyFingerprint::for_impl(&ty);
         for id in def_crates
             .iter()
             .flat_map(|&id| Crate { id }.transitive_reverse_dependencies(db))
@@ -1590,13 +1605,12 @@ impl Impl {
             .chain(def_crates.iter().copied())
             .unique()
         {
-            match fp {
-                Some(fp) => all.extend(
-                    db.trait_impls_in_crate(id).for_self_ty(fp).map(Self::from).filter(filter),
-                ),
-                None => all
-                    .extend(db.trait_impls_in_crate(id).all_impls().map(Self::from).filter(filter)),
-            }
+            all.extend(
+                db.trait_impls_in_crate(id)
+                    .for_self_ty_without_blanket_impls(fp)
+                    .map(Self::from)
+                    .filter(filter),
+            );
         }
         all
     }
@@ -1613,16 +1627,16 @@ impl Impl {
 
     // FIXME: the return type is wrong. This should be a hir version of
     // `TraitRef` (ie, resolved `TypeRef`).
-    pub fn target_trait(self, db: &dyn HirDatabase) -> Option<TypeRef> {
-        db.impl_data(self.id).target_trait.clone()
+    pub fn trait_(self, db: &dyn HirDatabase) -> Option<TraitRef> {
+        db.impl_data(self.id).target_trait.as_deref().cloned()
     }
 
-    pub fn target_ty(self, db: &dyn HirDatabase) -> Type {
+    pub fn self_ty(self, db: &dyn HirDatabase) -> Type {
         let impl_data = db.impl_data(self.id);
         let resolver = self.id.resolver(db.upcast());
         let krate = self.id.lookup(db.upcast()).container.krate();
         let ctx = hir_ty::TyLoweringContext::new(db, &resolver);
-        let ty = ctx.lower_ty(&impl_data.target_type);
+        let ty = ctx.lower_ty(&impl_data.self_ty);
         Type::new_with_resolver_inner(db, krate, &resolver, ty)
     }
 
@@ -1702,30 +1716,29 @@ impl Type {
     fn from_def(
         db: &dyn HirDatabase,
         krate: CrateId,
-        def: impl HasResolver + Into<TyDefId> + Into<GenericDefId>,
+        def: impl HasResolver + Into<TyDefId>,
     ) -> Type {
-        let substs = Substitution::build_for_def(db, def).fill_with_unknown().build();
-        let ty = db.ty(def.into()).subst(&substs);
+        let ty = TyBuilder::def_ty(db, def.into()).fill_with_unknown().build();
         Type::new(db, krate, def, ty)
     }
 
     pub fn is_unit(&self) -> bool {
-        matches!(self.ty.interned(&Interner), TyKind::Tuple(0, ..))
+        matches!(self.ty.kind(&Interner), TyKind::Tuple(0, ..))
     }
     pub fn is_bool(&self) -> bool {
-        matches!(self.ty.interned(&Interner), TyKind::Scalar(Scalar::Bool))
+        matches!(self.ty.kind(&Interner), TyKind::Scalar(Scalar::Bool))
     }
 
     pub fn is_mutable_reference(&self) -> bool {
-        matches!(self.ty.interned(&Interner), TyKind::Ref(hir_ty::Mutability::Mut, ..))
+        matches!(self.ty.kind(&Interner), TyKind::Ref(hir_ty::Mutability::Mut, ..))
     }
 
     pub fn is_usize(&self) -> bool {
-        matches!(self.ty.interned(&Interner), TyKind::Scalar(Scalar::Uint(UintTy::Usize)))
+        matches!(self.ty.kind(&Interner), TyKind::Scalar(Scalar::Uint(UintTy::Usize)))
     }
 
     pub fn remove_ref(&self) -> Option<Type> {
-        match &self.ty.interned(&Interner) {
+        match &self.ty.kind(&Interner) {
             TyKind::Ref(.., ty) => Some(self.derived(ty.clone())),
             _ => None,
         }
@@ -1784,16 +1797,13 @@ impl Type {
     }
 
     pub fn impls_trait(&self, db: &dyn HirDatabase, trait_: Trait, args: &[Type]) -> bool {
-        let trait_ref = hir_ty::TraitRef {
-            trait_id: hir_ty::to_chalk_trait_id(trait_.id),
-            substitution: Substitution::build_for_def(db, trait_.id)
-                .push(self.ty.clone())
-                .fill(args.iter().map(|t| t.ty.clone()))
-                .build(),
-        };
+        let trait_ref = TyBuilder::trait_ref(db, trait_.id)
+            .push(self.ty.clone())
+            .fill(args.iter().map(|t| t.ty.clone()))
+            .build();
 
         let goal = Canonical {
-            value: hir_ty::InEnvironment::new(self.env.env.clone(), trait_ref.cast(&Interner)),
+            value: hir_ty::InEnvironment::new(&self.env.env, trait_ref.cast(&Interner)),
             binders: CanonicalVarKinds::empty(&Interner),
         };
 
@@ -1803,22 +1813,18 @@ impl Type {
     pub fn normalize_trait_assoc_type(
         &self,
         db: &dyn HirDatabase,
-        trait_: Trait,
         args: &[Type],
         alias: TypeAlias,
     ) -> Option<Type> {
-        let subst = Substitution::build_for_def(db, trait_.id)
+        let projection = TyBuilder::assoc_type_projection(db, alias.id)
             .push(self.ty.clone())
             .fill(args.iter().map(|t| t.ty.clone()))
             .build();
-        let goal = Canonical::new(
+        let goal = hir_ty::make_canonical(
             InEnvironment::new(
-                self.env.env.clone(),
+                &self.env.env,
                 AliasEq {
-                    alias: AliasTy::Projection(ProjectionTy {
-                        associated_ty_id: to_assoc_type_id(alias.id),
-                        substitution: subst,
-                    }),
+                    alias: AliasTy::Projection(projection),
                     ty: TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0))
                         .intern(&Interner),
                 }
@@ -1828,9 +1834,12 @@ impl Type {
         );
 
         match db.trait_solve(self.krate, goal)? {
-            Solution::Unique(SolutionVariables(subst)) => {
-                subst.value.first().map(|ty| self.derived(ty.clone()))
-            }
+            Solution::Unique(s) => s
+                .value
+                .subst
+                .as_slice(&Interner)
+                .first()
+                .map(|ty| self.derived(ty.assert_ty_ref(&Interner).clone())),
             Solution::Ambig(_) => None,
         }
     }
@@ -1852,15 +1861,15 @@ impl Type {
     }
 
     pub fn is_closure(&self) -> bool {
-        matches!(&self.ty.interned(&Interner), TyKind::Closure { .. })
+        matches!(&self.ty.kind(&Interner), TyKind::Closure { .. })
     }
 
     pub fn is_fn(&self) -> bool {
-        matches!(&self.ty.interned(&Interner), TyKind::FnDef(..) | TyKind::Function { .. })
+        matches!(&self.ty.kind(&Interner), TyKind::FnDef(..) | TyKind::Function { .. })
     }
 
     pub fn is_packed(&self, db: &dyn HirDatabase) -> bool {
-        let adt_id = match self.ty.interned(&Interner) {
+        let adt_id = match self.ty.kind(&Interner) {
             &TyKind::Adt(hir_ty::AdtId(adt_id), ..) => adt_id,
             _ => return false,
         };
@@ -1873,27 +1882,30 @@ impl Type {
     }
 
     pub fn is_raw_ptr(&self) -> bool {
-        matches!(&self.ty.interned(&Interner), TyKind::Raw(..))
+        matches!(&self.ty.kind(&Interner), TyKind::Raw(..))
     }
 
     pub fn contains_unknown(&self) -> bool {
         return go(&self.ty);
 
         fn go(ty: &Ty) -> bool {
-            match ty.interned(&Interner) {
-                TyKind::Unknown => true,
+            match ty.kind(&Interner) {
+                TyKind::Error => true,
 
                 TyKind::Adt(_, substs)
                 | TyKind::AssociatedType(_, substs)
                 | TyKind::Tuple(_, substs)
                 | TyKind::OpaqueType(_, substs)
                 | TyKind::FnDef(_, substs)
-                | TyKind::Closure(_, substs) => substs.iter().any(go),
-
-                TyKind::Array(ty) | TyKind::Slice(ty) | TyKind::Raw(_, ty) | TyKind::Ref(_, ty) => {
-                    go(ty)
+                | TyKind::Closure(_, substs) => {
+                    substs.iter(&Interner).filter_map(|a| a.ty(&Interner)).any(go)
                 }
 
+                TyKind::Array(ty, _)
+                | TyKind::Slice(ty)
+                | TyKind::Raw(_, ty)
+                | TyKind::Ref(_, _, ty) => go(ty),
+
                 TyKind::Scalar(_)
                 | TyKind::Str
                 | TyKind::Never
@@ -1903,13 +1915,15 @@ impl Type {
                 | TyKind::Dyn(_)
                 | TyKind::Function(_)
                 | TyKind::Alias(_)
-                | TyKind::ForeignType(_) => false,
+                | TyKind::Foreign(_)
+                | TyKind::Generator(..)
+                | TyKind::GeneratorWitness(..) => false,
             }
         }
     }
 
     pub fn fields(&self, db: &dyn HirDatabase) -> Vec<(Field, Type)> {
-        let (variant_id, substs) = match self.ty.interned(&Interner) {
+        let (variant_id, substs) = match self.ty.kind(&Interner) {
             &TyKind::Adt(hir_ty::AdtId(AdtId::StructId(s)), ref substs) => (s.into(), substs),
             &TyKind::Adt(hir_ty::AdtId(AdtId::UnionId(u)), ref substs) => (u.into(), substs),
             _ => return Vec::new(),
@@ -1919,15 +1933,18 @@ impl Type {
             .iter()
             .map(|(local_id, ty)| {
                 let def = Field { parent: variant_id.into(), id: local_id };
-                let ty = ty.clone().subst(substs);
+                let ty = ty.clone().substitute(&Interner, substs);
                 (def, self.derived(ty))
             })
             .collect()
     }
 
     pub fn tuple_fields(&self, _db: &dyn HirDatabase) -> Vec<Type> {
-        if let TyKind::Tuple(_, substs) = &self.ty.interned(&Interner) {
-            substs.iter().map(|ty| self.derived(ty.clone())).collect()
+        if let TyKind::Tuple(_, substs) = &self.ty.kind(&Interner) {
+            substs
+                .iter(&Interner)
+                .map(|ty| self.derived(ty.assert_ty_ref(&Interner).clone()))
+                .collect()
         } else {
             Vec::new()
         }
@@ -1953,7 +1970,7 @@ impl Type {
         krate: Crate,
         mut callback: impl FnMut(AssocItem) -> Option<T>,
     ) -> Option<T> {
-        for krate in self.ty.def_crates(db, krate.id)? {
+        for krate in def_crates(db, &self.ty, krate.id)? {
             let impls = db.inherent_impls_in_crate(krate);
 
             for impl_def in impls.for_self_ty(&self.ty) {
@@ -1970,10 +1987,11 @@ impl Type {
     pub fn type_parameters(&self) -> impl Iterator<Item = Type> + '_ {
         self.ty
             .strip_references()
-            .substs()
+            .as_adt()
             .into_iter()
-            .flat_map(|substs| substs.iter())
-            .map(move |ty| self.derived(ty.clone()))
+            .flat_map(|(_, substs)| substs.iter(&Interner))
+            .filter_map(|arg| arg.ty(&Interner).cloned())
+            .map(move |ty| self.derived(ty))
     }
 
     pub fn iterate_method_candidates<T>(
@@ -2048,6 +2066,18 @@ impl Type {
         self.ty.dyn_trait().map(Into::into)
     }
 
+    /// If a type can be represented as `dyn Trait`, returns all traits accessible via this type,
+    /// or an empty iterator otherwise.
+    pub fn applicable_inherent_traits<'a>(
+        &'a self,
+        db: &'a dyn HirDatabase,
+    ) -> impl Iterator<Item = Trait> + 'a {
+        self.autoderef(db)
+            .filter_map(|derefed_type| derefed_type.ty.dyn_trait())
+            .flat_map(move |dyn_trait_id| hir_ty::all_super_traits(db.upcast(), dyn_trait_id))
+            .map(Trait::from)
+    }
+
     pub fn as_impl_traits(&self, db: &dyn HirDatabase) -> Option<Vec<Trait>> {
         self.ty.impl_trait_bounds(db).map(|it| {
             it.into_iter()
@@ -2079,7 +2109,7 @@ impl Type {
             substs: &Substitution,
             cb: &mut impl FnMut(Type),
         ) {
-            for ty in substs.iter() {
+            for ty in substs.iter(&Interner).filter_map(|a| a.ty(&Interner)) {
                 walk_type(db, &type_.derived(ty.clone()), cb);
             }
         }
@@ -2095,7 +2125,12 @@ impl Type {
                     WhereClause::Implemented(trait_ref) => {
                         cb(type_.clone());
                         // skip the self type. it's likely the type we just got the bounds from
-                        for ty in trait_ref.substitution.iter().skip(1) {
+                        for ty in trait_ref
+                            .substitution
+                            .iter(&Interner)
+                            .skip(1)
+                            .filter_map(|a| a.ty(&Interner))
+                        {
                             walk_type(db, &type_.derived(ty.clone()), cb);
                         }
                     }
@@ -2106,19 +2141,23 @@ impl Type {
 
         fn walk_type(db: &dyn HirDatabase, type_: &Type, cb: &mut impl FnMut(Type)) {
             let ty = type_.ty.strip_references();
-            match ty.interned(&Interner) {
-                TyKind::Adt(..) => {
+            match ty.kind(&Interner) {
+                TyKind::Adt(_, substs) => {
                     cb(type_.derived(ty.clone()));
+                    walk_substs(db, type_, &substs, cb);
                 }
-                TyKind::AssociatedType(..) => {
+                TyKind::AssociatedType(_, substs) => {
                     if let Some(_) = ty.associated_type_parent_trait(db) {
                         cb(type_.derived(ty.clone()));
                     }
+                    walk_substs(db, type_, &substs, cb);
                 }
-                TyKind::OpaqueType(..) => {
+                TyKind::OpaqueType(_, subst) => {
                     if let Some(bounds) = ty.impl_trait_bounds(db) {
                         walk_bounds(db, &type_.derived(ty.clone()), &bounds, cb);
                     }
+
+                    walk_substs(db, type_, subst, cb);
                 }
                 TyKind::Alias(AliasTy::Opaque(opaque_ty)) => {
                     if let Some(bounds) = ty.impl_trait_bounds(db) {
@@ -2141,15 +2180,24 @@ impl Type {
                     );
                 }
 
-                TyKind::Ref(_, ty) | TyKind::Raw(_, ty) | TyKind::Array(ty) | TyKind::Slice(ty) => {
+                TyKind::Ref(_, _, ty)
+                | TyKind::Raw(_, ty)
+                | TyKind::Array(ty, _)
+                | TyKind::Slice(ty) => {
                     walk_type(db, &type_.derived(ty.clone()), cb);
                 }
 
+                TyKind::FnDef(_, substs)
+                | TyKind::Tuple(_, substs)
+                | TyKind::Closure(.., substs) => {
+                    walk_substs(db, type_, &substs, cb);
+                }
+                TyKind::Function(hir_ty::FnPointer { substitution, .. }) => {
+                    walk_substs(db, type_, &substitution.0, cb);
+                }
+
                 _ => {}
             }
-            if let Some(substs) = ty.substs() {
-                walk_substs(db, type_, &substs, cb);
-            }
         }
 
         walk_type(db, self, &mut cb);
diff --git a/crates/hir/src/semantics.rs b/crates/hir/src/semantics.rs
index d3caeef4e..7955bf0b5 100644
--- a/crates/hir/src/semantics.rs
+++ b/crates/hir/src/semantics.rs
@@ -76,9 +76,11 @@ impl PathResolution {
     pub fn assoc_type_shorthand_candidates<R>(
         &self,
         db: &dyn HirDatabase,
-        mut cb: impl FnMut(TypeAlias) -> Option<R>,
+        mut cb: impl FnMut(&Name, TypeAlias) -> Option<R>,
     ) -> Option<R> {
-        associated_type_shorthand_candidates(db, self.in_type_ns()?, |_, _, id| cb(id.into()))
+        associated_type_shorthand_candidates(db, self.in_type_ns()?, |name, _, id| {
+            cb(name, id.into())
+        })
     }
 }
 
@@ -492,9 +494,9 @@ impl<'db> SemanticsImpl<'db> {
     fn resolve_method_call_as_callable(&self, call: &ast::MethodCallExpr) -> Option<Callable> {
         // FIXME: this erases Substs
         let func = self.resolve_method_call(call)?;
-        let ty = self.db.value_ty(func.into());
+        let (ty, _) = self.db.value_ty(func.into()).into_value_and_skipped_binders();
         let resolver = self.analyze(call.syntax()).resolver;
-        let ty = Type::new_with_resolver(self.db, &resolver, ty.value)?;
+        let ty = Type::new_with_resolver(self.db, &resolver, ty)?;
         let mut res = ty.as_callable(self.db)?;
         res.is_bound_method = true;
         Some(res)
diff --git a/crates/hir/src/source_analyzer.rs b/crates/hir/src/source_analyzer.rs
index 37d162b32..847d2537d 100644
--- a/crates/hir/src/source_analyzer.rs
+++ b/crates/hir/src/source_analyzer.rs
@@ -20,7 +20,7 @@ use hir_def::{
 use hir_expand::{hygiene::Hygiene, name::AsName, HirFileId, InFile};
 use hir_ty::{
     diagnostics::{record_literal_missing_fields, record_pattern_missing_fields},
-    InferenceResult, Substitution,
+    InferenceResult, Interner, Substitution, TyExt, TyLoweringContext,
 };
 use syntax::{
     ast::{self, AstNode},
@@ -161,14 +161,15 @@ impl SourceAnalyzer {
         db: &dyn HirDatabase,
         field: &ast::RecordExprField,
     ) -> Option<(Field, Option<Local>)> {
-        let expr_id =
-            self.body_source_map.as_ref()?.node_field(InFile::new(self.file_id, field))?;
+        let record_expr = ast::RecordExpr::cast(field.syntax().parent().and_then(|p| p.parent())?)?;
+        let expr = ast::Expr::from(record_expr);
+        let expr_id = self.body_source_map.as_ref()?.node_expr(InFile::new(self.file_id, &expr))?;
 
+        let local_name = field.field_name()?.as_name();
         let local = if field.name_ref().is_some() {
             None
         } else {
-            let local_name = field.field_name()?.as_name();
-            let path = ModPath::from_segments(PathKind::Plain, once(local_name));
+            let path = ModPath::from_segments(PathKind::Plain, once(local_name.clone()));
             match self.resolver.resolve_path_in_value_ns_fully(db.upcast(), &path) {
                 Some(ValueNs::LocalBinding(pat_id)) => {
                     Some(Local { pat_id, parent: self.resolver.body_owner()? })
@@ -176,18 +177,24 @@ impl SourceAnalyzer {
                 _ => None,
             }
         };
-        let struct_field = self.infer.as_ref()?.record_field_resolution(expr_id)?;
-        Some((struct_field.into(), local))
+        let variant = self.infer.as_ref()?.variant_resolution_for_expr(expr_id)?;
+        let variant_data = variant.variant_data(db.upcast());
+        let field = FieldId { parent: variant, local_id: variant_data.field(&local_name)? };
+        Some((field.into(), local))
     }
 
     pub(crate) fn resolve_record_pat_field(
         &self,
-        _db: &dyn HirDatabase,
+        db: &dyn HirDatabase,
         field: &ast::RecordPatField,
     ) -> Option<Field> {
-        let pat_id = self.pat_id(&field.pat()?)?;
-        let struct_field = self.infer.as_ref()?.record_pat_field_resolution(pat_id)?;
-        Some(struct_field.into())
+        let field_name = field.field_name()?.as_name();
+        let record_pat = ast::RecordPat::cast(field.syntax().parent().and_then(|p| p.parent())?)?;
+        let pat_id = self.pat_id(&record_pat.into())?;
+        let variant = self.infer.as_ref()?.variant_resolution_for_pat(pat_id)?;
+        let variant_data = variant.variant_data(db.upcast());
+        let field = FieldId { parent: variant, local_id: variant_data.field(&field_name)? };
+        Some(field.into())
     }
 
     pub(crate) fn resolve_macro_call(
@@ -299,7 +306,7 @@ impl SourceAnalyzer {
         let infer = self.infer.as_ref()?;
 
         let expr_id = self.expr_id(db, &literal.clone().into())?;
-        let substs = infer.type_of_expr[expr_id].substs()?;
+        let substs = infer.type_of_expr[expr_id].as_adt()?.1;
 
         let (variant, missing_fields, _exhaustive) =
             record_literal_missing_fields(db, infer, expr_id, &body[expr_id])?;
@@ -317,7 +324,7 @@ impl SourceAnalyzer {
         let infer = self.infer.as_ref()?;
 
         let pat_id = self.pat_id(&pattern.clone().into())?;
-        let substs = infer.type_of_pat[pat_id].substs()?;
+        let substs = infer.type_of_pat[pat_id].as_adt()?.1;
 
         let (variant, missing_fields, _exhaustive) =
             record_pattern_missing_fields(db, infer, pat_id, &body[pat_id])?;
@@ -339,7 +346,7 @@ impl SourceAnalyzer {
             .into_iter()
             .map(|local_id| {
                 let field = FieldId { parent: variant, local_id };
-                let ty = field_types[local_id].clone().subst(substs);
+                let ty = field_types[local_id].clone().substitute(&Interner, substs);
                 (field.into(), Type::new_with_resolver_inner(db, krate, &self.resolver, ty))
             })
             .collect()
@@ -466,7 +473,21 @@ fn resolve_hir_path_(
     prefer_value_ns: bool,
 ) -> Option<PathResolution> {
     let types = || {
-        resolver.resolve_path_in_type_ns_fully(db.upcast(), path.mod_path()).map(|ty| match ty {
+        let (ty, unresolved) = match path.type_anchor() {
+            Some(type_ref) => {
+                let (_, res) = TyLoweringContext::new(db, resolver).lower_ty_ext(type_ref);
+                res.map(|ty_ns| (ty_ns, path.segments().first()))
+            }
+            None => {
+                let (ty, remaining) =
+                    resolver.resolve_path_in_type_ns(db.upcast(), path.mod_path())?;
+                match remaining {
+                    Some(remaining) if remaining > 1 => None,
+                    _ => Some((ty, path.segments().get(1))),
+                }
+            }
+        }?;
+        let res = match ty {
             TypeNs::SelfType(it) => PathResolution::SelfType(it.into()),
             TypeNs::GenericParam(id) => PathResolution::TypeParam(TypeParam { id }),
             TypeNs::AdtSelfType(it) | TypeNs::AdtId(it) => {
@@ -476,7 +497,17 @@ fn resolve_hir_path_(
             TypeNs::TypeAliasId(it) => PathResolution::Def(TypeAlias::from(it).into()),
             TypeNs::BuiltinType(it) => PathResolution::Def(BuiltinType::from(it).into()),
             TypeNs::TraitId(it) => PathResolution::Def(Trait::from(it).into()),
-        })
+        };
+        match unresolved {
+            Some(unresolved) => res
+                .assoc_type_shorthand_candidates(db, |name, alias| {
+                    (name == unresolved.name).then(|| alias)
+                })
+                .map(TypeAlias::from)
+                .map(Into::into)
+                .map(PathResolution::Def),
+            None => Some(res),
+        }
     };
 
     let body_owner = resolver.body_owner();
diff --git a/crates/hir_def/Cargo.toml b/crates/hir_def/Cargo.toml
index 475d337f3..43324d8d9 100644
--- a/crates/hir_def/Cargo.toml
+++ b/crates/hir_def/Cargo.toml
@@ -11,6 +11,7 @@ doctest = false
 
 [dependencies]
 cov-mark = { version = "1.1", features = ["thread-local"] }
+dashmap = { version = "4.0.2", features = ["raw-api"] }
 log = "0.4.8"
 once_cell = "1.3.1"
 rustc-hash = "1.1.0"
diff --git a/crates/hir_def/src/adt.rs b/crates/hir_def/src/adt.rs
index 58e35353b..402fb1d8d 100644
--- a/crates/hir_def/src/adt.rs
+++ b/crates/hir_def/src/adt.rs
@@ -15,6 +15,7 @@ use tt::{Delimiter, DelimiterKind, Leaf, Subtree, TokenTree};
 use crate::{
     body::{CfgExpander, LowerCtx},
     db::DefDatabase,
+    intern::Interned,
     item_tree::{AttrOwner, Field, Fields, ItemTree, ModItem, RawVisibilityId},
     src::HasChildSource,
     src::HasSource,
@@ -58,7 +59,7 @@ pub enum VariantData {
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct FieldData {
     pub name: Name,
-    pub type_ref: TypeRef,
+    pub type_ref: Interned<TypeRef>,
     pub visibility: RawVisibility,
 }
 
@@ -292,7 +293,7 @@ fn lower_struct(
                     || Either::Left(fd.clone()),
                     || FieldData {
                         name: Name::new_tuple_field(i),
-                        type_ref: TypeRef::from_ast_opt(&ctx, fd.ty()),
+                        type_ref: Interned::new(TypeRef::from_ast_opt(&ctx, fd.ty())),
                         visibility: RawVisibility::from_ast(db, ast.with_value(fd.visibility())),
                     },
                 );
@@ -309,7 +310,7 @@ fn lower_struct(
                     || Either::Right(fd.clone()),
                     || FieldData {
                         name: fd.name().map(|n| n.as_name()).unwrap_or_else(Name::missing),
-                        type_ref: TypeRef::from_ast_opt(&ctx, fd.ty()),
+                        type_ref: Interned::new(TypeRef::from_ast_opt(&ctx, fd.ty())),
                         visibility: RawVisibility::from_ast(db, ast.with_value(fd.visibility())),
                     },
                 );
@@ -358,7 +359,7 @@ fn lower_field(
 ) -> FieldData {
     FieldData {
         name: field.name.clone(),
-        type_ref: item_tree[field.type_ref].clone(),
+        type_ref: field.type_ref.clone(),
         visibility: item_tree[override_visibility.unwrap_or(field.visibility)].clone(),
     }
 }
diff --git a/crates/hir_def/src/attr.rs b/crates/hir_def/src/attr.rs
index 52a2bce9b..786fad6e1 100644
--- a/crates/hir_def/src/attr.rs
+++ b/crates/hir_def/src/attr.rs
@@ -1,23 +1,28 @@
 //! A higher level attributes based on TokenTree, with also some shortcuts.
 
-use std::{ops, sync::Arc};
+use std::{
+    convert::{TryFrom, TryInto},
+    ops,
+    sync::Arc,
+};
 
 use base_db::CrateId;
 use cfg::{CfgExpr, CfgOptions};
 use either::Either;
-use hir_expand::{hygiene::Hygiene, name::AsName, AstId, InFile};
+use hir_expand::{hygiene::Hygiene, name::AsName, AstId, AttrId, InFile};
 use itertools::Itertools;
 use la_arena::ArenaMap;
 use mbe::ast_to_token_tree;
 use smallvec::{smallvec, SmallVec};
 use syntax::{
     ast::{self, AstNode, AttrsOwner},
-    match_ast, AstToken, SmolStr, SyntaxNode,
+    match_ast, AstPtr, AstToken, SmolStr, SyntaxNode, TextRange, TextSize,
 };
 use tt::Subtree;
 
 use crate::{
     db::DefDatabase,
+    intern::Interned,
     item_tree::{ItemTreeId, ItemTreeNode},
     nameres::ModuleSource,
     path::{ModPath, PathKind},
@@ -93,13 +98,16 @@ impl RawAttrs {
     pub(crate) fn new(owner: &dyn ast::AttrsOwner, hygiene: &Hygiene) -> Self {
         let entries = collect_attrs(owner)
             .enumerate()
-            .flat_map(|(i, attr)| match attr {
-                Either::Left(attr) => Attr::from_src(attr, hygiene, i as u32),
-                Either::Right(comment) => comment.doc_comment().map(|doc| Attr {
-                    index: i as u32,
-                    input: Some(AttrInput::Literal(SmolStr::new(doc))),
-                    path: ModPath::from(hir_expand::name!(doc)),
-                }),
+            .flat_map(|(i, attr)| {
+                let index = AttrId(i as u32);
+                match attr {
+                    Either::Left(attr) => Attr::from_src(attr, hygiene, index),
+                    Either::Right(comment) => comment.doc_comment().map(|doc| Attr {
+                        id: index,
+                        input: Some(AttrInput::Literal(SmolStr::new(doc))),
+                        path: Interned::new(ModPath::from(hir_expand::name!(doc))),
+                    }),
+                }
             })
             .collect::<Arc<_>>();
 
@@ -156,7 +164,7 @@ impl RawAttrs {
                 let cfg = parts.next().unwrap();
                 let cfg = Subtree { delimiter: subtree.delimiter, token_trees: cfg.to_vec() };
                 let cfg = CfgExpr::parse(&cfg);
-                let index = attr.index;
+                let index = attr.id;
                 let attrs = parts.filter(|a| !a.is_empty()).filter_map(|attr| {
                     let tree = Subtree { delimiter: None, token_trees: attr.to_vec() };
                     let attr = ast::Attr::parse(&format!("#[{}]", tree)).ok()?;
@@ -210,12 +218,11 @@ impl Attrs {
         let mut res = ArenaMap::default();
 
         for (id, fld) in src.value.iter() {
-            let attrs = match fld {
-                Either::Left(_tuple) => Attrs::default(),
-                Either::Right(record) => {
-                    RawAttrs::from_attrs_owner(db, src.with_value(record)).filter(db, krate)
-                }
+            let owner: &dyn AttrsOwner = match fld {
+                Either::Left(tuple) => tuple,
+                Either::Right(record) => record,
             };
+            let attrs = RawAttrs::from_attrs_owner(db, src.with_value(owner)).filter(db, krate);
 
             res.insert(id, attrs);
         }
@@ -399,10 +406,14 @@ impl AttrsWithOwner {
                 return AttrSourceMap { attrs };
             }
             AttrDefId::FieldId(id) => {
-                id.parent.child_source(db).map(|source| match &source[id.local_id] {
-                    Either::Left(field) => ast::AttrsOwnerNode::new(field.clone()),
-                    Either::Right(field) => ast::AttrsOwnerNode::new(field.clone()),
-                })
+                let map = db.fields_attrs_source_map(id.parent);
+                let file_id = id.parent.file_id(db);
+                let root = db.parse_or_expand(file_id).unwrap();
+                let owner = match &map[id.local_id] {
+                    Either::Left(it) => ast::AttrsOwnerNode::new(it.to_node(&root)),
+                    Either::Right(it) => ast::AttrsOwnerNode::new(it.to_node(&root)),
+                };
+                InFile::new(file_id, owner)
             }
             AttrDefId::AdtId(adt) => match adt {
                 AdtId::StructId(id) => id.lookup(db).source(db).map(ast::AttrsOwnerNode::new),
@@ -410,10 +421,12 @@ impl AttrsWithOwner {
                 AdtId::EnumId(id) => id.lookup(db).source(db).map(ast::AttrsOwnerNode::new),
             },
             AttrDefId::FunctionId(id) => id.lookup(db).source(db).map(ast::AttrsOwnerNode::new),
-            AttrDefId::EnumVariantId(id) => id
-                .parent
-                .child_source(db)
-                .map(|source| ast::AttrsOwnerNode::new(source[id.local_id].clone())),
+            AttrDefId::EnumVariantId(id) => {
+                let map = db.variants_attrs_source_map(id.parent);
+                let file_id = id.parent.lookup(db).id.file_id();
+                let root = db.parse_or_expand(file_id).unwrap();
+                InFile::new(file_id, ast::AttrsOwnerNode::new(map[id.local_id].to_node(&root)))
+            }
             AttrDefId::StaticId(id) => id.lookup(db).source(db).map(ast::AttrsOwnerNode::new),
             AttrDefId::ConstId(id) => id.lookup(db).source(db).map(ast::AttrsOwnerNode::new),
             AttrDefId::TraitId(id) => id.lookup(db).source(db).map(ast::AttrsOwnerNode::new),
@@ -451,6 +464,55 @@ impl AttrsWithOwner {
                 .collect(),
         }
     }
+
+    pub fn docs_with_rangemap(
+        &self,
+        db: &dyn DefDatabase,
+    ) -> Option<(Documentation, DocsRangeMap)> {
+        // FIXME: code duplication in `docs` above
+        let docs = self.by_key("doc").attrs().flat_map(|attr| match attr.input.as_ref()? {
+            AttrInput::Literal(s) => Some((s, attr.id)),
+            AttrInput::TokenTree(_) => None,
+        });
+        let indent = docs
+            .clone()
+            .flat_map(|(s, _)| s.lines())
+            .filter(|line| !line.chars().all(|c| c.is_whitespace()))
+            .map(|line| line.chars().take_while(|c| c.is_whitespace()).count())
+            .min()
+            .unwrap_or(0);
+        let mut buf = String::new();
+        let mut mapping = Vec::new();
+        for (doc, idx) in docs {
+            // str::lines doesn't yield anything for the empty string
+            if !doc.is_empty() {
+                for line in doc.split('\n') {
+                    let line = line.trim_end();
+                    let line_len = line.len();
+                    let (offset, line) = match line.char_indices().nth(indent) {
+                        Some((offset, _)) => (offset, &line[offset..]),
+                        None => (0, line),
+                    };
+                    let buf_offset = buf.len();
+                    buf.push_str(line);
+                    mapping.push((
+                        TextRange::new(buf_offset.try_into().ok()?, buf.len().try_into().ok()?),
+                        idx,
+                        TextRange::new(offset.try_into().ok()?, line_len.try_into().ok()?),
+                    ));
+                    buf.push('\n');
+                }
+            } else {
+                buf.push('\n');
+            }
+        }
+        buf.pop();
+        if buf.is_empty() {
+            None
+        } else {
+            Some((Documentation(buf), DocsRangeMap { mapping, source: self.source_map(db).attrs }))
+        }
+    }
 }
 
 fn inner_attributes(
@@ -501,16 +563,54 @@ impl AttrSourceMap {
     /// the attribute represented by `Attr`.
     pub fn source_of(&self, attr: &Attr) -> InFile<&Either<ast::Attr, ast::Comment>> {
         self.attrs
-            .get(attr.index as usize)
-            .unwrap_or_else(|| panic!("cannot find `Attr` at index {}", attr.index))
+            .get(attr.id.0 as usize)
+            .unwrap_or_else(|| panic!("cannot find `Attr` at index {:?}", attr.id))
             .as_ref()
     }
 }
 
+/// A struct to map text ranges from [`Documentation`] back to TextRanges in the syntax tree.
+pub struct DocsRangeMap {
+    source: Vec<InFile<Either<ast::Attr, ast::Comment>>>,
+    // (docstring-line-range, attr_index, attr-string-range)
+    // a mapping from the text range of a line of the [`Documentation`] to the attribute index and
+    // the original (untrimmed) syntax doc line
+    mapping: Vec<(TextRange, AttrId, TextRange)>,
+}
+
+impl DocsRangeMap {
+    pub fn map(&self, range: TextRange) -> Option<InFile<TextRange>> {
+        let found = self.mapping.binary_search_by(|(probe, ..)| probe.ordering(range)).ok()?;
+        let (line_docs_range, idx, original_line_src_range) = self.mapping[found].clone();
+        if !line_docs_range.contains_range(range) {
+            return None;
+        }
+
+        let relative_range = range - line_docs_range.start();
+
+        let &InFile { file_id, value: ref source } = &self.source[idx.0 as usize];
+        match source {
+            Either::Left(_) => None, // FIXME, figure out a nice way to handle doc attributes here
+            // as well as for whats done in syntax highlight doc injection
+            Either::Right(comment) => {
+                let text_range = comment.syntax().text_range();
+                let range = TextRange::at(
+                    text_range.start()
+                        + TextSize::try_from(comment.prefix().len()).ok()?
+                        + original_line_src_range.start()
+                        + relative_range.start(),
+                    text_range.len().min(range.len()),
+                );
+                Some(InFile { file_id, value: range })
+            }
+        }
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct Attr {
-    index: u32,
-    pub(crate) path: ModPath,
+    pub(crate) id: AttrId,
+    pub(crate) path: Interned<ModPath>,
     pub(crate) input: Option<AttrInput>,
 }
 
@@ -523,8 +623,8 @@ pub enum AttrInput {
 }
 
 impl Attr {
-    fn from_src(ast: ast::Attr, hygiene: &Hygiene, index: u32) -> Option<Attr> {
-        let path = ModPath::from_src(ast.path()?, hygiene)?;
+    fn from_src(ast: ast::Attr, hygiene: &Hygiene, id: AttrId) -> Option<Attr> {
+        let path = Interned::new(ModPath::from_src(ast.path()?, hygiene)?);
         let input = if let Some(ast::Expr::Literal(lit)) = ast.expr() {
             let value = match lit.kind() {
                 ast::LiteralKind::String(string) => string.value()?.into(),
@@ -532,11 +632,11 @@ impl Attr {
             };
             Some(AttrInput::Literal(value))
         } else if let Some(tt) = ast.token_tree() {
-            Some(AttrInput::TokenTree(ast_to_token_tree(&tt)?.0))
+            Some(AttrInput::TokenTree(ast_to_token_tree(&tt).0))
         } else {
             None
         };
-        Some(Attr { index, path, input })
+        Some(Attr { id, path, input })
     }
 
     /// Parses this attribute as a `#[derive]`, returns an iterator that yields all contained paths
@@ -651,7 +751,38 @@ fn collect_attrs(
         .chain(inner_docs.into_iter().flatten())
         .map(|docs_text| (docs_text.syntax().text_range().start(), Either::Right(docs_text)));
     // sort here by syntax node offset because the source can have doc attributes and doc strings be interleaved
-    let attrs: Vec<_> = docs.chain(attrs).sorted_by_key(|&(offset, _)| offset).collect();
+    docs.chain(attrs).sorted_by_key(|&(offset, _)| offset).map(|(_, attr)| attr)
+}
+
+pub(crate) fn variants_attrs_source_map(
+    db: &dyn DefDatabase,
+    def: EnumId,
+) -> Arc<ArenaMap<LocalEnumVariantId, AstPtr<ast::Variant>>> {
+    let mut res = ArenaMap::default();
+    let child_source = def.child_source(db);
+
+    for (idx, variant) in child_source.value.iter() {
+        res.insert(idx, AstPtr::new(variant));
+    }
+
+    Arc::new(res)
+}
+
+pub(crate) fn fields_attrs_source_map(
+    db: &dyn DefDatabase,
+    def: VariantId,
+) -> Arc<ArenaMap<LocalFieldId, Either<AstPtr<ast::TupleField>, AstPtr<ast::RecordField>>>> {
+    let mut res = ArenaMap::default();
+    let child_source = def.child_source(db);
+
+    for (idx, variant) in child_source.value.iter() {
+        res.insert(
+            idx,
+            variant
+                .as_ref()
+                .either(|l| Either::Left(AstPtr::new(l)), |r| Either::Right(AstPtr::new(r))),
+        );
+    }
 
-    attrs.into_iter().map(|(_, attr)| attr)
+    Arc::new(res)
 }
diff --git a/crates/hir_def/src/body.rs b/crates/hir_def/src/body.rs
index 1080d9c2c..96b959967 100644
--- a/crates/hir_def/src/body.rs
+++ b/crates/hir_def/src/body.rs
@@ -226,7 +226,7 @@ pub struct Body {
     /// The `ExprId` of the actual body expression.
     pub body_expr: ExprId,
     /// Block expressions in this body that may contain inner items.
-    pub block_scopes: Vec<BlockId>,
+    block_scopes: Vec<BlockId>,
     _c: Count<Self>,
 }
 
@@ -302,7 +302,8 @@ impl Body {
             }
         };
         let expander = Expander::new(db, file_id, module);
-        let (body, source_map) = Body::new(db, expander, params, body);
+        let (mut body, source_map) = Body::new(db, expander, params, body);
+        body.shrink_to_fit();
         (Arc::new(body), Arc::new(source_map))
     }
 
@@ -310,6 +311,16 @@ impl Body {
         db.body_with_source_map(def).0
     }
 
+    /// Returns an iterator over all block expressions in this body that define inner items.
+    pub fn blocks<'a>(
+        &'a self,
+        db: &'a dyn DefDatabase,
+    ) -> impl Iterator<Item = (BlockId, Arc<DefMap>)> + '_ {
+        self.block_scopes
+            .iter()
+            .map(move |block| (*block, db.block_def_map(*block).expect("block ID without DefMap")))
+    }
+
     fn new(
         db: &dyn DefDatabase,
         expander: Expander,
@@ -318,6 +329,15 @@ impl Body {
     ) -> (Body, BodySourceMap) {
         lower::lower(db, expander, params, body)
     }
+
+    fn shrink_to_fit(&mut self) {
+        let Self { _c: _, body_expr: _, block_scopes, exprs, labels, params, pats } = self;
+        block_scopes.shrink_to_fit();
+        exprs.shrink_to_fit();
+        labels.shrink_to_fit();
+        params.shrink_to_fit();
+        pats.shrink_to_fit();
+    }
 }
 
 impl Index<ExprId> for Body {
diff --git a/crates/hir_def/src/body/lower.rs b/crates/hir_def/src/body/lower.rs
index 229e81dd4..c0b0b7841 100644
--- a/crates/hir_def/src/body/lower.rs
+++ b/crates/hir_def/src/body/lower.rs
@@ -30,6 +30,7 @@ use crate::{
         LabelId, Literal, LogicOp, MatchArm, Ordering, Pat, PatId, RecordFieldPat, RecordLitField,
         Statement,
     },
+    intern::Interned,
     item_scope::BuiltinShadowMode,
     path::{GenericArgs, Path},
     type_ref::{Mutability, Rawness, TypeRef},
@@ -322,8 +323,10 @@ impl ExprCollector<'_> {
                     Vec::new()
                 };
                 let method_name = e.name_ref().map(|nr| nr.as_name()).unwrap_or_else(Name::missing);
-                let generic_args =
-                    e.generic_arg_list().and_then(|it| GenericArgs::from_ast(&self.ctx(), it));
+                let generic_args = e
+                    .generic_arg_list()
+                    .and_then(|it| GenericArgs::from_ast(&self.ctx(), it))
+                    .map(Box::new);
                 self.alloc_expr(
                     Expr::MethodCall { receiver, method_name, args, generic_args },
                     syntax_ptr,
@@ -385,7 +388,7 @@ impl ExprCollector<'_> {
                 self.alloc_expr(Expr::Yield { expr }, syntax_ptr)
             }
             ast::Expr::RecordExpr(e) => {
-                let path = e.path().and_then(|path| self.expander.parse_path(path));
+                let path = e.path().and_then(|path| self.expander.parse_path(path)).map(Box::new);
                 let record_lit = if let Some(nfl) = e.record_expr_field_list() {
                     let fields = nfl
                         .fields()
@@ -430,7 +433,7 @@ impl ExprCollector<'_> {
             }
             ast::Expr::CastExpr(e) => {
                 let expr = self.collect_expr_opt(e.expr());
-                let type_ref = TypeRef::from_ast_opt(&self.ctx(), e.ty());
+                let type_ref = Interned::new(TypeRef::from_ast_opt(&self.ctx(), e.ty()));
                 self.alloc_expr(Expr::Cast { expr, type_ref }, syntax_ptr)
             }
             ast::Expr::RefExpr(e) => {
@@ -464,13 +467,16 @@ impl ExprCollector<'_> {
                 if let Some(pl) = e.param_list() {
                     for param in pl.params() {
                         let pat = self.collect_pat_opt(param.pat());
-                        let type_ref = param.ty().map(|it| TypeRef::from_ast(&self.ctx(), it));
+                        let type_ref =
+                            param.ty().map(|it| Interned::new(TypeRef::from_ast(&self.ctx(), it)));
                         args.push(pat);
                         arg_types.push(type_ref);
                     }
                 }
-                let ret_type =
-                    e.ret_type().and_then(|r| r.ty()).map(|it| TypeRef::from_ast(&self.ctx(), it));
+                let ret_type = e
+                    .ret_type()
+                    .and_then(|r| r.ty())
+                    .map(|it| Interned::new(TypeRef::from_ast(&self.ctx(), it)));
                 let body = self.collect_expr_opt(e.body());
                 self.alloc_expr(Expr::Lambda { args, arg_types, ret_type, body }, syntax_ptr)
             }
@@ -525,8 +531,9 @@ impl ExprCollector<'_> {
                 }
             }
             ast::Expr::MacroCall(e) => {
+                let macro_ptr = AstPtr::new(&e);
                 let mut ids = vec![];
-                self.collect_macro_call(e, syntax_ptr.clone(), true, |this, expansion| {
+                self.collect_macro_call(e, macro_ptr, true, |this, expansion| {
                     ids.push(match expansion {
                         Some(it) => this.collect_expr(it),
                         None => this.alloc_expr(Expr::Missing, syntax_ptr.clone()),
@@ -549,7 +556,7 @@ impl ExprCollector<'_> {
     fn collect_macro_call<F: FnMut(&mut Self, Option<T>), T: ast::AstNode>(
         &mut self,
         e: ast::MacroCall,
-        syntax_ptr: AstPtr<ast::Expr>,
+        syntax_ptr: AstPtr<ast::MacroCall>,
         is_error_recoverable: bool,
         mut collector: F,
     ) {
@@ -561,9 +568,13 @@ impl ExprCollector<'_> {
 
         let res = match res {
             Ok(res) => res,
-            Err(UnresolvedMacro) => {
+            Err(UnresolvedMacro { path }) => {
                 self.source_map.diagnostics.push(BodyDiagnostic::UnresolvedMacroCall(
-                    UnresolvedMacroCall { file: outer_file, node: syntax_ptr.cast().unwrap() },
+                    UnresolvedMacroCall {
+                        file: outer_file,
+                        node: syntax_ptr.cast().unwrap(),
+                        path,
+                    },
                 ));
                 collector(self, None);
                 return;
@@ -625,7 +636,8 @@ impl ExprCollector<'_> {
                     return;
                 }
                 let pat = self.collect_pat_opt(stmt.pat());
-                let type_ref = stmt.ty().map(|it| TypeRef::from_ast(&self.ctx(), it));
+                let type_ref =
+                    stmt.ty().map(|it| Interned::new(TypeRef::from_ast(&self.ctx(), it)));
                 let initializer = stmt.initializer().map(|e| self.collect_expr(e));
                 self.statements_in_scope.push(Statement::Let { pat, type_ref, initializer });
             }
@@ -636,10 +648,14 @@ impl ExprCollector<'_> {
 
                 // Note that macro could be expended to multiple statements
                 if let Some(ast::Expr::MacroCall(m)) = stmt.expr() {
+                    let macro_ptr = AstPtr::new(&m);
                     let syntax_ptr = AstPtr::new(&stmt.expr().unwrap());
 
-                    self.collect_macro_call(m, syntax_ptr.clone(), false, |this, expansion| {
-                        match expansion {
+                    self.collect_macro_call(
+                        m,
+                        macro_ptr,
+                        false,
+                        |this, expansion| match expansion {
                             Some(expansion) => {
                                 let statements: ast::MacroStmts = expansion;
 
@@ -653,8 +669,8 @@ impl ExprCollector<'_> {
                                 let expr = this.alloc_expr(Expr::Missing, syntax_ptr.clone());
                                 this.statements_in_scope.push(Statement::Expr(expr));
                             }
-                        }
-                    });
+                        },
+                    );
                 } else {
                     let expr = self.collect_expr_opt(stmt.expr());
                     self.statements_in_scope.push(Statement::Expr(expr));
@@ -673,12 +689,14 @@ impl ExprCollector<'_> {
         let block_loc =
             BlockLoc { ast_id, module: self.expander.def_map.module_id(self.expander.module) };
         let block_id = self.db.intern_block(block_loc);
-        self.body.block_scopes.push(block_id);
 
-        let opt_def_map = self.db.block_def_map(block_id);
-        let has_def_map = opt_def_map.is_some();
-        let def_map = opt_def_map.unwrap_or_else(|| self.expander.def_map.clone());
-        let module = if has_def_map { def_map.root() } else { self.expander.module };
+        let (module, def_map) = match self.db.block_def_map(block_id) {
+            Some(def_map) => {
+                self.body.block_scopes.push(block_id);
+                (def_map.root(), def_map)
+            }
+            None => (self.expander.module, self.expander.def_map.clone()),
+        };
         let prev_def_map = mem::replace(&mut self.expander.def_map, def_map);
         let prev_local_module = mem::replace(&mut self.expander.module, module);
         let prev_statements = std::mem::take(&mut self.statements_in_scope);
@@ -753,7 +771,7 @@ impl ExprCollector<'_> {
                 }
             }
             ast::Pat::TupleStructPat(p) => {
-                let path = p.path().and_then(|path| self.expander.parse_path(path));
+                let path = p.path().and_then(|path| self.expander.parse_path(path)).map(Box::new);
                 let (args, ellipsis) = self.collect_tuple_pat(p.fields());
                 Pat::TupleStruct { path, args, ellipsis }
             }
@@ -763,7 +781,7 @@ impl ExprCollector<'_> {
                 Pat::Ref { pat, mutability }
             }
             ast::Pat::PathPat(p) => {
-                let path = p.path().and_then(|path| self.expander.parse_path(path));
+                let path = p.path().and_then(|path| self.expander.parse_path(path)).map(Box::new);
                 path.map(Pat::Path).unwrap_or(Pat::Missing)
             }
             ast::Pat::OrPat(p) => {
@@ -777,7 +795,7 @@ impl ExprCollector<'_> {
             }
             ast::Pat::WildcardPat(_) => Pat::Wild,
             ast::Pat::RecordPat(p) => {
-                let path = p.path().and_then(|path| self.expander.parse_path(path));
+                let path = p.path().and_then(|path| self.expander.parse_path(path)).map(Box::new);
                 let args: Vec<_> = p
                     .record_pat_field_list()
                     .expect("every struct should have a field list")
@@ -839,8 +857,23 @@ impl ExprCollector<'_> {
                     Pat::Missing
                 }
             }
+            ast::Pat::MacroPat(mac) => match mac.macro_call() {
+                Some(call) => {
+                    let macro_ptr = AstPtr::new(&call);
+                    let mut pat = None;
+                    self.collect_macro_call(call, macro_ptr, true, |this, expanded_pat| {
+                        pat = Some(this.collect_pat_opt(expanded_pat));
+                    });
+
+                    match pat {
+                        Some(pat) => return pat,
+                        None => Pat::Missing,
+                    }
+                }
+                None => Pat::Missing,
+            },
             // FIXME: implement
-            ast::Pat::RangePat(_) | ast::Pat::MacroPat(_) => Pat::Missing,
+            ast::Pat::RangePat(_) => Pat::Missing,
         };
         let ptr = AstPtr::new(&pat);
         self.alloc_pat(pattern, Either::Left(ptr))
diff --git a/crates/hir_def/src/body/tests.rs b/crates/hir_def/src/body/tests.rs
index faa133297..63f5fe88d 100644
--- a/crates/hir_def/src/body/tests.rs
+++ b/crates/hir_def/src/body/tests.rs
@@ -143,7 +143,7 @@ fn f() {
   //^^^^^^^^^^^^^ could not convert tokens
 
     env!("OUT_DIR");
-  //^^^^^^^^^^^^^^^ `OUT_DIR` not set, enable "load out dirs from check" to fix
+  //^^^^^^^^^^^^^^^ `OUT_DIR` not set, enable "run build scripts" to fix
 
     compile_error!("compile_error works");
   //^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ compile_error works
@@ -180,7 +180,7 @@ fn unresolved_macro_diag() {
         r#"
 fn f() {
     m!();
-  //^^^^ unresolved macro call
+  //^^^^ unresolved macro `m!`
 }
       "#,
     );
diff --git a/crates/hir_def/src/child_by_source.rs b/crates/hir_def/src/child_by_source.rs
index 2a331dcaf..f2e809ca9 100644
--- a/crates/hir_def/src/child_by_source.rs
+++ b/crates/hir_def/src/child_by_source.rs
@@ -80,6 +80,10 @@ impl ChildBySource for ModuleId {
 impl ChildBySource for ItemScope {
     fn child_by_source_to(&self, db: &dyn DefDatabase, res: &mut DynMap) {
         self.declarations().for_each(|item| add_module_def(db, res, item));
+        self.unnamed_consts().for_each(|konst| {
+            let src = konst.lookup(db).source(db);
+            res[keys::CONST].insert(src, konst);
+        });
         self.impls().for_each(|imp| add_impl(db, res, imp));
 
         fn add_module_def(db: &dyn DefDatabase, map: &mut DynMap, item: ModuleDefId) {
@@ -160,7 +164,7 @@ impl ChildBySource for EnumId {
 impl ChildBySource for DefWithBodyId {
     fn child_by_source_to(&self, db: &dyn DefDatabase, res: &mut DynMap) {
         let body = db.body(*self);
-        for def_map in body.block_scopes.iter().filter_map(|block| db.block_def_map(*block)) {
+        for (_, def_map) in body.blocks(db) {
             // All block expressions are merged into the same map, because they logically all add
             // inner items to the containing `DefWithBodyId`.
             def_map[def_map.root()].scope.child_by_source_to(db, res);
diff --git a/crates/hir_def/src/data.rs b/crates/hir_def/src/data.rs
index 0be868ba2..135a6698e 100644
--- a/crates/hir_def/src/data.rs
+++ b/crates/hir_def/src/data.rs
@@ -9,8 +9,9 @@ use crate::{
     attr::Attrs,
     body::Expander,
     db::DefDatabase,
-    item_tree::{AssocItem, FunctionQualifier, ItemTreeId, ModItem, Param},
-    type_ref::{TypeBound, TypeRef},
+    intern::Interned,
+    item_tree::{AssocItem, FnFlags, ItemTreeId, ModItem, Param},
+    type_ref::{TraitRef, TypeBound, TypeRef},
     visibility::RawVisibility,
     AssocContainerId, AssocItemId, ConstId, ConstLoc, FunctionId, FunctionLoc, HasModule, ImplId,
     Intern, Lookup, ModuleId, StaticId, TraitId, TypeAliasId, TypeAliasLoc,
@@ -19,17 +20,12 @@ use crate::{
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct FunctionData {
     pub name: Name,
-    pub params: Vec<TypeRef>,
-    pub ret_type: TypeRef,
+    pub params: Vec<Interned<TypeRef>>,
+    pub ret_type: Interned<TypeRef>,
     pub attrs: Attrs,
-    /// True if the first param is `self`. This is relevant to decide whether this
-    /// can be called as a method.
-    pub has_self_param: bool,
-    pub has_body: bool,
-    pub qualifier: FunctionQualifier,
-    pub is_in_extern_block: bool,
-    pub is_varargs: bool,
     pub visibility: RawVisibility,
+    pub abi: Option<Interned<str>>,
+    flags: FnFlags,
 }
 
 impl FunctionData {
@@ -52,31 +48,67 @@ impl FunctionData {
             .next_back()
             .map_or(false, |param| matches!(item_tree[param], Param::Varargs));
 
+        let mut flags = func.flags;
+        if is_varargs {
+            flags.bits |= FnFlags::IS_VARARGS;
+        }
+
         Arc::new(FunctionData {
             name: func.name.clone(),
             params: enabled_params
                 .clone()
                 .filter_map(|id| match &item_tree[id] {
-                    Param::Normal(ty) => Some(item_tree[*ty].clone()),
+                    Param::Normal(ty) => Some(ty.clone()),
                     Param::Varargs => None,
                 })
                 .collect(),
-            ret_type: item_tree[func.ret_type].clone(),
+            ret_type: func.ret_type.clone(),
             attrs: item_tree.attrs(db, krate, ModItem::from(loc.id.value).into()),
-            has_self_param: func.has_self_param,
-            has_body: func.has_body,
-            qualifier: func.qualifier.clone(),
-            is_in_extern_block: func.is_in_extern_block,
-            is_varargs,
             visibility: item_tree[func.visibility].clone(),
+            abi: func.abi.clone(),
+            flags,
         })
     }
+
+    pub fn has_body(&self) -> bool {
+        self.flags.bits & FnFlags::HAS_BODY != 0
+    }
+
+    /// True if the first param is `self`. This is relevant to decide whether this
+    /// can be called as a method.
+    pub fn has_self_param(&self) -> bool {
+        self.flags.bits & FnFlags::HAS_SELF_PARAM != 0
+    }
+
+    pub fn is_default(&self) -> bool {
+        self.flags.bits & FnFlags::IS_DEFAULT != 0
+    }
+
+    pub fn is_const(&self) -> bool {
+        self.flags.bits & FnFlags::IS_CONST != 0
+    }
+
+    pub fn is_async(&self) -> bool {
+        self.flags.bits & FnFlags::IS_ASYNC != 0
+    }
+
+    pub fn is_unsafe(&self) -> bool {
+        self.flags.bits & FnFlags::IS_UNSAFE != 0
+    }
+
+    pub fn is_in_extern_block(&self) -> bool {
+        self.flags.bits & FnFlags::IS_IN_EXTERN_BLOCK != 0
+    }
+
+    pub fn is_varargs(&self) -> bool {
+        self.flags.bits & FnFlags::IS_VARARGS != 0
+    }
 }
 
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct TypeAliasData {
     pub name: Name,
-    pub type_ref: Option<TypeRef>,
+    pub type_ref: Option<Interned<TypeRef>>,
     pub visibility: RawVisibility,
     pub is_extern: bool,
     /// Bounds restricting the type alias itself (eg. `type Ty: Bound;` in a trait or impl).
@@ -94,7 +126,7 @@ impl TypeAliasData {
 
         Arc::new(TypeAliasData {
             name: typ.name.clone(),
-            type_ref: typ.type_ref.map(|id| item_tree[id].clone()),
+            type_ref: typ.type_ref.clone(),
             visibility: item_tree[typ.visibility].clone(),
             is_extern: typ.is_extern,
             bounds: typ.bounds.to_vec(),
@@ -156,8 +188,8 @@ impl TraitData {
 
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct ImplData {
-    pub target_trait: Option<TypeRef>,
-    pub target_type: TypeRef,
+    pub target_trait: Option<Interned<TraitRef>>,
+    pub self_ty: Interned<TypeRef>,
     pub items: Vec<AssocItemId>,
     pub is_negative: bool,
 }
@@ -169,8 +201,8 @@ impl ImplData {
 
         let item_tree = impl_loc.id.item_tree(db);
         let impl_def = &item_tree[impl_loc.id.value];
-        let target_trait = impl_def.target_trait.map(|id| item_tree[id].clone());
-        let target_type = item_tree[impl_def.target_type].clone();
+        let target_trait = impl_def.target_trait.clone();
+        let self_ty = impl_def.self_ty.clone();
         let is_negative = impl_def.is_negative;
         let module_id = impl_loc.container;
         let container = AssocContainerId::ImplId(id);
@@ -187,7 +219,7 @@ impl ImplData {
         );
         let items = items.into_iter().map(|(_, item)| item).collect();
 
-        Arc::new(ImplData { target_trait, target_type, items, is_negative })
+        Arc::new(ImplData { target_trait, self_ty, items, is_negative })
     }
 }
 
@@ -195,7 +227,7 @@ impl ImplData {
 pub struct ConstData {
     /// const _: () = ();
     pub name: Option<Name>,
-    pub type_ref: TypeRef,
+    pub type_ref: Interned<TypeRef>,
     pub visibility: RawVisibility,
 }
 
@@ -207,7 +239,7 @@ impl ConstData {
 
         Arc::new(ConstData {
             name: konst.name.clone(),
-            type_ref: item_tree[konst.type_ref].clone(),
+            type_ref: konst.type_ref.clone(),
             visibility: item_tree[konst.visibility].clone(),
         })
     }
@@ -216,7 +248,7 @@ impl ConstData {
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct StaticData {
     pub name: Option<Name>,
-    pub type_ref: TypeRef,
+    pub type_ref: Interned<TypeRef>,
     pub visibility: RawVisibility,
     pub mutable: bool,
     pub is_extern: bool,
@@ -230,7 +262,7 @@ impl StaticData {
 
         Arc::new(StaticData {
             name: Some(statik.name.clone()),
-            type_ref: item_tree[statik.type_ref].clone(),
+            type_ref: statik.type_ref.clone(),
             visibility: item_tree[statik.visibility].clone(),
             mutable: statik.mutable,
             is_extern: statik.is_extern,
diff --git a/crates/hir_def/src/db.rs b/crates/hir_def/src/db.rs
index 068b2ee38..7eadc8e0d 100644
--- a/crates/hir_def/src/db.rs
+++ b/crates/hir_def/src/db.rs
@@ -2,9 +2,10 @@
 use std::sync::Arc;
 
 use base_db::{salsa, CrateId, SourceDatabase, Upcast};
+use either::Either;
 use hir_expand::{db::AstDatabase, HirFileId};
 use la_arena::ArenaMap;
-use syntax::SmolStr;
+use syntax::{ast, AstPtr, SmolStr};
 
 use crate::{
     adt::{EnumData, StructData},
@@ -13,6 +14,7 @@ use crate::{
     data::{ConstData, FunctionData, ImplData, StaticData, TraitData, TypeAliasData},
     generics::GenericParams,
     import_map::ImportMap,
+    intern::Interned,
     item_tree::ItemTree,
     lang_item::{LangItemTarget, LangItems},
     nameres::DefMap,
@@ -113,7 +115,7 @@ pub trait DefDatabase: InternDatabase + AstDatabase + Upcast<dyn AstDatabase> {
     fn expr_scopes(&self, def: DefWithBodyId) -> Arc<ExprScopes>;
 
     #[salsa::invoke(GenericParams::generic_params_query)]
-    fn generic_params(&self, def: GenericDefId) -> Arc<GenericParams>;
+    fn generic_params(&self, def: GenericDefId) -> Interned<GenericParams>;
 
     #[salsa::invoke(Attrs::variants_attrs_query)]
     fn variants_attrs(&self, def: EnumId) -> Arc<ArenaMap<LocalEnumVariantId, Attrs>>;
@@ -121,6 +123,18 @@ pub trait DefDatabase: InternDatabase + AstDatabase + Upcast<dyn AstDatabase> {
     #[salsa::invoke(Attrs::fields_attrs_query)]
     fn fields_attrs(&self, def: VariantId) -> Arc<ArenaMap<LocalFieldId, Attrs>>;
 
+    #[salsa::invoke(crate::attr::variants_attrs_source_map)]
+    fn variants_attrs_source_map(
+        &self,
+        def: EnumId,
+    ) -> Arc<ArenaMap<LocalEnumVariantId, AstPtr<ast::Variant>>>;
+
+    #[salsa::invoke(crate::attr::fields_attrs_source_map)]
+    fn fields_attrs_source_map(
+        &self,
+        def: VariantId,
+    ) -> Arc<ArenaMap<LocalFieldId, Either<AstPtr<ast::TupleField>, AstPtr<ast::RecordField>>>>;
+
     #[salsa::invoke(AttrsWithOwner::attrs_query)]
     fn attrs(&self, def: AttrDefId) -> AttrsWithOwner;
 
diff --git a/crates/hir_def/src/diagnostics.rs b/crates/hir_def/src/diagnostics.rs
index 97abf8653..a71ae2668 100644
--- a/crates/hir_def/src/diagnostics.rs
+++ b/crates/hir_def/src/diagnostics.rs
@@ -8,7 +8,7 @@ use hir_expand::diagnostics::{Diagnostic, DiagnosticCode, DiagnosticSink};
 use hir_expand::{HirFileId, InFile};
 use syntax::{ast, AstPtr, SyntaxNodePtr, TextRange};
 
-use crate::{db::DefDatabase, DefWithBodyId};
+use crate::{db::DefDatabase, path::ModPath, DefWithBodyId};
 
 pub fn validate_body(db: &dyn DefDatabase, owner: DefWithBodyId, sink: &mut DiagnosticSink<'_>) {
     let source_map = db.body_with_source_map(owner).1;
@@ -103,6 +103,7 @@ impl Diagnostic for UnresolvedImport {
 pub struct UnresolvedMacroCall {
     pub file: HirFileId,
     pub node: AstPtr<ast::MacroCall>,
+    pub path: ModPath,
 }
 
 impl Diagnostic for UnresolvedMacroCall {
@@ -110,7 +111,7 @@ impl Diagnostic for UnresolvedMacroCall {
         DiagnosticCode("unresolved-macro-call")
     }
     fn message(&self) -> String {
-        "unresolved macro call".to_string()
+        format!("unresolved macro `{}!`", self.path)
     }
     fn display_source(&self) -> InFile<SyntaxNodePtr> {
         InFile::new(self.file, self.node.clone().into())
diff --git a/crates/hir_def/src/expr.rs b/crates/hir_def/src/expr.rs
index 6c7376fad..b4ad984bd 100644
--- a/crates/hir_def/src/expr.rs
+++ b/crates/hir_def/src/expr.rs
@@ -18,6 +18,7 @@ use syntax::ast::RangeOp;
 
 use crate::{
     builtin_type::{BuiltinFloat, BuiltinInt, BuiltinUint},
+    intern::Interned,
     path::{GenericArgs, Path},
     type_ref::{Mutability, Rawness, TypeRef},
     BlockId,
@@ -86,7 +87,7 @@ pub enum Expr {
         receiver: ExprId,
         method_name: Name,
         args: Vec<ExprId>,
-        generic_args: Option<GenericArgs>,
+        generic_args: Option<Box<GenericArgs>>,
     },
     Match {
         expr: ExprId,
@@ -106,7 +107,7 @@ pub enum Expr {
         expr: Option<ExprId>,
     },
     RecordLit {
-        path: Option<Path>,
+        path: Option<Box<Path>>,
         fields: Vec<RecordLitField>,
         spread: Option<ExprId>,
     },
@@ -131,7 +132,7 @@ pub enum Expr {
     },
     Cast {
         expr: ExprId,
-        type_ref: TypeRef,
+        type_ref: Interned<TypeRef>,
     },
     Ref {
         expr: ExprId,
@@ -161,8 +162,8 @@ pub enum Expr {
     },
     Lambda {
         args: Vec<PatId>,
-        arg_types: Vec<Option<TypeRef>>,
-        ret_type: Option<TypeRef>,
+        arg_types: Vec<Option<Interned<TypeRef>>>,
+        ret_type: Option<Interned<TypeRef>>,
         body: ExprId,
     },
     Tuple {
@@ -240,7 +241,7 @@ pub struct RecordLitField {
 
 #[derive(Debug, Clone, Eq, PartialEq)]
 pub enum Statement {
-    Let { pat: PatId, type_ref: Option<TypeRef>, initializer: Option<ExprId> },
+    Let { pat: PatId, type_ref: Option<Interned<TypeRef>>, initializer: Option<ExprId> },
     Expr(ExprId),
 }
 
@@ -412,13 +413,13 @@ pub enum Pat {
     Wild,
     Tuple { args: Vec<PatId>, ellipsis: Option<usize> },
     Or(Vec<PatId>),
-    Record { path: Option<Path>, args: Vec<RecordFieldPat>, ellipsis: bool },
+    Record { path: Option<Box<Path>>, args: Vec<RecordFieldPat>, ellipsis: bool },
     Range { start: ExprId, end: ExprId },
     Slice { prefix: Vec<PatId>, slice: Option<PatId>, suffix: Vec<PatId> },
-    Path(Path),
+    Path(Box<Path>),
     Lit(ExprId),
     Bind { mode: BindingAnnotation, name: Name, subpat: Option<PatId> },
-    TupleStruct { path: Option<Path>, args: Vec<PatId>, ellipsis: Option<usize> },
+    TupleStruct { path: Option<Box<Path>>, args: Vec<PatId>, ellipsis: Option<usize> },
     Ref { pat: PatId, mutability: Mutability },
     Box { inner: PatId },
     ConstBlock(ExprId),
diff --git a/crates/hir_def/src/find_path.rs b/crates/hir_def/src/find_path.rs
index 109d3552f..2c4bbe585 100644
--- a/crates/hir_def/src/find_path.rs
+++ b/crates/hir_def/src/find_path.rs
@@ -425,106 +425,142 @@ mod tests {
 
     #[test]
     fn same_module() {
-        let code = r#"
-            //- /main.rs
-            struct S;
-            $0
-        "#;
-        check_found_path(code, "S", "S", "crate::S", "self::S");
+        check_found_path(
+            r#"
+struct S;
+$0
+        "#,
+            "S",
+            "S",
+            "crate::S",
+            "self::S",
+        );
     }
 
     #[test]
     fn enum_variant() {
-        let code = r#"
-            //- /main.rs
-            enum E { A }
-            $0
-        "#;
-        check_found_path(code, "E::A", "E::A", "E::A", "E::A");
+        check_found_path(
+            r#"
+enum E { A }
+$0
+        "#,
+            "E::A",
+            "E::A",
+            "E::A",
+            "E::A",
+        );
     }
 
     #[test]
     fn sub_module() {
-        let code = r#"
-            //- /main.rs
-            mod foo {
-                pub struct S;
-            }
-            $0
-        "#;
-        check_found_path(code, "foo::S", "foo::S", "crate::foo::S", "self::foo::S");
+        check_found_path(
+            r#"
+mod foo {
+    pub struct S;
+}
+$0
+        "#,
+            "foo::S",
+            "foo::S",
+            "crate::foo::S",
+            "self::foo::S",
+        );
     }
 
     #[test]
     fn super_module() {
-        let code = r#"
-            //- /main.rs
-            mod foo;
-            //- /foo.rs
-            mod bar;
-            struct S;
-            //- /foo/bar.rs
-            $0
-        "#;
-        check_found_path(code, "super::S", "super::S", "crate::foo::S", "super::S");
+        check_found_path(
+            r#"
+//- /main.rs
+mod foo;
+//- /foo.rs
+mod bar;
+struct S;
+//- /foo/bar.rs
+$0
+        "#,
+            "super::S",
+            "super::S",
+            "crate::foo::S",
+            "super::S",
+        );
     }
 
     #[test]
     fn self_module() {
-        let code = r#"
-            //- /main.rs
-            mod foo;
-            //- /foo.rs
-            $0
-        "#;
-        check_found_path(code, "self", "self", "crate::foo", "self");
+        check_found_path(
+            r#"
+//- /main.rs
+mod foo;
+//- /foo.rs
+$0
+        "#,
+            "self",
+            "self",
+            "crate::foo",
+            "self",
+        );
     }
 
     #[test]
     fn crate_root() {
-        let code = r#"
-            //- /main.rs
-            mod foo;
-            //- /foo.rs
-            $0
-        "#;
-        check_found_path(code, "crate", "crate", "crate", "crate");
+        check_found_path(
+            r#"
+//- /main.rs
+mod foo;
+//- /foo.rs
+$0
+        "#,
+            "crate",
+            "crate",
+            "crate",
+            "crate",
+        );
     }
 
     #[test]
     fn same_crate() {
-        let code = r#"
-            //- /main.rs
-            mod foo;
-            struct S;
-            //- /foo.rs
-            $0
-        "#;
-        check_found_path(code, "crate::S", "crate::S", "crate::S", "crate::S");
+        check_found_path(
+            r#"
+//- /main.rs
+mod foo;
+struct S;
+//- /foo.rs
+$0
+        "#,
+            "crate::S",
+            "crate::S",
+            "crate::S",
+            "crate::S",
+        );
     }
 
     #[test]
     fn different_crate() {
-        let code = r#"
-            //- /main.rs crate:main deps:std
-            $0
-            //- /std.rs crate:std
-            pub struct S;
-        "#;
-        check_found_path(code, "std::S", "std::S", "std::S", "std::S");
+        check_found_path(
+            r#"
+//- /main.rs crate:main deps:std
+$0
+//- /std.rs crate:std
+pub struct S;
+        "#,
+            "std::S",
+            "std::S",
+            "std::S",
+            "std::S",
+        );
     }
 
     #[test]
     fn different_crate_renamed() {
-        let code = r#"
-            //- /main.rs crate:main deps:std
-            extern crate std as std_renamed;
-            $0
-            //- /std.rs crate:std
-            pub struct S;
-        "#;
         check_found_path(
-            code,
+            r#"
+//- /main.rs crate:main deps:std
+extern crate std as std_renamed;
+$0
+//- /std.rs crate:std
+pub struct S;
+        "#,
             "std_renamed::S",
             "std_renamed::S",
             "std_renamed::S",
@@ -537,41 +573,38 @@ mod tests {
         cov_mark::check!(partially_imported);
         // Tests that short paths are used even for external items, when parts of the path are
         // already in scope.
-        let code = r#"
-            //- /main.rs crate:main deps:syntax
+        check_found_path(
+            r#"
+//- /main.rs crate:main deps:syntax
 
-            use syntax::ast;
-            $0
+use syntax::ast;
+$0
 
-            //- /lib.rs crate:syntax
-            pub mod ast {
-                pub enum ModuleItem {
-                    A, B, C,
-                }
-            }
-        "#;
-        check_found_path(
-            code,
+//- /lib.rs crate:syntax
+pub mod ast {
+    pub enum ModuleItem {
+        A, B, C,
+    }
+}
+        "#,
             "ast::ModuleItem",
             "syntax::ast::ModuleItem",
             "syntax::ast::ModuleItem",
             "syntax::ast::ModuleItem",
         );
 
-        let code = r#"
-            //- /main.rs crate:main deps:syntax
-
-            $0
-
-            //- /lib.rs crate:syntax
-            pub mod ast {
-                pub enum ModuleItem {
-                    A, B, C,
-                }
-            }
-        "#;
         check_found_path(
-            code,
+            r#"
+//- /main.rs crate:main deps:syntax
+$0
+
+//- /lib.rs crate:syntax
+pub mod ast {
+    pub enum ModuleItem {
+        A, B, C,
+    }
+}
+        "#,
             "syntax::ast::ModuleItem",
             "syntax::ast::ModuleItem",
             "syntax::ast::ModuleItem",
@@ -581,68 +614,86 @@ mod tests {
 
     #[test]
     fn same_crate_reexport() {
-        let code = r#"
-            //- /main.rs
-            mod bar {
-                mod foo { pub(super) struct S; }
-                pub(crate) use foo::*;
-            }
-            $0
-        "#;
-        check_found_path(code, "bar::S", "bar::S", "crate::bar::S", "self::bar::S");
+        check_found_path(
+            r#"
+mod bar {
+    mod foo { pub(super) struct S; }
+    pub(crate) use foo::*;
+}
+$0
+        "#,
+            "bar::S",
+            "bar::S",
+            "crate::bar::S",
+            "self::bar::S",
+        );
     }
 
     #[test]
     fn same_crate_reexport_rename() {
-        let code = r#"
-            //- /main.rs
-            mod bar {
-                mod foo { pub(super) struct S; }
-                pub(crate) use foo::S as U;
-            }
-            $0
-        "#;
-        check_found_path(code, "bar::U", "bar::U", "crate::bar::U", "self::bar::U");
+        check_found_path(
+            r#"
+mod bar {
+    mod foo { pub(super) struct S; }
+    pub(crate) use foo::S as U;
+}
+$0
+        "#,
+            "bar::U",
+            "bar::U",
+            "crate::bar::U",
+            "self::bar::U",
+        );
     }
 
     #[test]
     fn different_crate_reexport() {
-        let code = r#"
-            //- /main.rs crate:main deps:std
-            $0
-            //- /std.rs crate:std deps:core
-            pub use core::S;
-            //- /core.rs crate:core
-            pub struct S;
-        "#;
-        check_found_path(code, "std::S", "std::S", "std::S", "std::S");
+        check_found_path(
+            r#"
+//- /main.rs crate:main deps:std
+$0
+//- /std.rs crate:std deps:core
+pub use core::S;
+//- /core.rs crate:core
+pub struct S;
+        "#,
+            "std::S",
+            "std::S",
+            "std::S",
+            "std::S",
+        );
     }
 
     #[test]
     fn prelude() {
-        let code = r#"
-            //- /main.rs crate:main deps:std
-            $0
-            //- /std.rs crate:std
-            pub mod prelude { pub struct S; }
-            #[prelude_import]
-            pub use prelude::*;
-        "#;
-        check_found_path(code, "S", "S", "S", "S");
+        check_found_path(
+            r#"
+//- /main.rs crate:main deps:std
+$0
+//- /std.rs crate:std
+pub mod prelude { pub struct S; }
+#[prelude_import]
+pub use prelude::*;
+        "#,
+            "S",
+            "S",
+            "S",
+            "S",
+        );
     }
 
     #[test]
     fn enum_variant_from_prelude() {
         let code = r#"
-            //- /main.rs crate:main deps:std
-            $0
-            //- /std.rs crate:std
-            pub mod prelude {
-                pub enum Option<T> { Some(T), None }
-                pub use Option::*;
-            }
-            #[prelude_import]
-            pub use prelude::*;
+//- /main.rs crate:main deps:std
+$0
+//- /std.rs crate:std
+pub mod prelude {
+    pub enum Option<T> { Some(T), None }
+    pub use Option::*;
+}
+#[prelude_import]
+pub use prelude::*;
         "#;
         check_found_path(code, "None", "None", "None", "None");
         check_found_path(code, "Some", "Some", "Some", "Some");
@@ -650,71 +701,85 @@ mod tests {
 
     #[test]
     fn shortest_path() {
-        let code = r#"
-            //- /main.rs
-            pub mod foo;
-            pub mod baz;
-            struct S;
-            $0
-            //- /foo.rs
-            pub mod bar { pub struct S; }
-            //- /baz.rs
-            pub use crate::foo::bar::S;
-        "#;
-        check_found_path(code, "baz::S", "baz::S", "crate::baz::S", "self::baz::S");
+        check_found_path(
+            r#"
+//- /main.rs
+pub mod foo;
+pub mod baz;
+struct S;
+$0
+//- /foo.rs
+pub mod bar { pub struct S; }
+//- /baz.rs
+pub use crate::foo::bar::S;
+        "#,
+            "baz::S",
+            "baz::S",
+            "crate::baz::S",
+            "self::baz::S",
+        );
     }
 
     #[test]
     fn discount_private_imports() {
-        let code = r#"
-            //- /main.rs
-            mod foo;
-            pub mod bar { pub struct S; }
-            use bar::S;
-            //- /foo.rs
-            $0
-        "#;
-        // crate::S would be shorter, but using private imports seems wrong
-        check_found_path(code, "crate::bar::S", "crate::bar::S", "crate::bar::S", "crate::bar::S");
+        check_found_path(
+            r#"
+//- /main.rs
+mod foo;
+pub mod bar { pub struct S; }
+use bar::S;
+//- /foo.rs
+$0
+        "#,
+            // crate::S would be shorter, but using private imports seems wrong
+            "crate::bar::S",
+            "crate::bar::S",
+            "crate::bar::S",
+            "crate::bar::S",
+        );
     }
 
     #[test]
     fn import_cycle() {
-        let code = r#"
-            //- /main.rs
-            pub mod foo;
-            pub mod bar;
-            pub mod baz;
-            //- /bar.rs
-            $0
-            //- /foo.rs
-            pub use super::baz;
-            pub struct S;
-            //- /baz.rs
-            pub use super::foo;
-        "#;
-        check_found_path(code, "crate::foo::S", "crate::foo::S", "crate::foo::S", "crate::foo::S");
+        check_found_path(
+            r#"
+//- /main.rs
+pub mod foo;
+pub mod bar;
+pub mod baz;
+//- /bar.rs
+$0
+//- /foo.rs
+pub use super::baz;
+pub struct S;
+//- /baz.rs
+pub use super::foo;
+        "#,
+            "crate::foo::S",
+            "crate::foo::S",
+            "crate::foo::S",
+            "crate::foo::S",
+        );
     }
 
     #[test]
     fn prefer_std_paths_over_alloc() {
         cov_mark::check!(prefer_std_paths);
-        let code = r#"
-        //- /main.rs crate:main deps:alloc,std
-        $0
+        check_found_path(
+            r#"
+//- /main.rs crate:main deps:alloc,std
+$0
 
-        //- /std.rs crate:std deps:alloc
-        pub mod sync {
-            pub use alloc::sync::Arc;
-        }
+//- /std.rs crate:std deps:alloc
+pub mod sync {
+    pub use alloc::sync::Arc;
+}
 
-        //- /zzz.rs crate:alloc
-        pub mod sync {
-            pub struct Arc;
-        }
-        "#;
-        check_found_path(
-            code,
+//- /zzz.rs crate:alloc
+pub mod sync {
+    pub struct Arc;
+}
+        "#,
             "std::sync::Arc",
             "std::sync::Arc",
             "std::sync::Arc",
@@ -725,26 +790,25 @@ mod tests {
     #[test]
     fn prefer_core_paths_over_std() {
         cov_mark::check!(prefer_no_std_paths);
-        let code = r#"
-        //- /main.rs crate:main deps:core,std
-        #![no_std]
+        check_found_path(
+            r#"
+//- /main.rs crate:main deps:core,std
+#![no_std]
 
-        $0
+$0
 
-        //- /std.rs crate:std deps:core
+//- /std.rs crate:std deps:core
 
-        pub mod fmt {
-            pub use core::fmt::Error;
-        }
+pub mod fmt {
+    pub use core::fmt::Error;
+}
 
-        //- /zzz.rs crate:core
+//- /zzz.rs crate:core
 
-        pub mod fmt {
-            pub struct Error;
-        }
-        "#;
-        check_found_path(
-            code,
+pub mod fmt {
+    pub struct Error;
+}
+        "#,
             "core::fmt::Error",
             "core::fmt::Error",
             "core::fmt::Error",
@@ -754,26 +818,25 @@ mod tests {
 
     #[test]
     fn prefer_alloc_paths_over_std() {
-        let code = r#"
-        //- /main.rs crate:main deps:alloc,std
-        #![no_std]
+        check_found_path(
+            r#"
+//- /main.rs crate:main deps:alloc,std
+#![no_std]
 
-        $0
+$0
 
-        //- /std.rs crate:std deps:alloc
+//- /std.rs crate:std deps:alloc
 
-        pub mod sync {
-            pub use alloc::sync::Arc;
-        }
+pub mod sync {
+    pub use alloc::sync::Arc;
+}
 
-        //- /zzz.rs crate:alloc
+//- /zzz.rs crate:alloc
 
-        pub mod sync {
-            pub struct Arc;
-        }
-        "#;
-        check_found_path(
-            code,
+pub mod sync {
+    pub struct Arc;
+}
+            "#,
             "alloc::sync::Arc",
             "alloc::sync::Arc",
             "alloc::sync::Arc",
@@ -783,20 +846,19 @@ mod tests {
 
     #[test]
     fn prefer_shorter_paths_if_not_alloc() {
-        let code = r#"
-        //- /main.rs crate:main deps:megaalloc,std
-        $0
+        check_found_path(
+            r#"
+//- /main.rs crate:main deps:megaalloc,std
+$0
 
-        //- /std.rs crate:std deps:megaalloc
-        pub mod sync {
-            pub use megaalloc::sync::Arc;
-        }
+//- /std.rs crate:std deps:megaalloc
+pub mod sync {
+    pub use megaalloc::sync::Arc;
+}
 
-        //- /zzz.rs crate:megaalloc
-        pub struct Arc;
-        "#;
-        check_found_path(
-            code,
+//- /zzz.rs crate:megaalloc
+pub struct Arc;
+            "#,
             "megaalloc::Arc",
             "megaalloc::Arc",
             "megaalloc::Arc",
@@ -807,12 +869,11 @@ mod tests {
     #[test]
     fn builtins_are_in_scope() {
         let code = r#"
-        //- /main.rs
-        $0
+$0
 
-        pub mod primitive {
-            pub use u8;
-        }
+pub mod primitive {
+    pub use u8;
+}
         "#;
         check_found_path(code, "u8", "u8", "u8", "u8");
         check_found_path(code, "u16", "u16", "u16", "u16");
@@ -822,10 +883,10 @@ mod tests {
     fn inner_items() {
         check_found_path(
             r#"
-            fn main() {
-                struct Inner {}
-                $0
-            }
+fn main() {
+    struct Inner {}
+    $0
+}
         "#,
             "Inner",
             "Inner",
@@ -838,12 +899,12 @@ mod tests {
     fn inner_items_from_outer_scope() {
         check_found_path(
             r#"
-            fn main() {
-                struct Struct {}
-                {
-                    $0
-                }
-            }
+fn main() {
+    struct Struct {}
+    {
+        $0
+    }
+}
         "#,
             "Struct",
             "Struct",
@@ -857,14 +918,14 @@ mod tests {
         cov_mark::check!(prefixed_in_block_expression);
         check_found_path(
             r#"
-            fn main() {
-                mod module {
-                    struct Struct {}
-                }
-                {
-                    $0
-                }
-            }
+fn main() {
+    mod module {
+        struct Struct {}
+    }
+    {
+        $0
+    }
+}
         "#,
             "module::Struct",
             "module::Struct",
@@ -877,14 +938,14 @@ mod tests {
     fn outer_items_with_inner_items_present() {
         check_found_path(
             r#"
-            mod module {
-                pub struct CompleteMe;
-            }
+mod module {
+    pub struct CompleteMe;
+}
 
-            fn main() {
-                fn inner() {}
-                $0
-            }
+fn main() {
+    fn inner() {}
+    $0
+}
             "#,
             "module::CompleteMe",
             "module::CompleteMe",
@@ -894,6 +955,29 @@ mod tests {
     }
 
     #[test]
+    fn from_inside_module() {
+        // This worked correctly, but the test suite logic was broken.
+        cov_mark::check!(submodule_in_testdb);
+        check_found_path(
+            r#"
+mod baz {
+    pub struct Foo {}
+}
+
+mod bar {
+    fn bar() {
+        $0
+    }
+}
+            "#,
+            "crate::baz::Foo",
+            "crate::baz::Foo",
+            "crate::baz::Foo",
+            "crate::baz::Foo",
+        )
+    }
+
+    #[test]
     fn recursive_pub_mod_reexport() {
         cov_mark::check!(recursive_imports);
         check_found_path(
diff --git a/crates/hir_def/src/generics.rs b/crates/hir_def/src/generics.rs
index 7c6cbff11..de5acced8 100644
--- a/crates/hir_def/src/generics.rs
+++ b/crates/hir_def/src/generics.rs
@@ -2,7 +2,6 @@
 //! structs, impls, traits, etc. This module provides a common HIR for these
 //! generic parameters. See also the `Generics` type and the `generics_of` query
 //! in rustc.
-use std::sync::Arc;
 
 use base_db::FileId;
 use either::Either;
@@ -18,6 +17,7 @@ use crate::{
     child_by_source::ChildBySource,
     db::DefDatabase,
     dyn_map::DynMap,
+    intern::Interned,
     keys,
     src::{HasChildSource, HasSource},
     type_ref::{LifetimeRef, TypeBound, TypeRef},
@@ -26,27 +26,27 @@ use crate::{
 };
 
 /// Data about a generic type parameter (to a function, struct, impl, ...).
-#[derive(Clone, PartialEq, Eq, Debug)]
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
 pub struct TypeParamData {
     pub name: Option<Name>,
-    pub default: Option<TypeRef>,
+    pub default: Option<Interned<TypeRef>>,
     pub provenance: TypeParamProvenance,
 }
 
 /// Data about a generic lifetime parameter (to a function, struct, impl, ...).
-#[derive(Clone, PartialEq, Eq, Debug)]
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
 pub struct LifetimeParamData {
     pub name: Name,
 }
 
 /// Data about a generic const parameter (to a function, struct, impl, ...).
-#[derive(Clone, PartialEq, Eq, Debug)]
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
 pub struct ConstParamData {
     pub name: Name,
-    pub ty: TypeRef,
+    pub ty: Interned<TypeRef>,
 }
 
-#[derive(Copy, Clone, PartialEq, Eq, Debug)]
+#[derive(Copy, Clone, PartialEq, Eq, Debug, Hash)]
 pub enum TypeParamProvenance {
     TypeParamList,
     TraitSelf,
@@ -54,7 +54,7 @@ pub enum TypeParamProvenance {
 }
 
 /// Data about the generic parameters of a function, struct, impl, etc.
-#[derive(Clone, PartialEq, Eq, Debug, Default)]
+#[derive(Clone, PartialEq, Eq, Debug, Default, Hash)]
 pub struct GenericParams {
     pub types: Arena<TypeParamData>,
     pub lifetimes: Arena<LifetimeParamData>,
@@ -66,16 +66,16 @@ pub struct GenericParams {
 /// where clauses like `where T: Foo + Bar` are turned into multiple of these.
 /// It might still result in multiple actual predicates though, because of
 /// associated type bindings like `Iterator<Item = u32>`.
-#[derive(Clone, PartialEq, Eq, Debug)]
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
 pub enum WherePredicate {
     TypeBound { target: WherePredicateTypeTarget, bound: TypeBound },
     Lifetime { target: LifetimeRef, bound: LifetimeRef },
     ForLifetime { lifetimes: Box<[Name]>, target: WherePredicateTypeTarget, bound: TypeBound },
 }
 
-#[derive(Clone, PartialEq, Eq, Debug)]
+#[derive(Clone, PartialEq, Eq, Debug, Hash)]
 pub enum WherePredicateTypeTarget {
-    TypeRef(TypeRef),
+    TypeRef(Interned<TypeRef>),
     /// For desugared where predicates that can directly refer to a type param.
     TypeParam(LocalTypeParamId),
 }
@@ -91,7 +91,7 @@ impl GenericParams {
     pub(crate) fn generic_params_query(
         db: &dyn DefDatabase,
         def: GenericDefId,
-    ) -> Arc<GenericParams> {
+    ) -> Interned<GenericParams> {
         let _p = profile::span("generic_params_query");
 
         let generics = match def {
@@ -99,47 +99,49 @@ impl GenericParams {
                 let id = id.lookup(db).id;
                 let tree = id.item_tree(db);
                 let item = &tree[id.value];
-                tree[item.generic_params].clone()
+                item.generic_params.clone()
             }
             GenericDefId::AdtId(AdtId::StructId(id)) => {
                 let id = id.lookup(db).id;
                 let tree = id.item_tree(db);
                 let item = &tree[id.value];
-                tree[item.generic_params].clone()
+                item.generic_params.clone()
             }
             GenericDefId::AdtId(AdtId::EnumId(id)) => {
                 let id = id.lookup(db).id;
                 let tree = id.item_tree(db);
                 let item = &tree[id.value];
-                tree[item.generic_params].clone()
+                item.generic_params.clone()
             }
             GenericDefId::AdtId(AdtId::UnionId(id)) => {
                 let id = id.lookup(db).id;
                 let tree = id.item_tree(db);
                 let item = &tree[id.value];
-                tree[item.generic_params].clone()
+                item.generic_params.clone()
             }
             GenericDefId::TraitId(id) => {
                 let id = id.lookup(db).id;
                 let tree = id.item_tree(db);
                 let item = &tree[id.value];
-                tree[item.generic_params].clone()
+                item.generic_params.clone()
             }
             GenericDefId::TypeAliasId(id) => {
                 let id = id.lookup(db).id;
                 let tree = id.item_tree(db);
                 let item = &tree[id.value];
-                tree[item.generic_params].clone()
+                item.generic_params.clone()
             }
             GenericDefId::ImplId(id) => {
                 let id = id.lookup(db).id;
                 let tree = id.item_tree(db);
                 let item = &tree[id.value];
-                tree[item.generic_params].clone()
+                item.generic_params.clone()
+            }
+            GenericDefId::EnumVariantId(_) | GenericDefId::ConstId(_) => {
+                Interned::new(GenericParams::default())
             }
-            GenericDefId::EnumVariantId(_) | GenericDefId::ConstId(_) => GenericParams::default(),
         };
-        Arc::new(generics)
+        generics
     }
 
     fn new(db: &dyn DefDatabase, def: GenericDefId) -> (GenericParams, InFile<SourceMap>) {
@@ -217,6 +219,7 @@ impl GenericParams {
             GenericDefId::EnumVariantId(_) | GenericDefId::ConstId(_) => FileId(!0).into(),
         };
 
+        generics.shrink_to_fit();
         (generics, InFile::new(file_id, sm))
     }
 
@@ -256,7 +259,8 @@ impl GenericParams {
         for type_param in params.type_params() {
             let name = type_param.name().map_or_else(Name::missing, |it| it.as_name());
             // FIXME: Use `Path::from_src`
-            let default = type_param.default_type().map(|it| TypeRef::from_ast(lower_ctx, it));
+            let default =
+                type_param.default_type().map(|it| Interned::new(TypeRef::from_ast(lower_ctx, it)));
             let param = TypeParamData {
                 name: Some(name.clone()),
                 default,
@@ -280,7 +284,7 @@ impl GenericParams {
         for const_param in params.const_params() {
             let name = const_param.name().map_or_else(Name::missing, |it| it.as_name());
             let ty = const_param.ty().map_or(TypeRef::Error, |it| TypeRef::from_ast(lower_ctx, it));
-            let param = ConstParamData { name, ty };
+            let param = ConstParamData { name, ty: Interned::new(ty) };
             let param_id = self.consts.alloc(param);
             sm.const_params.insert(param_id, const_param.clone());
         }
@@ -334,11 +338,11 @@ impl GenericParams {
             (Either::Left(type_ref), bound) => match hrtb_lifetimes {
                 Some(hrtb_lifetimes) => WherePredicate::ForLifetime {
                     lifetimes: hrtb_lifetimes.clone(),
-                    target: WherePredicateTypeTarget::TypeRef(type_ref),
+                    target: WherePredicateTypeTarget::TypeRef(Interned::new(type_ref)),
                     bound,
                 },
                 None => WherePredicate::TypeBound {
-                    target: WherePredicateTypeTarget::TypeRef(type_ref),
+                    target: WherePredicateTypeTarget::TypeRef(Interned::new(type_ref)),
                     bound,
                 },
             },
@@ -369,6 +373,14 @@ impl GenericParams {
         });
     }
 
+    pub(crate) fn shrink_to_fit(&mut self) {
+        let Self { consts, lifetimes, types, where_predicates } = self;
+        consts.shrink_to_fit();
+        lifetimes.shrink_to_fit();
+        types.shrink_to_fit();
+        where_predicates.shrink_to_fit();
+    }
+
     pub fn find_type_by_name(&self, name: &Name) -> Option<LocalTypeParamId> {
         self.types
             .iter()
diff --git a/crates/hir_def/src/intern.rs b/crates/hir_def/src/intern.rs
new file mode 100644
index 000000000..abc304ef0
--- /dev/null
+++ b/crates/hir_def/src/intern.rs
@@ -0,0 +1,216 @@
+//! Global `Arc`-based object interning infrastructure.
+//!
+//! Eventually this should probably be replaced with salsa-based interning.
+
+use std::{
+    collections::HashMap,
+    fmt::{self, Debug},
+    hash::{BuildHasherDefault, Hash, Hasher},
+    ops::Deref,
+    sync::Arc,
+};
+
+use dashmap::{lock::RwLockWriteGuard, DashMap, SharedValue};
+use once_cell::sync::OnceCell;
+use rustc_hash::FxHasher;
+
+use crate::generics::GenericParams;
+
+type InternMap<T> = DashMap<Arc<T>, (), BuildHasherDefault<FxHasher>>;
+type Guard<T> =
+    RwLockWriteGuard<'static, HashMap<Arc<T>, SharedValue<()>, BuildHasherDefault<FxHasher>>>;
+
+pub struct Interned<T: Internable + ?Sized> {
+    arc: Arc<T>,
+}
+
+impl<T: Internable> Interned<T> {
+    pub fn new(obj: T) -> Self {
+        match Interned::lookup(&obj) {
+            Ok(this) => this,
+            Err(shard) => {
+                let arc = Arc::new(obj);
+                Self::alloc(arc, shard)
+            }
+        }
+    }
+}
+
+impl<T: Internable + ?Sized> Interned<T> {
+    fn lookup(obj: &T) -> Result<Self, Guard<T>> {
+        let storage = T::storage().get();
+        let shard_idx = storage.determine_map(obj);
+        let shard = &storage.shards()[shard_idx];
+        let shard = shard.write();
+
+        // Atomically,
+        // - check if `obj` is already in the map
+        //   - if so, clone its `Arc` and return it
+        //   - if not, box it up, insert it, and return a clone
+        // This needs to be atomic (locking the shard) to avoid races with other thread, which could
+        // insert the same object between us looking it up and inserting it.
+
+        // FIXME: avoid double lookup/hashing by using raw entry API (once stable, or when
+        // hashbrown can be plugged into dashmap)
+        match shard.get_key_value(obj) {
+            Some((arc, _)) => Ok(Self { arc: arc.clone() }),
+            None => Err(shard),
+        }
+    }
+
+    fn alloc(arc: Arc<T>, mut shard: Guard<T>) -> Self {
+        let arc2 = arc.clone();
+
+        shard.insert(arc2, SharedValue::new(()));
+
+        Self { arc }
+    }
+}
+
+impl Interned<str> {
+    pub fn new_str(s: &str) -> Self {
+        match Interned::lookup(s) {
+            Ok(this) => this,
+            Err(shard) => {
+                let arc = Arc::<str>::from(s);
+                Self::alloc(arc, shard)
+            }
+        }
+    }
+}
+
+impl<T: Internable + ?Sized> Drop for Interned<T> {
+    #[inline]
+    fn drop(&mut self) {
+        // When the last `Ref` is dropped, remove the object from the global map.
+        if Arc::strong_count(&self.arc) == 2 {
+            // Only `self` and the global map point to the object.
+
+            self.drop_slow();
+        }
+    }
+}
+
+impl<T: Internable + ?Sized> Interned<T> {
+    #[cold]
+    fn drop_slow(&mut self) {
+        let storage = T::storage().get();
+        let shard_idx = storage.determine_map(&self.arc);
+        let shard = &storage.shards()[shard_idx];
+        let mut shard = shard.write();
+
+        // FIXME: avoid double lookup
+        let (arc, _) = shard.get_key_value(&self.arc).expect("interned value removed prematurely");
+
+        if Arc::strong_count(arc) != 2 {
+            // Another thread has interned another copy
+            return;
+        }
+
+        shard.remove(&self.arc);
+
+        // Shrink the backing storage if the shard is less than 50% occupied.
+        if shard.len() * 2 < shard.capacity() {
+            shard.shrink_to_fit();
+        }
+    }
+}
+
+/// Compares interned `Ref`s using pointer equality.
+impl<T: Internable> PartialEq for Interned<T> {
+    // NOTE: No `?Sized` because `ptr_eq` doesn't work right with trait objects.
+
+    #[inline]
+    fn eq(&self, other: &Self) -> bool {
+        Arc::ptr_eq(&self.arc, &other.arc)
+    }
+}
+
+impl<T: Internable> Eq for Interned<T> {}
+
+impl PartialEq for Interned<str> {
+    fn eq(&self, other: &Self) -> bool {
+        Arc::ptr_eq(&self.arc, &other.arc)
+    }
+}
+
+impl Eq for Interned<str> {}
+
+impl<T: Internable + ?Sized> Hash for Interned<T> {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        // NOTE: Cast disposes vtable pointer / slice/str length.
+        state.write_usize(Arc::as_ptr(&self.arc) as *const () as usize)
+    }
+}
+
+impl<T: Internable + ?Sized> AsRef<T> for Interned<T> {
+    #[inline]
+    fn as_ref(&self) -> &T {
+        &self.arc
+    }
+}
+
+impl<T: Internable + ?Sized> Deref for Interned<T> {
+    type Target = T;
+
+    #[inline]
+    fn deref(&self) -> &Self::Target {
+        &self.arc
+    }
+}
+
+impl<T: Internable + ?Sized> Clone for Interned<T> {
+    fn clone(&self) -> Self {
+        Self { arc: self.arc.clone() }
+    }
+}
+
+impl<T: Debug + Internable + ?Sized> Debug for Interned<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        (*self.arc).fmt(f)
+    }
+}
+
+pub struct InternStorage<T: ?Sized> {
+    map: OnceCell<InternMap<T>>,
+}
+
+impl<T: ?Sized> InternStorage<T> {
+    pub const fn new() -> Self {
+        Self { map: OnceCell::new() }
+    }
+}
+
+impl<T: Internable + ?Sized> InternStorage<T> {
+    fn get(&self) -> &InternMap<T> {
+        self.map.get_or_init(DashMap::default)
+    }
+}
+
+pub trait Internable: Hash + Eq + 'static {
+    fn storage() -> &'static InternStorage<Self>;
+}
+
+/// Implements `Internable` for a given list of types, making them usable with `Interned`.
+#[macro_export]
+#[doc(hidden)]
+macro_rules! _impl_internable {
+    ( $($t:path),+ $(,)? ) => { $(
+        impl Internable for $t {
+            fn storage() -> &'static InternStorage<Self> {
+                static STORAGE: InternStorage<$t> = InternStorage::new();
+                &STORAGE
+            }
+        }
+    )+ };
+}
+
+pub use crate::_impl_internable as impl_internable;
+
+impl_internable!(
+    crate::type_ref::TypeRef,
+    crate::type_ref::TraitRef,
+    crate::path::ModPath,
+    GenericParams,
+    str,
+);
diff --git a/crates/hir_def/src/item_scope.rs b/crates/hir_def/src/item_scope.rs
index f3ebe7c72..9014468ea 100644
--- a/crates/hir_def/src/item_scope.rs
+++ b/crates/hir_def/src/item_scope.rs
@@ -11,7 +11,7 @@ use rustc_hash::{FxHashMap, FxHashSet};
 use stdx::format_to;
 
 use crate::{
-    db::DefDatabase, per_ns::PerNs, visibility::Visibility, AdtId, BuiltinType, ImplId,
+    db::DefDatabase, per_ns::PerNs, visibility::Visibility, AdtId, BuiltinType, ConstId, ImplId,
     LocalModuleId, MacroDefId, ModuleDefId, ModuleId, TraitId,
 };
 
@@ -37,6 +37,7 @@ pub struct ItemScope {
 
     defs: Vec<ModuleDefId>,
     impls: Vec<ImplId>,
+    unnamed_consts: Vec<ConstId>,
     /// Traits imported via `use Trait as _;`.
     unnamed_trait_imports: FxHashMap<TraitId, Visibility>,
     /// Macros visible in current module in legacy textual scope
@@ -106,6 +107,10 @@ impl ItemScope {
             .map(|(_, v)| v)
     }
 
+    pub fn unnamed_consts(&self) -> impl Iterator<Item = ConstId> + '_ {
+        self.unnamed_consts.iter().copied()
+    }
+
     /// Iterate over all module scoped macros
     pub(crate) fn macros<'a>(&'a self) -> impl Iterator<Item = (&'a Name, MacroDefId)> + 'a {
         self.entries().filter_map(|(name, def)| def.take_macros().map(|macro_| (name, macro_)))
@@ -156,6 +161,10 @@ impl ItemScope {
         self.impls.push(imp)
     }
 
+    pub(crate) fn define_unnamed_const(&mut self, konst: ConstId) {
+        self.unnamed_consts.push(konst);
+    }
+
     pub(crate) fn define_legacy_macro(&mut self, name: Name, mac: MacroDefId) {
         self.legacy_macros.insert(name, mac);
     }
@@ -285,6 +294,30 @@ impl ItemScope {
             buf.push('\n');
         }
     }
+
+    pub(crate) fn shrink_to_fit(&mut self) {
+        // Exhaustive match to require handling new fields.
+        let Self {
+            types,
+            values,
+            macros,
+            unresolved,
+            defs,
+            impls,
+            unnamed_consts,
+            unnamed_trait_imports,
+            legacy_macros,
+        } = self;
+        types.shrink_to_fit();
+        values.shrink_to_fit();
+        macros.shrink_to_fit();
+        unresolved.shrink_to_fit();
+        defs.shrink_to_fit();
+        impls.shrink_to_fit();
+        unnamed_consts.shrink_to_fit();
+        unnamed_trait_imports.shrink_to_fit();
+        legacy_macros.shrink_to_fit();
+    }
 }
 
 impl PerNs {
diff --git a/crates/hir_def/src/item_tree.rs b/crates/hir_def/src/item_tree.rs
index ca0048b16..94e08f835 100644
--- a/crates/hir_def/src/item_tree.rs
+++ b/crates/hir_def/src/item_tree.rs
@@ -24,14 +24,15 @@ use la_arena::{Arena, Idx, RawIdx};
 use profile::Count;
 use rustc_hash::FxHashMap;
 use smallvec::SmallVec;
-use syntax::{ast, match_ast, SmolStr, SyntaxKind};
+use syntax::{ast, match_ast, SyntaxKind};
 
 use crate::{
     attr::{Attrs, RawAttrs},
     db::DefDatabase,
     generics::GenericParams,
+    intern::Interned,
     path::{path, AssociatedTypeBinding, GenericArgs, ImportAlias, ModPath, Path, PathKind},
-    type_ref::{Mutability, TypeBound, TypeRef},
+    type_ref::{Mutability, TraitRef, TypeBound, TypeRef},
     visibility::RawVisibility,
 };
 
@@ -57,13 +58,6 @@ impl fmt::Debug for RawVisibilityId {
     }
 }
 
-#[derive(Debug, Copy, Clone, Eq, PartialEq)]
-pub struct GenericParamsId(u32);
-
-impl GenericParamsId {
-    pub const EMPTY: Self = GenericParamsId(u32::max_value());
-}
-
 /// The item tree of a source file.
 #[derive(Debug, Default, Eq, PartialEq)]
 pub struct ItemTree {
@@ -105,6 +99,11 @@ impl ItemTree {
                     // items.
                     ctx.lower_macro_stmts(stmts)
                 },
+                ast::Pat(_pat) => {
+                    // FIXME: This occurs because macros in pattern position are treated as inner
+                    // items and expanded during block DefMap computation
+                    return Default::default();
+                },
                 ast::Expr(e) => {
                     // Macros can expand to expressions. We return an empty item tree in this case, but
                     // still need to collect inner items.
@@ -145,8 +144,6 @@ impl ItemTree {
                 macro_rules,
                 macro_defs,
                 vis,
-                generics,
-                type_refs,
                 inner_items,
             } = &mut **data;
 
@@ -170,9 +167,6 @@ impl ItemTree {
             macro_defs.shrink_to_fit();
 
             vis.arena.shrink_to_fit();
-            generics.arena.shrink_to_fit();
-            type_refs.arena.shrink_to_fit();
-            type_refs.map.shrink_to_fit();
 
             inner_items.shrink_to_fit();
         }
@@ -244,58 +238,6 @@ static VIS_PRIV: RawVisibility = RawVisibility::Module(ModPath::from_kind(PathKi
 static VIS_PUB_CRATE: RawVisibility = RawVisibility::Module(ModPath::from_kind(PathKind::Crate));
 
 #[derive(Default, Debug, Eq, PartialEq)]
-struct GenericParamsStorage {
-    arena: Arena<GenericParams>,
-}
-
-impl GenericParamsStorage {
-    fn alloc(&mut self, params: GenericParams) -> GenericParamsId {
-        if params.types.is_empty()
-            && params.lifetimes.is_empty()
-            && params.consts.is_empty()
-            && params.where_predicates.is_empty()
-        {
-            return GenericParamsId::EMPTY;
-        }
-
-        GenericParamsId(self.arena.alloc(params).into_raw().into())
-    }
-}
-
-static EMPTY_GENERICS: GenericParams = GenericParams {
-    types: Arena::new(),
-    lifetimes: Arena::new(),
-    consts: Arena::new(),
-    where_predicates: Vec::new(),
-};
-
-/// `TypeRef` interner.
-#[derive(Default, Debug, Eq, PartialEq)]
-struct TypeRefStorage {
-    arena: Arena<Arc<TypeRef>>,
-    map: FxHashMap<Arc<TypeRef>, Idx<Arc<TypeRef>>>,
-}
-
-impl TypeRefStorage {
-    // Note: We lie about the `Idx<TypeRef>` to hide the interner details.
-
-    fn intern(&mut self, ty: TypeRef) -> Idx<TypeRef> {
-        if let Some(id) = self.map.get(&ty) {
-            return Idx::from_raw(id.into_raw());
-        }
-
-        let ty = Arc::new(ty);
-        let idx = self.arena.alloc(ty.clone());
-        self.map.insert(ty, idx);
-        Idx::from_raw(idx.into_raw())
-    }
-
-    fn lookup(&self, id: Idx<TypeRef>) -> &TypeRef {
-        &self.arena[Idx::from_raw(id.into_raw())]
-    }
-}
-
-#[derive(Default, Debug, Eq, PartialEq)]
 struct ItemTreeData {
     imports: Arena<Import>,
     extern_crates: Arena<ExternCrate>,
@@ -317,8 +259,6 @@ struct ItemTreeData {
     macro_defs: Arena<MacroDef>,
 
     vis: ItemVisibilities,
-    generics: GenericParamsStorage,
-    type_refs: TypeRefStorage,
 
     inner_items: FxHashMap<FileAstId<ast::BlockExpr>, SmallVec<[ModItem; 1]>>,
 }
@@ -537,25 +477,6 @@ impl Index<RawVisibilityId> for ItemTree {
     }
 }
 
-impl Index<GenericParamsId> for ItemTree {
-    type Output = GenericParams;
-
-    fn index(&self, index: GenericParamsId) -> &Self::Output {
-        match index {
-            GenericParamsId::EMPTY => &EMPTY_GENERICS,
-            _ => &self.data().generics.arena[Idx::from_raw(index.0.into())],
-        }
-    }
-}
-
-impl Index<Idx<TypeRef>> for ItemTree {
-    type Output = TypeRef;
-
-    fn index(&self, id: Idx<TypeRef>) -> &Self::Output {
-        self.data().type_refs.lookup(id)
-    }
-}
-
 impl<N: ItemTreeNode> Index<FileItemTreeId<N>> for ItemTree {
     type Output = N;
     fn index(&self, id: FileItemTreeId<N>) -> &N {
@@ -566,7 +487,7 @@ impl<N: ItemTreeNode> Index<FileItemTreeId<N>> for ItemTree {
 /// A desugared `use` import.
 #[derive(Debug, Clone, Eq, PartialEq)]
 pub struct Import {
-    pub path: ModPath,
+    pub path: Interned<ModPath>,
     pub alias: Option<ImportAlias>,
     pub visibility: RawVisibilityId,
     pub is_glob: bool,
@@ -592,38 +513,42 @@ pub struct ExternCrate {
 pub struct Function {
     pub name: Name,
     pub visibility: RawVisibilityId,
-    pub generic_params: GenericParamsId,
-    pub has_self_param: bool,
-    pub has_body: bool,
-    pub qualifier: FunctionQualifier,
-    /// Whether the function is located in an `extern` block (*not* whether it is an
-    /// `extern "abi" fn`).
-    pub is_in_extern_block: bool,
+    pub generic_params: Interned<GenericParams>,
+    pub abi: Option<Interned<str>>,
     pub params: IdRange<Param>,
-    pub ret_type: Idx<TypeRef>,
+    pub ret_type: Interned<TypeRef>,
     pub ast_id: FileAstId<ast::Fn>,
+    pub(crate) flags: FnFlags,
 }
 
 #[derive(Debug, Clone, Eq, PartialEq)]
 pub enum Param {
-    Normal(Idx<TypeRef>),
+    Normal(Interned<TypeRef>),
     Varargs,
 }
 
-#[derive(Debug, Clone, PartialEq, Eq)]
-pub struct FunctionQualifier {
-    pub is_default: bool,
-    pub is_const: bool,
-    pub is_async: bool,
-    pub is_unsafe: bool,
-    pub abi: Option<SmolStr>,
+#[derive(Debug, Clone, Copy, Eq, PartialEq, Default)]
+pub(crate) struct FnFlags {
+    pub(crate) bits: u8,
+}
+impl FnFlags {
+    pub(crate) const HAS_SELF_PARAM: u8 = 1 << 0;
+    pub(crate) const HAS_BODY: u8 = 1 << 1;
+    pub(crate) const IS_DEFAULT: u8 = 1 << 2;
+    pub(crate) const IS_CONST: u8 = 1 << 3;
+    pub(crate) const IS_ASYNC: u8 = 1 << 4;
+    pub(crate) const IS_UNSAFE: u8 = 1 << 5;
+    /// Whether the function is located in an `extern` block (*not* whether it is an
+    /// `extern "abi" fn`).
+    pub(crate) const IS_IN_EXTERN_BLOCK: u8 = 1 << 6;
+    pub(crate) const IS_VARARGS: u8 = 1 << 7;
 }
 
 #[derive(Debug, Clone, Eq, PartialEq)]
 pub struct Struct {
     pub name: Name,
     pub visibility: RawVisibilityId,
-    pub generic_params: GenericParamsId,
+    pub generic_params: Interned<GenericParams>,
     pub fields: Fields,
     pub ast_id: FileAstId<ast::Struct>,
     pub kind: StructDefKind,
@@ -643,7 +568,7 @@ pub enum StructDefKind {
 pub struct Union {
     pub name: Name,
     pub visibility: RawVisibilityId,
-    pub generic_params: GenericParamsId,
+    pub generic_params: Interned<GenericParams>,
     pub fields: Fields,
     pub ast_id: FileAstId<ast::Union>,
 }
@@ -652,7 +577,7 @@ pub struct Union {
 pub struct Enum {
     pub name: Name,
     pub visibility: RawVisibilityId,
-    pub generic_params: GenericParamsId,
+    pub generic_params: Interned<GenericParams>,
     pub variants: IdRange<Variant>,
     pub ast_id: FileAstId<ast::Enum>,
 }
@@ -662,7 +587,7 @@ pub struct Const {
     /// const _: () = ();
     pub name: Option<Name>,
     pub visibility: RawVisibilityId,
-    pub type_ref: Idx<TypeRef>,
+    pub type_ref: Interned<TypeRef>,
     pub ast_id: FileAstId<ast::Const>,
 }
 
@@ -673,7 +598,7 @@ pub struct Static {
     pub mutable: bool,
     /// Whether the static is in an `extern` block.
     pub is_extern: bool,
-    pub type_ref: Idx<TypeRef>,
+    pub type_ref: Interned<TypeRef>,
     pub ast_id: FileAstId<ast::Static>,
 }
 
@@ -681,7 +606,7 @@ pub struct Static {
 pub struct Trait {
     pub name: Name,
     pub visibility: RawVisibilityId,
-    pub generic_params: GenericParamsId,
+    pub generic_params: Interned<GenericParams>,
     pub is_auto: bool,
     pub is_unsafe: bool,
     pub bounds: Box<[TypeBound]>,
@@ -691,9 +616,9 @@ pub struct Trait {
 
 #[derive(Debug, Clone, Eq, PartialEq)]
 pub struct Impl {
-    pub generic_params: GenericParamsId,
-    pub target_trait: Option<Idx<TypeRef>>,
-    pub target_type: Idx<TypeRef>,
+    pub generic_params: Interned<GenericParams>,
+    pub target_trait: Option<Interned<TraitRef>>,
+    pub self_ty: Interned<TypeRef>,
     pub is_negative: bool,
     pub items: Box<[AssocItem]>,
     pub ast_id: FileAstId<ast::Impl>,
@@ -705,8 +630,8 @@ pub struct TypeAlias {
     pub visibility: RawVisibilityId,
     /// Bounds on the type alias itself. Only valid in trait declarations, eg. `type Assoc: Copy;`.
     pub bounds: Box<[TypeBound]>,
-    pub generic_params: GenericParamsId,
-    pub type_ref: Option<Idx<TypeRef>>,
+    pub generic_params: Interned<GenericParams>,
+    pub type_ref: Option<Interned<TypeRef>>,
     pub is_extern: bool,
     pub ast_id: FileAstId<ast::TypeAlias>,
 }
@@ -731,7 +656,7 @@ pub enum ModKind {
 #[derive(Debug, Clone, Eq, PartialEq)]
 pub struct MacroCall {
     /// Path to the called macro.
-    pub path: ModPath,
+    pub path: Interned<ModPath>,
     pub ast_id: FileAstId<ast::MacroCall>,
 }
 
@@ -896,6 +821,6 @@ pub enum Fields {
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct Field {
     pub name: Name,
-    pub type_ref: Idx<TypeRef>,
+    pub type_ref: Interned<TypeRef>,
     pub visibility: RawVisibilityId,
 }
diff --git a/crates/hir_def/src/item_tree/lower.rs b/crates/hir_def/src/item_tree/lower.rs
index 3f558edd8..45b099cf3 100644
--- a/crates/hir_def/src/item_tree/lower.rs
+++ b/crates/hir_def/src/item_tree/lower.rs
@@ -11,7 +11,7 @@ use syntax::{
 
 use crate::{
     generics::{GenericParams, TypeParamData, TypeParamProvenance},
-    type_ref::LifetimeRef,
+    type_ref::{LifetimeRef, TraitRef},
 };
 
 use super::*;
@@ -174,6 +174,12 @@ impl Ctx {
         let forced_vis = self.forced_visibility.take();
 
         let mut block_stack = Vec::new();
+
+        // if container itself is block, add it to the stack
+        if let Some(block) = ast::BlockExpr::cast(container.clone()) {
+            block_stack.push(self.source_ast_id_map.ast_id(&block));
+        }
+
         for event in container.preorder().skip(1) {
             match event {
                 WalkEvent::Enter(node) => {
@@ -183,7 +189,7 @@ impl Ctx {
                                 block_stack.push(self.source_ast_id_map.ast_id(&block));
                             },
                             ast::Item(item) => {
-                                // FIXME: This triggers for macro calls in expression position
+                                // FIXME: This triggers for macro calls in expression/pattern/type position
                                 let mod_items = self.lower_mod_item(&item, true);
                                 let current_block = block_stack.last();
                                 if let (Some(mod_items), Some(block)) = (mod_items, current_block) {
@@ -356,7 +362,7 @@ impl Ctx {
                         }
                     }
                 };
-                let ty = self.data().type_refs.intern(self_type);
+                let ty = Interned::new(self_type);
                 let idx = self.data().params.alloc(Param::Normal(ty));
                 self.add_attrs(idx.into(), RawAttrs::new(&self_param, &self.hygiene));
                 has_self_param = true;
@@ -366,7 +372,7 @@ impl Ctx {
                     Some(_) => self.data().params.alloc(Param::Varargs),
                     None => {
                         let type_ref = TypeRef::from_ast_opt(&self.body_ctx, param.ty());
-                        let ty = self.data().type_refs.intern(type_ref);
+                        let ty = Interned::new(type_ref);
                         self.data().params.alloc(Param::Normal(ty))
                     }
                 };
@@ -389,41 +395,51 @@ impl Ctx {
             ret_type
         };
 
-        let ret_type = self.data().type_refs.intern(ret_type);
-
-        let has_body = func.body().is_some();
+        let abi = func.abi().map(|abi| {
+            // FIXME: Abi::abi() -> Option<SyntaxToken>?
+            match abi.syntax().last_token() {
+                Some(tok) if tok.kind() == SyntaxKind::STRING => {
+                    // FIXME: Better way to unescape?
+                    Interned::new_str(tok.text().trim_matches('"'))
+                }
+                _ => {
+                    // `extern` default to be `extern "C"`.
+                    Interned::new_str("C")
+                }
+            }
+        });
 
         let ast_id = self.source_ast_id_map.ast_id(func);
-        let qualifier = FunctionQualifier {
-            is_default: func.default_token().is_some(),
-            is_const: func.const_token().is_some(),
-            is_async: func.async_token().is_some(),
-            is_unsafe: func.unsafe_token().is_some(),
-            abi: func.abi().map(|abi| {
-                // FIXME: Abi::abi() -> Option<SyntaxToken>?
-                match abi.syntax().last_token() {
-                    Some(tok) if tok.kind() == SyntaxKind::STRING => {
-                        // FIXME: Better way to unescape?
-                        tok.text().trim_matches('"').into()
-                    }
-                    _ => {
-                        // `extern` default to be `extern "C"`.
-                        "C".into()
-                    }
-                }
-            }),
-        };
+
+        let mut flags = FnFlags::default();
+        if func.body().is_some() {
+            flags.bits |= FnFlags::HAS_BODY;
+        }
+        if has_self_param {
+            flags.bits |= FnFlags::HAS_SELF_PARAM;
+        }
+        if func.default_token().is_some() {
+            flags.bits |= FnFlags::IS_DEFAULT;
+        }
+        if func.const_token().is_some() {
+            flags.bits |= FnFlags::IS_CONST;
+        }
+        if func.async_token().is_some() {
+            flags.bits |= FnFlags::IS_ASYNC;
+        }
+        if func.unsafe_token().is_some() {
+            flags.bits |= FnFlags::IS_UNSAFE;
+        }
+
         let mut res = Function {
             name,
             visibility,
-            generic_params: GenericParamsId::EMPTY,
-            has_self_param,
-            has_body,
-            qualifier,
-            is_in_extern_block: false,
+            generic_params: Interned::new(GenericParams::default()),
+            abi,
             params,
-            ret_type,
+            ret_type: Interned::new(ret_type),
             ast_id,
+            flags,
         };
         res.generic_params = self.lower_generic_params(GenericsOwner::Function(&res), func);
 
@@ -536,8 +552,11 @@ impl Ctx {
     fn lower_impl(&mut self, impl_def: &ast::Impl) -> Option<FileItemTreeId<Impl>> {
         let generic_params =
             self.lower_generic_params_and_inner_items(GenericsOwner::Impl, impl_def);
-        let target_trait = impl_def.trait_().map(|tr| self.lower_type_ref(&tr));
-        let target_type = self.lower_type_ref(&impl_def.self_ty()?);
+        // FIXME: If trait lowering fails, due to a non PathType for example, we treat this impl
+        // as if it was an non-trait impl. Ideally we want to create a unique missing ref that only
+        // equals itself.
+        let target_trait = impl_def.trait_().and_then(|tr| self.lower_trait_ref(&tr));
+        let self_ty = self.lower_type_ref(&impl_def.self_ty()?);
         let is_negative = impl_def.excl_token().is_some();
 
         // We cannot use `assoc_items()` here as that does not include macro calls.
@@ -554,7 +573,7 @@ impl Ctx {
             })
             .collect();
         let ast_id = self.source_ast_id_map.ast_id(impl_def);
-        let res = Impl { generic_params, target_trait, target_type, is_negative, items, ast_id };
+        let res = Impl { generic_params, target_trait, self_ty, is_negative, items, ast_id };
         Some(id(self.data().impls.alloc(res)))
     }
 
@@ -570,7 +589,7 @@ impl Ctx {
             &self.hygiene,
             |path, _use_tree, is_glob, alias| {
                 imports.push(id(tree.imports.alloc(Import {
-                    path,
+                    path: Interned::new(path),
                     alias,
                     visibility,
                     is_glob,
@@ -599,7 +618,7 @@ impl Ctx {
     }
 
     fn lower_macro_call(&mut self, m: &ast::MacroCall) -> Option<FileItemTreeId<MacroCall>> {
-        let path = ModPath::from_src(m.path()?, &self.hygiene)?;
+        let path = Interned::new(ModPath::from_src(m.path()?, &self.hygiene)?);
         let ast_id = self.source_ast_id_map.ast_id(m);
         let res = MacroCall { path, ast_id };
         Some(id(self.data().macro_calls.alloc(res)))
@@ -633,8 +652,10 @@ impl Ctx {
                         ast::ExternItem::Fn(ast) => {
                             let func_id = self.lower_function(&ast)?;
                             let func = &mut self.data().functions[func_id.index];
-                            func.qualifier.is_unsafe = is_intrinsic_fn_unsafe(&func.name);
-                            func.is_in_extern_block = true;
+                            if is_intrinsic_fn_unsafe(&func.name) {
+                                func.flags.bits |= FnFlags::IS_UNSAFE;
+                            }
+                            func.flags.bits |= FnFlags::IS_IN_EXTERN_BLOCK;
                             func_id.into()
                         }
                         ast::ExternItem::Static(ast) => {
@@ -661,7 +682,7 @@ impl Ctx {
         &mut self,
         owner: GenericsOwner<'_>,
         node: &impl ast::GenericParamsOwner,
-    ) -> GenericParamsId {
+    ) -> Interned<GenericParams> {
         // Generics are part of item headers and may contain inner items we need to collect.
         if let Some(params) = node.generic_param_list() {
             self.collect_inner_items(params.syntax());
@@ -677,7 +698,7 @@ impl Ctx {
         &mut self,
         owner: GenericsOwner<'_>,
         node: &impl ast::GenericParamsOwner,
-    ) -> GenericParamsId {
+    ) -> Interned<GenericParams> {
         let mut sm = &mut Default::default();
         let mut generics = GenericParams::default();
         match owner {
@@ -685,8 +706,7 @@ impl Ctx {
                 generics.fill(&self.body_ctx, sm, node);
                 // lower `impl Trait` in arguments
                 for id in func.params.clone() {
-                    if let Param::Normal(ty) = self.data().params[id] {
-                        let ty = self.data().type_refs.lookup(ty);
+                    if let Param::Normal(ty) = &self.data().params[id] {
                         generics.fill_implicit_impl_trait_args(ty);
                     }
                 }
@@ -719,7 +739,8 @@ impl Ctx {
             }
         }
 
-        self.data().generics.alloc(generics)
+        generics.shrink_to_fit();
+        Interned::new(generics)
     }
 
     fn lower_type_bounds(&mut self, node: &impl ast::TypeBoundsOwner) -> Vec<TypeBound> {
@@ -740,14 +761,20 @@ impl Ctx {
         self.data().vis.alloc(vis)
     }
 
-    fn lower_type_ref(&mut self, type_ref: &ast::Type) -> Idx<TypeRef> {
+    fn lower_trait_ref(&mut self, trait_ref: &ast::Type) -> Option<Interned<TraitRef>> {
+        let trait_ref = TraitRef::from_ast(&self.body_ctx, trait_ref.clone())?;
+        Some(Interned::new(trait_ref))
+    }
+
+    fn lower_type_ref(&mut self, type_ref: &ast::Type) -> Interned<TypeRef> {
         let tyref = TypeRef::from_ast(&self.body_ctx, type_ref.clone());
-        self.data().type_refs.intern(tyref)
+        Interned::new(tyref)
     }
-    fn lower_type_ref_opt(&mut self, type_ref: Option<ast::Type>) -> Idx<TypeRef> {
+
+    fn lower_type_ref_opt(&mut self, type_ref: Option<ast::Type>) -> Interned<TypeRef> {
         match type_ref.map(|ty| self.lower_type_ref(&ty)) {
             Some(it) => it,
-            None => self.data().type_refs.intern(TypeRef::Error),
+            None => Interned::new(TypeRef::Error),
         }
     }
 
diff --git a/crates/hir_def/src/lib.rs b/crates/hir_def/src/lib.rs
index c9e07de86..000567d99 100644
--- a/crates/hir_def/src/lib.rs
+++ b/crates/hir_def/src/lib.rs
@@ -27,6 +27,7 @@ pub mod dyn_map;
 pub mod keys;
 
 pub mod item_tree;
+pub mod intern;
 
 pub mod adt;
 pub mod data;
@@ -55,15 +56,17 @@ use std::{
     sync::Arc,
 };
 
+use adt::VariantData;
 use base_db::{impl_intern_key, salsa, CrateId};
 use hir_expand::{
     ast_id_map::FileAstId,
     eager::{expand_eager_macro, ErrorEmitted, ErrorSink},
     hygiene::Hygiene,
-    AstId, HirFileId, InFile, MacroCallId, MacroCallKind, MacroDefId, MacroDefKind,
+    AstId, AttrId, HirFileId, InFile, MacroCallId, MacroCallKind, MacroDefId, MacroDefKind,
 };
 use la_arena::Idx;
 use nameres::DefMap;
+use path::ModPath;
 use syntax::ast;
 
 use crate::builtin_type::BuiltinType;
@@ -433,6 +436,16 @@ impl_from!(
     for AttrDefId
 );
 
+impl From<AssocContainerId> for AttrDefId {
+    fn from(acid: AssocContainerId) -> Self {
+        match acid {
+            AssocContainerId::ModuleId(mid) => AttrDefId::ModuleId(mid),
+            AssocContainerId::ImplId(iid) => AttrDefId::ImplId(iid),
+            AssocContainerId::TraitId(tid) => AttrDefId::TraitId(tid),
+        }
+    }
+}
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub enum VariantId {
     EnumVariantId(EnumVariantId),
@@ -441,6 +454,26 @@ pub enum VariantId {
 }
 impl_from!(EnumVariantId, StructId, UnionId for VariantId);
 
+impl VariantId {
+    pub fn variant_data(self, db: &dyn db::DefDatabase) -> Arc<VariantData> {
+        match self {
+            VariantId::StructId(it) => db.struct_data(it).variant_data.clone(),
+            VariantId::UnionId(it) => db.union_data(it).variant_data.clone(),
+            VariantId::EnumVariantId(it) => {
+                db.enum_data(it.parent).variants[it.local_id].variant_data.clone()
+            }
+        }
+    }
+
+    pub fn file_id(self, db: &dyn db::DefDatabase) -> HirFileId {
+        match self {
+            VariantId::EnumVariantId(it) => it.parent.lookup(db).id.file_id(),
+            VariantId::StructId(it) => it.lookup(db).id.file_id(),
+            VariantId::UnionId(it) => it.lookup(db).id.file_id(),
+        }
+    }
+}
+
 trait Intern {
     type ID;
     fn intern(self, db: &dyn db::DefDatabase) -> Self::ID;
@@ -643,7 +676,9 @@ impl<T: ast::AstNode> AstIdWithPath<T> {
     }
 }
 
-pub struct UnresolvedMacro;
+pub struct UnresolvedMacro {
+    pub path: ModPath,
+}
 
 fn macro_call_as_call_id(
     call: &AstIdWithPath<ast::MacroCall>,
@@ -652,7 +687,8 @@ fn macro_call_as_call_id(
     resolver: impl Fn(path::ModPath) -> Option<MacroDefId>,
     error_sink: &mut dyn FnMut(mbe::ExpandError),
 ) -> Result<Result<MacroCallId, ErrorEmitted>, UnresolvedMacro> {
-    let def: MacroDefId = resolver(call.path.clone()).ok_or(UnresolvedMacro)?;
+    let def: MacroDefId =
+        resolver(call.path.clone()).ok_or_else(|| UnresolvedMacro { path: call.path.clone() })?;
 
     let res = if let MacroDefKind::BuiltInEager(..) = def.kind {
         let macro_call = InFile::new(call.ast_id.file_id, call.ast_id.to_node(db.upcast()));
@@ -668,24 +704,36 @@ fn macro_call_as_call_id(
         )
         .map(MacroCallId::from)
     } else {
-        Ok(def.as_lazy_macro(db.upcast(), krate, MacroCallKind::FnLike(call.ast_id)).into())
+        Ok(def
+            .as_lazy_macro(db.upcast(), krate, MacroCallKind::FnLike { ast_id: call.ast_id })
+            .into())
     };
     Ok(res)
 }
 
 fn derive_macro_as_call_id(
     item_attr: &AstIdWithPath<ast::Item>,
+    derive_attr: AttrId,
     db: &dyn db::DefDatabase,
     krate: CrateId,
     resolver: impl Fn(path::ModPath) -> Option<MacroDefId>,
 ) -> Result<MacroCallId, UnresolvedMacro> {
-    let def: MacroDefId = resolver(item_attr.path.clone()).ok_or(UnresolvedMacro)?;
-    let last_segment = item_attr.path.segments().last().ok_or(UnresolvedMacro)?;
+    let def: MacroDefId = resolver(item_attr.path.clone())
+        .ok_or_else(|| UnresolvedMacro { path: item_attr.path.clone() })?;
+    let last_segment = item_attr
+        .path
+        .segments()
+        .last()
+        .ok_or_else(|| UnresolvedMacro { path: item_attr.path.clone() })?;
     let res = def
         .as_lazy_macro(
             db.upcast(),
             krate,
-            MacroCallKind::Derive(item_attr.ast_id, last_segment.to_string()),
+            MacroCallKind::Derive {
+                ast_id: item_attr.ast_id,
+                derive_name: last_segment.to_string(),
+                derive_attr,
+            },
         )
         .into();
     Ok(res)
diff --git a/crates/hir_def/src/nameres.rs b/crates/hir_def/src/nameres.rs
index 9e8e4e9ec..542f190a1 100644
--- a/crates/hir_def/src/nameres.rs
+++ b/crates/hir_def/src/nameres.rs
@@ -409,6 +409,31 @@ impl DefMap {
             }
         }
     }
+
+    fn shrink_to_fit(&mut self) {
+        // Exhaustive match to require handling new fields.
+        let Self {
+            _c: _,
+            exported_proc_macros,
+            extern_prelude,
+            diagnostics,
+            modules,
+            block: _,
+            edition: _,
+            krate: _,
+            prelude: _,
+            root: _,
+        } = self;
+
+        extern_prelude.shrink_to_fit();
+        exported_proc_macros.shrink_to_fit();
+        diagnostics.shrink_to_fit();
+        modules.shrink_to_fit();
+        for (_, module) in modules.iter_mut() {
+            module.children.shrink_to_fit();
+            module.scope.shrink_to_fit();
+        }
+    }
 }
 
 impl ModuleData {
@@ -456,7 +481,7 @@ mod diagnostics {
 
         UnresolvedProcMacro { ast: MacroCallKind },
 
-        UnresolvedMacroCall { ast: AstId<ast::MacroCall> },
+        UnresolvedMacroCall { ast: AstId<ast::MacroCall>, path: ModPath },
 
         MacroError { ast: MacroCallKind, message: String },
     }
@@ -521,8 +546,9 @@ mod diagnostics {
         pub(super) fn unresolved_macro_call(
             container: LocalModuleId,
             ast: AstId<ast::MacroCall>,
+            path: ModPath,
         ) -> Self {
-            Self { in_module: container, kind: DiagnosticKind::UnresolvedMacroCall { ast } }
+            Self { in_module: container, kind: DiagnosticKind::UnresolvedMacroCall { ast, path } }
         }
 
         pub(super) fn add_to(
@@ -588,12 +614,12 @@ mod diagnostics {
                 DiagnosticKind::UnresolvedProcMacro { ast } => {
                     let mut precise_location = None;
                     let (file, ast, name) = match ast {
-                        MacroCallKind::FnLike(ast) => {
-                            let node = ast.to_node(db.upcast());
-                            (ast.file_id, SyntaxNodePtr::from(AstPtr::new(&node)), None)
+                        MacroCallKind::FnLike { ast_id } => {
+                            let node = ast_id.to_node(db.upcast());
+                            (ast_id.file_id, SyntaxNodePtr::from(AstPtr::new(&node)), None)
                         }
-                        MacroCallKind::Derive(ast, name) => {
-                            let node = ast.to_node(db.upcast());
+                        MacroCallKind::Derive { ast_id, derive_name, .. } => {
+                            let node = ast_id.to_node(db.upcast());
 
                             // Compute the precise location of the macro name's token in the derive
                             // list.
@@ -614,7 +640,7 @@ mod diagnostics {
                                     });
                                 for token in tokens {
                                     if token.kind() == SyntaxKind::IDENT
-                                        && token.text() == name.as_str()
+                                        && token.text() == derive_name.as_str()
                                     {
                                         precise_location = Some(token.text_range());
                                         break 'outer;
@@ -623,9 +649,9 @@ mod diagnostics {
                             }
 
                             (
-                                ast.file_id,
+                                ast_id.file_id,
                                 SyntaxNodePtr::from(AstPtr::new(&node)),
-                                Some(name.clone()),
+                                Some(derive_name.clone()),
                             )
                         }
                     };
@@ -637,20 +663,24 @@ mod diagnostics {
                     });
                 }
 
-                DiagnosticKind::UnresolvedMacroCall { ast } => {
+                DiagnosticKind::UnresolvedMacroCall { ast, path } => {
                     let node = ast.to_node(db.upcast());
-                    sink.push(UnresolvedMacroCall { file: ast.file_id, node: AstPtr::new(&node) });
+                    sink.push(UnresolvedMacroCall {
+                        file: ast.file_id,
+                        node: AstPtr::new(&node),
+                        path: path.clone(),
+                    });
                 }
 
                 DiagnosticKind::MacroError { ast, message } => {
                     let (file, ast) = match ast {
-                        MacroCallKind::FnLike(ast) => {
-                            let node = ast.to_node(db.upcast());
-                            (ast.file_id, SyntaxNodePtr::from(AstPtr::new(&node)))
+                        MacroCallKind::FnLike { ast_id, .. } => {
+                            let node = ast_id.to_node(db.upcast());
+                            (ast_id.file_id, SyntaxNodePtr::from(AstPtr::new(&node)))
                         }
-                        MacroCallKind::Derive(ast, _) => {
-                            let node = ast.to_node(db.upcast());
-                            (ast.file_id, SyntaxNodePtr::from(AstPtr::new(&node)))
+                        MacroCallKind::Derive { ast_id, .. } => {
+                            let node = ast_id.to_node(db.upcast());
+                            (ast_id.file_id, SyntaxNodePtr::from(AstPtr::new(&node)))
                         }
                     };
                     sink.push(MacroError { file, node: ast, message: message.clone() });
diff --git a/crates/hir_def/src/nameres/collector.rs b/crates/hir_def/src/nameres/collector.rs
index d58135ec9..05ceb1efb 100644
--- a/crates/hir_def/src/nameres/collector.rs
+++ b/crates/hir_def/src/nameres/collector.rs
@@ -13,7 +13,7 @@ use hir_expand::{
     builtin_macro::find_builtin_macro,
     name::{AsName, Name},
     proc_macro::ProcMacroExpander,
-    HirFileId, MacroCallId, MacroCallKind, MacroDefId, MacroDefKind,
+    AttrId, HirFileId, MacroCallId, MacroCallKind, MacroDefId, MacroDefKind,
 };
 use hir_expand::{InFile, MacroCallLoc};
 use rustc_hash::{FxHashMap, FxHashSet};
@@ -23,6 +23,7 @@ use crate::{
     attr::Attrs,
     db::DefDatabase,
     derive_macro_as_call_id,
+    intern::Interned,
     item_scope::{ImportType, PerNsGlobImports},
     item_tree::{
         self, FileItemTreeId, ItemTree, ItemTreeId, MacroCall, MacroDef, MacroRules, Mod, ModItem,
@@ -54,20 +55,22 @@ pub(super) fn collect_defs(
 ) -> DefMap {
     let crate_graph = db.crate_graph();
 
-    // populate external prelude
-    for dep in &crate_graph[def_map.krate].dependencies {
-        log::debug!("crate dep {:?} -> {:?}", dep.name, dep.crate_id);
-        let dep_def_map = db.crate_def_map(dep.crate_id);
-        def_map
-            .extern_prelude
-            .insert(dep.as_name(), dep_def_map.module_id(dep_def_map.root).into());
-
-        // look for the prelude
-        // If the dependency defines a prelude, we overwrite an already defined
-        // prelude. This is necessary to import the "std" prelude if a crate
-        // depends on both "core" and "std".
-        if dep_def_map.prelude.is_some() {
-            def_map.prelude = dep_def_map.prelude;
+    if block.is_none() {
+        // populate external prelude
+        for dep in &crate_graph[def_map.krate].dependencies {
+            log::debug!("crate dep {:?} -> {:?}", dep.name, dep.crate_id);
+            let dep_def_map = db.crate_def_map(dep.crate_id);
+            def_map
+                .extern_prelude
+                .insert(dep.as_name(), dep_def_map.module_id(dep_def_map.root).into());
+
+            // look for the prelude
+            // If the dependency defines a prelude, we overwrite an already defined
+            // prelude. This is necessary to import the "std" prelude if a crate
+            // depends on both "core" and "std".
+            if dep_def_map.prelude.is_some() {
+                def_map.prelude = dep_def_map.prelude;
+            }
         }
     }
 
@@ -106,7 +109,9 @@ pub(super) fn collect_defs(
         }
     }
     collector.collect();
-    collector.finish()
+    let mut def_map = collector.finish();
+    def_map.shrink_to_fit();
+    def_map
 }
 
 #[derive(Copy, Clone, Debug, Eq, PartialEq)]
@@ -137,7 +142,7 @@ enum ImportSource {
 
 #[derive(Clone, Debug, Eq, PartialEq)]
 struct Import {
-    path: ModPath,
+    path: Interned<ModPath>,
     alias: Option<ImportAlias>,
     visibility: RawVisibility,
     is_glob: bool,
@@ -179,7 +184,10 @@ impl Import {
         let attrs = &tree.attrs(db, krate, ModItem::from(id.value).into());
         let visibility = &tree[it.visibility];
         Self {
-            path: ModPath::from_segments(PathKind::Plain, iter::once(it.name.clone())),
+            path: Interned::new(ModPath::from_segments(
+                PathKind::Plain,
+                iter::once(it.name.clone()),
+            )),
             alias: it.alias.clone(),
             visibility: visibility.clone(),
             is_glob: false,
@@ -207,8 +215,8 @@ struct MacroDirective {
 
 #[derive(Clone, Debug, Eq, PartialEq)]
 enum MacroDirectiveKind {
-    FnLike { ast_id: AstIdWithPath<ast::MacroCall>, legacy: Option<MacroCallId> },
-    Derive { ast_id: AstIdWithPath<ast::Item> },
+    FnLike { ast_id: AstIdWithPath<ast::MacroCall> },
+    Derive { ast_id: AstIdWithPath<ast::Item>, derive_attr: AttrId },
 }
 
 struct DefData<'a> {
@@ -470,7 +478,7 @@ impl DefCollector<'_> {
             self.def_map.edition,
         );
 
-        let res = self.def_map.resolve_name_in_extern_prelude(&extern_crate.name);
+        let res = self.def_map.resolve_name_in_extern_prelude(self.db, &extern_crate.name);
 
         if let Some(ModuleDefId::ModuleId(m)) = res.take_types() {
             cov_mark::hit!(macro_rules_from_other_crates_are_visible_with_macro_use);
@@ -526,6 +534,7 @@ impl DefCollector<'_> {
         log::debug!("resolving import: {:?} ({:?})", import, self.def_map.edition);
         if import.is_extern_crate {
             let res = self.def_map.resolve_name_in_extern_prelude(
+                self.db,
                 &import
                     .path
                     .as_ident()
@@ -798,13 +807,7 @@ impl DefCollector<'_> {
         let mut res = ReachedFixedPoint::Yes;
         macros.retain(|directive| {
             match &directive.kind {
-                MacroDirectiveKind::FnLike { ast_id, legacy } => {
-                    if let Some(call_id) = legacy {
-                        res = ReachedFixedPoint::No;
-                        resolved.push((directive.module_id, *call_id, directive.depth));
-                        return false;
-                    }
-
+                MacroDirectiveKind::FnLike { ast_id } => {
                     match macro_call_as_call_id(
                         ast_id,
                         self.db,
@@ -826,19 +829,23 @@ impl DefCollector<'_> {
                             res = ReachedFixedPoint::No;
                             return false;
                         }
-                        Err(UnresolvedMacro) | Ok(Err(_)) => {}
+                        Err(UnresolvedMacro { .. }) | Ok(Err(_)) => {}
                     }
                 }
-                MacroDirectiveKind::Derive { ast_id } => {
-                    match derive_macro_as_call_id(ast_id, self.db, self.def_map.krate, |path| {
-                        self.resolve_derive_macro(directive.module_id, &path)
-                    }) {
+                MacroDirectiveKind::Derive { ast_id, derive_attr } => {
+                    match derive_macro_as_call_id(
+                        ast_id,
+                        *derive_attr,
+                        self.db,
+                        self.def_map.krate,
+                        |path| self.resolve_derive_macro(directive.module_id, &path),
+                    ) {
                         Ok(call_id) => {
-                            resolved.push((directive.module_id, call_id, 0));
+                            resolved.push((directive.module_id, call_id, directive.depth));
                             res = ReachedFixedPoint::No;
                             return false;
                         }
-                        Err(UnresolvedMacro) => (),
+                        Err(UnresolvedMacro { .. }) => (),
                     }
                 }
             }
@@ -936,10 +943,11 @@ impl DefCollector<'_> {
                     &mut |_| (),
                 ) {
                     Ok(_) => (),
-                    Err(UnresolvedMacro) => {
+                    Err(UnresolvedMacro { path }) => {
                         self.def_map.diagnostics.push(DefDiagnostic::unresolved_macro_call(
                             directive.module_id,
                             ast_id.ast_id,
+                            path,
                         ));
                     }
                 },
@@ -1161,19 +1169,27 @@ impl ModCollector<'_, '_> {
                 }
                 ModItem::Const(id) => {
                     let it = &self.item_tree[id];
-
-                    if let Some(name) = &it.name {
-                        def = Some(DefData {
-                            id: ConstLoc {
-                                container: module.into(),
-                                id: ItemTreeId::new(self.file_id, id),
-                            }
-                            .intern(self.def_collector.db)
-                            .into(),
-                            name,
-                            visibility: &self.item_tree[it.visibility],
-                            has_constructor: false,
-                        });
+                    let const_id = ConstLoc {
+                        container: module.into(),
+                        id: ItemTreeId::new(self.file_id, id),
+                    }
+                    .intern(self.def_collector.db);
+
+                    match &it.name {
+                        Some(name) => {
+                            def = Some(DefData {
+                                id: const_id.into(),
+                                name,
+                                visibility: &self.item_tree[it.visibility],
+                                has_constructor: false,
+                            });
+                        }
+                        None => {
+                            // const _: T = ...;
+                            self.def_collector.def_map.modules[self.module_id]
+                                .scope
+                                .define_unnamed_const(const_id);
+                        }
                     }
                 }
                 ModItem::Static(id) => {
@@ -1358,7 +1374,7 @@ impl ModCollector<'_, '_> {
                         self.def_collector.unexpanded_macros.push(MacroDirective {
                             module_id: self.module_id,
                             depth: self.macro_depth + 1,
-                            kind: MacroDirectiveKind::Derive { ast_id },
+                            kind: MacroDirectiveKind::Derive { ast_id, derive_attr: derive.id },
                         });
                     }
                 }
@@ -1400,8 +1416,18 @@ impl ModCollector<'_, '_> {
 
         // Case 1: builtin macros
         if attrs.by_key("rustc_builtin_macro").exists() {
+            // `#[rustc_builtin_macro = "builtin_name"]` overrides the `macro_rules!` name.
+            let name;
+            let name = match attrs.by_key("rustc_builtin_macro").string_value() {
+                Some(it) => {
+                    // FIXME: a hacky way to create a Name from string.
+                    name = tt::Ident { text: it.clone(), id: tt::TokenId::unspecified() }.as_name();
+                    &name
+                }
+                None => &mac.name,
+            };
             let krate = self.def_collector.def_map.krate;
-            if let Some(macro_id) = find_builtin_macro(&mac.name, krate, ast_id) {
+            if let Some(macro_id) = find_builtin_macro(name, krate, ast_id) {
                 self.def_collector.define_macro_rules(
                     self.module_id,
                     mac.name.clone(),
@@ -1464,7 +1490,7 @@ impl ModCollector<'_, '_> {
     }
 
     fn collect_macro_call(&mut self, mac: &MacroCall) {
-        let mut ast_id = AstIdWithPath::new(self.file_id, mac.ast_id, mac.path.clone());
+        let mut ast_id = AstIdWithPath::new(self.file_id, mac.ast_id, (*mac.path).clone());
 
         // Case 1: try to resolve in legacy scope and expand macro_rules
         let mut error = None;
@@ -1500,12 +1526,12 @@ impl ModCollector<'_, '_> {
                 // Built-in macro failed eager expansion.
                 self.def_collector.def_map.diagnostics.push(DefDiagnostic::macro_error(
                     self.module_id,
-                    MacroCallKind::FnLike(ast_id.ast_id),
+                    MacroCallKind::FnLike { ast_id: ast_id.ast_id },
                     error.unwrap().to_string(),
                 ));
                 return;
             }
-            Err(UnresolvedMacro) => (),
+            Err(UnresolvedMacro { .. }) => (),
         }
 
         // Case 2: resolve in module scope, expand during name resolution.
@@ -1517,7 +1543,7 @@ impl ModCollector<'_, '_> {
         self.def_collector.unexpanded_macros.push(MacroDirective {
             module_id: self.module_id,
             depth: self.macro_depth + 1,
-            kind: MacroDirectiveKind::FnLike { ast_id, legacy: None },
+            kind: MacroDirectiveKind::FnLike { ast_id },
         });
     }
 
diff --git a/crates/hir_def/src/nameres/path_resolution.rs b/crates/hir_def/src/nameres/path_resolution.rs
index 60471937c..c984148c3 100644
--- a/crates/hir_def/src/nameres/path_resolution.rs
+++ b/crates/hir_def/src/nameres/path_resolution.rs
@@ -60,12 +60,26 @@ impl ResolvePathResult {
 }
 
 impl DefMap {
-    pub(super) fn resolve_name_in_extern_prelude(&self, name: &Name) -> PerNs {
+    pub(super) fn resolve_name_in_extern_prelude(
+        &self,
+        db: &dyn DefDatabase,
+        name: &Name,
+    ) -> PerNs {
         if name == &name!(self) {
             cov_mark::hit!(extern_crate_self_as);
             return PerNs::types(self.module_id(self.root).into(), Visibility::Public);
         }
-        self.extern_prelude
+
+        let arc;
+        let root = match self.block {
+            Some(_) => {
+                arc = self.crate_root(db).def_map(db);
+                &*arc
+            }
+            None => self,
+        };
+
+        root.extern_prelude
             .get(name)
             .map_or(PerNs::none(), |&it| PerNs::types(it, Visibility::Public))
     }
@@ -191,7 +205,7 @@ impl DefMap {
                     None => return ResolvePathResult::empty(ReachedFixedPoint::Yes),
                 };
                 log::debug!("resolving {:?} in crate root (+ extern prelude)", segment);
-                self.resolve_name_in_crate_root_or_extern_prelude(&segment)
+                self.resolve_name_in_crate_root_or_extern_prelude(db, &segment)
             }
             PathKind::Plain => {
                 let (_, segment) = match segments.next() {
@@ -373,7 +387,13 @@ impl DefMap {
             .get_legacy_macro(name)
             .map_or_else(PerNs::none, |m| PerNs::macros(m, Visibility::Public));
         let from_scope = self[module].scope.get(name);
-        let from_builtin = BUILTIN_SCOPE.get(name).copied().unwrap_or_else(PerNs::none);
+        let from_builtin = match self.block {
+            Some(_) => {
+                // Only resolve to builtins in the root `DefMap`.
+                PerNs::none()
+            }
+            None => BUILTIN_SCOPE.get(name).copied().unwrap_or_else(PerNs::none),
+        };
         let from_scope_or_builtin = match shadow {
             BuiltinShadowMode::Module => from_scope.or(from_builtin),
             BuiltinShadowMode::Other => {
@@ -384,24 +404,31 @@ impl DefMap {
                 }
             }
         };
-        // Give precedence to names in outer `DefMap`s over the extern prelude; only check prelude
-        // from the crate DefMap.
-        let from_extern_prelude = match self.block {
-            Some(_) => PerNs::none(),
-            None => self
-                .extern_prelude
-                .get(name)
-                .map_or(PerNs::none(), |&it| PerNs::types(it, Visibility::Public)),
-        };
+        let from_extern_prelude = self
+            .extern_prelude
+            .get(name)
+            .map_or(PerNs::none(), |&it| PerNs::types(it, Visibility::Public));
 
         let from_prelude = self.resolve_in_prelude(db, name);
 
         from_legacy_macro.or(from_scope_or_builtin).or(from_extern_prelude).or(from_prelude)
     }
 
-    fn resolve_name_in_crate_root_or_extern_prelude(&self, name: &Name) -> PerNs {
-        let from_crate_root = self[self.root].scope.get(name);
-        let from_extern_prelude = self.resolve_name_in_extern_prelude(name);
+    fn resolve_name_in_crate_root_or_extern_prelude(
+        &self,
+        db: &dyn DefDatabase,
+        name: &Name,
+    ) -> PerNs {
+        let arc;
+        let crate_def_map = match self.block {
+            Some(_) => {
+                arc = self.crate_root(db).def_map(db);
+                &arc
+            }
+            None => self,
+        };
+        let from_crate_root = crate_def_map[crate_def_map.root].scope.get(name);
+        let from_extern_prelude = self.resolve_name_in_extern_prelude(db, name);
 
         from_crate_root.or(from_extern_prelude)
     }
diff --git a/crates/hir_def/src/nameres/tests/diagnostics.rs b/crates/hir_def/src/nameres/tests/diagnostics.rs
index a89061c2e..543975e07 100644
--- a/crates/hir_def/src/nameres/tests/diagnostics.rs
+++ b/crates/hir_def/src/nameres/tests/diagnostics.rs
@@ -7,6 +7,11 @@ fn check_diagnostics(ra_fixture: &str) {
     db.check_diagnostics();
 }
 
+fn check_no_diagnostics(ra_fixture: &str) {
+    let db: TestDB = TestDB::with_files(ra_fixture);
+    db.check_no_diagnostics();
+}
+
 #[test]
 fn unresolved_import() {
     check_diagnostics(
@@ -165,7 +170,7 @@ fn unresolved_legacy_scope_macro() {
 
           m!();
           m2!();
-        //^^^^^^ unresolved macro call
+        //^^^^^^ unresolved macro `self::m2!`
         "#,
     );
 }
@@ -182,7 +187,7 @@ fn unresolved_module_scope_macro() {
 
           self::m!();
           self::m2!();
-        //^^^^^^^^^^^^ unresolved macro call
+        //^^^^^^^^^^^^ unresolved macro `self::m2!`
         "#,
     );
 }
@@ -202,6 +207,21 @@ fn builtin_macro_fails_expansion() {
 }
 
 #[test]
+fn include_macro_should_allow_empty_content() {
+    check_no_diagnostics(
+        r#"
+        //- /lib.rs
+          #[rustc_builtin_macro]
+          macro_rules! include { () => {} }
+
+          include!("bar.rs");
+        //- /bar.rs
+          // empty
+        "#,
+    );
+}
+
+#[test]
 fn good_out_dir_diagnostic() {
     check_diagnostics(
         r#"
@@ -213,7 +233,7 @@ fn good_out_dir_diagnostic() {
         macro_rules! concat { () => {} }
 
         include!(concat!(env!("OUT_DIR"), "/out.rs"));
-      //^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `OUT_DIR` not set, enable "load out dirs from check" to fix
+      //^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `OUT_DIR` not set, enable "run build scripts" to fix
         "#,
     );
 }
diff --git a/crates/hir_def/src/path.rs b/crates/hir_def/src/path.rs
index 8c923bb7b..b528ff8ba 100644
--- a/crates/hir_def/src/path.rs
+++ b/crates/hir_def/src/path.rs
@@ -7,7 +7,7 @@ use std::{
     sync::Arc,
 };
 
-use crate::{body::LowerCtx, type_ref::LifetimeRef};
+use crate::{body::LowerCtx, intern::Interned, type_ref::LifetimeRef};
 use base_db::CrateId;
 use hir_expand::{
     hygiene::Hygiene,
@@ -48,7 +48,7 @@ pub enum ImportAlias {
 
 impl ModPath {
     pub fn from_src(path: ast::Path, hygiene: &Hygiene) -> Option<ModPath> {
-        lower::lower_path(path, hygiene).map(|it| it.mod_path)
+        lower::lower_path(path, hygiene).map(|it| (*it.mod_path).clone())
     }
 
     pub fn from_segments(kind: PathKind, segments: impl IntoIterator<Item = Name>) -> ModPath {
@@ -122,8 +122,8 @@ impl ModPath {
 pub struct Path {
     /// Type based path like `<T>::foo`.
     /// Note that paths like `<Type as Trait>::foo` are desugard to `Trait::<Self=Type>::foo`.
-    type_anchor: Option<Box<TypeRef>>,
-    mod_path: ModPath,
+    type_anchor: Option<Interned<TypeRef>>,
+    mod_path: Interned<ModPath>,
     /// Invariant: the same len as `self.mod_path.segments`
     generic_args: Vec<Option<Arc<GenericArgs>>>,
 }
@@ -176,7 +176,7 @@ impl Path {
         path: ModPath,
         generic_args: Vec<Option<Arc<GenericArgs>>>,
     ) -> Path {
-        Path { type_anchor: None, mod_path: path, generic_args }
+        Path { type_anchor: None, mod_path: Interned::new(path), generic_args }
     }
 
     pub fn kind(&self) -> &PathKind {
@@ -204,10 +204,10 @@ impl Path {
         }
         let res = Path {
             type_anchor: self.type_anchor.clone(),
-            mod_path: ModPath::from_segments(
+            mod_path: Interned::new(ModPath::from_segments(
                 self.mod_path.kind.clone(),
                 self.mod_path.segments[..self.mod_path.segments.len() - 1].iter().cloned(),
-            ),
+            )),
             generic_args: self.generic_args[..self.generic_args.len() - 1].to_vec(),
         };
         Some(res)
@@ -283,12 +283,18 @@ impl From<Name> for Path {
     fn from(name: Name) -> Path {
         Path {
             type_anchor: None,
-            mod_path: ModPath::from_segments(PathKind::Plain, iter::once(name)),
+            mod_path: Interned::new(ModPath::from_segments(PathKind::Plain, iter::once(name))),
             generic_args: vec![None],
         }
     }
 }
 
+impl From<Name> for Box<Path> {
+    fn from(name: Name) -> Box<Path> {
+        Box::new(Path::from(name))
+    }
+}
+
 impl From<Name> for ModPath {
     fn from(name: Name) -> ModPath {
         ModPath::from_segments(PathKind::Plain, iter::once(name))
diff --git a/crates/hir_def/src/path/lower.rs b/crates/hir_def/src/path/lower.rs
index 505493a74..7b29d9d4f 100644
--- a/crates/hir_def/src/path/lower.rs
+++ b/crates/hir_def/src/path/lower.rs
@@ -2,6 +2,7 @@
 
 mod lower_use;
 
+use crate::intern::Interned;
 use std::sync::Arc;
 
 use either::Either;
@@ -68,15 +69,17 @@ pub(super) fn lower_path(mut path: ast::Path, hygiene: &Hygiene) -> Option<Path>
                 match trait_ref {
                     // <T>::foo
                     None => {
-                        type_anchor = Some(Box::new(self_type));
+                        type_anchor = Some(Interned::new(self_type));
                         kind = PathKind::Plain;
                     }
                     // <T as Trait<A>>::Foo desugars to Trait<Self=T, A>::Foo
                     Some(trait_ref) => {
                         let path = Path::from_src(trait_ref.path()?, hygiene)?;
-                        kind = path.mod_path.kind;
+                        let mod_path = (*path.mod_path).clone();
+                        let num_segments = path.mod_path.segments.len();
+                        kind = mod_path.kind;
 
-                        let mut prefix_segments = path.mod_path.segments;
+                        let mut prefix_segments = mod_path.segments;
                         prefix_segments.reverse();
                         segments.extend(prefix_segments);
 
@@ -85,7 +88,8 @@ pub(super) fn lower_path(mut path: ast::Path, hygiene: &Hygiene) -> Option<Path>
                         generic_args.extend(prefix_args);
 
                         // Insert the type reference (T in the above example) as Self parameter for the trait
-                        let last_segment = generic_args.last_mut()?;
+                        let last_segment =
+                            generic_args.iter_mut().rev().nth(num_segments.saturating_sub(1))?;
                         if last_segment.is_none() {
                             *last_segment = Some(Arc::new(GenericArgs::empty()));
                         };
@@ -138,7 +142,7 @@ pub(super) fn lower_path(mut path: ast::Path, hygiene: &Hygiene) -> Option<Path>
         }
     }
 
-    let mod_path = ModPath::from_segments(kind, segments);
+    let mod_path = Interned::new(ModPath::from_segments(kind, segments));
     return Some(Path { type_anchor, mod_path, generic_args });
 
     fn qualifier(path: &ast::Path) -> Option<ast::Path> {
diff --git a/crates/hir_def/src/resolver.rs b/crates/hir_def/src/resolver.rs
index a73585ee7..0391cc49b 100644
--- a/crates/hir_def/src/resolver.rs
+++ b/crates/hir_def/src/resolver.rs
@@ -14,6 +14,7 @@ use crate::{
     db::DefDatabase,
     expr::{ExprId, LabelId, PatId},
     generics::GenericParams,
+    intern::Interned,
     item_scope::{BuiltinShadowMode, BUILTIN_SCOPE},
     nameres::DefMap,
     path::{ModPath, PathKind},
@@ -50,7 +51,7 @@ enum Scope {
     /// All the items and imported names of a module
     ModuleScope(ModuleItemMap),
     /// Brings the generic parameters of an item into scope
-    GenericParams { def: GenericDefId, params: Arc<GenericParams> },
+    GenericParams { def: GenericDefId, params: Interned<GenericParams> },
     /// Brings `Self` in `impl` block into scope
     ImplDefScope(ImplId),
     /// Brings `Self` in enum, struct and union definitions into scope
diff --git a/crates/hir_def/src/test_db.rs b/crates/hir_def/src/test_db.rs
index 10977761c..8fa703a57 100644
--- a/crates/hir_def/src/test_db.rs
+++ b/crates/hir_def/src/test_db.rs
@@ -15,7 +15,12 @@ use rustc_hash::FxHashSet;
 use syntax::{algo, ast, AstNode, TextRange, TextSize};
 use test_utils::extract_annotations;
 
-use crate::{db::DefDatabase, nameres::DefMap, src::HasSource, Lookup, ModuleDefId, ModuleId};
+use crate::{
+    db::DefDatabase,
+    nameres::{DefMap, ModuleSource},
+    src::HasSource,
+    LocalModuleId, Lookup, ModuleDefId, ModuleId,
+};
 
 #[salsa::database(
     base_db::SourceDatabaseExtStorage,
@@ -87,10 +92,11 @@ impl TestDB {
     pub(crate) fn module_at_position(&self, position: FilePosition) -> ModuleId {
         let file_module = self.module_for_file(position.file_id);
         let mut def_map = file_module.def_map(self);
+        let module = self.mod_at_position(&def_map, position);
 
         def_map = match self.block_at_position(&def_map, position) {
             Some(it) => it,
-            None => return file_module,
+            None => return def_map.module_id(module),
         };
         loop {
             let new_map = self.block_at_position(&def_map, position);
@@ -106,6 +112,47 @@ impl TestDB {
         }
     }
 
+    /// Finds the smallest/innermost module in `def_map` containing `position`.
+    fn mod_at_position(&self, def_map: &DefMap, position: FilePosition) -> LocalModuleId {
+        let mut size = None;
+        let mut res = def_map.root();
+        for (module, data) in def_map.modules() {
+            let src = data.definition_source(self);
+            if src.file_id != position.file_id.into() {
+                continue;
+            }
+
+            let range = match src.value {
+                ModuleSource::SourceFile(it) => it.syntax().text_range(),
+                ModuleSource::Module(it) => it.syntax().text_range(),
+                ModuleSource::BlockExpr(it) => it.syntax().text_range(),
+            };
+
+            if !range.contains(position.offset) {
+                continue;
+            }
+
+            let new_size = match size {
+                None => range.len(),
+                Some(size) => {
+                    if range.len() < size {
+                        range.len()
+                    } else {
+                        size
+                    }
+                }
+            };
+
+            if size != Some(new_size) {
+                cov_mark::hit!(submodule_in_testdb);
+                size = Some(new_size);
+                res = module;
+            }
+        }
+
+        res
+    }
+
     fn block_at_position(&self, def_map: &DefMap, position: FilePosition) -> Option<Arc<DefMap>> {
         // Find the smallest (innermost) function in `def_map` containing the cursor.
         let mut size = None;
@@ -265,4 +312,17 @@ impl TestDB {
 
         assert_eq!(annotations, actual);
     }
+
+    pub(crate) fn check_no_diagnostics(&self) {
+        let db: &TestDB = self;
+        let annotations = db.extract_annotations();
+        assert!(annotations.is_empty());
+
+        let mut has_diagnostics = false;
+        db.diagnostics(|_| {
+            has_diagnostics = true;
+        });
+
+        assert!(!has_diagnostics);
+    }
 }
diff --git a/crates/hir_def/src/type_ref.rs b/crates/hir_def/src/type_ref.rs
index 049b2e462..4c24aae94 100644
--- a/crates/hir_def/src/type_ref.rs
+++ b/crates/hir_def/src/type_ref.rs
@@ -51,6 +51,23 @@ impl Rawness {
     }
 }
 
+#[derive(Clone, PartialEq, Eq, Hash, Debug)]
+pub struct TraitRef {
+    pub path: Path,
+}
+
+impl TraitRef {
+    /// Converts an `ast::PathType` to a `hir::TraitRef`.
+    pub(crate) fn from_ast(ctx: &LowerCtx, node: ast::Type) -> Option<Self> {
+        // FIXME: Use `Path::from_src`
+        match node {
+            ast::Type::PathType(path) => {
+                path.path().and_then(|it| ctx.lower_path(it)).map(|path| TraitRef { path })
+            }
+            _ => None,
+        }
+    }
+}
 /// Compare ty::Ty
 #[derive(Clone, PartialEq, Eq, Hash, Debug)]
 pub enum TypeRef {
diff --git a/crates/hir_def/src/visibility.rs b/crates/hir_def/src/visibility.rs
index 7d00a37c4..9908cd926 100644
--- a/crates/hir_def/src/visibility.rs
+++ b/crates/hir_def/src/visibility.rs
@@ -11,7 +11,7 @@ use crate::{
     nameres::DefMap,
     path::{ModPath, PathKind},
     resolver::HasResolver,
-    FunctionId, HasModule, LocalFieldId, ModuleDefId, ModuleId, VariantId,
+    FunctionId, HasModule, LocalFieldId, ModuleId, VariantId,
 };
 
 /// Visibility of an item, not yet resolved.
@@ -25,7 +25,7 @@ pub enum RawVisibility {
 }
 
 impl RawVisibility {
-    pub(crate) const fn private() -> RawVisibility {
+    pub(crate) fn private() -> RawVisibility {
         RawVisibility::Module(ModPath::from_kind(PathKind::Super(0)))
     }
 
@@ -217,6 +217,6 @@ pub(crate) fn field_visibilities_query(
 
 /// Resolve visibility of a function.
 pub(crate) fn function_visibility_query(db: &dyn DefDatabase, def: FunctionId) -> Visibility {
-    let resolver = ModuleDefId::from(def).module(db).unwrap().resolver(db);
+    let resolver = def.resolver(db);
     db.function_data(def).visibility.resolve(db, &resolver)
 }
diff --git a/crates/hir_expand/src/builtin_derive.rs b/crates/hir_expand/src/builtin_derive.rs
index 6ece4b289..537c03028 100644
--- a/crates/hir_expand/src/builtin_derive.rs
+++ b/crates/hir_expand/src/builtin_derive.rs
@@ -269,7 +269,7 @@ mod tests {
     use expect_test::{expect, Expect};
     use name::AsName;
 
-    use crate::{test_db::TestDB, AstId, MacroCallId, MacroCallKind, MacroCallLoc};
+    use crate::{test_db::TestDB, AstId, AttrId, MacroCallId, MacroCallKind, MacroCallLoc};
 
     use super::*;
 
@@ -308,7 +308,7 @@ $0
 
         let expander = BuiltinDeriveExpander::find_by_name(&name).unwrap();
 
-        let attr_id = AstId::new(file_id.into(), ast_id_map.ast_id(&items[0]));
+        let ast_id = AstId::new(file_id.into(), ast_id_map.ast_id(&items[0]));
 
         let loc = MacroCallLoc {
             def: MacroDefId {
@@ -317,7 +317,11 @@ $0
                 local_inner: false,
             },
             krate: CrateId(0),
-            kind: MacroCallKind::Derive(attr_id, name.to_string()),
+            kind: MacroCallKind::Derive {
+                ast_id,
+                derive_name: name.to_string(),
+                derive_attr: AttrId(0),
+            },
         };
 
         let id: MacroCallId = db.intern_macro(loc).into();
diff --git a/crates/hir_expand/src/builtin_macro.rs b/crates/hir_expand/src/builtin_macro.rs
index 4d52904b9..80365fc16 100644
--- a/crates/hir_expand/src/builtin_macro.rs
+++ b/crates/hir_expand/src/builtin_macro.rs
@@ -1,10 +1,10 @@
 //! Builtin macro
 use crate::{
     db::AstDatabase, name, quote, AstId, CrateId, EagerMacroId, LazyMacroId, MacroCallId,
-    MacroDefId, MacroDefKind, TextSize,
+    MacroCallLoc, MacroDefId, MacroDefKind, TextSize,
 };
 
-use base_db::{AnchoredPath, FileId};
+use base_db::{AnchoredPath, Edition, FileId};
 use cfg::CfgExpr;
 use either::Either;
 use mbe::{parse_exprs_with_sep, parse_to_token_tree, ExpandResult};
@@ -111,6 +111,8 @@ register_builtin! {
     (llvm_asm, LlvmAsm) => asm_expand,
     (asm, Asm) => asm_expand,
     (cfg, Cfg) => cfg_expand,
+    (core_panic, CorePanic) => panic_expand,
+    (std_panic, StdPanic) => panic_expand,
 
     EAGER:
     (compile_error, CompileError) => compile_error_expand,
@@ -284,6 +286,25 @@ fn cfg_expand(
     ExpandResult::ok(expanded)
 }
 
+fn panic_expand(
+    db: &dyn AstDatabase,
+    id: LazyMacroId,
+    tt: &tt::Subtree,
+) -> ExpandResult<tt::Subtree> {
+    let loc: MacroCallLoc = db.lookup_intern_macro(id);
+    // Expand to a macro call `$crate::panic::panic_{edition}`
+    let krate = tt::Ident { text: "$crate".into(), id: tt::TokenId::unspecified() };
+    let mut call = if db.crate_graph()[loc.krate].edition == Edition::Edition2021 {
+        quote!(#krate::panic::panic_2021!)
+    } else {
+        quote!(#krate::panic::panic_2015!)
+    };
+
+    // Pass the original arguments
+    call.token_trees.push(tt::TokenTree::Subtree(tt.clone()));
+    ExpandResult::ok(call)
+}
+
 fn unquote_str(lit: &tt::Literal) -> Option<String> {
     let lit = ast::make::tokens::literal(&lit.to_string());
     let token = ast::String::cast(lit)?;
@@ -469,7 +490,7 @@ fn env_expand(
         // unnecessary diagnostics for eg. `CARGO_PKG_NAME`.
         if key == "OUT_DIR" {
             err = Some(mbe::ExpandError::Other(
-                r#"`OUT_DIR` not set, enable "load out dirs from check" to fix"#.into(),
+                r#"`OUT_DIR` not set, enable "run build scripts" to fix"#.into(),
             ));
         }
 
@@ -545,10 +566,9 @@ mod tests {
                 let loc = MacroCallLoc {
                     def,
                     krate,
-                    kind: MacroCallKind::FnLike(AstId::new(
-                        file_id.into(),
-                        ast_id_map.ast_id(&macro_call),
-                    )),
+                    kind: MacroCallKind::FnLike {
+                        ast_id: AstId::new(file_id.into(), ast_id_map.ast_id(&macro_call)),
+                    },
                 };
 
                 let id: MacroCallId = db.intern_macro(loc).into();
@@ -563,7 +583,7 @@ mod tests {
                 };
 
                 let args = macro_call.token_tree().unwrap();
-                let parsed_args = mbe::ast_to_token_tree(&args).unwrap().0;
+                let parsed_args = mbe::ast_to_token_tree(&args).0;
                 let call_id = AstId::new(file_id.into(), ast_id_map.ast_id(&macro_call));
 
                 let arg_id = db.intern_eager_expansion({
diff --git a/crates/hir_expand/src/db.rs b/crates/hir_expand/src/db.rs
index c0ab70b60..ca705ee9d 100644
--- a/crates/hir_expand/src/db.rs
+++ b/crates/hir_expand/src/db.rs
@@ -119,7 +119,7 @@ pub fn expand_hypothetical(
     token_to_map: syntax::SyntaxToken,
 ) -> Option<(SyntaxNode, syntax::SyntaxToken)> {
     let macro_file = MacroFile { macro_call_id: actual_macro_call };
-    let (tt, tmap_1) = mbe::syntax_node_to_token_tree(hypothetical_args.syntax()).unwrap();
+    let (tt, tmap_1) = mbe::syntax_node_to_token_tree(hypothetical_args.syntax());
     let range =
         token_to_map.text_range().checked_sub(hypothetical_args.syntax().text_range().start())?;
     let token_id = tmap_1.token_by_range(range)?;
@@ -143,10 +143,7 @@ fn macro_def(db: &dyn AstDatabase, id: MacroDefId) -> Option<Arc<(TokenExpander,
         MacroDefKind::Declarative(ast_id) => match ast_id.to_node(db) {
             syntax::ast::Macro::MacroRules(macro_rules) => {
                 let arg = macro_rules.token_tree()?;
-                let (tt, tmap) = mbe::ast_to_token_tree(&arg).or_else(|| {
-                    log::warn!("fail on macro_rules to token tree: {:#?}", arg);
-                    None
-                })?;
+                let (tt, tmap) = mbe::ast_to_token_tree(&arg);
                 let rules = match MacroRules::parse(&tt) {
                     Ok(it) => it,
                     Err(err) => {
@@ -159,10 +156,7 @@ fn macro_def(db: &dyn AstDatabase, id: MacroDefId) -> Option<Arc<(TokenExpander,
             }
             syntax::ast::Macro::MacroDef(macro_def) => {
                 let arg = macro_def.body()?;
-                let (tt, tmap) = mbe::ast_to_token_tree(&arg).or_else(|| {
-                    log::warn!("fail on macro_def to token tree: {:#?}", arg);
-                    None
-                })?;
+                let (tt, tmap) = mbe::ast_to_token_tree(&arg);
                 let rules = match MacroDef::parse(&tt) {
                     Ok(it) => it,
                     Err(err) => {
@@ -202,7 +196,7 @@ fn macro_arg_text(db: &dyn AstDatabase, id: MacroCallId) -> Option<GreenNode> {
 
 fn macro_arg(db: &dyn AstDatabase, id: MacroCallId) -> Option<Arc<(tt::Subtree, mbe::TokenMap)>> {
     let arg = db.macro_arg_text(id)?;
-    let (tt, tmap) = mbe::syntax_node_to_token_tree(&SyntaxNode::new_root(arg))?;
+    let (tt, tmap) = mbe::syntax_node_to_token_tree(&SyntaxNode::new_root(arg));
     Some(Arc::new((tt, tmap)))
 }
 
@@ -445,6 +439,7 @@ fn to_fragment_kind(db: &dyn AstDatabase, id: MacroCallId) -> FragmentKind {
     match parent.kind() {
         MACRO_ITEMS | SOURCE_FILE => FragmentKind::Items,
         MACRO_STMTS => FragmentKind::Statements,
+        MACRO_PAT => FragmentKind::Pattern,
         ITEM_LIST => FragmentKind::Items,
         LET_STMT => {
             // FIXME: Handle LHS Pattern
diff --git a/crates/hir_expand/src/eager.rs b/crates/hir_expand/src/eager.rs
index 9eedc8461..ef126e4ad 100644
--- a/crates/hir_expand/src/eager.rs
+++ b/crates/hir_expand/src/eager.rs
@@ -106,7 +106,7 @@ pub fn expand_eager_macro(
     mut diagnostic_sink: &mut dyn FnMut(mbe::ExpandError),
 ) -> Result<EagerMacroId, ErrorEmitted> {
     let parsed_args = diagnostic_sink.option_with(
-        || Some(mbe::ast_to_token_tree(&macro_call.value.token_tree()?)?.0),
+        || Some(mbe::ast_to_token_tree(&macro_call.value.token_tree()?).0),
         || err("malformed macro invocation"),
     )?;
 
@@ -161,7 +161,7 @@ pub fn expand_eager_macro(
 }
 
 fn to_subtree(node: &SyntaxNode) -> Option<tt::Subtree> {
-    let mut subtree = mbe::syntax_node_to_token_tree(node)?.0;
+    let mut subtree = mbe::syntax_node_to_token_tree(node).0;
     subtree.delimiter = None;
     Some(subtree)
 }
@@ -174,8 +174,9 @@ fn lazy_expand(
 ) -> ExpandResult<Option<InFile<SyntaxNode>>> {
     let ast_id = db.ast_id_map(macro_call.file_id).ast_id(&macro_call.value);
 
-    let id: MacroCallId =
-        def.as_lazy_macro(db, krate, MacroCallKind::FnLike(macro_call.with_value(ast_id))).into();
+    let id: MacroCallId = def
+        .as_lazy_macro(db, krate, MacroCallKind::FnLike { ast_id: macro_call.with_value(ast_id) })
+        .into();
 
     let err = db.macro_expand_error(id);
     let value = db.parse_or_expand(id.as_file()).map(|node| InFile::new(id.as_file(), node));
diff --git a/crates/hir_expand/src/lib.rs b/crates/hir_expand/src/lib.rs
index 3e332ee47..a0e6aec62 100644
--- a/crates/hir_expand/src/lib.rs
+++ b/crates/hir_expand/src/lib.rs
@@ -290,22 +290,27 @@ pub struct MacroCallLoc {
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub enum MacroCallKind {
-    FnLike(AstId<ast::MacroCall>),
-    Derive(AstId<ast::Item>, String),
+    FnLike { ast_id: AstId<ast::MacroCall> },
+    Derive { ast_id: AstId<ast::Item>, derive_name: String, derive_attr: AttrId },
 }
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct AttrId(pub u32);
+
 impl MacroCallKind {
     fn file_id(&self) -> HirFileId {
         match self {
-            MacroCallKind::FnLike(ast_id) => ast_id.file_id,
-            MacroCallKind::Derive(ast_id, _) => ast_id.file_id,
+            MacroCallKind::FnLike { ast_id, .. } => ast_id.file_id,
+            MacroCallKind::Derive { ast_id, .. } => ast_id.file_id,
         }
     }
 
     fn node(&self, db: &dyn db::AstDatabase) -> InFile<SyntaxNode> {
         match self {
-            MacroCallKind::FnLike(ast_id) => ast_id.with_value(ast_id.to_node(db).syntax().clone()),
-            MacroCallKind::Derive(ast_id, _) => {
+            MacroCallKind::FnLike { ast_id, .. } => {
+                ast_id.with_value(ast_id.to_node(db).syntax().clone())
+            }
+            MacroCallKind::Derive { ast_id, .. } => {
                 ast_id.with_value(ast_id.to_node(db).syntax().clone())
             }
         }
@@ -313,10 +318,10 @@ impl MacroCallKind {
 
     fn arg(&self, db: &dyn db::AstDatabase) -> Option<SyntaxNode> {
         match self {
-            MacroCallKind::FnLike(ast_id) => {
+            MacroCallKind::FnLike { ast_id, .. } => {
                 Some(ast_id.to_node(db).token_tree()?.syntax().clone())
             }
-            MacroCallKind::Derive(ast_id, _) => Some(ast_id.to_node(db).syntax().clone()),
+            MacroCallKind::Derive { ast_id, .. } => Some(ast_id.to_node(db).syntax().clone()),
         }
     }
 }
diff --git a/crates/hir_expand/src/name.rs b/crates/hir_expand/src/name.rs
index cd691b1d2..a0f8766b0 100644
--- a/crates/hir_expand/src/name.rs
+++ b/crates/hir_expand/src/name.rs
@@ -55,6 +55,15 @@ impl Name {
         }
     }
 
+    /// A fake name for things missing in the source code.
+    ///
+    /// For example, `impl Foo for {}` should be treated as a trait impl for a
+    /// type with a missing name. Similarly, `struct S { : u32 }` should have a
+    /// single field with a missing name.
+    ///
+    /// Ideally, we want a `gensym` semantics for missing names -- each missing
+    /// name is equal only to itself. It's not clear how to implement this in
+    /// salsa though, so we punt on that bit for a moment.
     pub fn missing() -> Name {
         Name::new_text("[missing name]".into())
     }
@@ -199,6 +208,8 @@ pub mod known {
         line,
         module_path,
         assert,
+        core_panic,
+        std_panic,
         stringify,
         concat,
         include,
diff --git a/crates/hir_expand/src/quote.rs b/crates/hir_expand/src/quote.rs
index 08bc5aa49..c82487ef0 100644
--- a/crates/hir_expand/src/quote.rs
+++ b/crates/hir_expand/src/quote.rs
@@ -104,6 +104,7 @@ macro_rules! __quote {
     ( . ) => {$crate::__quote!(@PUNCT '.')};
     ( < ) => {$crate::__quote!(@PUNCT '<')};
     ( > ) => {$crate::__quote!(@PUNCT '>')};
+    ( ! ) => {$crate::__quote!(@PUNCT '!')};
 
     ( $first:tt $($tail:tt)+ ) => {
         {
diff --git a/crates/hir_ty/Cargo.toml b/crates/hir_ty/Cargo.toml
index 030b7eebe..abc0e7532 100644
--- a/crates/hir_ty/Cargo.toml
+++ b/crates/hir_ty/Cargo.toml
@@ -12,7 +12,7 @@ doctest = false
 [dependencies]
 cov-mark = { version = "1.1", features = ["thread-local"] }
 itertools = "0.10.0"
-arrayvec = "0.6"
+arrayvec = "0.7"
 smallvec = "1.2.0"
 ena = "0.14.0"
 log = "0.4.8"
diff --git a/crates/hir_ty/src/autoderef.rs b/crates/hir_ty/src/autoderef.rs
index dc5fc759a..2c07494a9 100644
--- a/crates/hir_ty/src/autoderef.rs
+++ b/crates/hir_ty/src/autoderef.rs
@@ -6,18 +6,15 @@
 use std::iter::successors;
 
 use base_db::CrateId;
-use chalk_ir::cast::Cast;
+use chalk_ir::{cast::Cast, fold::Fold, interner::HasInterner, VariableKind};
 use hir_def::lang_item::LangItemTarget;
 use hir_expand::name::name;
 use log::{info, warn};
 
 use crate::{
-    db::HirDatabase,
-    to_assoc_type_id, to_chalk_trait_id,
-    traits::{InEnvironment, Solution},
-    utils::generics,
-    AliasEq, AliasTy, BoundVar, Canonical, CanonicalVarKinds, DebruijnIndex, Interner,
-    ProjectionTy, Substitution, TraitRef, Ty, TyKind,
+    db::HirDatabase, static_lifetime, AliasEq, AliasTy, BoundVar, Canonical, CanonicalVarKinds,
+    DebruijnIndex, InEnvironment, Interner, ProjectionTyExt, Solution, Substitution, Ty, TyBuilder,
+    TyKind,
 };
 
 const AUTODEREF_RECURSION_LIMIT: usize = 10;
@@ -39,39 +36,48 @@ pub(crate) fn deref(
     krate: CrateId,
     ty: InEnvironment<&Canonical<Ty>>,
 ) -> Option<Canonical<Ty>> {
-    if let Some(derefed) = ty.goal.value.builtin_deref() {
+    let _p = profile::span("deref");
+    if let Some(derefed) = builtin_deref(&ty.goal.value) {
         Some(Canonical { value: derefed, binders: ty.goal.binders.clone() })
     } else {
         deref_by_trait(db, krate, ty)
     }
 }
 
+fn builtin_deref(ty: &Ty) -> Option<Ty> {
+    match ty.kind(&Interner) {
+        TyKind::Ref(.., ty) => Some(ty.clone()),
+        TyKind::Raw(.., ty) => Some(ty.clone()),
+        _ => None,
+    }
+}
+
 fn deref_by_trait(
     db: &dyn HirDatabase,
     krate: CrateId,
     ty: InEnvironment<&Canonical<Ty>>,
 ) -> Option<Canonical<Ty>> {
+    let _p = profile::span("deref_by_trait");
     let deref_trait = match db.lang_item(krate, "deref".into())? {
         LangItemTarget::TraitId(it) => it,
         _ => return None,
     };
     let target = db.trait_data(deref_trait).associated_type_by_name(&name![Target])?;
 
-    let generic_params = generics(db.upcast(), target.into());
-    if generic_params.len() != 1 {
-        // the Target type + Deref trait should only have one generic parameter,
-        // namely Deref's Self type
-        return None;
-    }
+    let projection = {
+        let b = TyBuilder::assoc_type_projection(db, target);
+        if b.remaining() != 1 {
+            // the Target type + Deref trait should only have one generic parameter,
+            // namely Deref's Self type
+            return None;
+        }
+        b.push(ty.goal.value.clone()).build()
+    };
 
     // FIXME make the Canonical / bound var handling nicer
 
-    let parameters =
-        Substitution::build_for_generics(&generic_params).push(ty.goal.value.clone()).build();
-
     // Check that the type implements Deref at all
-    let trait_ref =
-        TraitRef { trait_id: to_chalk_trait_id(deref_trait), substitution: parameters.clone() };
+    let trait_ref = projection.trait_ref(db);
     let implements_goal = Canonical {
         binders: ty.goal.binders.clone(),
         value: InEnvironment {
@@ -84,11 +90,8 @@ fn deref_by_trait(
     }
 
     // Now do the assoc type projection
-    let projection = AliasEq {
-        alias: AliasTy::Projection(ProjectionTy {
-            associated_ty_id: to_assoc_type_id(target),
-            substitution: parameters,
-        }),
+    let alias_eq = AliasEq {
+        alias: AliasTy::Projection(projection),
         ty: TyKind::BoundVar(BoundVar::new(
             DebruijnIndex::INNERMOST,
             ty.goal.binders.len(&Interner),
@@ -96,16 +99,14 @@ fn deref_by_trait(
         .intern(&Interner),
     };
 
-    let obligation = projection.cast(&Interner);
-
-    let in_env = InEnvironment { goal: obligation, environment: ty.environment };
+    let in_env = InEnvironment { goal: alias_eq.cast(&Interner), environment: ty.environment };
 
     let canonical = Canonical {
         value: in_env,
         binders: CanonicalVarKinds::from_iter(
             &Interner,
             ty.goal.binders.iter(&Interner).cloned().chain(Some(chalk_ir::WithKind::new(
-                chalk_ir::VariableKind::Ty(chalk_ir::TyVariableKind::General),
+                VariableKind::Ty(chalk_ir::TyVariableKind::General),
                 chalk_ir::UniverseIndex::ROOT,
             ))),
         ),
@@ -130,18 +131,25 @@ fn deref_by_trait(
             // assumptions will be broken. We would need to properly introduce
             // new variables in that case
 
-            for i in 1..vars.0.binders.len(&Interner) {
-                if vars.0.value[i - 1].interned(&Interner)
+            for i in 1..vars.binders.len(&Interner) {
+                if vars.value.subst.at(&Interner, i - 1).assert_ty_ref(&Interner).kind(&Interner)
                     != &TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, i - 1))
                 {
                     warn!("complex solution for derefing {:?}: {:?}, ignoring", ty.goal, solution);
                     return None;
                 }
             }
-            Some(Canonical {
-                value: vars.0.value[vars.0.value.len() - 1].clone(),
-                binders: vars.0.binders.clone(),
-            })
+            // FIXME: we remove lifetime variables here since they can confuse
+            // the method resolution code later
+            Some(fixup_lifetime_variables(Canonical {
+                value: vars
+                    .value
+                    .subst
+                    .at(&Interner, vars.value.subst.len(&Interner) - 1)
+                    .assert_ty_ref(&Interner)
+                    .clone(),
+                binders: vars.binders.clone(),
+            }))
         }
         Solution::Ambig(_) => {
             info!("Ambiguous solution for derefing {:?}: {:?}", ty.goal, solution);
@@ -149,3 +157,32 @@ fn deref_by_trait(
         }
     }
 }
+
+fn fixup_lifetime_variables<T: Fold<Interner, Result = T> + HasInterner<Interner = Interner>>(
+    c: Canonical<T>,
+) -> Canonical<T> {
+    // Removes lifetime variables from the Canonical, replacing them by static lifetimes.
+    let mut i = 0;
+    let subst = Substitution::from_iter(
+        &Interner,
+        c.binders.iter(&Interner).map(|vk| match vk.kind {
+            VariableKind::Ty(_) => {
+                let index = i;
+                i += 1;
+                BoundVar::new(DebruijnIndex::INNERMOST, index).to_ty(&Interner).cast(&Interner)
+            }
+            VariableKind::Lifetime => static_lifetime().cast(&Interner),
+            VariableKind::Const(_) => unimplemented!(),
+        }),
+    );
+    let binders = CanonicalVarKinds::from_iter(
+        &Interner,
+        c.binders.iter(&Interner).filter(|vk| match vk.kind {
+            VariableKind::Ty(_) => true,
+            VariableKind::Lifetime => false,
+            VariableKind::Const(_) => true,
+        }),
+    );
+    let value = subst.apply(c.value, &Interner);
+    Canonical { binders, value }
+}
diff --git a/crates/hir_ty/src/builder.rs b/crates/hir_ty/src/builder.rs
new file mode 100644
index 000000000..e25ef866d
--- /dev/null
+++ b/crates/hir_ty/src/builder.rs
@@ -0,0 +1,223 @@
+//! `TyBuilder`, a helper for building instances of `Ty` and related types.
+
+use std::iter;
+
+use chalk_ir::{
+    cast::{Cast, CastTo, Caster},
+    fold::Fold,
+    interner::HasInterner,
+    AdtId, BoundVar, DebruijnIndex, Safety, Scalar,
+};
+use hir_def::{builtin_type::BuiltinType, GenericDefId, TraitId, TypeAliasId};
+use smallvec::SmallVec;
+
+use crate::{
+    db::HirDatabase, primitive, to_assoc_type_id, to_chalk_trait_id, utils::generics, Binders,
+    CallableSig, FnPointer, FnSig, FnSubst, GenericArg, Interner, ProjectionTy, Substitution,
+    TraitRef, Ty, TyDefId, TyExt, TyKind, ValueTyDefId,
+};
+
+/// This is a builder for `Ty` or anything that needs a `Substitution`.
+pub struct TyBuilder<D> {
+    /// The `data` field is used to keep track of what we're building (e.g. an
+    /// ADT, a `TraitRef`, ...).
+    data: D,
+    vec: SmallVec<[GenericArg; 2]>,
+    param_count: usize,
+}
+
+impl<D> TyBuilder<D> {
+    fn new(data: D, param_count: usize) -> TyBuilder<D> {
+        TyBuilder { data, param_count, vec: SmallVec::with_capacity(param_count) }
+    }
+
+    fn build_internal(self) -> (D, Substitution) {
+        assert_eq!(self.vec.len(), self.param_count);
+        let subst = Substitution::from_iter(&Interner, self.vec);
+        (self.data, subst)
+    }
+
+    pub fn push(mut self, arg: impl CastTo<GenericArg>) -> Self {
+        self.vec.push(arg.cast(&Interner));
+        self
+    }
+
+    pub fn remaining(&self) -> usize {
+        self.param_count - self.vec.len()
+    }
+
+    pub fn fill_with_bound_vars(self, debruijn: DebruijnIndex, starting_from: usize) -> Self {
+        self.fill(
+            (starting_from..)
+                .map(|idx| TyKind::BoundVar(BoundVar::new(debruijn, idx)).intern(&Interner)),
+        )
+    }
+
+    pub fn fill_with_unknown(self) -> Self {
+        self.fill(iter::repeat(TyKind::Error.intern(&Interner)))
+    }
+
+    pub fn fill(mut self, filler: impl Iterator<Item = impl CastTo<GenericArg>>) -> Self {
+        self.vec.extend(filler.take(self.remaining()).casted(&Interner));
+        assert_eq!(self.remaining(), 0);
+        self
+    }
+
+    pub fn use_parent_substs(mut self, parent_substs: &Substitution) -> Self {
+        assert!(self.vec.is_empty());
+        assert!(parent_substs.len(&Interner) <= self.param_count);
+        self.vec.extend(parent_substs.iter(&Interner).cloned());
+        self
+    }
+}
+
+impl TyBuilder<()> {
+    pub fn unit() -> Ty {
+        TyKind::Tuple(0, Substitution::empty(&Interner)).intern(&Interner)
+    }
+
+    pub fn fn_ptr(sig: CallableSig) -> Ty {
+        TyKind::Function(FnPointer {
+            num_binders: 0,
+            sig: FnSig { abi: (), safety: Safety::Safe, variadic: sig.is_varargs },
+            substitution: FnSubst(Substitution::from_iter(
+                &Interner,
+                sig.params_and_return.iter().cloned(),
+            )),
+        })
+        .intern(&Interner)
+    }
+
+    pub fn builtin(builtin: BuiltinType) -> Ty {
+        match builtin {
+            BuiltinType::Char => TyKind::Scalar(Scalar::Char).intern(&Interner),
+            BuiltinType::Bool => TyKind::Scalar(Scalar::Bool).intern(&Interner),
+            BuiltinType::Str => TyKind::Str.intern(&Interner),
+            BuiltinType::Int(t) => {
+                TyKind::Scalar(Scalar::Int(primitive::int_ty_from_builtin(t))).intern(&Interner)
+            }
+            BuiltinType::Uint(t) => {
+                TyKind::Scalar(Scalar::Uint(primitive::uint_ty_from_builtin(t))).intern(&Interner)
+            }
+            BuiltinType::Float(t) => {
+                TyKind::Scalar(Scalar::Float(primitive::float_ty_from_builtin(t))).intern(&Interner)
+            }
+        }
+    }
+
+    pub fn type_params_subst(db: &dyn HirDatabase, def: impl Into<GenericDefId>) -> Substitution {
+        let params = generics(db.upcast(), def.into());
+        params.type_params_subst(db)
+    }
+
+    pub fn subst_for_def(db: &dyn HirDatabase, def: impl Into<GenericDefId>) -> TyBuilder<()> {
+        let def = def.into();
+        let params = generics(db.upcast(), def);
+        let param_count = params.len();
+        TyBuilder::new((), param_count)
+    }
+
+    pub fn build(self) -> Substitution {
+        let ((), subst) = self.build_internal();
+        subst
+    }
+}
+
+impl TyBuilder<hir_def::AdtId> {
+    pub fn adt(db: &dyn HirDatabase, adt: hir_def::AdtId) -> TyBuilder<hir_def::AdtId> {
+        let generics = generics(db.upcast(), adt.into());
+        let param_count = generics.len();
+        TyBuilder::new(adt, param_count)
+    }
+
+    pub fn fill_with_defaults(
+        mut self,
+        db: &dyn HirDatabase,
+        mut fallback: impl FnMut() -> Ty,
+    ) -> Self {
+        let defaults = db.generic_defaults(self.data.into());
+        for default_ty in defaults.iter().skip(self.vec.len()) {
+            if default_ty.skip_binders().is_unknown() {
+                self.vec.push(fallback().cast(&Interner));
+            } else {
+                // each default can depend on the previous parameters
+                let subst_so_far = Substitution::from_iter(&Interner, self.vec.clone());
+                self.vec
+                    .push(default_ty.clone().substitute(&Interner, &subst_so_far).cast(&Interner));
+            }
+        }
+        self
+    }
+
+    pub fn build(self) -> Ty {
+        let (adt, subst) = self.build_internal();
+        TyKind::Adt(AdtId(adt), subst).intern(&Interner)
+    }
+}
+
+pub struct Tuple(usize);
+impl TyBuilder<Tuple> {
+    pub fn tuple(size: usize) -> TyBuilder<Tuple> {
+        TyBuilder::new(Tuple(size), size)
+    }
+
+    pub fn build(self) -> Ty {
+        let (Tuple(size), subst) = self.build_internal();
+        TyKind::Tuple(size, subst).intern(&Interner)
+    }
+}
+
+impl TyBuilder<TraitId> {
+    pub fn trait_ref(db: &dyn HirDatabase, trait_id: TraitId) -> TyBuilder<TraitId> {
+        let generics = generics(db.upcast(), trait_id.into());
+        let param_count = generics.len();
+        TyBuilder::new(trait_id, param_count)
+    }
+
+    pub fn build(self) -> TraitRef {
+        let (trait_id, substitution) = self.build_internal();
+        TraitRef { trait_id: to_chalk_trait_id(trait_id), substitution }
+    }
+}
+
+impl TyBuilder<TypeAliasId> {
+    pub fn assoc_type_projection(
+        db: &dyn HirDatabase,
+        type_alias: TypeAliasId,
+    ) -> TyBuilder<TypeAliasId> {
+        let generics = generics(db.upcast(), type_alias.into());
+        let param_count = generics.len();
+        TyBuilder::new(type_alias, param_count)
+    }
+
+    pub fn build(self) -> ProjectionTy {
+        let (type_alias, substitution) = self.build_internal();
+        ProjectionTy { associated_ty_id: to_assoc_type_id(type_alias), substitution }
+    }
+}
+
+impl<T: HasInterner<Interner = Interner> + Fold<Interner>> TyBuilder<Binders<T>> {
+    fn subst_binders(b: Binders<T>) -> Self {
+        let param_count = b.binders.len(&Interner);
+        TyBuilder::new(b, param_count)
+    }
+
+    pub fn build(self) -> <T as Fold<Interner>>::Result {
+        let (b, subst) = self.build_internal();
+        b.substitute(&Interner, &subst)
+    }
+}
+
+impl TyBuilder<Binders<Ty>> {
+    pub fn def_ty(db: &dyn HirDatabase, def: TyDefId) -> TyBuilder<Binders<Ty>> {
+        TyBuilder::subst_binders(db.ty(def.into()))
+    }
+
+    pub fn impl_self_ty(db: &dyn HirDatabase, def: hir_def::ImplId) -> TyBuilder<Binders<Ty>> {
+        TyBuilder::subst_binders(db.impl_self_ty(def))
+    }
+
+    pub fn value_ty(db: &dyn HirDatabase, def: ValueTyDefId) -> TyBuilder<Binders<Ty>> {
+        TyBuilder::subst_binders(db.value_ty(def))
+    }
+}
diff --git a/crates/hir_ty/src/chalk_cast.rs b/crates/hir_ty/src/chalk_cast.rs
deleted file mode 100644
index bf884ae15..000000000
--- a/crates/hir_ty/src/chalk_cast.rs
+++ /dev/null
@@ -1,53 +0,0 @@
-//! Implementations of the Chalk `Cast` trait for our types.
-
-use chalk_ir::{
-    cast::{Cast, CastTo},
-    interner::HasInterner,
-};
-
-use crate::{AliasEq, DomainGoal, Interner, TraitRef, WhereClause};
-
-macro_rules! has_interner {
-    ($t:ty) => {
-        impl HasInterner for $t {
-            type Interner = crate::Interner;
-        }
-    };
-}
-
-has_interner!(WhereClause);
-has_interner!(DomainGoal);
-
-impl CastTo<WhereClause> for TraitRef {
-    fn cast_to(self, _interner: &Interner) -> WhereClause {
-        WhereClause::Implemented(self)
-    }
-}
-
-impl CastTo<WhereClause> for AliasEq {
-    fn cast_to(self, _interner: &Interner) -> WhereClause {
-        WhereClause::AliasEq(self)
-    }
-}
-
-impl CastTo<DomainGoal> for WhereClause {
-    fn cast_to(self, _interner: &Interner) -> DomainGoal {
-        DomainGoal::Holds(self)
-    }
-}
-
-macro_rules! transitive_impl {
-    ($a:ty, $b:ty, $c:ty) => {
-        impl CastTo<$c> for $a {
-            fn cast_to(self, interner: &Interner) -> $c {
-                self.cast::<$b>(interner).cast(interner)
-            }
-        }
-    };
-}
-
-// In Chalk, these can be done as blanket impls, but that doesn't work here
-// because of coherence
-
-transitive_impl!(TraitRef, WhereClause, DomainGoal);
-transitive_impl!(AliasEq, WhereClause, DomainGoal);
diff --git a/crates/hir_ty/src/traits/chalk.rs b/crates/hir_ty/src/chalk_db.rs
index 011bef6f6..8f054d06b 100644
--- a/crates/hir_ty/src/traits/chalk.rs
+++ b/crates/hir_ty/src/chalk_db.rs
@@ -1,52 +1,47 @@
-//! Conversion code from/to Chalk.
+//! The implementation of `RustIrDatabase` for Chalk, which provides information
+//! about the code that Chalk needs.
 use std::sync::Arc;
 
 use log::debug;
 
-use chalk_ir::{fold::shift::Shift, CanonicalVarKinds, GenericArg};
+use chalk_ir::{cast::Cast, fold::shift::Shift, CanonicalVarKinds};
 use chalk_solve::rust_ir::{self, OpaqueTyDatumBound, WellKnownTrait};
 
-use base_db::{salsa::InternKey, CrateId};
+use base_db::CrateId;
 use hir_def::{
     lang_item::{lang_attr, LangItemTarget},
-    AssocContainerId, AssocItemId, HasModule, Lookup, TypeAliasId,
+    AssocContainerId, AssocItemId, GenericDefId, HasModule, Lookup, TypeAliasId,
 };
 use hir_expand::name::name;
 
-use super::ChalkContext;
 use crate::{
     db::HirDatabase,
     display::HirDisplay,
-    from_assoc_type_id,
+    from_assoc_type_id, from_chalk_trait_id, make_only_type_binders,
+    mapping::{from_chalk, ToChalk, TypeAliasAsValue},
     method_resolution::{TyFingerprint, ALL_FLOAT_FPS, ALL_INT_FPS},
     to_assoc_type_id, to_chalk_trait_id,
+    traits::ChalkContext,
     utils::generics,
-    AliasEq, AliasTy, BoundVar, CallableDefId, DebruijnIndex, FnDefId, ProjectionTy, Substitution,
-    TraitRef, Ty, TyKind, WhereClause,
+    AliasEq, AliasTy, BoundVar, CallableDefId, DebruijnIndex, FnDefId, Interner, ProjectionTy,
+    ProjectionTyExt, QuantifiedWhereClause, Substitution, TraitRef, TraitRefExt, Ty, TyBuilder,
+    TyExt, TyKind, WhereClause,
 };
-use mapping::{
-    convert_where_clauses, generic_predicate_to_inline_bound, make_binders, TypeAliasAsValue,
-};
-
-pub use self::interner::Interner;
-pub(crate) use self::interner::*;
 
-pub(super) mod tls;
-mod interner;
-mod mapping;
-
-pub(crate) trait ToChalk {
-    type Chalk;
-    fn to_chalk(self, db: &dyn HirDatabase) -> Self::Chalk;
-    fn from_chalk(db: &dyn HirDatabase, chalk: Self::Chalk) -> Self;
-}
-
-pub(crate) fn from_chalk<T, ChalkT>(db: &dyn HirDatabase, chalk: ChalkT) -> T
-where
-    T: ToChalk<Chalk = ChalkT>,
-{
-    T::from_chalk(db, chalk)
-}
+pub(crate) type AssociatedTyDatum = chalk_solve::rust_ir::AssociatedTyDatum<Interner>;
+pub(crate) type TraitDatum = chalk_solve::rust_ir::TraitDatum<Interner>;
+pub(crate) type StructDatum = chalk_solve::rust_ir::AdtDatum<Interner>;
+pub(crate) type ImplDatum = chalk_solve::rust_ir::ImplDatum<Interner>;
+pub(crate) type OpaqueTyDatum = chalk_solve::rust_ir::OpaqueTyDatum<Interner>;
+
+pub(crate) type AssocTypeId = chalk_ir::AssocTypeId<Interner>;
+pub(crate) type TraitId = chalk_ir::TraitId<Interner>;
+pub(crate) type AdtId = chalk_ir::AdtId<Interner>;
+pub(crate) type ImplId = chalk_ir::ImplId<Interner>;
+pub(crate) type AssociatedTyValueId = chalk_solve::rust_ir::AssociatedTyValueId<Interner>;
+pub(crate) type AssociatedTyValue = chalk_solve::rust_ir::AssociatedTyValue<Interner>;
+pub(crate) type FnDefDatum = chalk_solve::rust_ir::FnDefDatum<Interner>;
+pub(crate) type Variances = chalk_ir::Variances<Interner>;
 
 impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
     fn associated_ty_data(&self, id: AssocTypeId) -> Arc<AssociatedTyDatum> {
@@ -80,19 +75,19 @@ impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
     fn impls_for_trait(
         &self,
         trait_id: TraitId,
-        parameters: &[GenericArg<Interner>],
+        parameters: &[chalk_ir::GenericArg<Interner>],
         binders: &CanonicalVarKinds<Interner>,
     ) -> Vec<ImplId> {
         debug!("impls_for_trait {:?}", trait_id);
-        let trait_: hir_def::TraitId = from_chalk(self.db, trait_id);
+        let trait_: hir_def::TraitId = from_chalk_trait_id(trait_id);
 
-        let ty: Ty = from_chalk(self.db, parameters[0].assert_ty_ref(&Interner).clone());
+        let ty: Ty = parameters[0].assert_ty_ref(&Interner).clone();
 
         fn binder_kind(
             ty: &Ty,
             binders: &CanonicalVarKinds<Interner>,
         ) -> Option<chalk_ir::TyVariableKind> {
-            if let TyKind::BoundVar(bv) = ty.interned(&Interner) {
+            if let TyKind::BoundVar(bv) = ty.kind(&Interner) {
                 let binders = binders.as_slice(&Interner);
                 if bv.debruijn == DebruijnIndex::INNERMOST {
                     if let chalk_ir::VariableKind::Ty(tk) = binders[bv.index].kind {
@@ -103,7 +98,7 @@ impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
             None
         }
 
-        let self_ty_fp = TyFingerprint::for_impl(&ty);
+        let self_ty_fp = TyFingerprint::for_trait_impl(&ty);
         let fps: &[TyFingerprint] = match binder_kind(&ty, binders) {
             Some(chalk_ir::TyVariableKind::Integer) => &ALL_INT_FPS,
             Some(chalk_ir::TyVariableKind::Float) => &ALL_FLOAT_FPS,
@@ -166,7 +161,7 @@ impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
             Some(LangItemTarget::TraitId(trait_)) => trait_,
             _ => return None,
         };
-        Some(trait_.to_chalk(self.db))
+        Some(to_chalk_trait_id(trait_))
     }
 
     fn program_clauses_for_env(
@@ -184,16 +179,16 @@ impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
                     .db
                     .return_type_impl_traits(func)
                     .expect("impl trait id without impl traits");
-                let data = &datas.value.impl_traits[idx as usize];
+                let (datas, binders) = (*datas).as_ref().into_value_and_skipped_binders();
+                let data = &datas.impl_traits[idx as usize];
                 let bound = OpaqueTyDatumBound {
-                    bounds: make_binders(
-                        data.bounds.value.iter().cloned().map(|b| b.to_chalk(self.db)).collect(),
+                    bounds: make_only_type_binders(
                         1,
+                        data.bounds.skip_binders().iter().cloned().collect(),
                     ),
-                    where_clauses: make_binders(vec![], 0),
+                    where_clauses: make_only_type_binders(0, vec![]),
                 };
-                let num_vars = datas.num_binders;
-                make_binders(bound, num_vars)
+                chalk_ir::Binders::new(binders, bound)
             }
             crate::ImplTraitId::AsyncBlockTypeImplTrait(..) => {
                 if let Some((future_trait, future_output)) = self
@@ -215,7 +210,8 @@ impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
                     let impl_bound = WhereClause::Implemented(TraitRef {
                         trait_id: to_chalk_trait_id(future_trait),
                         // Self type as the first parameter.
-                        substitution: Substitution::single(
+                        substitution: Substitution::from1(
+                            &Interner,
                             TyKind::BoundVar(BoundVar {
                                 debruijn: DebruijnIndex::INNERMOST,
                                 index: 0,
@@ -227,7 +223,8 @@ impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
                         alias: AliasTy::Projection(ProjectionTy {
                             associated_ty_id: to_assoc_type_id(future_output),
                             // Self type as the first parameter.
-                            substitution: Substitution::single(
+                            substitution: Substitution::from1(
+                                &Interner,
                                 TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0))
                                     .intern(&Interner),
                             ),
@@ -237,25 +234,25 @@ impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
                             .intern(&Interner),
                     });
                     let bound = OpaqueTyDatumBound {
-                        bounds: make_binders(
+                        bounds: make_only_type_binders(
+                            1,
                             vec![
-                                wrap_in_empty_binders(impl_bound).to_chalk(self.db),
-                                wrap_in_empty_binders(proj_bound).to_chalk(self.db),
+                                crate::wrap_empty_binders(impl_bound),
+                                crate::wrap_empty_binders(proj_bound),
                             ],
-                            1,
                         ),
-                        where_clauses: make_binders(vec![], 0),
+                        where_clauses: make_only_type_binders(0, vec![]),
                     };
                     // The opaque type has 1 parameter.
-                    make_binders(bound, 1)
+                    make_only_type_binders(1, bound)
                 } else {
                     // If failed to find Symbol’s value as variable is void: Future::Output, return empty bounds as fallback.
                     let bound = OpaqueTyDatumBound {
-                        bounds: make_binders(vec![], 0),
-                        where_clauses: make_binders(vec![], 0),
+                        bounds: make_only_type_binders(0, vec![]),
+                        where_clauses: make_only_type_binders(0, vec![]),
                     };
                     // The opaque type has 1 parameter.
-                    make_binders(bound, 1)
+                    make_only_type_binders(1, bound)
                 }
             }
         };
@@ -265,7 +262,7 @@ impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
 
     fn hidden_opaque_type(&self, _id: chalk_ir::OpaqueTyId<Interner>) -> chalk_ir::Ty<Interner> {
         // FIXME: actually provide the hidden type; it is relevant for auto traits
-        TyKind::Unknown.intern(&Interner).to_chalk(self.db)
+        TyKind::Error.intern(&Interner)
     }
 
     fn is_object_safe(&self, _trait_id: chalk_ir::TraitId<Interner>) -> bool {
@@ -286,33 +283,32 @@ impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
         _closure_id: chalk_ir::ClosureId<Interner>,
         substs: &chalk_ir::Substitution<Interner>,
     ) -> chalk_ir::Binders<rust_ir::FnDefInputsAndOutputDatum<Interner>> {
-        let sig_ty: Ty =
-            from_chalk(self.db, substs.at(&Interner, 0).assert_ty_ref(&Interner).clone());
+        let sig_ty = substs.at(&Interner, 0).assert_ty_ref(&Interner).clone();
         let sig = &sig_ty.callable_sig(self.db).expect("first closure param should be fn ptr");
         let io = rust_ir::FnDefInputsAndOutputDatum {
-            argument_types: sig.params().iter().map(|ty| ty.clone().to_chalk(self.db)).collect(),
-            return_type: sig.ret().clone().to_chalk(self.db),
+            argument_types: sig.params().iter().cloned().collect(),
+            return_type: sig.ret().clone(),
         };
-        make_binders(io.shifted_in(&Interner), 0)
+        make_only_type_binders(0, io.shifted_in(&Interner))
     }
     fn closure_upvars(
         &self,
         _closure_id: chalk_ir::ClosureId<Interner>,
         _substs: &chalk_ir::Substitution<Interner>,
     ) -> chalk_ir::Binders<chalk_ir::Ty<Interner>> {
-        let ty = Ty::unit().to_chalk(self.db);
-        make_binders(ty, 0)
+        let ty = TyBuilder::unit();
+        make_only_type_binders(0, ty)
     }
     fn closure_fn_substitution(
         &self,
         _closure_id: chalk_ir::ClosureId<Interner>,
         _substs: &chalk_ir::Substitution<Interner>,
     ) -> chalk_ir::Substitution<Interner> {
-        Substitution::empty().to_chalk(self.db)
+        Substitution::empty(&Interner)
     }
 
     fn trait_name(&self, trait_id: chalk_ir::TraitId<Interner>) -> String {
-        let id = from_chalk(self.db, trait_id);
+        let id = from_chalk_trait_id(trait_id);
         self.db.trait_data(id).name.to_string()
     }
     fn adt_name(&self, chalk_ir::AdtId(adt_id): AdtId) -> String {
@@ -387,7 +383,7 @@ pub(crate) fn associated_ty_data_query(
     // Lower bounds -- we could/should maybe move this to a separate query in `lower`
     let type_alias_data = db.type_alias_data(type_alias);
     let generic_params = generics(db.upcast(), type_alias.into());
-    let bound_vars = Substitution::bound_vars(&generic_params, DebruijnIndex::INNERMOST);
+    let bound_vars = generic_params.bound_vars_subst(DebruijnIndex::INNERMOST);
     let resolver = hir_def::resolver::HasResolver::resolver(type_alias, db.upcast());
     let ctx = crate::TyLoweringContext::new(db, &resolver)
         .with_type_param_mode(crate::lower::TypeParamLoweringMode::Variable);
@@ -403,10 +399,10 @@ pub(crate) fn associated_ty_data_query(
     let where_clauses = convert_where_clauses(db, type_alias.into(), &bound_vars);
     let bound_data = rust_ir::AssociatedTyDatumBound { bounds, where_clauses };
     let datum = AssociatedTyDatum {
-        trait_id: trait_.to_chalk(db),
+        trait_id: to_chalk_trait_id(trait_),
         id,
         name: type_alias,
-        binders: make_binders(bound_data, generic_params.len()),
+        binders: make_only_type_binders(generic_params.len(), bound_data),
     };
     Arc::new(datum)
 }
@@ -417,11 +413,11 @@ pub(crate) fn trait_datum_query(
     trait_id: TraitId,
 ) -> Arc<TraitDatum> {
     debug!("trait_datum {:?}", trait_id);
-    let trait_: hir_def::TraitId = from_chalk(db, trait_id);
+    let trait_ = from_chalk_trait_id(trait_id);
     let trait_data = db.trait_data(trait_);
     debug!("trait {:?} = {:?}", trait_id, trait_data.name);
     let generic_params = generics(db.upcast(), trait_.into());
-    let bound_vars = Substitution::bound_vars(&generic_params, DebruijnIndex::INNERMOST);
+    let bound_vars = generic_params.bound_vars_subst(DebruijnIndex::INNERMOST);
     let flags = rust_ir::TraitFlags {
         auto: trait_data.is_auto,
         upstream: trait_.lookup(db.upcast()).container.krate() != krate,
@@ -439,7 +435,7 @@ pub(crate) fn trait_datum_query(
         lang_attr(db.upcast(), trait_).and_then(|name| well_known_trait_from_lang_attr(&name));
     let trait_datum = TraitDatum {
         id: trait_id,
-        binders: make_binders(trait_datum_bound, bound_vars.len()),
+        binders: make_only_type_binders(bound_vars.len(&Interner), trait_datum_bound),
         flags,
         associated_ty_ids,
         well_known,
@@ -490,7 +486,7 @@ pub(crate) fn struct_datum_query(
     let upstream = adt_id.module(db.upcast()).krate() != krate;
     let where_clauses = {
         let generic_params = generics(db.upcast(), adt_id.into());
-        let bound_vars = Substitution::bound_vars(&generic_params, DebruijnIndex::INNERMOST);
+        let bound_vars = generic_params.bound_vars_subst(DebruijnIndex::INNERMOST);
         convert_where_clauses(db, adt_id.into(), &bound_vars)
     };
     let flags = rust_ir::AdtFlags {
@@ -508,7 +504,7 @@ pub(crate) fn struct_datum_query(
         // FIXME set ADT kind
         kind: rust_ir::AdtKind::Struct,
         id: struct_id,
-        binders: make_binders(struct_datum_bound, num_params),
+        binders: make_only_type_binders(num_params, struct_datum_bound),
         flags,
     };
     Arc::new(struct_datum)
@@ -535,11 +531,12 @@ fn impl_def_datum(
         .impl_trait(impl_id)
         // ImplIds for impls where the trait ref can't be resolved should never reach Chalk
         .expect("invalid impl passed to Chalk")
-        .value;
+        .into_value_and_skipped_binders()
+        .0;
     let impl_data = db.impl_data(impl_id);
 
     let generic_params = generics(db.upcast(), impl_id.into());
-    let bound_vars = Substitution::bound_vars(&generic_params, DebruijnIndex::INNERMOST);
+    let bound_vars = generic_params.bound_vars_subst(DebruijnIndex::INNERMOST);
     let trait_ = trait_ref.hir_trait_id();
     let impl_type = if impl_id.lookup(db.upcast()).container.krate() == krate {
         rust_ir::ImplType::Local
@@ -555,7 +552,6 @@ fn impl_def_datum(
         trait_ref.display(db),
         where_clauses
     );
-    let trait_ref = trait_ref.to_chalk(db);
 
     let polarity = if negative { rust_ir::Polarity::Negative } else { rust_ir::Polarity::Positive };
 
@@ -577,7 +573,7 @@ fn impl_def_datum(
         .collect();
     debug!("impl_datum: {:?}", impl_datum_bound);
     let impl_datum = ImplDatum {
-        binders: make_binders(impl_datum_bound, bound_vars.len()),
+        binders: make_only_type_binders(bound_vars.len(&Interner), impl_datum_bound),
         impl_type,
         polarity,
         associated_ty_value_ids,
@@ -605,18 +601,22 @@ fn type_alias_associated_ty_value(
         _ => panic!("assoc ty value should be in impl"),
     };
 
-    let trait_ref = db.impl_trait(impl_id).expect("assoc ty value should not exist").value; // we don't return any assoc ty values if the impl'd trait can't be resolved
+    let trait_ref = db
+        .impl_trait(impl_id)
+        .expect("assoc ty value should not exist")
+        .into_value_and_skipped_binders()
+        .0; // we don't return any assoc ty values if the impl'd trait can't be resolved
 
     let assoc_ty = db
         .trait_data(trait_ref.hir_trait_id())
         .associated_type_by_name(&type_alias_data.name)
         .expect("assoc ty value should not exist"); // validated when building the impl data as well
-    let ty = db.ty(type_alias.into());
-    let value_bound = rust_ir::AssociatedTyValueBound { ty: ty.value.to_chalk(db) };
+    let (ty, binders) = db.ty(type_alias.into()).into_value_and_skipped_binders();
+    let value_bound = rust_ir::AssociatedTyValueBound { ty };
     let value = rust_ir::AssociatedTyValue {
         impl_id: impl_id.to_chalk(db),
         associated_ty_id: to_assoc_type_id(assoc_ty),
-        value: make_binders(value_bound, ty.num_binders),
+        value: chalk_ir::Binders::new(binders, value_bound),
     };
     Arc::new(value)
 }
@@ -628,34 +628,25 @@ pub(crate) fn fn_def_datum_query(
 ) -> Arc<FnDefDatum> {
     let callable_def: CallableDefId = from_chalk(db, fn_def_id);
     let generic_params = generics(db.upcast(), callable_def.into());
-    let sig = db.callable_item_signature(callable_def);
-    let bound_vars = Substitution::bound_vars(&generic_params, DebruijnIndex::INNERMOST);
+    let (sig, binders) = db.callable_item_signature(callable_def).into_value_and_skipped_binders();
+    let bound_vars = generic_params.bound_vars_subst(DebruijnIndex::INNERMOST);
     let where_clauses = convert_where_clauses(db, callable_def.into(), &bound_vars);
     let bound = rust_ir::FnDefDatumBound {
         // Note: Chalk doesn't actually use this information yet as far as I am aware, but we provide it anyway
-        inputs_and_output: make_binders(
+        inputs_and_output: make_only_type_binders(
+            0,
             rust_ir::FnDefInputsAndOutputDatum {
-                argument_types: sig
-                    .value
-                    .params()
-                    .iter()
-                    .map(|ty| ty.clone().to_chalk(db))
-                    .collect(),
-                return_type: sig.value.ret().clone().to_chalk(db),
+                argument_types: sig.params().iter().cloned().collect(),
+                return_type: sig.ret().clone(),
             }
             .shifted_in(&Interner),
-            0,
         ),
         where_clauses,
     };
     let datum = FnDefDatum {
         id: fn_def_id,
-        sig: chalk_ir::FnSig {
-            abi: (),
-            safety: chalk_ir::Safety::Safe,
-            variadic: sig.value.is_varargs,
-        },
-        binders: make_binders(bound, sig.num_binders),
+        sig: chalk_ir::FnSig { abi: (), safety: chalk_ir::Safety::Safe, variadic: sig.is_varargs },
+        binders: chalk_ir::Binders::new(binders, bound),
     };
     Arc::new(datum)
 }
@@ -685,42 +676,65 @@ pub(crate) fn adt_variance_query(
     )
 }
 
-impl From<FnDefId> for crate::db::InternedCallableDefId {
-    fn from(fn_def_id: FnDefId) -> Self {
-        InternKey::from_intern_id(fn_def_id.0)
-    }
-}
-
-impl From<crate::db::InternedCallableDefId> for FnDefId {
-    fn from(callable_def_id: crate::db::InternedCallableDefId) -> Self {
-        chalk_ir::FnDefId(callable_def_id.as_intern_id())
-    }
-}
-
-impl From<OpaqueTyId> for crate::db::InternedOpaqueTyId {
-    fn from(id: OpaqueTyId) -> Self {
-        InternKey::from_intern_id(id.0)
-    }
-}
-
-impl From<crate::db::InternedOpaqueTyId> for OpaqueTyId {
-    fn from(id: crate::db::InternedOpaqueTyId) -> Self {
-        chalk_ir::OpaqueTyId(id.as_intern_id())
-    }
-}
-
-impl From<chalk_ir::ClosureId<Interner>> for crate::db::InternedClosureId {
-    fn from(id: chalk_ir::ClosureId<Interner>) -> Self {
-        Self::from_intern_id(id.0)
-    }
+pub(super) fn convert_where_clauses(
+    db: &dyn HirDatabase,
+    def: GenericDefId,
+    substs: &Substitution,
+) -> Vec<chalk_ir::QuantifiedWhereClause<Interner>> {
+    let generic_predicates = db.generic_predicates(def);
+    let mut result = Vec::with_capacity(generic_predicates.len());
+    for pred in generic_predicates.iter() {
+        result.push(pred.clone().substitute(&Interner, substs));
+    }
+    result
 }
 
-impl From<crate::db::InternedClosureId> for chalk_ir::ClosureId<Interner> {
-    fn from(id: crate::db::InternedClosureId) -> Self {
-        chalk_ir::ClosureId(id.as_intern_id())
+pub(super) fn generic_predicate_to_inline_bound(
+    db: &dyn HirDatabase,
+    pred: &QuantifiedWhereClause,
+    self_ty: &Ty,
+) -> Option<chalk_ir::Binders<rust_ir::InlineBound<Interner>>> {
+    // An InlineBound is like a GenericPredicate, except the self type is left out.
+    // We don't have a special type for this, but Chalk does.
+    let self_ty_shifted_in = self_ty.clone().shifted_in_from(&Interner, DebruijnIndex::ONE);
+    let (pred, binders) = pred.as_ref().into_value_and_skipped_binders();
+    match pred {
+        WhereClause::Implemented(trait_ref) => {
+            if trait_ref.self_type_parameter(&Interner) != self_ty_shifted_in {
+                // we can only convert predicates back to type bounds if they
+                // have the expected self type
+                return None;
+            }
+            let args_no_self = trait_ref.substitution.as_slice(&Interner)[1..]
+                .iter()
+                .map(|ty| ty.clone().cast(&Interner))
+                .collect();
+            let trait_bound = rust_ir::TraitBound { trait_id: trait_ref.trait_id, args_no_self };
+            Some(chalk_ir::Binders::new(binders, rust_ir::InlineBound::TraitBound(trait_bound)))
+        }
+        WhereClause::AliasEq(AliasEq { alias: AliasTy::Projection(projection_ty), ty }) => {
+            if projection_ty.self_type_parameter(&Interner) != self_ty_shifted_in {
+                return None;
+            }
+            let trait_ = projection_ty.trait_(db);
+            let args_no_self = projection_ty.substitution.as_slice(&Interner)[1..]
+                .iter()
+                .map(|ty| ty.clone().cast(&Interner))
+                .collect();
+            let alias_eq_bound = rust_ir::AliasEqBound {
+                value: ty.clone(),
+                trait_bound: rust_ir::TraitBound {
+                    trait_id: to_chalk_trait_id(trait_),
+                    args_no_self,
+                },
+                associated_ty_id: projection_ty.associated_ty_id,
+                parameters: Vec::new(), // FIXME we don't support generic associated types yet
+            };
+            Some(chalk_ir::Binders::new(
+                binders,
+                rust_ir::InlineBound::AliasEqBound(alias_eq_bound),
+            ))
+        }
+        _ => None,
     }
 }
-
-fn wrap_in_empty_binders<T: crate::TypeWalk>(value: T) -> crate::Binders<T> {
-    crate::Binders::wrap_empty(value)
-}
diff --git a/crates/hir_ty/src/chalk_ext.rs b/crates/hir_ty/src/chalk_ext.rs
new file mode 100644
index 000000000..8c4542956
--- /dev/null
+++ b/crates/hir_ty/src/chalk_ext.rs
@@ -0,0 +1,305 @@
+//! Various extensions traits for Chalk types.
+
+use chalk_ir::Mutability;
+use hir_def::{
+    type_ref::Rawness, AssocContainerId, FunctionId, GenericDefId, HasModule, Lookup, TraitId,
+};
+
+use crate::{
+    db::HirDatabase, from_assoc_type_id, from_chalk_trait_id, from_foreign_def_id,
+    from_placeholder_idx, to_chalk_trait_id, AdtId, AliasEq, AliasTy, Binders, CallableDefId,
+    CallableSig, FnPointer, ImplTraitId, Interner, Lifetime, ProjectionTy, QuantifiedWhereClause,
+    Substitution, TraitRef, Ty, TyBuilder, TyKind, WhereClause,
+};
+
+pub trait TyExt {
+    fn is_unit(&self) -> bool;
+    fn is_never(&self) -> bool;
+    fn is_unknown(&self) -> bool;
+
+    fn as_adt(&self) -> Option<(hir_def::AdtId, &Substitution)>;
+    fn as_tuple(&self) -> Option<&Substitution>;
+    fn as_fn_def(&self, db: &dyn HirDatabase) -> Option<FunctionId>;
+    fn as_reference(&self) -> Option<(&Ty, Lifetime, Mutability)>;
+    fn as_reference_or_ptr(&self) -> Option<(&Ty, Rawness, Mutability)>;
+    fn as_generic_def(&self, db: &dyn HirDatabase) -> Option<GenericDefId>;
+
+    fn callable_def(&self, db: &dyn HirDatabase) -> Option<CallableDefId>;
+    fn callable_sig(&self, db: &dyn HirDatabase) -> Option<CallableSig>;
+
+    fn strip_references(&self) -> &Ty;
+
+    /// If this is a `dyn Trait`, returns that trait.
+    fn dyn_trait(&self) -> Option<TraitId>;
+
+    fn impl_trait_bounds(&self, db: &dyn HirDatabase) -> Option<Vec<QuantifiedWhereClause>>;
+    fn associated_type_parent_trait(&self, db: &dyn HirDatabase) -> Option<TraitId>;
+
+    /// FIXME: Get rid of this, it's not a good abstraction
+    fn equals_ctor(&self, other: &Ty) -> bool;
+}
+
+impl TyExt for Ty {
+    fn is_unit(&self) -> bool {
+        matches!(self.kind(&Interner), TyKind::Tuple(0, _))
+    }
+
+    fn is_never(&self) -> bool {
+        matches!(self.kind(&Interner), TyKind::Never)
+    }
+
+    fn is_unknown(&self) -> bool {
+        matches!(self.kind(&Interner), TyKind::Error)
+    }
+
+    fn as_adt(&self) -> Option<(hir_def::AdtId, &Substitution)> {
+        match self.kind(&Interner) {
+            TyKind::Adt(AdtId(adt), parameters) => Some((*adt, parameters)),
+            _ => None,
+        }
+    }
+
+    fn as_tuple(&self) -> Option<&Substitution> {
+        match self.kind(&Interner) {
+            TyKind::Tuple(_, substs) => Some(substs),
+            _ => None,
+        }
+    }
+
+    fn as_fn_def(&self, db: &dyn HirDatabase) -> Option<FunctionId> {
+        if let Some(CallableDefId::FunctionId(func)) = self.callable_def(db) {
+            Some(func)
+        } else {
+            None
+        }
+    }
+    fn as_reference(&self) -> Option<(&Ty, Lifetime, Mutability)> {
+        match self.kind(&Interner) {
+            TyKind::Ref(mutability, lifetime, ty) => Some((ty, lifetime.clone(), *mutability)),
+            _ => None,
+        }
+    }
+
+    fn as_reference_or_ptr(&self) -> Option<(&Ty, Rawness, Mutability)> {
+        match self.kind(&Interner) {
+            TyKind::Ref(mutability, _, ty) => Some((ty, Rawness::Ref, *mutability)),
+            TyKind::Raw(mutability, ty) => Some((ty, Rawness::RawPtr, *mutability)),
+            _ => None,
+        }
+    }
+
+    fn as_generic_def(&self, db: &dyn HirDatabase) -> Option<GenericDefId> {
+        match *self.kind(&Interner) {
+            TyKind::Adt(AdtId(adt), ..) => Some(adt.into()),
+            TyKind::FnDef(callable, ..) => {
+                Some(db.lookup_intern_callable_def(callable.into()).into())
+            }
+            TyKind::AssociatedType(type_alias, ..) => Some(from_assoc_type_id(type_alias).into()),
+            TyKind::Foreign(type_alias, ..) => Some(from_foreign_def_id(type_alias).into()),
+            _ => None,
+        }
+    }
+
+    fn callable_def(&self, db: &dyn HirDatabase) -> Option<CallableDefId> {
+        match self.kind(&Interner) {
+            &TyKind::FnDef(def, ..) => Some(db.lookup_intern_callable_def(def.into())),
+            _ => None,
+        }
+    }
+
+    fn callable_sig(&self, db: &dyn HirDatabase) -> Option<CallableSig> {
+        match self.kind(&Interner) {
+            TyKind::Function(fn_ptr) => Some(CallableSig::from_fn_ptr(fn_ptr)),
+            TyKind::FnDef(def, parameters) => {
+                let callable_def = db.lookup_intern_callable_def((*def).into());
+                let sig = db.callable_item_signature(callable_def);
+                Some(sig.substitute(&Interner, &parameters))
+            }
+            TyKind::Closure(.., substs) => {
+                let sig_param = substs.at(&Interner, 0).assert_ty_ref(&Interner);
+                sig_param.callable_sig(db)
+            }
+            _ => None,
+        }
+    }
+
+    fn dyn_trait(&self) -> Option<TraitId> {
+        let trait_ref = match self.kind(&Interner) {
+            TyKind::Dyn(dyn_ty) => dyn_ty.bounds.skip_binders().interned().get(0).and_then(|b| {
+                match b.skip_binders() {
+                    WhereClause::Implemented(trait_ref) => Some(trait_ref),
+                    _ => None,
+                }
+            }),
+            _ => None,
+        }?;
+        Some(from_chalk_trait_id(trait_ref.trait_id))
+    }
+
+    fn strip_references(&self) -> &Ty {
+        let mut t: &Ty = self;
+        while let TyKind::Ref(_mutability, _lifetime, ty) = t.kind(&Interner) {
+            t = ty;
+        }
+        t
+    }
+
+    fn impl_trait_bounds(&self, db: &dyn HirDatabase) -> Option<Vec<QuantifiedWhereClause>> {
+        match self.kind(&Interner) {
+            TyKind::OpaqueType(opaque_ty_id, ..) => {
+                match db.lookup_intern_impl_trait_id((*opaque_ty_id).into()) {
+                    ImplTraitId::AsyncBlockTypeImplTrait(def, _expr) => {
+                        let krate = def.module(db.upcast()).krate();
+                        if let Some(future_trait) = db
+                            .lang_item(krate, "future_trait".into())
+                            .and_then(|item| item.as_trait())
+                        {
+                            // This is only used by type walking.
+                            // Parameters will be walked outside, and projection predicate is not used.
+                            // So just provide the Future trait.
+                            let impl_bound = Binders::empty(
+                                &Interner,
+                                WhereClause::Implemented(TraitRef {
+                                    trait_id: to_chalk_trait_id(future_trait),
+                                    substitution: Substitution::empty(&Interner),
+                                }),
+                            );
+                            Some(vec![impl_bound])
+                        } else {
+                            None
+                        }
+                    }
+                    ImplTraitId::ReturnTypeImplTrait(..) => None,
+                }
+            }
+            TyKind::Alias(AliasTy::Opaque(opaque_ty)) => {
+                let predicates = match db.lookup_intern_impl_trait_id(opaque_ty.opaque_ty_id.into())
+                {
+                    ImplTraitId::ReturnTypeImplTrait(func, idx) => {
+                        db.return_type_impl_traits(func).map(|it| {
+                            let data = (*it)
+                                .as_ref()
+                                .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
+                            data.substitute(&Interner, &opaque_ty.substitution)
+                        })
+                    }
+                    // It always has an parameter for Future::Output type.
+                    ImplTraitId::AsyncBlockTypeImplTrait(..) => unreachable!(),
+                };
+
+                predicates.map(|it| it.into_value_and_skipped_binders().0)
+            }
+            TyKind::Placeholder(idx) => {
+                let id = from_placeholder_idx(db, *idx);
+                let generic_params = db.generic_params(id.parent);
+                let param_data = &generic_params.types[id.local_id];
+                match param_data.provenance {
+                    hir_def::generics::TypeParamProvenance::ArgumentImplTrait => {
+                        let substs = TyBuilder::type_params_subst(db, id.parent);
+                        let predicates = db
+                            .generic_predicates(id.parent)
+                            .into_iter()
+                            .map(|pred| pred.clone().substitute(&Interner, &substs))
+                            .filter(|wc| match &wc.skip_binders() {
+                                WhereClause::Implemented(tr) => {
+                                    &tr.self_type_parameter(&Interner) == self
+                                }
+                                WhereClause::AliasEq(AliasEq {
+                                    alias: AliasTy::Projection(proj),
+                                    ty: _,
+                                }) => &proj.self_type_parameter(&Interner) == self,
+                                _ => false,
+                            })
+                            .collect::<Vec<_>>();
+
+                        Some(predicates)
+                    }
+                    _ => None,
+                }
+            }
+            _ => None,
+        }
+    }
+
+    fn associated_type_parent_trait(&self, db: &dyn HirDatabase) -> Option<TraitId> {
+        match self.kind(&Interner) {
+            TyKind::AssociatedType(id, ..) => {
+                match from_assoc_type_id(*id).lookup(db.upcast()).container {
+                    AssocContainerId::TraitId(trait_id) => Some(trait_id),
+                    _ => None,
+                }
+            }
+            TyKind::Alias(AliasTy::Projection(projection_ty)) => {
+                match from_assoc_type_id(projection_ty.associated_ty_id)
+                    .lookup(db.upcast())
+                    .container
+                {
+                    AssocContainerId::TraitId(trait_id) => Some(trait_id),
+                    _ => None,
+                }
+            }
+            _ => None,
+        }
+    }
+
+    fn equals_ctor(&self, other: &Ty) -> bool {
+        match (self.kind(&Interner), other.kind(&Interner)) {
+            (TyKind::Adt(adt, ..), TyKind::Adt(adt2, ..)) => adt == adt2,
+            (TyKind::Slice(_), TyKind::Slice(_)) | (TyKind::Array(_, _), TyKind::Array(_, _)) => {
+                true
+            }
+            (TyKind::FnDef(def_id, ..), TyKind::FnDef(def_id2, ..)) => def_id == def_id2,
+            (TyKind::OpaqueType(ty_id, ..), TyKind::OpaqueType(ty_id2, ..)) => ty_id == ty_id2,
+            (TyKind::AssociatedType(ty_id, ..), TyKind::AssociatedType(ty_id2, ..)) => {
+                ty_id == ty_id2
+            }
+            (TyKind::Foreign(ty_id, ..), TyKind::Foreign(ty_id2, ..)) => ty_id == ty_id2,
+            (TyKind::Closure(id1, _), TyKind::Closure(id2, _)) => id1 == id2,
+            (TyKind::Ref(mutability, ..), TyKind::Ref(mutability2, ..))
+            | (TyKind::Raw(mutability, ..), TyKind::Raw(mutability2, ..)) => {
+                mutability == mutability2
+            }
+            (
+                TyKind::Function(FnPointer { num_binders, sig, .. }),
+                TyKind::Function(FnPointer { num_binders: num_binders2, sig: sig2, .. }),
+            ) => num_binders == num_binders2 && sig == sig2,
+            (TyKind::Tuple(cardinality, _), TyKind::Tuple(cardinality2, _)) => {
+                cardinality == cardinality2
+            }
+            (TyKind::Str, TyKind::Str) | (TyKind::Never, TyKind::Never) => true,
+            (TyKind::Scalar(scalar), TyKind::Scalar(scalar2)) => scalar == scalar2,
+            _ => false,
+        }
+    }
+}
+
+pub trait ProjectionTyExt {
+    fn trait_ref(&self, db: &dyn HirDatabase) -> TraitRef;
+    fn trait_(&self, db: &dyn HirDatabase) -> TraitId;
+}
+
+impl ProjectionTyExt for ProjectionTy {
+    fn trait_ref(&self, db: &dyn HirDatabase) -> TraitRef {
+        TraitRef {
+            trait_id: to_chalk_trait_id(self.trait_(db)),
+            substitution: self.substitution.clone(),
+        }
+    }
+
+    fn trait_(&self, db: &dyn HirDatabase) -> TraitId {
+        match from_assoc_type_id(self.associated_ty_id).lookup(db.upcast()).container {
+            AssocContainerId::TraitId(it) => it,
+            _ => panic!("projection ty without parent trait"),
+        }
+    }
+}
+
+pub trait TraitRefExt {
+    fn hir_trait_id(&self) -> TraitId;
+}
+
+impl TraitRefExt for TraitRef {
+    fn hir_trait_id(&self) -> TraitId {
+        from_chalk_trait_id(self.trait_id)
+    }
+}
diff --git a/crates/hir_ty/src/db.rs b/crates/hir_ty/src/db.rs
index 58e4247c6..cf67d4266 100644
--- a/crates/hir_ty/src/db.rs
+++ b/crates/hir_ty/src/db.rs
@@ -1,18 +1,19 @@
-//! FIXME: write short doc here
+//! The home of `HirDatabase`, which is the Salsa database containing all the
+//! type inference-related queries.
 
 use std::sync::Arc;
 
 use base_db::{impl_intern_key, salsa, CrateId, Upcast};
 use hir_def::{
     db::DefDatabase, expr::ExprId, ConstParamId, DefWithBodyId, FunctionId, GenericDefId, ImplId,
-    LocalFieldId, TypeParamId, VariantId,
+    LifetimeParamId, LocalFieldId, TypeParamId, VariantId,
 };
 use la_arena::ArenaMap;
 
 use crate::{
+    chalk_db,
     method_resolution::{InherentImpls, TraitImpls},
-    traits::chalk,
-    Binders, CallableDefId, FnDefId, ImplTraitId, InferenceResult, PolyFnSig,
+    Binders, CallableDefId, FnDefId, ImplTraitId, InferenceResult, Interner, PolyFnSig,
     QuantifiedWhereClause, ReturnTypeImplTraits, TraitRef, Ty, TyDefId, ValueTyDefId,
 };
 use hir_expand::name::Name;
@@ -86,51 +87,68 @@ pub trait HirDatabase: DefDatabase + Upcast<dyn DefDatabase> {
     #[salsa::interned]
     fn intern_type_param_id(&self, param_id: TypeParamId) -> InternedTypeParamId;
     #[salsa::interned]
+    fn intern_lifetime_param_id(&self, param_id: LifetimeParamId) -> InternedLifetimeParamId;
+    #[salsa::interned]
+    fn intern_const_param_id(&self, param_id: ConstParamId) -> InternedConstParamId;
+    #[salsa::interned]
     fn intern_impl_trait_id(&self, id: ImplTraitId) -> InternedOpaqueTyId;
     #[salsa::interned]
     fn intern_closure(&self, id: (DefWithBodyId, ExprId)) -> InternedClosureId;
 
-    #[salsa::invoke(chalk::associated_ty_data_query)]
-    fn associated_ty_data(&self, id: chalk::AssocTypeId) -> Arc<chalk::AssociatedTyDatum>;
+    #[salsa::invoke(chalk_db::associated_ty_data_query)]
+    fn associated_ty_data(&self, id: chalk_db::AssocTypeId) -> Arc<chalk_db::AssociatedTyDatum>;
 
-    #[salsa::invoke(chalk::trait_datum_query)]
-    fn trait_datum(&self, krate: CrateId, trait_id: chalk::TraitId) -> Arc<chalk::TraitDatum>;
+    #[salsa::invoke(chalk_db::trait_datum_query)]
+    fn trait_datum(&self, krate: CrateId, trait_id: chalk_db::TraitId)
+        -> Arc<chalk_db::TraitDatum>;
 
-    #[salsa::invoke(chalk::struct_datum_query)]
-    fn struct_datum(&self, krate: CrateId, struct_id: chalk::AdtId) -> Arc<chalk::StructDatum>;
+    #[salsa::invoke(chalk_db::struct_datum_query)]
+    fn struct_datum(
+        &self,
+        krate: CrateId,
+        struct_id: chalk_db::AdtId,
+    ) -> Arc<chalk_db::StructDatum>;
 
-    #[salsa::invoke(crate::traits::chalk::impl_datum_query)]
-    fn impl_datum(&self, krate: CrateId, impl_id: chalk::ImplId) -> Arc<chalk::ImplDatum>;
+    #[salsa::invoke(chalk_db::impl_datum_query)]
+    fn impl_datum(&self, krate: CrateId, impl_id: chalk_db::ImplId) -> Arc<chalk_db::ImplDatum>;
 
-    #[salsa::invoke(crate::traits::chalk::fn_def_datum_query)]
-    fn fn_def_datum(&self, krate: CrateId, fn_def_id: FnDefId) -> Arc<chalk::FnDefDatum>;
+    #[salsa::invoke(chalk_db::fn_def_datum_query)]
+    fn fn_def_datum(&self, krate: CrateId, fn_def_id: FnDefId) -> Arc<chalk_db::FnDefDatum>;
 
-    #[salsa::invoke(crate::traits::chalk::fn_def_variance_query)]
-    fn fn_def_variance(&self, krate: CrateId, fn_def_id: FnDefId) -> chalk::Variances;
+    #[salsa::invoke(chalk_db::fn_def_variance_query)]
+    fn fn_def_variance(&self, krate: CrateId, fn_def_id: FnDefId) -> chalk_db::Variances;
 
-    #[salsa::invoke(crate::traits::chalk::adt_variance_query)]
-    fn adt_variance(&self, krate: CrateId, adt_id: chalk::AdtId) -> chalk::Variances;
+    #[salsa::invoke(chalk_db::adt_variance_query)]
+    fn adt_variance(&self, krate: CrateId, adt_id: chalk_db::AdtId) -> chalk_db::Variances;
 
-    #[salsa::invoke(crate::traits::chalk::associated_ty_value_query)]
+    #[salsa::invoke(chalk_db::associated_ty_value_query)]
     fn associated_ty_value(
         &self,
         krate: CrateId,
-        id: chalk::AssociatedTyValueId,
-    ) -> Arc<chalk::AssociatedTyValue>;
+        id: chalk_db::AssociatedTyValueId,
+    ) -> Arc<chalk_db::AssociatedTyValue>;
 
-    #[salsa::invoke(crate::traits::trait_solve_query)]
+    #[salsa::invoke(trait_solve_wait)]
+    #[salsa::transparent]
     fn trait_solve(
         &self,
         krate: CrateId,
         goal: crate::Canonical<crate::InEnvironment<crate::DomainGoal>>,
-    ) -> Option<crate::traits::Solution>;
+    ) -> Option<crate::Solution>;
 
-    #[salsa::invoke(crate::traits::chalk::program_clauses_for_chalk_env_query)]
+    #[salsa::invoke(crate::traits::trait_solve_query)]
+    fn trait_solve_query(
+        &self,
+        krate: CrateId,
+        goal: crate::Canonical<crate::InEnvironment<crate::DomainGoal>>,
+    ) -> Option<crate::Solution>;
+
+    #[salsa::invoke(chalk_db::program_clauses_for_chalk_env_query)]
     fn program_clauses_for_chalk_env(
         &self,
         krate: CrateId,
-        env: chalk_ir::Environment<chalk::Interner>,
-    ) -> chalk_ir::ProgramClauses<chalk::Interner>;
+        env: chalk_ir::Environment<Interner>,
+    ) -> chalk_ir::ProgramClauses<Interner>;
 }
 
 fn infer_wait(db: &dyn HirDatabase, def: DefWithBodyId) -> Arc<InferenceResult> {
@@ -146,6 +164,15 @@ fn infer_wait(db: &dyn HirDatabase, def: DefWithBodyId) -> Arc<InferenceResult>
     db.infer_query(def)
 }
 
+fn trait_solve_wait(
+    db: &dyn HirDatabase,
+    krate: CrateId,
+    goal: crate::Canonical<crate::InEnvironment<crate::DomainGoal>>,
+) -> Option<crate::Solution> {
+    let _p = profile::span("trait_solve::wait");
+    db.trait_solve_query(krate, goal)
+}
+
 #[test]
 fn hir_database_is_object_safe() {
     fn _assert_object_safe(_: &dyn HirDatabase) {}
@@ -156,6 +183,14 @@ pub struct InternedTypeParamId(salsa::InternId);
 impl_intern_key!(InternedTypeParamId);
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct InternedLifetimeParamId(salsa::InternId);
+impl_intern_key!(InternedLifetimeParamId);
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct InternedConstParamId(salsa::InternId);
+impl_intern_key!(InternedConstParamId);
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub struct InternedOpaqueTyId(salsa::InternId);
 impl_intern_key!(InternedOpaqueTyId);
 
diff --git a/crates/hir_ty/src/diagnostics.rs b/crates/hir_ty/src/diagnostics.rs
index 86f937e1d..84fc8ce14 100644
--- a/crates/hir_ty/src/diagnostics.rs
+++ b/crates/hir_ty/src/diagnostics.rs
@@ -1,4 +1,4 @@
-//! FIXME: write short doc here
+//! Type inference-based diagnostics.
 mod expr;
 mod match_check;
 mod unsafe_check;
diff --git a/crates/hir_ty/src/diagnostics/decl_check.rs b/crates/hir_ty/src/diagnostics/decl_check.rs
index 33a0f4d7d..075dc4131 100644
--- a/crates/hir_ty/src/diagnostics/decl_check.rs
+++ b/crates/hir_ty/src/diagnostics/decl_check.rs
@@ -35,6 +35,8 @@ use crate::{
 };
 
 mod allow {
+    pub(super) const BAD_STYLE: &str = "bad_style";
+    pub(super) const NONSTANDARD_STYLE: &str = "nonstandard_style";
     pub(super) const NON_SNAKE_CASE: &str = "non_snake_case";
     pub(super) const NON_UPPER_CASE_GLOBAL: &str = "non_upper_case_globals";
     pub(super) const NON_CAMEL_CASE_TYPES: &str = "non_camel_case_types";
@@ -83,15 +85,44 @@ impl<'a, 'b> DeclValidator<'a, 'b> {
     }
 
     /// Checks whether not following the convention is allowed for this item.
-    ///
-    /// Currently this method doesn't check parent attributes.
-    fn allowed(&self, id: AttrDefId, allow_name: &str) -> bool {
-        self.db.attrs(id).by_key("allow").tt_values().any(|tt| tt.to_string().contains(allow_name))
+    fn allowed(&self, id: AttrDefId, allow_name: &str, recursing: bool) -> bool {
+        let is_allowed = |def_id| {
+            let attrs = self.db.attrs(def_id);
+            // don't bug the user about directly no_mangle annotated stuff, they can't do anything about it
+            (!recursing && attrs.by_key("no_mangle").exists())
+                || attrs.by_key("allow").tt_values().any(|tt| {
+                    let allows = tt.to_string();
+                    allows.contains(allow_name)
+                        || allows.contains(allow::BAD_STYLE)
+                        || allows.contains(allow::NONSTANDARD_STYLE)
+                })
+        };
+
+        is_allowed(id)
+            // go upwards one step or give up
+            || match id {
+                AttrDefId::ModuleId(m) => m.containing_module(self.db.upcast()).map(|v| v.into()),
+                AttrDefId::FunctionId(f) => Some(f.lookup(self.db.upcast()).container.into()),
+                AttrDefId::StaticId(sid) => Some(sid.lookup(self.db.upcast()).container.into()),
+                AttrDefId::ConstId(cid) => Some(cid.lookup(self.db.upcast()).container.into()),
+                AttrDefId::TraitId(tid) => Some(tid.lookup(self.db.upcast()).container.into()),
+                AttrDefId::ImplId(iid) => Some(iid.lookup(self.db.upcast()).container.into()),
+                // These warnings should not explore macro definitions at all
+                AttrDefId::MacroDefId(_) => None,
+                // Will never occur under an enum/struct/union/type alias
+                AttrDefId::AdtId(_) => None,
+                AttrDefId::FieldId(_) => None,
+                AttrDefId::EnumVariantId(_) => None,
+                AttrDefId::TypeAliasId(_) => None,
+                AttrDefId::GenericParamId(_) => None,
+            }
+            .map(|mid| self.allowed(mid, allow_name, true))
+            .unwrap_or(false)
     }
 
     fn validate_func(&mut self, func: FunctionId) {
         let data = self.db.function_data(func);
-        if data.is_in_extern_block {
+        if data.is_in_extern_block() {
             cov_mark::hit!(extern_func_incorrect_case_ignored);
             return;
         }
@@ -99,8 +130,7 @@ impl<'a, 'b> DeclValidator<'a, 'b> {
         let body = self.db.body(func.into());
 
         // Recursively validate inner scope items, such as static variables and constants.
-        let db = self.db;
-        for block_def_map in body.block_scopes.iter().filter_map(|block| db.block_def_map(*block)) {
+        for (_, block_def_map) in body.blocks(self.db.upcast()) {
             for (_, module) in block_def_map.modules() {
                 for def_id in module.scope.declarations() {
                     let mut validator = DeclValidator::new(self.db, self.krate, self.sink);
@@ -110,7 +140,7 @@ impl<'a, 'b> DeclValidator<'a, 'b> {
         }
 
         // Check whether non-snake case identifiers are allowed for this function.
-        if self.allowed(func.into(), allow::NON_SNAKE_CASE) {
+        if self.allowed(func.into(), allow::NON_SNAKE_CASE, false) {
             return;
         }
 
@@ -329,8 +359,9 @@ impl<'a, 'b> DeclValidator<'a, 'b> {
     fn validate_struct(&mut self, struct_id: StructId) {
         let data = self.db.struct_data(struct_id);
 
-        let non_camel_case_allowed = self.allowed(struct_id.into(), allow::NON_CAMEL_CASE_TYPES);
-        let non_snake_case_allowed = self.allowed(struct_id.into(), allow::NON_SNAKE_CASE);
+        let non_camel_case_allowed =
+            self.allowed(struct_id.into(), allow::NON_CAMEL_CASE_TYPES, false);
+        let non_snake_case_allowed = self.allowed(struct_id.into(), allow::NON_SNAKE_CASE, false);
 
         // Check the structure name.
         let struct_name = data.name.to_string();
@@ -462,7 +493,7 @@ impl<'a, 'b> DeclValidator<'a, 'b> {
         let data = self.db.enum_data(enum_id);
 
         // Check whether non-camel case names are allowed for this enum.
-        if self.allowed(enum_id.into(), allow::NON_CAMEL_CASE_TYPES) {
+        if self.allowed(enum_id.into(), allow::NON_CAMEL_CASE_TYPES, false) {
             return;
         }
 
@@ -585,7 +616,7 @@ impl<'a, 'b> DeclValidator<'a, 'b> {
     fn validate_const(&mut self, const_id: ConstId) {
         let data = self.db.const_data(const_id);
 
-        if self.allowed(const_id.into(), allow::NON_UPPER_CASE_GLOBAL) {
+        if self.allowed(const_id.into(), allow::NON_UPPER_CASE_GLOBAL, false) {
             return;
         }
 
@@ -633,7 +664,7 @@ impl<'a, 'b> DeclValidator<'a, 'b> {
             return;
         }
 
-        if self.allowed(static_id.into(), allow::NON_UPPER_CASE_GLOBAL) {
+        if self.allowed(static_id.into(), allow::NON_UPPER_CASE_GLOBAL, false) {
             return;
         }
 
@@ -868,23 +899,116 @@ fn main() {
     fn allow_attributes() {
         check_diagnostics(
             r#"
-            #[allow(non_snake_case)]
-    fn NonSnakeCaseName(SOME_VAR: u8) -> u8{
-        let OtherVar = SOME_VAR + 1;
-        OtherVar
+#[allow(non_snake_case)]
+fn NonSnakeCaseName(SOME_VAR: u8) -> u8{
+    // cov_flags generated output from elsewhere in this file
+    extern "C" {
+        #[no_mangle]
+        static lower_case: u8;
     }
 
-    #[allow(non_snake_case, non_camel_case_types)]
-    pub struct some_type {
-        SOME_FIELD: u8,
-        SomeField: u16,
+    let OtherVar = SOME_VAR + 1;
+    OtherVar
+}
+
+#[allow(nonstandard_style)]
+mod CheckNonstandardStyle {
+    fn HiImABadFnName() {}
+}
+
+#[allow(bad_style)]
+mod CheckBadStyle {
+    fn HiImABadFnName() {}
+}
+
+mod F {
+    #![allow(non_snake_case)]
+    fn CheckItWorksWithModAttr(BAD_NAME_HI: u8) {}
+}
+
+#[allow(non_snake_case, non_camel_case_types)]
+pub struct some_type {
+    SOME_FIELD: u8,
+    SomeField: u16,
+}
+
+#[allow(non_upper_case_globals)]
+pub const some_const: u8 = 10;
+
+#[allow(non_upper_case_globals)]
+pub static SomeStatic: u8 = 10;
+    "#,
+        );
     }
 
-    #[allow(non_upper_case_globals)]
-    pub const some_const: u8 = 10;
+    #[test]
+    fn allow_attributes_crate_attr() {
+        check_diagnostics(
+            r#"
+#![allow(non_snake_case)]
 
-    #[allow(non_upper_case_globals)]
-    pub static SomeStatic: u8 = 10;
+mod F {
+    fn CheckItWorksWithCrateAttr(BAD_NAME_HI: u8) {}
+}
+    "#,
+        );
+    }
+
+    #[test]
+    #[ignore]
+    fn bug_trait_inside_fn() {
+        // FIXME:
+        // This is broken, and in fact, should not even be looked at by this
+        // lint in the first place. There's weird stuff going on in the
+        // collection phase.
+        // It's currently being brought in by:
+        // * validate_func on `a` recursing into modules
+        // * then it finds the trait and then the function while iterating
+        //   through modules
+        // * then validate_func is called on Dirty
+        // * ... which then proceeds to look at some unknown module taking no
+        //   attrs from either the impl or the fn a, and then finally to the root
+        //   module
+        //
+        // It should find the attribute on the trait, but it *doesn't even see
+        // the trait* as far as I can tell.
+
+        check_diagnostics(
+            r#"
+trait T { fn a(); }
+struct U {}
+impl T for U {
+    fn a() {
+        // this comes out of bitflags, mostly
+        #[allow(non_snake_case)]
+        trait __BitFlags {
+            const HiImAlsoBad: u8 = 2;
+            #[inline]
+            fn Dirty(&self) -> bool {
+                false
+            }
+        }
+
+    }
+}
+    "#,
+        );
+    }
+
+    #[test]
+    #[ignore]
+    fn bug_traits_arent_checked() {
+        // FIXME: Traits and functions in traits aren't currently checked by
+        // r-a, even though rustc will complain about them.
+        check_diagnostics(
+            r#"
+trait BAD_TRAIT {
+    // ^^^^^^^^^ Trait `BAD_TRAIT` should have CamelCase name, e.g. `BadTrait`
+    fn BAD_FUNCTION();
+    // ^^^^^^^^^^^^ Function `BAD_FUNCTION` should have snake_case name, e.g. `bad_function`
+    fn BadFunction();
+    // ^^^^^^^^^^^^ Function `BadFunction` should have snake_case name, e.g. `bad_function`
+}
     "#,
         );
     }
diff --git a/crates/hir_ty/src/diagnostics/expr.rs b/crates/hir_ty/src/diagnostics/expr.rs
index 3909ad354..79602c3dd 100644
--- a/crates/hir_ty/src/diagnostics/expr.rs
+++ b/crates/hir_ty/src/diagnostics/expr.rs
@@ -14,8 +14,7 @@ use crate::{
         MismatchedArgCount, MissingFields, MissingMatchArms, MissingOkOrSomeInTailExpr,
         MissingPatFields, RemoveThisSemicolon,
     },
-    utils::variant_data,
-    AdtId, InferenceResult, Interner, Ty, TyKind,
+    AdtId, InferenceResult, Interner, TyExt, TyKind,
 };
 
 pub(crate) use hir_def::{
@@ -104,7 +103,7 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
             let root = source_ptr.file_syntax(db.upcast());
             if let ast::Expr::RecordExpr(record_expr) = &source_ptr.value.to_node(&root) {
                 if let Some(_) = record_expr.record_expr_field_list() {
-                    let variant_data = variant_data(db.upcast(), variant_def);
+                    let variant_data = variant_def.variant_data(db.upcast());
                     let missed_fields = missed_fields
                         .into_iter()
                         .map(|idx| variant_data.fields()[idx].name.clone())
@@ -135,7 +134,7 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
                 let root = source_ptr.file_syntax(db.upcast());
                 if let ast::Pat::RecordPat(record_pat) = expr.to_node(&root) {
                     if let Some(_) = record_pat.record_pat_field_list() {
-                        let variant_data = variant_data(db.upcast(), variant_def);
+                        let variant_data = variant_def.variant_data(db.upcast());
                         let missed_fields = missed_fields
                             .into_iter()
                             .map(|idx| variant_data.fields()[idx].name.clone())
@@ -245,7 +244,8 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
                     Some(callee) => callee,
                     None => return,
                 };
-                let sig = db.callable_item_signature(callee.into()).value;
+                let sig =
+                    db.callable_item_signature(callee.into()).into_value_and_skipped_binders().0;
 
                 (sig, args)
             }
@@ -314,7 +314,7 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
                 if pat_ty == match_expr_ty
                     || match_expr_ty
                         .as_reference()
-                        .map(|(match_expr_ty, _)| match_expr_ty == pat_ty)
+                        .map(|(match_expr_ty, ..)| match_expr_ty == pat_ty)
                         .unwrap_or(false)
                 {
                     // If we had a NotUsefulMatchArm diagnostic, we could
@@ -378,7 +378,7 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
             _ => return,
         };
 
-        let (params, required) = match mismatch.expected.interned(&Interner) {
+        let (params, required) = match mismatch.expected.kind(&Interner) {
             TyKind::Adt(AdtId(hir_def::AdtId::EnumId(enum_id)), ref parameters)
                 if *enum_id == core_result_enum =>
             {
@@ -392,7 +392,9 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
             _ => return,
         };
 
-        if params.len() > 0 && params[0] == mismatch.actual {
+        if params.len(&Interner) > 0
+            && params.at(&Interner, 0).ty(&Interner) == Some(&mismatch.actual)
+        {
             let (_, source_map) = db.body_with_source_map(self.owner);
 
             if let Ok(source_ptr) = source_map.expr_syntax(id) {
@@ -421,7 +423,7 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
             None => return,
         };
 
-        if mismatch.actual != Ty::unit() || mismatch.expected != *possible_tail_ty {
+        if !mismatch.actual.is_unit() || mismatch.expected != *possible_tail_ty {
             return;
         }
 
@@ -450,7 +452,7 @@ pub fn record_literal_missing_fields(
         return None;
     }
 
-    let variant_data = variant_data(db.upcast(), variant_def);
+    let variant_data = variant_def.variant_data(db.upcast());
 
     let specified_fields: FxHashSet<_> = fields.iter().map(|f| &f.name).collect();
     let missed_fields: Vec<LocalFieldId> = variant_data
@@ -480,7 +482,7 @@ pub fn record_pattern_missing_fields(
         return None;
     }
 
-    let variant_data = variant_data(db.upcast(), variant_def);
+    let variant_data = variant_def.variant_data(db.upcast());
 
     let specified_fields: FxHashSet<_> = fields.iter().map(|f| &f.name).collect();
     let missed_fields: Vec<LocalFieldId> = variant_data
diff --git a/crates/hir_ty/src/diagnostics/match_check.rs b/crates/hir_ty/src/diagnostics/match_check.rs
index 5a5cdcbf3..e9762622f 100644
--- a/crates/hir_ty/src/diagnostics/match_check.rs
+++ b/crates/hir_ty/src/diagnostics/match_check.rs
@@ -227,7 +227,7 @@ use hir_def::{
 use la_arena::Idx;
 use smallvec::{smallvec, SmallVec};
 
-use crate::{db::HirDatabase, AdtId, InferenceResult, Interner, TyKind};
+use crate::{db::HirDatabase, AdtId, InferenceResult, Interner, TyExt, TyKind};
 
 #[derive(Debug, Clone, Copy)]
 /// Either a pattern from the source code being analyzed, represented as
@@ -539,7 +539,7 @@ impl Matrix {
         if let Some(Pat::Or(pat_ids)) = row.get_head().map(|pat_id| pat_id.as_pat(cx)) {
             // Or patterns are expanded here
             for pat_id in pat_ids {
-                self.0.push(PatStack::from_pattern(pat_id));
+                self.0.push(row.replace_head_with([pat_id].iter()));
             }
         } else {
             self.0.push(row);
@@ -626,7 +626,7 @@ pub(super) fn is_useful(
     // - enum with no variants
     // - `!` type
     // In those cases, no match arm is useful.
-    match cx.infer[cx.match_expr].strip_references().interned(&Interner) {
+    match cx.infer[cx.match_expr].strip_references().kind(&Interner) {
         TyKind::Adt(AdtId(hir_def::AdtId::EnumId(enum_id)), ..) => {
             if cx.db.enum_data(*enum_id).variants.is_empty() {
                 return Ok(Usefulness::NotUseful);
@@ -792,7 +792,10 @@ fn pat_constructor(cx: &MatchCheckCtx, pat: PatIdOrWild) -> MatchCheckResult<Opt
         Pat::Tuple { .. } => {
             let pat_id = pat.as_id().expect("we already know this pattern is not a wild");
             Some(Constructor::Tuple {
-                arity: cx.infer.type_of_pat[pat_id].as_tuple().ok_or(MatchCheckErr::Unknown)?.len(),
+                arity: cx.infer.type_of_pat[pat_id]
+                    .as_tuple()
+                    .ok_or(MatchCheckErr::Unknown)?
+                    .len(&Interner),
             })
         }
         Pat::Lit(lit_expr) => match cx.body.exprs[lit_expr] {
@@ -1085,6 +1088,20 @@ fn main() {
     }
 
     #[test]
+    fn or_pattern_no_diagnostic() {
+        check_diagnostics(
+            r#"
+enum Either {A, B}
+
+fn main() {
+    match (Either::A, Either::B) {
+        (Either::A | Either::B, _) => (),
+    }
+}"#,
+        )
+    }
+
+    #[test]
     fn mismatched_types() {
         // Match statements with arms that don't match the
         // expression pattern do not fire this diagnostic.
@@ -1336,30 +1353,6 @@ fn bang(never: !) {
     }
 
     #[test]
-    fn or_pattern_panic() {
-        check_diagnostics(
-            r#"
-pub enum Category { Infinity, Zero }
-
-fn panic(a: Category, b: Category) {
-    match (a, b) {
-        (Category::Zero | Category::Infinity, _) => (),
-        (_, Category::Zero | Category::Infinity) => (),
-    }
-
-    // FIXME: This is a false positive, but the code used to cause a panic in the match checker,
-    // so this acts as a regression test for that.
-    match (a, b) {
-        //^^^^^^ Missing match arm
-        (Category::Infinity, Category::Infinity) | (Category::Zero, Category::Zero) => (),
-        (Category::Infinity | Category::Zero, _) => (),
-    }
-}
-"#,
-        );
-    }
-
-    #[test]
     fn unknown_type() {
         check_diagnostics(
             r#"
diff --git a/crates/hir_ty/src/diagnostics/unsafe_check.rs b/crates/hir_ty/src/diagnostics/unsafe_check.rs
index 1f49a4909..ed97dc0e3 100644
--- a/crates/hir_ty/src/diagnostics/unsafe_check.rs
+++ b/crates/hir_ty/src/diagnostics/unsafe_check.rs
@@ -11,7 +11,9 @@ use hir_def::{
 };
 use hir_expand::diagnostics::DiagnosticSink;
 
-use crate::{db::HirDatabase, diagnostics::MissingUnsafe, InferenceResult, Interner, TyKind};
+use crate::{
+    db::HirDatabase, diagnostics::MissingUnsafe, InferenceResult, Interner, TyExt, TyKind,
+};
 
 pub(super) struct UnsafeValidator<'a, 'b: 'a> {
     owner: DefWithBodyId,
@@ -32,7 +34,7 @@ impl<'a, 'b> UnsafeValidator<'a, 'b> {
         let def = self.owner;
         let unsafe_expressions = unsafe_expressions(db, self.infer.as_ref(), def);
         let is_unsafe = match self.owner {
-            DefWithBodyId::FunctionId(it) => db.function_data(it).qualifier.is_unsafe,
+            DefWithBodyId::FunctionId(it) => db.function_data(it).is_unsafe(),
             DefWithBodyId::StaticId(_) | DefWithBodyId::ConstId(_) => false,
         };
         if is_unsafe
@@ -86,7 +88,7 @@ fn walk_unsafe(
     match expr {
         &Expr::Call { callee, .. } => {
             if let Some(func) = infer[callee].as_fn_def(db) {
-                if db.function_data(func).qualifier.is_unsafe {
+                if db.function_data(func).is_unsafe() {
                     unsafe_exprs.push(UnsafeExpr { expr: current, inside_unsafe_block });
                 }
             }
@@ -103,14 +105,14 @@ fn walk_unsafe(
         Expr::MethodCall { .. } => {
             if infer
                 .method_resolution(current)
-                .map(|func| db.function_data(func).qualifier.is_unsafe)
+                .map(|func| db.function_data(func).is_unsafe())
                 .unwrap_or(false)
             {
                 unsafe_exprs.push(UnsafeExpr { expr: current, inside_unsafe_block });
             }
         }
         Expr::UnaryOp { expr, op: UnaryOp::Deref } => {
-            if let TyKind::Raw(..) = &infer[*expr].interned(&Interner) {
+            if let TyKind::Raw(..) = &infer[*expr].kind(&Interner) {
                 unsafe_exprs.push(UnsafeExpr { expr: current, inside_unsafe_block });
             }
         }
diff --git a/crates/hir_ty/src/display.rs b/crates/hir_ty/src/display.rs
index 51480304b..e7c9dabc2 100644
--- a/crates/hir_ty/src/display.rs
+++ b/crates/hir_ty/src/display.rs
@@ -1,14 +1,19 @@
-//! FIXME: write short doc here
+//! The `HirDisplay` trait, which serves two purposes: Turning various bits from
+//! HIR back into source code, and just displaying them for debugging/testing
+//! purposes.
 
-use std::{array, fmt};
+use std::{
+    array,
+    fmt::{self, Debug},
+};
 
-use chalk_ir::Mutability;
+use chalk_ir::BoundVar;
 use hir_def::{
     db::DefDatabase,
     find_path,
     generics::TypeParamProvenance,
     item_scope::ItemInNs,
-    path::{GenericArg, Path, PathKind},
+    path::{Path, PathKind},
     type_ref::{TypeBound, TypeRef},
     visibility::Visibility,
     AssocContainerId, Lookup, ModuleId, TraitId,
@@ -16,10 +21,12 @@ use hir_def::{
 use hir_expand::name::Name;
 
 use crate::{
-    db::HirDatabase, from_assoc_type_id, from_foreign_def_id, from_placeholder_idx, primitive,
-    to_assoc_type_id, traits::chalk::from_chalk, utils::generics, AdtId, AliasEq, AliasTy,
-    CallableDefId, CallableSig, DomainGoal, ImplTraitId, Interner, Lifetime, OpaqueTy,
-    ProjectionTy, QuantifiedWhereClause, Scalar, Substitution, TraitRef, Ty, TyKind, WhereClause,
+    const_from_placeholder_idx, db::HirDatabase, from_assoc_type_id, from_foreign_def_id,
+    from_placeholder_idx, lt_from_placeholder_idx, mapping::from_chalk, primitive, subst_prefix,
+    to_assoc_type_id, utils::generics, AdtId, AliasEq, AliasTy, CallableDefId, CallableSig, Const,
+    ConstValue, DomainGoal, GenericArg, ImplTraitId, Interner, Lifetime, LifetimeData,
+    LifetimeOutlives, Mutability, OpaqueTy, ProjectionTy, ProjectionTyExt, QuantifiedWhereClause,
+    Scalar, TraitRef, TraitRefExt, Ty, TyExt, TyKind, WhereClause,
 };
 
 pub struct HirFormatter<'a> {
@@ -46,6 +53,10 @@ pub trait HirDisplay {
     where
         Self: Sized,
     {
+        assert!(
+            !matches!(display_target, DisplayTarget::SourceCode { .. }),
+            "HirDisplayWrapper cannot fail with DisplaySourceCodeError, use HirDisplay::hir_fmt directly instead"
+        );
         HirDisplayWrapper { db, t: self, max_size, omit_verbose_types, display_target }
     }
 
@@ -230,7 +241,7 @@ where
             Err(HirDisplayError::FmtError) => Err(fmt::Error),
             Err(HirDisplayError::DisplaySourceCodeError(_)) => {
                 // This should never happen
-                panic!("HirDisplay failed when calling Display::fmt!")
+                panic!("HirDisplay::hir_fmt failed with DisplaySourceCodeError when calling Display::fmt!")
             }
         }
     }
@@ -251,16 +262,12 @@ impl HirDisplay for ProjectionTy {
         }
 
         let trait_ = f.db.trait_data(self.trait_(f.db));
-        let first_parameter = self.substitution[0].into_displayable(
-            f.db,
-            f.max_size,
-            f.omit_verbose_types,
-            f.display_target,
-        );
-        write!(f, "<{} as {}", first_parameter, trait_.name)?;
-        if self.substitution.len() > 1 {
+        write!(f, "<")?;
+        self.self_type_parameter(&Interner).hir_fmt(f)?;
+        write!(f, " as {}", trait_.name)?;
+        if self.substitution.len(&Interner) > 1 {
             write!(f, "<")?;
-            f.write_joined(&self.substitution[1..], ", ")?;
+            f.write_joined(&self.substitution.as_slice(&Interner)[1..], ", ")?;
             write!(f, ">")?;
         }
         write!(f, ">::{}", f.db.type_alias_data(from_assoc_type_id(self.associated_ty_id)).name)?;
@@ -274,7 +281,40 @@ impl HirDisplay for OpaqueTy {
             return write!(f, "{}", TYPE_HINT_TRUNCATION);
         }
 
-        self.substitution[0].hir_fmt(f)
+        self.substitution.at(&Interner, 0).hir_fmt(f)
+    }
+}
+
+impl HirDisplay for GenericArg {
+    fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
+        match self.interned() {
+            crate::GenericArgData::Ty(ty) => ty.hir_fmt(f),
+            crate::GenericArgData::Lifetime(lt) => lt.hir_fmt(f),
+            crate::GenericArgData::Const(c) => c.hir_fmt(f),
+        }
+    }
+}
+
+impl HirDisplay for Const {
+    fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
+        let data = self.interned();
+        match data.value {
+            ConstValue::BoundVar(idx) => idx.hir_fmt(f),
+            ConstValue::InferenceVar(..) => write!(f, "_"),
+            ConstValue::Placeholder(idx) => {
+                let id = const_from_placeholder_idx(f.db, idx);
+                let generics = generics(f.db.upcast(), id.parent);
+                let param_data = &generics.params.consts[id.local_id];
+                write!(f, "{}", param_data.name)
+            }
+            ConstValue::Concrete(_) => write!(f, "_"),
+        }
+    }
+}
+
+impl HirDisplay for BoundVar {
+    fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
+        write!(f, "?{}.{}", self.debruijn.depth(), self.index)
     }
 }
 
@@ -284,7 +324,7 @@ impl HirDisplay for Ty {
             return write!(f, "{}", TYPE_HINT_TRUNCATION);
         }
 
-        match self.interned(&Interner) {
+        match self.kind(&Interner) {
             TyKind::Never => write!(f, "!")?,
             TyKind::Str => write!(f, "str")?,
             TyKind::Scalar(Scalar::Bool) => write!(f, "bool")?,
@@ -297,16 +337,15 @@ impl HirDisplay for Ty {
                 t.hir_fmt(f)?;
                 write!(f, "]")?;
             }
-            TyKind::Array(t) => {
+            TyKind::Array(t, c) => {
                 write!(f, "[")?;
                 t.hir_fmt(f)?;
-                write!(f, "; _]")?;
+                write!(f, "; ")?;
+                c.hir_fmt(f)?;
+                write!(f, "]")?;
             }
-            TyKind::Raw(m, t) | TyKind::Ref(m, t) => {
-                let ty_display =
-                    t.into_displayable(f.db, f.max_size, f.omit_verbose_types, f.display_target);
-
-                if matches!(self.interned(&Interner), TyKind::Raw(..)) {
+            TyKind::Raw(m, t) | TyKind::Ref(m, _, t) => {
+                if matches!(self.kind(&Interner), TyKind::Raw(..)) {
                     write!(
                         f,
                         "*{}",
@@ -328,7 +367,7 @@ impl HirDisplay for Ty {
 
                 // FIXME: all this just to decide whether to use parentheses...
                 let datas;
-                let predicates: Vec<_> = match t.interned(&Interner) {
+                let predicates: Vec<_> = match t.kind(&Interner) {
                     TyKind::Dyn(dyn_ty) if dyn_ty.bounds.skip_binders().interned().len() > 1 => {
                         dyn_ty.bounds.skip_binders().interned().iter().cloned().collect()
                     }
@@ -344,8 +383,8 @@ impl HirDisplay for Ty {
                             let data = (*datas)
                                 .as_ref()
                                 .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
-                            let bounds = data.subst(parameters);
-                            bounds.value
+                            let bounds = data.substitute(&Interner, parameters);
+                            bounds.into_value_and_skipped_binders().0
                         } else {
                             Vec::new()
                         }
@@ -360,26 +399,26 @@ impl HirDisplay for Ty {
                     if fn_traits(f.db.upcast(), trait_).any(|it| it == trait_)
                         && predicates.len() <= 2
                     {
-                        return write!(f, "{}", ty_display);
+                        return t.hir_fmt(f);
                     }
                 }
 
                 if predicates.len() > 1 {
                     write!(f, "(")?;
-                    write!(f, "{}", ty_display)?;
+                    t.hir_fmt(f)?;
                     write!(f, ")")?;
                 } else {
-                    write!(f, "{}", ty_display)?;
+                    t.hir_fmt(f)?;
                 }
             }
             TyKind::Tuple(_, substs) => {
-                if substs.len() == 1 {
+                if substs.len(&Interner) == 1 {
                     write!(f, "(")?;
-                    substs[0].hir_fmt(f)?;
+                    substs.at(&Interner, 0).hir_fmt(f)?;
                     write!(f, ",)")?;
                 } else {
                     write!(f, "(")?;
-                    f.write_joined(&*substs.0, ", ")?;
+                    f.write_joined(&*substs.as_slice(&Interner), ", ")?;
                     write!(f, ")")?;
                 }
             }
@@ -389,7 +428,7 @@ impl HirDisplay for Ty {
             }
             TyKind::FnDef(def, parameters) => {
                 let def = from_chalk(f.db, *def);
-                let sig = f.db.callable_item_signature(def).subst(parameters);
+                let sig = f.db.callable_item_signature(def).substitute(&Interner, parameters);
                 match def {
                     CallableDefId::FunctionId(ff) => {
                         write!(f, "fn {}", f.db.function_data(ff).name)?
@@ -399,7 +438,7 @@ impl HirDisplay for Ty {
                         write!(f, "{}", f.db.enum_data(e.parent).variants[e.local_id].name)?
                     }
                 };
-                if parameters.len() > 0 {
+                if parameters.len(&Interner) > 0 {
                     let generics = generics(f.db.upcast(), def.into());
                     let (parent_params, self_param, type_params, _impl_trait_params) =
                         generics.provenance_split();
@@ -407,7 +446,7 @@ impl HirDisplay for Ty {
                     // We print all params except implicit impl Trait params. Still a bit weird; should we leave out parent and self?
                     if total_len > 0 {
                         write!(f, "<")?;
-                        f.write_joined(&parameters.0[..total_len], ", ")?;
+                        f.write_joined(&parameters.as_slice(&Interner)[..total_len], ", ")?;
                         write!(f, ">")?;
                     }
                 }
@@ -415,15 +454,9 @@ impl HirDisplay for Ty {
                 f.write_joined(sig.params(), ", ")?;
                 write!(f, ")")?;
                 let ret = sig.ret();
-                if *ret != Ty::unit() {
-                    let ret_display = ret.into_displayable(
-                        f.db,
-                        f.max_size,
-                        f.omit_verbose_types,
-                        f.display_target,
-                    );
-
-                    write!(f, " -> {}", ret_display)?;
+                if !ret.is_unit() {
+                    write!(f, " -> ")?;
+                    ret.hir_fmt(f)?;
                 }
             }
             TyKind::Adt(AdtId(def_id), parameters) => {
@@ -451,7 +484,7 @@ impl HirDisplay for Ty {
                     }
                 }
 
-                if parameters.len() > 0 {
+                if parameters.len(&Interner) > 0 {
                     let parameters_to_write = if f.display_target.is_source_code()
                         || f.omit_verbose_types()
                     {
@@ -460,30 +493,35 @@ impl HirDisplay for Ty {
                             .map(|generic_def_id| f.db.generic_defaults(generic_def_id))
                             .filter(|defaults| !defaults.is_empty())
                         {
-                            None => parameters.0.as_ref(),
+                            None => parameters.as_slice(&Interner),
                             Some(default_parameters) => {
                                 let mut default_from = 0;
-                                for (i, parameter) in parameters.iter().enumerate() {
-                                    match (parameter.interned(&Interner), default_parameters.get(i))
-                                    {
-                                        (&TyKind::Unknown, _) | (_, None) => {
+                                for (i, parameter) in parameters.iter(&Interner).enumerate() {
+                                    match (
+                                        parameter.assert_ty_ref(&Interner).kind(&Interner),
+                                        default_parameters.get(i),
+                                    ) {
+                                        (&TyKind::Error, _) | (_, None) => {
                                             default_from = i + 1;
                                         }
                                         (_, Some(default_parameter)) => {
-                                            let actual_default = default_parameter
-                                                .clone()
-                                                .subst(&parameters.prefix(i));
-                                            if parameter != &actual_default {
+                                            let actual_default =
+                                                default_parameter.clone().substitute(
+                                                    &Interner,
+                                                    &subst_prefix(parameters, i),
+                                                );
+                                            if parameter.assert_ty_ref(&Interner) != &actual_default
+                                            {
                                                 default_from = i + 1;
                                             }
                                         }
                                     }
                                 }
-                                &parameters.0[0..default_from]
+                                &parameters.as_slice(&Interner)[0..default_from]
                             }
                         }
                     } else {
-                        parameters.0.as_ref()
+                        parameters.as_slice(&Interner)
                     };
                     if !parameters_to_write.is_empty() {
                         write!(f, "<")?;
@@ -504,9 +542,9 @@ impl HirDisplay for Ty {
                 // Use placeholder associated types when the target is test (https://rust-lang.github.io/chalk/book/clauses/type_equality.html#placeholder-associated-types)
                 if f.display_target.is_test() {
                     write!(f, "{}::{}", trait_.name, type_alias_data.name)?;
-                    if parameters.len() > 0 {
+                    if parameters.len(&Interner) > 0 {
                         write!(f, "<")?;
-                        f.write_joined(&*parameters.0, ", ")?;
+                        f.write_joined(&*parameters.as_slice(&Interner), ", ")?;
                         write!(f, ">")?;
                     }
                 } else {
@@ -518,7 +556,7 @@ impl HirDisplay for Ty {
                     projection_ty.hir_fmt(f)?;
                 }
             }
-            TyKind::ForeignType(type_alias) => {
+            TyKind::Foreign(type_alias) => {
                 let type_alias = f.db.type_alias_data(from_foreign_def_id(*type_alias));
                 write!(f, "{}", type_alias.name)?;
             }
@@ -531,13 +569,13 @@ impl HirDisplay for Ty {
                         let data = (*datas)
                             .as_ref()
                             .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
-                        let bounds = data.subst(&parameters);
-                        write_bounds_like_dyn_trait_with_prefix("impl", &bounds.value, f)?;
+                        let bounds = data.substitute(&Interner, &parameters);
+                        write_bounds_like_dyn_trait_with_prefix("impl", bounds.skip_binders(), f)?;
                         // FIXME: it would maybe be good to distinguish this from the alias type (when debug printing), and to show the substitution
                     }
                     ImplTraitId::AsyncBlockTypeImplTrait(..) => {
                         write!(f, "impl Future<Output = ")?;
-                        parameters[0].hir_fmt(f)?;
+                        parameters.at(&Interner, 0).hir_fmt(f)?;
                         write!(f, ">")?;
                     }
                 }
@@ -548,7 +586,7 @@ impl HirDisplay for Ty {
                         DisplaySourceCodeError::Closure,
                     ));
                 }
-                let sig = substs[0].callable_sig(f.db);
+                let sig = substs.at(&Interner, 0).assert_ty_ref(&Interner).callable_sig(f.db);
                 if let Some(sig) = sig {
                     if sig.params().is_empty() {
                         write!(f, "||")?;
@@ -560,13 +598,8 @@ impl HirDisplay for Ty {
                         write!(f, "|")?;
                     };
 
-                    let ret_display = sig.ret().into_displayable(
-                        f.db,
-                        f.max_size,
-                        f.omit_verbose_types,
-                        f.display_target,
-                    );
-                    write!(f, " -> {}", ret_display)?;
+                    write!(f, " -> ")?;
+                    sig.ret().hir_fmt(f)?;
                 } else {
                     write!(f, "{{closure}}")?;
                 }
@@ -580,26 +613,27 @@ impl HirDisplay for Ty {
                         write!(f, "{}", param_data.name.clone().unwrap_or_else(Name::missing))?
                     }
                     TypeParamProvenance::ArgumentImplTrait => {
-                        let substs = Substitution::type_params_for_generics(f.db, &generics);
-                        let bounds = f
-                            .db
-                            .generic_predicates(id.parent)
-                            .into_iter()
-                            .map(|pred| pred.clone().subst(&substs))
-                            .filter(|wc| match &wc.skip_binders() {
-                                WhereClause::Implemented(tr) => tr.self_type_parameter() == self,
-                                WhereClause::AliasEq(AliasEq {
-                                    alias: AliasTy::Projection(proj),
-                                    ty: _,
-                                }) => proj.self_type_parameter() == self,
-                                _ => false,
-                            })
-                            .collect::<Vec<_>>();
+                        let substs = generics.type_params_subst(f.db);
+                        let bounds =
+                            f.db.generic_predicates(id.parent)
+                                .into_iter()
+                                .map(|pred| pred.clone().substitute(&Interner, &substs))
+                                .filter(|wc| match &wc.skip_binders() {
+                                    WhereClause::Implemented(tr) => {
+                                        &tr.self_type_parameter(&Interner) == self
+                                    }
+                                    WhereClause::AliasEq(AliasEq {
+                                        alias: AliasTy::Projection(proj),
+                                        ty: _,
+                                    }) => &proj.self_type_parameter(&Interner) == self,
+                                    _ => false,
+                                })
+                                .collect::<Vec<_>>();
                         write_bounds_like_dyn_trait_with_prefix("impl", &bounds, f)?;
                     }
                 }
             }
-            TyKind::BoundVar(idx) => write!(f, "?{}.{}", idx.debruijn.depth(), idx.index)?,
+            TyKind::BoundVar(idx) => idx.hir_fmt(f)?,
             TyKind::Dyn(dyn_ty) => {
                 write_bounds_like_dyn_trait_with_prefix(
                     "dyn",
@@ -617,15 +651,15 @@ impl HirDisplay for Ty {
                         let data = (*datas)
                             .as_ref()
                             .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
-                        let bounds = data.subst(&opaque_ty.substitution);
-                        write_bounds_like_dyn_trait_with_prefix("impl", &bounds.value, f)?;
+                        let bounds = data.substitute(&Interner, &opaque_ty.substitution);
+                        write_bounds_like_dyn_trait_with_prefix("impl", bounds.skip_binders(), f)?;
                     }
                     ImplTraitId::AsyncBlockTypeImplTrait(..) => {
                         write!(f, "{{async block}}")?;
                     }
                 };
             }
-            TyKind::Unknown => {
+            TyKind::Error => {
                 if f.display_target.is_source_code() {
                     return Err(HirDisplayError::DisplaySourceCodeError(
                         DisplaySourceCodeError::UnknownType,
@@ -634,6 +668,8 @@ impl HirDisplay for Ty {
                 write!(f, "{{unknown}}")?;
             }
             TyKind::InferenceVar(..) => write!(f, "_")?,
+            TyKind::Generator(..) => write!(f, "{{generator}}")?,
+            TyKind::GeneratorWitness(..) => write!(f, "{{generator witness}}")?,
         }
         Ok(())
     }
@@ -652,10 +688,9 @@ impl HirDisplay for CallableSig {
         }
         write!(f, ")")?;
         let ret = self.ret();
-        if *ret != Ty::unit() {
-            let ret_display =
-                ret.into_displayable(f.db, f.max_size, f.omit_verbose_types, f.display_target);
-            write!(f, " -> {}", ret_display)?;
+        if !ret.is_unit() {
+            write!(f, " -> ")?;
+            ret.hir_fmt(f)?;
         }
         Ok(())
     }
@@ -712,15 +747,17 @@ fn write_bounds_like_dyn_trait(
                 if !first {
                     write!(f, " + ")?;
                 }
-                // We assume that the self type is $0 (i.e. the
+                // We assume that the self type is ^0.0 (i.e. the
                 // existential) here, which is the only thing that's
                 // possible in actual Rust, and hence don't print it
                 write!(f, "{}", f.db.trait_data(trait_).name)?;
-                if let [_, params @ ..] = &*trait_ref.substitution.0 {
+                if let [_, params @ ..] = &*trait_ref.substitution.as_slice(&Interner) {
                     if is_fn_trait {
-                        if let Some(args) = params.first().and_then(|it| it.as_tuple()) {
+                        if let Some(args) =
+                            params.first().and_then(|it| it.assert_ty_ref(&Interner).as_tuple())
+                        {
                             write!(f, "(")?;
-                            f.write_joined(&*args.0, ", ")?;
+                            f.write_joined(args.as_slice(&Interner), ", ")?;
                             write!(f, ")")?;
                         }
                     } else if !params.is_empty() {
@@ -752,6 +789,10 @@ fn write_bounds_like_dyn_trait(
                 }
                 ty.hir_fmt(f)?;
             }
+
+            // FIXME implement these
+            WhereClause::LifetimeOutlives(_) => {}
+            WhereClause::TypeOutlives(_) => {}
         }
         first = false;
     }
@@ -761,31 +802,29 @@ fn write_bounds_like_dyn_trait(
     Ok(())
 }
 
-impl TraitRef {
-    fn hir_fmt_ext(&self, f: &mut HirFormatter, use_as: bool) -> Result<(), HirDisplayError> {
-        if f.should_truncate() {
-            return write!(f, "{}", TYPE_HINT_TRUNCATION);
-        }
+fn fmt_trait_ref(tr: &TraitRef, f: &mut HirFormatter, use_as: bool) -> Result<(), HirDisplayError> {
+    if f.should_truncate() {
+        return write!(f, "{}", TYPE_HINT_TRUNCATION);
+    }
 
-        self.substitution[0].hir_fmt(f)?;
-        if use_as {
-            write!(f, " as ")?;
-        } else {
-            write!(f, ": ")?;
-        }
-        write!(f, "{}", f.db.trait_data(self.hir_trait_id()).name)?;
-        if self.substitution.len() > 1 {
-            write!(f, "<")?;
-            f.write_joined(&self.substitution[1..], ", ")?;
-            write!(f, ">")?;
-        }
-        Ok(())
+    tr.self_type_parameter(&Interner).hir_fmt(f)?;
+    if use_as {
+        write!(f, " as ")?;
+    } else {
+        write!(f, ": ")?;
+    }
+    write!(f, "{}", f.db.trait_data(tr.hir_trait_id()).name)?;
+    if tr.substitution.len(&Interner) > 1 {
+        write!(f, "<")?;
+        f.write_joined(&tr.substitution.as_slice(&Interner)[1..], ", ")?;
+        write!(f, ">")?;
     }
+    Ok(())
 }
 
 impl HirDisplay for TraitRef {
     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
-        self.hir_fmt_ext(f, false)
+        fmt_trait_ref(self, f, false)
     }
 }
 
@@ -799,7 +838,7 @@ impl HirDisplay for WhereClause {
             WhereClause::Implemented(trait_ref) => trait_ref.hir_fmt(f)?,
             WhereClause::AliasEq(AliasEq { alias: AliasTy::Projection(projection_ty), ty }) => {
                 write!(f, "<")?;
-                projection_ty.trait_ref(f.db).hir_fmt_ext(f, true)?;
+                fmt_trait_ref(&projection_ty.trait_ref(f.db), f, true)?;
                 write!(
                     f,
                     ">::{} = ",
@@ -808,20 +847,44 @@ impl HirDisplay for WhereClause {
                 ty.hir_fmt(f)?;
             }
             WhereClause::AliasEq(_) => write!(f, "{{error}}")?,
+
+            // FIXME implement these
+            WhereClause::TypeOutlives(..) => {}
+            WhereClause::LifetimeOutlives(..) => {}
         }
         Ok(())
     }
 }
 
+impl HirDisplay for LifetimeOutlives {
+    fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
+        self.a.hir_fmt(f)?;
+        write!(f, ": ")?;
+        self.b.hir_fmt(f)
+    }
+}
+
 impl HirDisplay for Lifetime {
     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
+        self.interned().hir_fmt(f)
+    }
+}
+
+impl HirDisplay for LifetimeData {
+    fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
         match self {
-            Lifetime::Parameter(id) => {
+            LifetimeData::BoundVar(idx) => idx.hir_fmt(f),
+            LifetimeData::InferenceVar(_) => write!(f, "_"),
+            LifetimeData::Placeholder(idx) => {
+                let id = lt_from_placeholder_idx(f.db, *idx);
                 let generics = generics(f.db.upcast(), id.parent);
                 let param_data = &generics.params.lifetimes[id.local_id];
-                write!(f, "{}", &param_data.name)
+                write!(f, "{}", param_data.name)
             }
-            Lifetime::Static => write!(f, "'static"),
+            LifetimeData::Static => write!(f, "'static"),
+            LifetimeData::Empty(_) => Ok(()),
+            LifetimeData::Erased => Ok(()),
+            LifetimeData::Phantom(_, _) => Ok(()),
         }
     }
 }
@@ -832,9 +895,11 @@ impl HirDisplay for DomainGoal {
             DomainGoal::Holds(wc) => {
                 write!(f, "Holds(")?;
                 wc.hir_fmt(f)?;
-                write!(f, ")")
+                write!(f, ")")?;
             }
+            _ => write!(f, "?")?,
         }
+        Ok(())
     }
 }
 
@@ -1016,11 +1081,11 @@ impl HirDisplay for Path {
     }
 }
 
-impl HirDisplay for GenericArg {
+impl HirDisplay for hir_def::path::GenericArg {
     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
         match self {
-            GenericArg::Type(ty) => ty.hir_fmt(f),
-            GenericArg::Lifetime(lifetime) => write!(f, "{}", lifetime.name),
+            hir_def::path::GenericArg::Type(ty) => ty.hir_fmt(f),
+            hir_def::path::GenericArg::Lifetime(lifetime) => write!(f, "{}", lifetime.name),
         }
     }
 }
diff --git a/crates/hir_ty/src/infer.rs b/crates/hir_ty/src/infer.rs
index e4407ff50..bf2da2d4a 100644
--- a/crates/hir_ty/src/infer.rs
+++ b/crates/hir_ty/src/infer.rs
@@ -18,7 +18,7 @@ use std::mem;
 use std::ops::Index;
 use std::sync::Arc;
 
-use chalk_ir::{cast::Cast, Mutability};
+use chalk_ir::{cast::Cast, DebruijnIndex, Mutability};
 use hir_def::{
     body::Body,
     data::{ConstData, FunctionData, StaticData},
@@ -37,12 +37,12 @@ use stdx::impl_from;
 use syntax::SmolStr;
 
 use super::{
-    traits::{DomainGoal, Guidance, Solution},
-    InEnvironment, ProjectionTy, Substitution, TraitEnvironment, TraitRef, Ty, TypeWalk,
+    DomainGoal, Guidance, InEnvironment, ProjectionTy, Solution, TraitEnvironment, TraitRef, Ty,
 };
 use crate::{
-    db::HirDatabase, infer::diagnostics::InferenceDiagnostic, lower::ImplTraitLoweringMode,
-    to_assoc_type_id, to_chalk_trait_id, AliasEq, AliasTy, Interner, TyKind,
+    db::HirDatabase, fold_tys, infer::diagnostics::InferenceDiagnostic,
+    lower::ImplTraitLoweringMode, to_assoc_type_id, AliasEq, AliasTy, Canonical, Interner,
+    TyBuilder, TyExt, TyKind,
 };
 
 // This lint has a false positive here. See the link below for details.
@@ -120,7 +120,7 @@ struct InternedStandardTypes {
 
 impl Default for InternedStandardTypes {
     fn default() -> Self {
-        InternedStandardTypes { unknown: TyKind::Unknown.intern(&Interner) }
+        InternedStandardTypes { unknown: TyKind::Error.intern(&Interner) }
     }
 }
 
@@ -131,10 +131,7 @@ pub struct InferenceResult {
     method_resolutions: FxHashMap<ExprId, FunctionId>,
     /// For each field access expr, records the field it resolves to.
     field_resolutions: FxHashMap<ExprId, FieldId>,
-    /// For each field in record literal, records the field it resolves to.
-    record_field_resolutions: FxHashMap<ExprId, FieldId>,
-    record_pat_field_resolutions: FxHashMap<PatId, FieldId>,
-    /// For each struct literal, records the variant it resolves to.
+    /// For each struct literal or pattern, records the variant it resolves to.
     variant_resolutions: FxHashMap<ExprOrPatId, VariantId>,
     /// For each associated item record what it resolves to
     assoc_resolutions: FxHashMap<ExprOrPatId, AssocItemId>,
@@ -153,12 +150,6 @@ impl InferenceResult {
     pub fn field_resolution(&self, expr: ExprId) -> Option<FieldId> {
         self.field_resolutions.get(&expr).copied()
     }
-    pub fn record_field_resolution(&self, expr: ExprId) -> Option<FieldId> {
-        self.record_field_resolutions.get(&expr).copied()
-    }
-    pub fn record_pat_field_resolution(&self, pat: PatId) -> Option<FieldId> {
-        self.record_pat_field_resolutions.get(&pat).copied()
-    }
     pub fn variant_resolution_for_expr(&self, id: ExprId) -> Option<VariantId> {
         self.variant_resolutions.get(&id.into()).copied()
     }
@@ -210,6 +201,7 @@ struct InferenceContext<'a> {
     table: unify::InferenceTable,
     trait_env: Arc<TraitEnvironment>,
     obligations: Vec<DomainGoal>,
+    last_obligations_check: Option<u32>,
     result: InferenceResult,
     /// The return type of the function being inferred, or the closure if we're
     /// currently within one.
@@ -245,7 +237,8 @@ impl<'a> InferenceContext<'a> {
             result: InferenceResult::default(),
             table: unify::InferenceTable::new(),
             obligations: Vec::default(),
-            return_ty: TyKind::Unknown.intern(&Interner), // set in collect_fn_signature
+            last_obligations_check: None,
+            return_ty: TyKind::Error.intern(&Interner), // set in collect_fn_signature
             trait_env: owner
                 .as_generic_def_id()
                 .map_or_else(Default::default, |d| db.trait_environment(d)),
@@ -259,7 +252,7 @@ impl<'a> InferenceContext<'a> {
     }
 
     fn err_ty(&self) -> Ty {
-        TyKind::Unknown.intern(&Interner)
+        TyKind::Error.intern(&Interner)
     }
 
     fn resolve_all(mut self) -> InferenceResult {
@@ -323,30 +316,44 @@ impl<'a> InferenceContext<'a> {
 
     /// Replaces Ty::Unknown by a new type var, so we can maybe still infer it.
     fn insert_type_vars_shallow(&mut self, ty: Ty) -> Ty {
-        match ty.interned(&Interner) {
-            TyKind::Unknown => self.table.new_type_var(),
+        match ty.kind(&Interner) {
+            TyKind::Error => self.table.new_type_var(),
             _ => ty,
         }
     }
 
     fn insert_type_vars(&mut self, ty: Ty) -> Ty {
-        ty.fold(&mut |ty| self.insert_type_vars_shallow(ty))
+        fold_tys(ty, |ty, _| self.insert_type_vars_shallow(ty), DebruijnIndex::INNERMOST)
     }
 
     fn resolve_obligations_as_possible(&mut self) {
+        if self.last_obligations_check == Some(self.table.revision) {
+            // no change
+            return;
+        }
+        let _span = profile::span("resolve_obligations_as_possible");
+
+        self.last_obligations_check = Some(self.table.revision);
         let obligations = mem::replace(&mut self.obligations, Vec::new());
         for obligation in obligations {
-            let in_env = InEnvironment::new(self.trait_env.env.clone(), obligation.clone());
+            let in_env = InEnvironment::new(&self.trait_env.env, obligation.clone());
             let canonicalized = self.canonicalizer().canonicalize_obligation(in_env);
             let solution =
                 self.db.trait_solve(self.resolver.krate().unwrap(), canonicalized.value.clone());
 
             match solution {
-                Some(Solution::Unique(substs)) => {
-                    canonicalized.apply_solution(self, substs.0);
+                Some(Solution::Unique(canonical_subst)) => {
+                    canonicalized.apply_solution(
+                        self,
+                        Canonical {
+                            binders: canonical_subst.binders,
+                            // FIXME: handle constraints
+                            value: canonical_subst.value.subst,
+                        },
+                    );
                 }
                 Some(Solution::Ambig(Guidance::Definite(substs))) => {
-                    canonicalized.apply_solution(self, substs.0);
+                    canonicalized.apply_solution(self, substs);
                     self.obligations.push(obligation);
                 }
                 Some(_) => {
@@ -360,6 +367,11 @@ impl<'a> InferenceContext<'a> {
         }
     }
 
+    fn push_obligation(&mut self, o: DomainGoal) {
+        self.obligations.push(o);
+        self.last_obligations_check = None;
+    }
+
     fn unify(&mut self, ty1: &Ty, ty2: &Ty) -> bool {
         self.table.unify(ty1, ty2)
     }
@@ -395,21 +407,19 @@ impl<'a> InferenceContext<'a> {
                     _ => panic!("resolve_associated_type called with non-associated type"),
                 };
                 let ty = self.table.new_type_var();
-                let substs = Substitution::build_for_def(self.db, res_assoc_ty)
+                let trait_ref = TyBuilder::trait_ref(self.db, trait_)
                     .push(inner_ty)
                     .fill(params.iter().cloned())
                     .build();
-                let trait_ref =
-                    TraitRef { trait_id: to_chalk_trait_id(trait_), substitution: substs.clone() };
                 let alias_eq = AliasEq {
                     alias: AliasTy::Projection(ProjectionTy {
                         associated_ty_id: to_assoc_type_id(res_assoc_ty),
-                        substitution: substs,
+                        substitution: trait_ref.substitution.clone(),
                     }),
                     ty: ty.clone(),
                 };
-                self.obligations.push(trait_ref.cast(&Interner));
-                self.obligations.push(alias_eq.cast(&Interner));
+                self.push_obligation(trait_ref.cast(&Interner));
+                self.push_obligation(alias_eq.cast(&Interner));
                 self.resolve_ty_as_possible(ty)
             }
             None => self.err_ty(),
@@ -424,19 +434,23 @@ impl<'a> InferenceContext<'a> {
     /// to do it as well.
     fn normalize_associated_types_in(&mut self, ty: Ty) -> Ty {
         let ty = self.resolve_ty_as_possible(ty);
-        ty.fold(&mut |ty| match ty.interned(&Interner) {
-            TyKind::Alias(AliasTy::Projection(proj_ty)) => {
-                self.normalize_projection_ty(proj_ty.clone())
-            }
-            _ => ty,
-        })
+        fold_tys(
+            ty,
+            |ty, _| match ty.kind(&Interner) {
+                TyKind::Alias(AliasTy::Projection(proj_ty)) => {
+                    self.normalize_projection_ty(proj_ty.clone())
+                }
+                _ => ty,
+            },
+            DebruijnIndex::INNERMOST,
+        )
     }
 
     fn normalize_projection_ty(&mut self, proj_ty: ProjectionTy) -> Ty {
         let var = self.table.new_type_var();
         let alias_eq = AliasEq { alias: AliasTy::Projection(proj_ty), ty: var.clone() };
         let obligation = alias_eq.cast(&Interner);
-        self.obligations.push(obligation);
+        self.push_obligation(obligation);
         var
     }
 
@@ -458,56 +472,32 @@ impl<'a> InferenceContext<'a> {
             TypeNs::AdtId(AdtId::StructId(strukt)) => {
                 let substs = ctx.substs_from_path(path, strukt.into(), true);
                 let ty = self.db.ty(strukt.into());
-                let ty = self.insert_type_vars(ty.subst(&substs));
+                let ty = self.insert_type_vars(ty.substitute(&Interner, &substs));
                 forbid_unresolved_segments((ty, Some(strukt.into())), unresolved)
             }
             TypeNs::AdtId(AdtId::UnionId(u)) => {
                 let substs = ctx.substs_from_path(path, u.into(), true);
                 let ty = self.db.ty(u.into());
-                let ty = self.insert_type_vars(ty.subst(&substs));
+                let ty = self.insert_type_vars(ty.substitute(&Interner, &substs));
                 forbid_unresolved_segments((ty, Some(u.into())), unresolved)
             }
             TypeNs::EnumVariantId(var) => {
                 let substs = ctx.substs_from_path(path, var.into(), true);
                 let ty = self.db.ty(var.parent.into());
-                let ty = self.insert_type_vars(ty.subst(&substs));
+                let ty = self.insert_type_vars(ty.substitute(&Interner, &substs));
                 forbid_unresolved_segments((ty, Some(var.into())), unresolved)
             }
             TypeNs::SelfType(impl_id) => {
                 let generics = crate::utils::generics(self.db.upcast(), impl_id.into());
-                let substs = Substitution::type_params_for_generics(self.db, &generics);
-                let ty = self.db.impl_self_ty(impl_id).subst(&substs);
-                match unresolved {
-                    None => {
-                        let variant = ty_variant(&ty);
-                        (ty, variant)
-                    }
-                    Some(1) => {
-                        let segment = path.mod_path().segments().last().unwrap();
-                        // this could be an enum variant or associated type
-                        if let Some((AdtId::EnumId(enum_id), _)) = ty.as_adt() {
-                            let enum_data = self.db.enum_data(enum_id);
-                            if let Some(local_id) = enum_data.variant(segment) {
-                                let variant = EnumVariantId { parent: enum_id, local_id };
-                                return (ty, Some(variant.into()));
-                            }
-                        }
-                        // FIXME potentially resolve assoc type
-                        (self.err_ty(), None)
-                    }
-                    Some(_) => {
-                        // FIXME diagnostic
-                        (self.err_ty(), None)
-                    }
-                }
+                let substs = generics.type_params_subst(self.db);
+                let ty = self.db.impl_self_ty(impl_id).substitute(&Interner, &substs);
+                self.resolve_variant_on_alias(ty, unresolved, path)
             }
             TypeNs::TypeAliasId(it) => {
-                let substs = Substitution::build_for_def(self.db, it)
+                let ty = TyBuilder::def_ty(self.db, it.into())
                     .fill(std::iter::repeat_with(|| self.table.new_type_var()))
                     .build();
-                let ty = self.db.ty(it.into()).subst(&substs);
-                let variant = ty_variant(&ty);
-                forbid_unresolved_segments((ty, variant), unresolved)
+                self.resolve_variant_on_alias(ty, unresolved, path)
             }
             TypeNs::AdtSelfType(_) => {
                 // FIXME this could happen in array size expressions, once we're checking them
@@ -531,19 +521,46 @@ impl<'a> InferenceContext<'a> {
                 result
             } else {
                 // FIXME diagnostic
-                (TyKind::Unknown.intern(&Interner), None)
+                (TyKind::Error.intern(&Interner), None)
             }
         }
+    }
 
-        fn ty_variant(ty: &Ty) -> Option<VariantId> {
-            ty.as_adt().and_then(|(adt_id, _)| match adt_id {
-                AdtId::StructId(s) => Some(VariantId::StructId(s)),
-                AdtId::UnionId(u) => Some(VariantId::UnionId(u)),
-                AdtId::EnumId(_) => {
-                    // FIXME Error E0071, expected struct, variant or union type, found enum `Foo`
-                    None
+    fn resolve_variant_on_alias(
+        &mut self,
+        ty: Ty,
+        unresolved: Option<usize>,
+        path: &Path,
+    ) -> (Ty, Option<VariantId>) {
+        match unresolved {
+            None => {
+                let variant = ty.as_adt().and_then(|(adt_id, _)| match adt_id {
+                    AdtId::StructId(s) => Some(VariantId::StructId(s)),
+                    AdtId::UnionId(u) => Some(VariantId::UnionId(u)),
+                    AdtId::EnumId(_) => {
+                        // FIXME Error E0071, expected struct, variant or union type, found enum `Foo`
+                        None
+                    }
+                });
+                (ty, variant)
+            }
+            Some(1) => {
+                let segment = path.mod_path().segments().last().unwrap();
+                // this could be an enum variant or associated type
+                if let Some((AdtId::EnumId(enum_id), _)) = ty.as_adt() {
+                    let enum_data = self.db.enum_data(enum_id);
+                    if let Some(local_id) = enum_data.variant(segment) {
+                        let variant = EnumVariantId { parent: enum_id, local_id };
+                        return (ty, Some(variant.into()));
+                    }
                 }
-            })
+                // FIXME potentially resolve assoc type
+                (self.err_ty(), None)
+            }
+            Some(_) => {
+                // FIXME diagnostic
+                (self.err_ty(), None)
+            }
         }
     }
 
@@ -681,25 +698,6 @@ impl<'a> InferenceContext<'a> {
     }
 }
 
-/// The kinds of placeholders we need during type inference. There's separate
-/// values for general types, and for integer and float variables. The latter
-/// two are used for inference of literal values (e.g. `100` could be one of
-/// several integer types).
-#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
-pub struct InferenceVar {
-    index: u32,
-}
-
-impl InferenceVar {
-    fn to_inner(self) -> unify::TypeVarId {
-        unify::TypeVarId(self.index)
-    }
-
-    fn from_inner(unify::TypeVarId(index): unify::TypeVarId) -> Self {
-        InferenceVar { index }
-    }
-}
-
 /// When inferring an expression, we propagate downward whatever type hint we
 /// are able in the form of an `Expectation`.
 #[derive(Clone, PartialEq, Eq, Debug)]
@@ -744,7 +742,7 @@ impl Expectation {
     fn none() -> Self {
         Expectation {
             // FIXME
-            ty: TyKind::Unknown.intern(&Interner),
+            ty: TyKind::Error.intern(&Interner),
             rvalue_hint: false,
         }
     }
@@ -752,7 +750,7 @@ impl Expectation {
     fn coercion_target(&self) -> Ty {
         if self.rvalue_hint {
             // FIXME
-            TyKind::Unknown.intern(&Interner)
+            TyKind::Error.intern(&Interner)
         } else {
             self.ty.clone()
         }
diff --git a/crates/hir_ty/src/infer/coerce.rs b/crates/hir_ty/src/infer/coerce.rs
index 9c62932b1..1f463a425 100644
--- a/crates/hir_ty/src/infer/coerce.rs
+++ b/crates/hir_ty/src/infer/coerce.rs
@@ -7,9 +7,7 @@
 use chalk_ir::{cast::Cast, Mutability, TyVariableKind};
 use hir_def::lang_item::LangItemTarget;
 
-use crate::{
-    autoderef, to_chalk_trait_id, traits::Solution, Interner, Substitution, TraitRef, Ty, TyKind,
-};
+use crate::{autoderef, Canonical, Interner, Solution, Ty, TyBuilder, TyExt, TyKind};
 
 use super::{InEnvironment, InferenceContext};
 
@@ -36,7 +34,7 @@ impl<'a> InferenceContext<'a> {
             ty1.clone()
         } else {
             if let (TyKind::FnDef(..), TyKind::FnDef(..)) =
-                (ty1.interned(&Interner), ty2.interned(&Interner))
+                (ty1.kind(&Interner), ty2.kind(&Interner))
             {
                 cov_mark::hit!(coerce_fn_reification);
                 // Special case: two function types. Try to coerce both to
@@ -44,8 +42,8 @@ impl<'a> InferenceContext<'a> {
                 // https://github.com/rust-lang/rust/blob/7b805396bf46dce972692a6846ce2ad8481c5f85/src/librustc_typeck/check/coercion.rs#L877-L916
                 let sig1 = ty1.callable_sig(self.db).expect("FnDef without callable sig");
                 let sig2 = ty2.callable_sig(self.db).expect("FnDef without callable sig");
-                let ptr_ty1 = Ty::fn_ptr(sig1);
-                let ptr_ty2 = Ty::fn_ptr(sig2);
+                let ptr_ty1 = TyBuilder::fn_ptr(sig1);
+                let ptr_ty2 = TyBuilder::fn_ptr(sig2);
                 self.coerce_merge_branch(&ptr_ty1, &ptr_ty2)
             } else {
                 cov_mark::hit!(coerce_merge_fail_fallback);
@@ -55,7 +53,7 @@ impl<'a> InferenceContext<'a> {
     }
 
     fn coerce_inner(&mut self, mut from_ty: Ty, to_ty: &Ty) -> bool {
-        match (from_ty.interned(&Interner), to_ty.interned(&Interner)) {
+        match (from_ty.kind(&Interner), to_ty.kind(&Interner)) {
             // Never type will make type variable to fallback to Never Type instead of Unknown.
             (TyKind::Never, TyKind::InferenceVar(tv, TyVariableKind::General)) => {
                 self.table.type_variable_table.set_diverging(*tv, true);
@@ -73,17 +71,19 @@ impl<'a> InferenceContext<'a> {
         }
 
         // Pointer weakening and function to pointer
-        match (from_ty.interned_mut(), to_ty.interned(&Interner)) {
+        match (from_ty.kind(&Interner), to_ty.kind(&Interner)) {
             // `*mut T` -> `*const T`
+            (TyKind::Raw(_, inner), TyKind::Raw(m2 @ Mutability::Not, ..)) => {
+                from_ty = TyKind::Raw(*m2, inner.clone()).intern(&Interner);
+            }
             // `&mut T` -> `&T`
-            (TyKind::Raw(m1, ..), TyKind::Raw(m2 @ Mutability::Not, ..))
-            | (TyKind::Ref(m1, ..), TyKind::Ref(m2 @ Mutability::Not, ..)) => {
-                *m1 = *m2;
+            (TyKind::Ref(_, lt, inner), TyKind::Ref(m2 @ Mutability::Not, ..)) => {
+                from_ty = TyKind::Ref(*m2, lt.clone(), inner.clone()).intern(&Interner);
             }
             // `&T` -> `*const T`
             // `&mut T` -> `*mut T`/`*const T`
             (TyKind::Ref(.., substs), &TyKind::Raw(m2 @ Mutability::Not, ..))
-            | (TyKind::Ref(Mutability::Mut, substs), &TyKind::Raw(m2, ..)) => {
+            | (TyKind::Ref(Mutability::Mut, _, substs), &TyKind::Raw(m2, ..)) => {
                 from_ty = TyKind::Raw(m2, substs.clone()).intern(&Interner);
             }
 
@@ -95,12 +95,12 @@ impl<'a> InferenceContext<'a> {
             (TyKind::FnDef(..), TyKind::Function { .. }) => match from_ty.callable_sig(self.db) {
                 None => return false,
                 Some(sig) => {
-                    from_ty = Ty::fn_ptr(sig);
+                    from_ty = TyBuilder::fn_ptr(sig);
                 }
             },
 
             (TyKind::Closure(.., substs), TyKind::Function { .. }) => {
-                from_ty = substs[0].clone();
+                from_ty = substs.at(&Interner, 0).assert_ty_ref(&Interner).clone();
             }
 
             _ => {}
@@ -111,9 +111,11 @@ impl<'a> InferenceContext<'a> {
         }
 
         // Auto Deref if cannot coerce
-        match (from_ty.interned(&Interner), to_ty.interned(&Interner)) {
+        match (from_ty.kind(&Interner), to_ty.kind(&Interner)) {
             // FIXME: DerefMut
-            (TyKind::Ref(_, st1), TyKind::Ref(_, st2)) => self.unify_autoderef_behind_ref(st1, st2),
+            (TyKind::Ref(.., st1), TyKind::Ref(.., st2)) => {
+                self.unify_autoderef_behind_ref(st1, st2)
+            }
 
             // Otherwise, normal unify
             _ => self.unify(&from_ty, to_ty),
@@ -130,19 +132,16 @@ impl<'a> InferenceContext<'a> {
             _ => return None,
         };
 
-        let generic_params = crate::utils::generics(self.db.upcast(), coerce_unsized_trait.into());
-        if generic_params.len() != 2 {
-            // The CoerceUnsized trait should have two generic params: Self and T.
-            return None;
-        }
+        let trait_ref = {
+            let b = TyBuilder::trait_ref(self.db, coerce_unsized_trait);
+            if b.remaining() != 2 {
+                // The CoerceUnsized trait should have two generic params: Self and T.
+                return None;
+            }
+            b.push(from_ty.clone()).push(to_ty.clone()).build()
+        };
 
-        let substs = Substitution::build_for_generics(&generic_params)
-            .push(from_ty.clone())
-            .push(to_ty.clone())
-            .build();
-        let trait_ref =
-            TraitRef { trait_id: to_chalk_trait_id(coerce_unsized_trait), substitution: substs };
-        let goal = InEnvironment::new(self.trait_env.env.clone(), trait_ref.cast(&Interner));
+        let goal = InEnvironment::new(&self.trait_env.env, trait_ref.cast(&Interner));
 
         let canonicalizer = self.canonicalizer();
         let canonicalized = canonicalizer.canonicalize_obligation(goal);
@@ -151,7 +150,14 @@ impl<'a> InferenceContext<'a> {
 
         match solution {
             Solution::Unique(v) => {
-                canonicalized.apply_solution(self, v.0);
+                canonicalized.apply_solution(
+                    self,
+                    Canonical {
+                        binders: v.binders,
+                        // FIXME handle constraints
+                        value: v.value.subst,
+                    },
+                );
             }
             _ => return None,
         };
diff --git a/crates/hir_ty/src/infer/expr.rs b/crates/hir_ty/src/infer/expr.rs
index e6ede05ca..50497eecb 100644
--- a/crates/hir_ty/src/infer/expr.rs
+++ b/crates/hir_ty/src/infer/expr.rs
@@ -3,7 +3,7 @@
 use std::iter::{repeat, repeat_with};
 use std::{mem, sync::Arc};
 
-use chalk_ir::{cast::Cast, Mutability, TyVariableKind};
+use chalk_ir::{cast::Cast, fold::Shift, Mutability, TyVariableKind};
 use hir_def::{
     expr::{Array, BinaryOp, Expr, ExprId, Literal, Statement, UnaryOp},
     path::{GenericArg, GenericArgs},
@@ -15,15 +15,16 @@ use stdx::always;
 use syntax::ast::RangeOp;
 
 use crate::{
-    autoderef,
+    autoderef, dummy_usize_const,
     lower::lower_to_chalk_mutability,
+    mapping::from_chalk,
     method_resolution, op,
     primitive::{self, UintTy},
-    to_assoc_type_id, to_chalk_trait_id,
-    traits::{chalk::from_chalk, FnTrait, InEnvironment},
-    utils::{generics, variant_data, Generics},
-    AdtId, Binders, CallableDefId, DomainGoal, FnPointer, FnSig, Interner, Rawness, Scalar,
-    Substitution, TraitRef, Ty, TyKind,
+    static_lifetime, to_chalk_trait_id,
+    traits::FnTrait,
+    utils::{generics, Generics},
+    AdtId, Binders, CallableDefId, FnPointer, FnSig, FnSubst, InEnvironment, Interner,
+    ProjectionTyExt, Rawness, Scalar, Substitution, TraitRef, Ty, TyBuilder, TyExt, TyKind,
 };
 
 use super::{
@@ -73,38 +74,33 @@ impl<'a> InferenceContext<'a> {
         let fn_once_trait = FnTrait::FnOnce.get_id(self.db, krate)?;
         let output_assoc_type =
             self.db.trait_data(fn_once_trait).associated_type_by_name(&name![Output])?;
-        let generic_params = generics(self.db.upcast(), fn_once_trait.into());
-        if generic_params.len() != 2 {
-            return None;
-        }
 
-        let mut param_builder = Substitution::builder(num_args);
         let mut arg_tys = vec![];
-        for _ in 0..num_args {
-            let arg = self.table.new_type_var();
-            param_builder = param_builder.push(arg.clone());
-            arg_tys.push(arg);
-        }
-        let parameters = param_builder.build();
-        let arg_ty = TyKind::Tuple(num_args, parameters).intern(&Interner);
-        let substs =
-            Substitution::build_for_generics(&generic_params).push(ty.clone()).push(arg_ty).build();
+        let arg_ty = TyBuilder::tuple(num_args)
+            .fill(repeat_with(|| {
+                let arg = self.table.new_type_var();
+                arg_tys.push(arg.clone());
+                arg
+            }))
+            .build();
+
+        let projection = {
+            let b = TyBuilder::assoc_type_projection(self.db, output_assoc_type);
+            if b.remaining() != 2 {
+                return None;
+            }
+            b.push(ty.clone()).push(arg_ty).build()
+        };
 
         let trait_env = self.trait_env.env.clone();
-        let implements_fn_trait: DomainGoal =
-            TraitRef { trait_id: to_chalk_trait_id(fn_once_trait), substitution: substs.clone() }
-                .cast(&Interner);
-        let goal = self.canonicalizer().canonicalize_obligation(InEnvironment {
-            goal: implements_fn_trait.clone(),
+        let obligation = InEnvironment {
+            goal: projection.trait_ref(self.db).cast(&Interner),
             environment: trait_env,
-        });
-        if self.db.trait_solve(krate, goal.value).is_some() {
-            self.obligations.push(implements_fn_trait);
-            let output_proj_ty = crate::ProjectionTy {
-                associated_ty_id: to_assoc_type_id(output_assoc_type),
-                substitution: substs,
-            };
-            let return_ty = self.normalize_projection_ty(output_proj_ty);
+        };
+        let canonical = self.canonicalizer().canonicalize_obligation(obligation.clone());
+        if self.db.trait_solve(krate, canonical.value).is_some() {
+            self.push_obligation(obligation.goal);
+            let return_ty = self.normalize_projection_ty(projection);
             Some((arg_tys, return_ty))
         } else {
             None
@@ -119,6 +115,8 @@ impl<'a> InferenceContext<'a> {
     }
 
     fn infer_expr_inner(&mut self, tgt_expr: ExprId, expected: &Expectation) -> Ty {
+        self.db.check_canceled();
+
         let body = Arc::clone(&self.body); // avoid borrow checker problem
         let ty = match &body[tgt_expr] {
             Expr::Missing => self.err_ty(),
@@ -136,7 +134,7 @@ impl<'a> InferenceContext<'a> {
                 both_arms_diverge &= mem::replace(&mut self.diverges, Diverges::Maybe);
                 let else_ty = match else_branch {
                     Some(else_branch) => self.infer_expr_inner(*else_branch, &expected),
-                    None => Ty::unit(),
+                    None => TyBuilder::unit(),
                 };
                 both_arms_diverge &= self.diverges;
 
@@ -183,7 +181,8 @@ impl<'a> InferenceContext<'a> {
                 let inner_ty = self.infer_expr(*body, &Expectation::none());
                 let impl_trait_id = crate::ImplTraitId::AsyncBlockTypeImplTrait(self.owner, *body);
                 let opaque_ty_id = self.db.intern_impl_trait_id(impl_trait_id).into();
-                TyKind::OpaqueType(opaque_ty_id, Substitution::single(inner_ty)).intern(&Interner)
+                TyKind::OpaqueType(opaque_ty_id, Substitution::from1(&Interner, inner_ty))
+                    .intern(&Interner)
             }
             Expr::Loop { body, label } => {
                 self.breakables.push(BreakableContext {
@@ -191,7 +190,7 @@ impl<'a> InferenceContext<'a> {
                     break_ty: self.table.new_type_var(),
                     label: label.map(|label| self.body[label].name.clone()),
                 });
-                self.infer_expr(*body, &Expectation::has_type(Ty::unit()));
+                self.infer_expr(*body, &Expectation::has_type(TyBuilder::unit()));
 
                 let ctxt = self.breakables.pop().expect("breakable stack broken");
                 if ctxt.may_break {
@@ -215,11 +214,11 @@ impl<'a> InferenceContext<'a> {
                     *condition,
                     &Expectation::has_type(TyKind::Scalar(Scalar::Bool).intern(&Interner)),
                 );
-                self.infer_expr(*body, &Expectation::has_type(Ty::unit()));
+                self.infer_expr(*body, &Expectation::has_type(TyBuilder::unit()));
                 let _ctxt = self.breakables.pop().expect("breakable stack broken");
                 // the body may not run, so it diverging doesn't mean we diverge
                 self.diverges = Diverges::Maybe;
-                Ty::unit()
+                TyBuilder::unit()
             }
             Expr::For { iterable, body, pat, label } => {
                 let iterable_ty = self.infer_expr(*iterable, &Expectation::none());
@@ -234,11 +233,11 @@ impl<'a> InferenceContext<'a> {
 
                 self.infer_pat(*pat, &pat_ty, BindingMode::default());
 
-                self.infer_expr(*body, &Expectation::has_type(Ty::unit()));
+                self.infer_expr(*body, &Expectation::has_type(TyBuilder::unit()));
                 let _ctxt = self.breakables.pop().expect("breakable stack broken");
                 // the body may not run, so it diverging doesn't mean we diverge
                 self.diverges = Diverges::Maybe;
-                Ty::unit()
+                TyBuilder::unit()
             }
             Expr::Lambda { body, args, ret_type, arg_types } => {
                 assert_eq!(args.len(), arg_types.len());
@@ -262,14 +261,17 @@ impl<'a> InferenceContext<'a> {
                 };
                 sig_tys.push(ret_ty.clone());
                 let sig_ty = TyKind::Function(FnPointer {
-                    num_args: sig_tys.len() - 1,
+                    num_binders: 0,
                     sig: FnSig { abi: (), safety: chalk_ir::Safety::Safe, variadic: false },
-                    substs: Substitution(sig_tys.clone().into()),
+                    substitution: FnSubst(
+                        Substitution::from_iter(&Interner, sig_tys.clone()).shifted_in(&Interner),
+                    ),
                 })
                 .intern(&Interner);
                 let closure_id = self.db.intern_closure((self.owner, tgt_expr)).into();
                 let closure_ty =
-                    TyKind::Closure(closure_id, Substitution::single(sig_ty)).intern(&Interner);
+                    TyKind::Closure(closure_id, Substitution::from1(&Interner, sig_ty))
+                        .intern(&Interner);
 
                 // Eagerly try to relate the closure type with the expected
                 // type, otherwise we often won't have enough information to
@@ -316,7 +318,13 @@ impl<'a> InferenceContext<'a> {
                 self.normalize_associated_types_in(ret_ty)
             }
             Expr::MethodCall { receiver, args, method_name, generic_args } => self
-                .infer_method_call(tgt_expr, *receiver, &args, &method_name, generic_args.as_ref()),
+                .infer_method_call(
+                    tgt_expr,
+                    *receiver,
+                    &args,
+                    &method_name,
+                    generic_args.as_deref(),
+                ),
             Expr::Match { expr, arms } => {
                 let input_ty = self.infer_expr(*expr, &Expectation::none());
 
@@ -358,7 +366,7 @@ impl<'a> InferenceContext<'a> {
                 let val_ty = if let Some(expr) = expr {
                     self.infer_expr(*expr, &Expectation::none())
                 } else {
-                    Ty::unit()
+                    TyBuilder::unit()
                 };
 
                 let last_ty =
@@ -384,7 +392,7 @@ impl<'a> InferenceContext<'a> {
                 if let Some(expr) = expr {
                     self.infer_expr_coerce(*expr, &Expectation::has_type(self.return_ty.clone()));
                 } else {
-                    let unit = Ty::unit();
+                    let unit = TyBuilder::unit();
                     self.coerce(&unit, &self.return_ty.clone());
                 }
                 TyKind::Never.intern(&Interner)
@@ -397,16 +405,19 @@ impl<'a> InferenceContext<'a> {
                 TyKind::Never.intern(&Interner)
             }
             Expr::RecordLit { path, fields, spread } => {
-                let (ty, def_id) = self.resolve_variant(path.as_ref());
+                let (ty, def_id) = self.resolve_variant(path.as_deref());
                 if let Some(variant) = def_id {
                     self.write_variant_resolution(tgt_expr.into(), variant);
                 }
 
                 self.unify(&ty, &expected.ty);
 
-                let substs = ty.substs().cloned().unwrap_or_else(Substitution::empty);
+                let substs = ty
+                    .as_adt()
+                    .map(|(_, s)| s.clone())
+                    .unwrap_or_else(|| Substitution::empty(&Interner));
                 let field_types = def_id.map(|it| self.db.field_types(it)).unwrap_or_default();
-                let variant_data = def_id.map(|it| variant_data(self.db.upcast(), it));
+                let variant_data = def_id.map(|it| it.variant_data(self.db.upcast()));
                 for field in fields.iter() {
                     let field_def =
                         variant_data.as_ref().and_then(|it| match it.field(&field.name) {
@@ -418,11 +429,8 @@ impl<'a> InferenceContext<'a> {
                                 None
                             }
                         });
-                    if let Some(field_def) = field_def {
-                        self.result.record_field_resolutions.insert(field.expr, field_def);
-                    }
                     let field_ty = field_def.map_or(self.err_ty(), |it| {
-                        field_types[it.local_id].clone().subst(&substs)
+                        field_types[it.local_id].clone().substitute(&Interner, &substs)
                     });
                     self.infer_expr_coerce(field.expr, &Expectation::has_type(field_ty));
                 }
@@ -453,10 +461,14 @@ impl<'a> InferenceContext<'a> {
                             })
                             .unwrap_or(true)
                     };
-                    match canonicalized.decanonicalize_ty(derefed_ty.value).interned(&Interner) {
-                        TyKind::Tuple(_, substs) => {
-                            name.as_tuple_index().and_then(|idx| substs.0.get(idx).cloned())
-                        }
+                    match canonicalized.decanonicalize_ty(derefed_ty.value).kind(&Interner) {
+                        TyKind::Tuple(_, substs) => name.as_tuple_index().and_then(|idx| {
+                            substs
+                                .as_slice(&Interner)
+                                .get(idx)
+                                .map(|a| a.assert_ty_ref(&Interner))
+                                .cloned()
+                        }),
                         TyKind::Adt(AdtId(hir_def::AdtId::StructId(s)), parameters) => {
                             let local_id = self.db.struct_data(*s).variant_data.field(name)?;
                             let field = FieldId { parent: (*s).into(), local_id };
@@ -465,7 +477,7 @@ impl<'a> InferenceContext<'a> {
                                 Some(
                                     self.db.field_types((*s).into())[field.local_id]
                                         .clone()
-                                        .subst(&parameters),
+                                        .substitute(&Interner, &parameters),
                                 )
                             } else {
                                 None
@@ -479,7 +491,7 @@ impl<'a> InferenceContext<'a> {
                                 Some(
                                     self.db.field_types((*u).into())[field.local_id]
                                         .clone()
-                                        .subst(&parameters),
+                                        .substitute(&Interner, &parameters),
                                 )
                             } else {
                                 None
@@ -526,24 +538,17 @@ impl<'a> InferenceContext<'a> {
                 let inner_ty = self.infer_expr_inner(*expr, &expectation);
                 match rawness {
                     Rawness::RawPtr => TyKind::Raw(mutability, inner_ty),
-                    Rawness::Ref => TyKind::Ref(mutability, inner_ty),
+                    Rawness::Ref => TyKind::Ref(mutability, static_lifetime(), inner_ty),
                 }
                 .intern(&Interner)
             }
             Expr::Box { expr } => {
                 let inner_ty = self.infer_expr_inner(*expr, &Expectation::none());
                 if let Some(box_) = self.resolve_boxed_box() {
-                    let mut sb =
-                        Substitution::build_for_generics(&generics(self.db.upcast(), box_.into()));
-                    sb = sb.push(inner_ty);
-                    match self.db.generic_defaults(box_.into()).get(1) {
-                        Some(alloc_ty) if !alloc_ty.value.is_unknown() && sb.remaining() > 0 => {
-                            sb = sb.push(alloc_ty.value.clone());
-                        }
-                        _ => (),
-                    }
-                    sb = sb.fill(repeat_with(|| self.table.new_type_var()));
-                    Ty::adt_ty(box_, sb.build())
+                    TyBuilder::adt(self.db, box_)
+                        .push(inner_ty)
+                        .fill_with_defaults(self.db, || self.table.new_type_var())
+                        .build()
                 } else {
                     self.err_ty()
                 }
@@ -571,7 +576,7 @@ impl<'a> InferenceContext<'a> {
                         None => self.err_ty(),
                     },
                     UnaryOp::Neg => {
-                        match inner_ty.interned(&Interner) {
+                        match inner_ty.kind(&Interner) {
                             // Fast path for builtins
                             TyKind::Scalar(Scalar::Int(_))
                             | TyKind::Scalar(Scalar::Uint(_))
@@ -584,7 +589,7 @@ impl<'a> InferenceContext<'a> {
                         }
                     }
                     UnaryOp::Not => {
-                        match inner_ty.interned(&Interner) {
+                        match inner_ty.kind(&Interner) {
                             // Fast path for builtins
                             TyKind::Scalar(Scalar::Bool)
                             | TyKind::Scalar(Scalar::Int(_))
@@ -633,31 +638,31 @@ impl<'a> InferenceContext<'a> {
                 let rhs_ty = rhs.map(|e| self.infer_expr(e, &rhs_expect));
                 match (range_type, lhs_ty, rhs_ty) {
                     (RangeOp::Exclusive, None, None) => match self.resolve_range_full() {
-                        Some(adt) => Ty::adt_ty(adt, Substitution::empty()),
+                        Some(adt) => TyBuilder::adt(self.db, adt).build(),
                         None => self.err_ty(),
                     },
                     (RangeOp::Exclusive, None, Some(ty)) => match self.resolve_range_to() {
-                        Some(adt) => Ty::adt_ty(adt, Substitution::single(ty)),
+                        Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
                         None => self.err_ty(),
                     },
                     (RangeOp::Inclusive, None, Some(ty)) => {
                         match self.resolve_range_to_inclusive() {
-                            Some(adt) => Ty::adt_ty(adt, Substitution::single(ty)),
+                            Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
                             None => self.err_ty(),
                         }
                     }
                     (RangeOp::Exclusive, Some(_), Some(ty)) => match self.resolve_range() {
-                        Some(adt) => Ty::adt_ty(adt, Substitution::single(ty)),
+                        Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
                         None => self.err_ty(),
                     },
                     (RangeOp::Inclusive, Some(_), Some(ty)) => {
                         match self.resolve_range_inclusive() {
-                            Some(adt) => Ty::adt_ty(adt, Substitution::single(ty)),
+                            Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
                             None => self.err_ty(),
                         }
                     }
                     (RangeOp::Exclusive, Some(ty), None) => match self.resolve_range_from() {
-                        Some(adt) => Ty::adt_ty(adt, Substitution::single(ty)),
+                        Some(adt) => TyBuilder::adt(self.db, adt).push(ty).build(),
                         None => self.err_ty(),
                     },
                     (RangeOp::Inclusive, _, None) => self.err_ty(),
@@ -690,10 +695,10 @@ impl<'a> InferenceContext<'a> {
                 }
             }
             Expr::Tuple { exprs } => {
-                let mut tys = match expected.ty.interned(&Interner) {
+                let mut tys = match expected.ty.kind(&Interner) {
                     TyKind::Tuple(_, substs) => substs
-                        .iter()
-                        .cloned()
+                        .iter(&Interner)
+                        .map(|a| a.assert_ty_ref(&Interner).clone())
                         .chain(repeat_with(|| self.table.new_type_var()))
                         .take(exprs.len())
                         .collect::<Vec<_>>(),
@@ -704,11 +709,11 @@ impl<'a> InferenceContext<'a> {
                     self.infer_expr_coerce(*expr, &Expectation::has_type(ty.clone()));
                 }
 
-                TyKind::Tuple(tys.len(), Substitution(tys.into())).intern(&Interner)
+                TyKind::Tuple(tys.len(), Substitution::from_iter(&Interner, tys)).intern(&Interner)
             }
             Expr::Array(array) => {
-                let elem_ty = match expected.ty.interned(&Interner) {
-                    TyKind::Array(st) | TyKind::Slice(st) => st.clone(),
+                let elem_ty = match expected.ty.kind(&Interner) {
+                    TyKind::Array(st, _) | TyKind::Slice(st) => st.clone(),
                     _ => self.table.new_type_var(),
                 };
 
@@ -732,17 +737,19 @@ impl<'a> InferenceContext<'a> {
                     }
                 }
 
-                TyKind::Array(elem_ty).intern(&Interner)
+                TyKind::Array(elem_ty, dummy_usize_const()).intern(&Interner)
             }
             Expr::Literal(lit) => match lit {
                 Literal::Bool(..) => TyKind::Scalar(Scalar::Bool).intern(&Interner),
                 Literal::String(..) => {
-                    TyKind::Ref(Mutability::Not, TyKind::Str.intern(&Interner)).intern(&Interner)
+                    TyKind::Ref(Mutability::Not, static_lifetime(), TyKind::Str.intern(&Interner))
+                        .intern(&Interner)
                 }
                 Literal::ByteString(..) => {
                     let byte_type = TyKind::Scalar(Scalar::Uint(UintTy::U8)).intern(&Interner);
-                    let array_type = TyKind::Array(byte_type).intern(&Interner);
-                    TyKind::Ref(Mutability::Not, array_type).intern(&Interner)
+                    let array_type =
+                        TyKind::Array(byte_type, dummy_usize_const()).intern(&Interner);
+                    TyKind::Ref(Mutability::Not, static_lifetime(), array_type).intern(&Interner)
                 }
                 Literal::Char(..) => TyKind::Scalar(Scalar::Char).intern(&Interner),
                 Literal::Int(_v, ty) => match ty {
@@ -822,8 +829,8 @@ impl<'a> InferenceContext<'a> {
                 // we don't even make an attempt at coercion
                 self.table.new_maybe_never_var()
             } else {
-                self.coerce(&Ty::unit(), &expected.coercion_target());
-                Ty::unit()
+                self.coerce(&TyBuilder::unit(), &expected.coercion_target());
+                TyBuilder::unit()
             }
         };
         ty
@@ -859,10 +866,10 @@ impl<'a> InferenceContext<'a> {
                 self.write_method_resolution(tgt_expr, func);
                 (ty, self.db.value_ty(func.into()), Some(generics(self.db.upcast(), func.into())))
             }
-            None => (receiver_ty, Binders::new(0, self.err_ty()), None),
+            None => (receiver_ty, Binders::empty(&Interner, self.err_ty()), None),
         };
         let substs = self.substs_for_method_call(def_generics, generic_args, &derefed_receiver_ty);
-        let method_ty = method_ty.subst(&substs);
+        let method_ty = method_ty.substitute(&Interner, &substs);
         let method_ty = self.insert_type_vars(method_ty);
         self.register_obligations_for_call(&method_ty);
         let (expected_receiver_ty, param_tys, ret_ty) = match method_ty.callable_sig(self.db) {
@@ -878,7 +885,9 @@ impl<'a> InferenceContext<'a> {
         // Apply autoref so the below unification works correctly
         // FIXME: return correct autorefs from lookup_method
         let actual_receiver_ty = match expected_receiver_ty.as_reference() {
-            Some((_, mutability)) => TyKind::Ref(mutability, derefed_receiver_ty).intern(&Interner),
+            Some((_, lifetime, mutability)) => {
+                TyKind::Ref(mutability, lifetime, derefed_receiver_ty).intern(&Interner)
+            }
             _ => derefed_receiver_ty,
         };
         self.unify(&expected_receiver_ty, &actual_receiver_ty);
@@ -951,18 +960,20 @@ impl<'a> InferenceContext<'a> {
             substs.push(self.err_ty());
         }
         assert_eq!(substs.len(), total_len);
-        Substitution(substs.into())
+        Substitution::from_iter(&Interner, substs)
     }
 
     fn register_obligations_for_call(&mut self, callable_ty: &Ty) {
-        if let TyKind::FnDef(fn_def, parameters) = callable_ty.interned(&Interner) {
+        if let TyKind::FnDef(fn_def, parameters) = callable_ty.kind(&Interner) {
             let def: CallableDefId = from_chalk(self.db, *fn_def);
             let generic_predicates = self.db.generic_predicates(def.into());
             for predicate in generic_predicates.iter() {
-                let (predicate, binders) =
-                    predicate.clone().subst(parameters).into_value_and_skipped_binders();
-                always!(binders == 0); // quantified where clauses not yet handled
-                self.obligations.push(predicate.cast(&Interner));
+                let (predicate, binders) = predicate
+                    .clone()
+                    .substitute(&Interner, parameters)
+                    .into_value_and_skipped_binders();
+                always!(binders.len(&Interner) == 0); // quantified where clauses not yet handled
+                self.push_obligation(predicate.cast(&Interner));
             }
             // add obligation for trait implementation, if this is a trait method
             match def {
@@ -970,9 +981,11 @@ impl<'a> InferenceContext<'a> {
                     if let AssocContainerId::TraitId(trait_) = f.lookup(self.db.upcast()).container
                     {
                         // construct a TraitRef
-                        let substs =
-                            parameters.prefix(generics(self.db.upcast(), trait_.into()).len());
-                        self.obligations.push(
+                        let substs = crate::subst_prefix(
+                            &*parameters,
+                            generics(self.db.upcast(), trait_.into()).len(),
+                        );
+                        self.push_obligation(
                             TraitRef { trait_id: to_chalk_trait_id(trait_), substitution: substs }
                                 .cast(&Interner),
                         );
diff --git a/crates/hir_ty/src/infer/pat.rs b/crates/hir_ty/src/infer/pat.rs
index 474363709..aea354cde 100644
--- a/crates/hir_ty/src/infer/pat.rs
+++ b/crates/hir_ty/src/infer/pat.rs
@@ -7,15 +7,13 @@ use chalk_ir::Mutability;
 use hir_def::{
     expr::{BindingAnnotation, Expr, Literal, Pat, PatId, RecordFieldPat},
     path::Path,
-    FieldId,
 };
 use hir_expand::name::Name;
 
 use super::{BindingMode, Expectation, InferenceContext};
 use crate::{
-    lower::lower_to_chalk_mutability,
-    utils::{generics, variant_data},
-    Interner, Substitution, Ty, TyKind,
+    lower::lower_to_chalk_mutability, static_lifetime, Interner, Substitution, Ty, TyBuilder,
+    TyExt, TyKind,
 };
 
 impl<'a> InferenceContext<'a> {
@@ -29,13 +27,14 @@ impl<'a> InferenceContext<'a> {
         ellipsis: Option<usize>,
     ) -> Ty {
         let (ty, def) = self.resolve_variant(path);
-        let var_data = def.map(|it| variant_data(self.db.upcast(), it));
+        let var_data = def.map(|it| it.variant_data(self.db.upcast()));
         if let Some(variant) = def {
             self.write_variant_resolution(id.into(), variant);
         }
         self.unify(&ty, expected);
 
-        let substs = ty.substs().cloned().unwrap_or_else(Substitution::empty);
+        let substs =
+            ty.as_adt().map(|(_, s)| s.clone()).unwrap_or_else(|| Substitution::empty(&Interner));
 
         let field_tys = def.map(|it| self.db.field_types(it)).unwrap_or_default();
         let (pre, post) = match ellipsis {
@@ -50,7 +49,9 @@ impl<'a> InferenceContext<'a> {
             let expected_ty = var_data
                 .as_ref()
                 .and_then(|d| d.field(&Name::new_tuple_field(i)))
-                .map_or(self.err_ty(), |field| field_tys[field].clone().subst(&substs));
+                .map_or(self.err_ty(), |field| {
+                    field_tys[field].clone().substitute(&Interner, &substs)
+                });
             let expected_ty = self.normalize_associated_types_in(expected_ty);
             self.infer_pat(subpat, &expected_ty, default_bm);
         }
@@ -67,25 +68,22 @@ impl<'a> InferenceContext<'a> {
         id: PatId,
     ) -> Ty {
         let (ty, def) = self.resolve_variant(path);
-        let var_data = def.map(|it| variant_data(self.db.upcast(), it));
+        let var_data = def.map(|it| it.variant_data(self.db.upcast()));
         if let Some(variant) = def {
             self.write_variant_resolution(id.into(), variant);
         }
 
         self.unify(&ty, expected);
 
-        let substs = ty.substs().cloned().unwrap_or_else(Substitution::empty);
+        let substs =
+            ty.as_adt().map(|(_, s)| s.clone()).unwrap_or_else(|| Substitution::empty(&Interner));
 
         let field_tys = def.map(|it| self.db.field_types(it)).unwrap_or_default();
         for subpat in subpats {
             let matching_field = var_data.as_ref().and_then(|it| it.field(&subpat.name));
-            if let Some(local_id) = matching_field {
-                let field_def = FieldId { parent: def.unwrap(), local_id };
-                self.result.record_pat_field_resolutions.insert(subpat.pat, field_def);
-            }
-
-            let expected_ty = matching_field
-                .map_or(self.err_ty(), |field| field_tys[field].clone().subst(&substs));
+            let expected_ty = matching_field.map_or(self.err_ty(), |field| {
+                field_tys[field].clone().substitute(&Interner, &substs)
+            });
             let expected_ty = self.normalize_associated_types_in(expected_ty);
             self.infer_pat(subpat.pat, &expected_ty, default_bm);
         }
@@ -102,7 +100,7 @@ impl<'a> InferenceContext<'a> {
         let body = Arc::clone(&self.body); // avoid borrow checker problem
 
         if is_non_ref_pat(&body, pat) {
-            while let Some((inner, mutability)) = expected.as_reference() {
+            while let Some((inner, _lifetime, mutability)) = expected.as_reference() {
                 expected = inner;
                 default_bm = match default_bm {
                     BindingMode::Move => BindingMode::Ref(mutability),
@@ -124,7 +122,7 @@ impl<'a> InferenceContext<'a> {
         let ty = match &body[pat] {
             &Pat::Tuple { ref args, ellipsis } => {
                 let expectations = match expected.as_tuple() {
-                    Some(parameters) => &*parameters.0,
+                    Some(parameters) => &*parameters.as_slice(&Interner),
                     _ => &[],
                 };
 
@@ -134,7 +132,8 @@ impl<'a> InferenceContext<'a> {
                 };
                 let n_uncovered_patterns = expectations.len().saturating_sub(args.len());
                 let err_ty = self.err_ty();
-                let mut expectations_iter = expectations.iter().chain(repeat(&err_ty));
+                let mut expectations_iter =
+                    expectations.iter().map(|a| a.assert_ty_ref(&Interner)).chain(repeat(&err_ty));
                 let mut infer_pat = |(&pat, ty)| self.infer_pat(pat, ty, default_bm);
 
                 let mut inner_tys = Vec::with_capacity(n_uncovered_patterns + args.len());
@@ -142,7 +141,8 @@ impl<'a> InferenceContext<'a> {
                 inner_tys.extend(expectations_iter.by_ref().take(n_uncovered_patterns).cloned());
                 inner_tys.extend(post.iter().zip(expectations_iter).map(infer_pat));
 
-                TyKind::Tuple(inner_tys.len(), Substitution(inner_tys.into())).intern(&Interner)
+                TyKind::Tuple(inner_tys.len(), Substitution::from_iter(&Interner, inner_tys))
+                    .intern(&Interner)
             }
             Pat::Or(ref pats) => {
                 if let Some((first_pat, rest)) = pats.split_first() {
@@ -158,7 +158,7 @@ impl<'a> InferenceContext<'a> {
             Pat::Ref { pat, mutability } => {
                 let mutability = lower_to_chalk_mutability(*mutability);
                 let expectation = match expected.as_reference() {
-                    Some((inner_ty, exp_mut)) => {
+                    Some((inner_ty, _lifetime, exp_mut)) => {
                         if mutability != exp_mut {
                             // FIXME: emit type error?
                         }
@@ -167,10 +167,10 @@ impl<'a> InferenceContext<'a> {
                     _ => self.result.standard_types.unknown.clone(),
                 };
                 let subty = self.infer_pat(*pat, &expectation, default_bm);
-                TyKind::Ref(mutability, subty).intern(&Interner)
+                TyKind::Ref(mutability, static_lifetime(), subty).intern(&Interner)
             }
             Pat::TupleStruct { path: p, args: subpats, ellipsis } => self.infer_tuple_struct_pat(
-                p.as_ref(),
+                p.as_deref(),
                 subpats,
                 expected,
                 default_bm,
@@ -178,7 +178,7 @@ impl<'a> InferenceContext<'a> {
                 *ellipsis,
             ),
             Pat::Record { path: p, args: fields, ellipsis: _ } => {
-                self.infer_record_pat(p.as_ref(), fields, expected, default_bm, pat)
+                self.infer_record_pat(p.as_deref(), fields, expected, default_bm, pat)
             }
             Pat::Path(path) => {
                 // FIXME use correct resolver for the surrounding expression
@@ -200,7 +200,8 @@ impl<'a> InferenceContext<'a> {
 
                 let bound_ty = match mode {
                     BindingMode::Ref(mutability) => {
-                        TyKind::Ref(mutability, inner_ty.clone()).intern(&Interner)
+                        TyKind::Ref(mutability, static_lifetime(), inner_ty.clone())
+                            .intern(&Interner)
                     }
                     BindingMode::Move => inner_ty.clone(),
                 };
@@ -209,17 +210,20 @@ impl<'a> InferenceContext<'a> {
                 return inner_ty;
             }
             Pat::Slice { prefix, slice, suffix } => {
-                let (container_ty, elem_ty): (fn(_) -> _, _) = match expected.interned(&Interner) {
-                    TyKind::Array(st) => (TyKind::Array, st.clone()),
-                    TyKind::Slice(st) => (TyKind::Slice, st.clone()),
-                    _ => (TyKind::Slice, self.err_ty()),
+                let elem_ty = match expected.kind(&Interner) {
+                    TyKind::Array(st, _) | TyKind::Slice(st) => st.clone(),
+                    _ => self.err_ty(),
                 };
 
                 for pat_id in prefix.iter().chain(suffix) {
                     self.infer_pat(*pat_id, &elem_ty, default_bm);
                 }
 
-                let pat_ty = container_ty(elem_ty).intern(&Interner);
+                let pat_ty = match expected.kind(&Interner) {
+                    TyKind::Array(_, const_) => TyKind::Array(elem_ty, const_.clone()),
+                    _ => TyKind::Slice(elem_ty),
+                }
+                .intern(&Interner);
                 if let Some(slice_pat_id) = slice {
                     self.infer_pat(*slice_pat_id, &pat_ty, default_bm);
                 }
@@ -236,30 +240,20 @@ impl<'a> InferenceContext<'a> {
             Pat::Box { inner } => match self.resolve_boxed_box() {
                 Some(box_adt) => {
                     let (inner_ty, alloc_ty) = match expected.as_adt() {
-                        Some((adt, subst)) if adt == box_adt => {
-                            (subst[0].clone(), subst.get(1).cloned())
-                        }
+                        Some((adt, subst)) if adt == box_adt => (
+                            subst.at(&Interner, 0).assert_ty_ref(&Interner).clone(),
+                            subst.as_slice(&Interner).get(1).and_then(|a| a.ty(&Interner).cloned()),
+                        ),
                         _ => (self.result.standard_types.unknown.clone(), None),
                     };
 
                     let inner_ty = self.infer_pat(*inner, &inner_ty, default_bm);
-                    let mut sb = Substitution::build_for_generics(&generics(
-                        self.db.upcast(),
-                        box_adt.into(),
-                    ));
-                    sb = sb.push(inner_ty);
-                    if sb.remaining() == 1 {
-                        sb = sb.push(match alloc_ty {
-                            Some(alloc_ty) if !alloc_ty.is_unknown() => alloc_ty,
-                            _ => match self.db.generic_defaults(box_adt.into()).get(1) {
-                                Some(alloc_ty) if !alloc_ty.value.is_unknown() => {
-                                    alloc_ty.value.clone()
-                                }
-                                _ => self.table.new_type_var(),
-                            },
-                        });
+                    let mut b = TyBuilder::adt(self.db, box_adt).push(inner_ty);
+
+                    if let Some(alloc_ty) = alloc_ty {
+                        b = b.push(alloc_ty);
                     }
-                    Ty::adt_ty(box_adt, sb.build())
+                    b.fill_with_defaults(self.db, || self.table.new_type_var()).build()
                 }
                 None => self.err_ty(),
             },
diff --git a/crates/hir_ty/src/infer/path.rs b/crates/hir_ty/src/infer/path.rs
index cefa38509..495282eba 100644
--- a/crates/hir_ty/src/infer/path.rs
+++ b/crates/hir_ty/src/infer/path.rs
@@ -11,7 +11,8 @@ use hir_def::{
 use hir_expand::name::Name;
 
 use crate::{
-    method_resolution, to_chalk_trait_id, Interner, Substitution, Ty, TyKind, ValueTyDefId,
+    method_resolution, Interner, Substitution, TraitRefExt, Ty, TyBuilder, TyExt, TyKind,
+    ValueTyDefId,
 };
 
 use super::{ExprOrPatId, InferenceContext, TraitRef};
@@ -82,10 +83,10 @@ impl<'a> InferenceContext<'a> {
             }
             ValueNs::ImplSelf(impl_id) => {
                 let generics = crate::utils::generics(self.db.upcast(), impl_id.into());
-                let substs = Substitution::type_params_for_generics(self.db, &generics);
-                let ty = self.db.impl_self_ty(impl_id).subst(&substs);
+                let substs = generics.type_params_subst(self.db);
+                let ty = self.db.impl_self_ty(impl_id).substitute(&Interner, &substs);
                 if let Some((AdtId::StructId(struct_id), substs)) = ty.as_adt() {
-                    let ty = self.db.value_ty(struct_id.into()).subst(&substs);
+                    let ty = self.db.value_ty(struct_id.into()).substitute(&Interner, &substs);
                     return Some(ty);
                 } else {
                     // FIXME: diagnostic, invalid Self reference
@@ -95,16 +96,13 @@ impl<'a> InferenceContext<'a> {
             ValueNs::GenericParam(it) => return Some(self.db.const_param_ty(it)),
         };
 
-        let ty = self.db.value_ty(typable);
-        // self_subst is just for the parent
-        let parent_substs = self_subst.unwrap_or_else(Substitution::empty);
+        let parent_substs = self_subst.unwrap_or_else(|| Substitution::empty(&Interner));
         let ctx = crate::lower::TyLoweringContext::new(self.db, &self.resolver);
         let substs = ctx.substs_from_path(path, typable, true);
-        let full_substs = Substitution::builder(substs.len())
+        let ty = TyBuilder::value_ty(self.db, typable)
             .use_parent_substs(&parent_substs)
-            .fill(substs.0[parent_substs.len()..].iter().cloned())
+            .fill(substs.as_slice(&Interner)[parent_substs.len(&Interner)..].iter().cloned())
             .build();
-        let ty = ty.subst(&full_substs);
         Some(ty)
     }
 
@@ -147,7 +145,7 @@ impl<'a> InferenceContext<'a> {
                     remaining_segments_for_ty,
                     true,
                 );
-                if let TyKind::Unknown = ty.interned(&Interner) {
+                if let TyKind::Error = ty.kind(&Interner) {
                     return None;
                 }
 
@@ -212,7 +210,7 @@ impl<'a> InferenceContext<'a> {
         name: &Name,
         id: ExprOrPatId,
     ) -> Option<(ValueNs, Option<Substitution>)> {
-        if let TyKind::Unknown = ty.interned(&Interner) {
+        if let TyKind::Error = ty.kind(&Interner) {
             return None;
         }
 
@@ -245,27 +243,22 @@ impl<'a> InferenceContext<'a> {
                 };
                 let substs = match container {
                     AssocContainerId::ImplId(impl_id) => {
-                        let impl_substs = Substitution::build_for_def(self.db, impl_id)
+                        let impl_substs = TyBuilder::subst_for_def(self.db, impl_id)
                             .fill(iter::repeat_with(|| self.table.new_type_var()))
                             .build();
-                        let impl_self_ty = self.db.impl_self_ty(impl_id).subst(&impl_substs);
+                        let impl_self_ty =
+                            self.db.impl_self_ty(impl_id).substitute(&Interner, &impl_substs);
                         self.unify(&impl_self_ty, &ty);
                         Some(impl_substs)
                     }
                     AssocContainerId::TraitId(trait_) => {
                         // we're picking this method
-                        let trait_substs = Substitution::build_for_def(self.db, trait_)
+                        let trait_ref = TyBuilder::trait_ref(self.db, trait_)
                             .push(ty.clone())
                             .fill(std::iter::repeat_with(|| self.table.new_type_var()))
                             .build();
-                        self.obligations.push(
-                            TraitRef {
-                                trait_id: to_chalk_trait_id(trait_),
-                                substitution: trait_substs.clone(),
-                            }
-                            .cast(&Interner),
-                        );
-                        Some(trait_substs)
+                        self.push_obligation(trait_ref.clone().cast(&Interner));
+                        Some(trait_ref.substitution)
                     }
                     AssocContainerId::ModuleId(_) => None,
                 };
diff --git a/crates/hir_ty/src/infer/unify.rs b/crates/hir_ty/src/infer/unify.rs
index 6e7b0f5a6..a887e20b0 100644
--- a/crates/hir_ty/src/infer/unify.rs
+++ b/crates/hir_ty/src/infer/unify.rs
@@ -2,13 +2,17 @@
 
 use std::borrow::Cow;
 
-use chalk_ir::{FloatTy, IntTy, TyVariableKind, UniverseIndex, VariableKind};
+use chalk_ir::{
+    cast::Cast, fold::Fold, interner::HasInterner, FloatTy, IntTy, TyVariableKind, UniverseIndex,
+    VariableKind,
+};
 use ena::unify::{InPlaceUnificationTable, NoError, UnifyKey, UnifyValue};
 
 use super::{DomainGoal, InferenceContext};
 use crate::{
-    AliasEq, AliasTy, BoundVar, Canonical, CanonicalVarKinds, DebruijnIndex, FnPointer,
-    InEnvironment, InferenceVar, Interner, Scalar, Substitution, Ty, TyKind, TypeWalk, WhereClause,
+    fold_tys, static_lifetime, AliasEq, AliasTy, BoundVar, Canonical, CanonicalVarKinds,
+    DebruijnIndex, FnPointer, FnSubst, InEnvironment, InferenceVar, Interner, Scalar, Substitution,
+    Ty, TyExt, TyKind, WhereClause,
 };
 
 impl<'a> InferenceContext<'a> {
@@ -33,7 +37,10 @@ where
 }
 
 #[derive(Debug)]
-pub(super) struct Canonicalized<T> {
+pub(super) struct Canonicalized<T>
+where
+    T: HasInterner<Interner = Interner>,
+{
     pub(super) value: Canonical<T>,
     free_vars: Vec<(InferenceVar, TyVariableKind)>,
 }
@@ -47,11 +54,16 @@ impl<'a, 'b> Canonicalizer<'a, 'b> {
         })
     }
 
-    fn do_canonicalize<T: TypeWalk>(&mut self, t: T, binders: DebruijnIndex) -> T {
-        t.fold_binders(
-            &mut |ty, binders| match ty.interned(&Interner) {
+    fn do_canonicalize<T: Fold<Interner, Result = T> + HasInterner<Interner = Interner>>(
+        &mut self,
+        t: T,
+        binders: DebruijnIndex,
+    ) -> T {
+        fold_tys(
+            t,
+            |ty, binders| match ty.kind(&Interner) {
                 &TyKind::InferenceVar(var, kind) => {
-                    let inner = var.to_inner();
+                    let inner = from_inference_var(var);
                     if self.var_stack.contains(&inner) {
                         // recursive type
                         return self.ctx.table.type_variable_table.fallback_value(var, kind);
@@ -65,7 +77,7 @@ impl<'a, 'b> Canonicalizer<'a, 'b> {
                         result
                     } else {
                         let root = self.ctx.table.var_unification_table.find(inner);
-                        let position = self.add(InferenceVar::from_inner(root), kind);
+                        let position = self.add(to_inference_var(root), kind);
                         TyKind::BoundVar(BoundVar::new(binders, position)).intern(&Interner)
                     }
                 }
@@ -75,7 +87,10 @@ impl<'a, 'b> Canonicalizer<'a, 'b> {
         )
     }
 
-    fn into_canonicalized<T>(self, result: T) -> Canonicalized<T> {
+    fn into_canonicalized<T: HasInterner<Interner = Interner>>(
+        self,
+        result: T,
+    ) -> Canonicalized<T> {
         let kinds = self
             .free_vars
             .iter()
@@ -102,25 +117,18 @@ impl<'a, 'b> Canonicalizer<'a, 'b> {
             DomainGoal::Holds(wc) => {
                 DomainGoal::Holds(self.do_canonicalize(wc, DebruijnIndex::INNERMOST))
             }
+            _ => unimplemented!(),
         };
         self.into_canonicalized(InEnvironment { goal: result, environment: obligation.environment })
     }
 }
 
-impl<T> Canonicalized<T> {
-    pub(super) fn decanonicalize_ty(&self, mut ty: Ty) -> Ty {
-        ty.walk_mut_binders(
-            &mut |ty, binders| {
-                if let &mut TyKind::BoundVar(bound) = ty.interned_mut() {
-                    if bound.debruijn >= binders {
-                        let (v, k) = self.free_vars[bound.index];
-                        *ty = TyKind::InferenceVar(v, k).intern(&Interner);
-                    }
-                }
-            },
-            DebruijnIndex::INNERMOST,
-        );
-        ty
+impl<T: HasInterner<Interner = Interner>> Canonicalized<T> {
+    pub(super) fn decanonicalize_ty(&self, ty: Ty) -> Ty {
+        crate::fold_free_vars(ty, |bound, _binders| {
+            let (v, k) = self.free_vars[bound.index];
+            TyKind::InferenceVar(v, k).intern(&Interner)
+        })
     }
 
     pub(super) fn apply_solution(
@@ -129,29 +137,30 @@ impl<T> Canonicalized<T> {
         solution: Canonical<Substitution>,
     ) {
         // the solution may contain new variables, which we need to convert to new inference vars
-        let new_vars = Substitution(
-            solution
-                .binders
-                .iter(&Interner)
-                .map(|k| match k.kind {
-                    VariableKind::Ty(TyVariableKind::General) => ctx.table.new_type_var(),
-                    VariableKind::Ty(TyVariableKind::Integer) => ctx.table.new_integer_var(),
-                    VariableKind::Ty(TyVariableKind::Float) => ctx.table.new_float_var(),
-                    // HACK: Chalk can sometimes return new lifetime variables. We
-                    // want to just skip them, but to not mess up the indices of
-                    // other variables, we'll just create a new type variable in
-                    // their place instead. This should not matter (we never see the
-                    // actual *uses* of the lifetime variable).
-                    VariableKind::Lifetime => ctx.table.new_type_var(),
-                    _ => panic!("const variable in solution"),
-                })
-                .collect(),
+        let new_vars = Substitution::from_iter(
+            &Interner,
+            solution.binders.iter(&Interner).map(|k| match k.kind {
+                VariableKind::Ty(TyVariableKind::General) => {
+                    ctx.table.new_type_var().cast(&Interner)
+                }
+                VariableKind::Ty(TyVariableKind::Integer) => {
+                    ctx.table.new_integer_var().cast(&Interner)
+                }
+                VariableKind::Ty(TyVariableKind::Float) => {
+                    ctx.table.new_float_var().cast(&Interner)
+                }
+                // Chalk can sometimes return new lifetime variables. We just use the static lifetime everywhere
+                VariableKind::Lifetime => static_lifetime().cast(&Interner),
+                _ => panic!("const variable in solution"),
+            }),
         );
-        for (i, ty) in solution.value.into_iter().enumerate() {
+        for (i, ty) in solution.value.iter(&Interner).enumerate() {
             let (v, k) = self.free_vars[i];
             // eagerly replace projections in the type; we may be getting types
             // e.g. from where clauses where this hasn't happened yet
-            let ty = ctx.normalize_associated_types_in(ty.clone().subst_bound_vars(&new_vars));
+            let ty = ctx.normalize_associated_types_in(
+                new_vars.apply(ty.assert_ty_ref(&Interner).clone(), &Interner),
+            );
             ctx.table.unify(&TyKind::InferenceVar(v, k).intern(&Interner), &ty);
         }
     }
@@ -163,22 +172,23 @@ pub fn could_unify(t1: &Ty, t2: &Ty) -> bool {
 
 pub(crate) fn unify(tys: &Canonical<(Ty, Ty)>) -> Option<Substitution> {
     let mut table = InferenceTable::new();
-    let vars = Substitution(
+    let vars = Substitution::from_iter(
+        &Interner,
         tys.binders
             .iter(&Interner)
             // we always use type vars here because we want everything to
             // fallback to Unknown in the end (kind of hacky, as below)
-            .map(|_| table.new_type_var())
-            .collect(),
+            .map(|_| table.new_type_var()),
     );
-    let ty1_with_vars = tys.value.0.clone().subst_bound_vars(&vars);
-    let ty2_with_vars = tys.value.1.clone().subst_bound_vars(&vars);
+    let ty1_with_vars = vars.apply(tys.value.0.clone(), &Interner);
+    let ty2_with_vars = vars.apply(tys.value.1.clone(), &Interner);
     if !table.unify(&ty1_with_vars, &ty2_with_vars) {
         return None;
     }
     // default any type vars that weren't unified back to their original bound vars
     // (kind of hacky)
-    for (i, var) in vars.iter().enumerate() {
+    for (i, var) in vars.iter(&Interner).enumerate() {
+        let var = var.assert_ty_ref(&Interner);
         if &*table.resolve_ty_shallow(var) == var {
             table.unify(
                 var,
@@ -186,11 +196,11 @@ pub(crate) fn unify(tys: &Canonical<(Ty, Ty)>) -> Option<Substitution> {
             );
         }
     }
-    Some(
-        Substitution::builder(tys.binders.len(&Interner))
-            .fill(vars.iter().map(|v| table.resolve_ty_completely(v.clone())))
-            .build(),
-    )
+    Some(Substitution::from_iter(
+        &Interner,
+        vars.iter(&Interner)
+            .map(|v| table.resolve_ty_completely(v.assert_ty_ref(&Interner).clone())),
+    ))
 }
 
 #[derive(Clone, Debug)]
@@ -204,17 +214,17 @@ impl TypeVariableTable {
     }
 
     pub(super) fn set_diverging(&mut self, iv: InferenceVar, diverging: bool) {
-        self.inner[iv.to_inner().0 as usize].diverging = diverging;
+        self.inner[from_inference_var(iv).0 as usize].diverging = diverging;
     }
 
     fn is_diverging(&mut self, iv: InferenceVar) -> bool {
-        self.inner[iv.to_inner().0 as usize].diverging
+        self.inner[from_inference_var(iv).0 as usize].diverging
     }
 
     fn fallback_value(&self, iv: InferenceVar, kind: TyVariableKind) -> Ty {
         match kind {
-            _ if self.inner[iv.to_inner().0 as usize].diverging => TyKind::Never,
-            TyVariableKind::General => TyKind::Unknown,
+            _ if self.inner[from_inference_var(iv).0 as usize].diverging => TyKind::Never,
+            TyVariableKind::General => TyKind::Error,
             TyVariableKind::Integer => TyKind::Scalar(Scalar::Int(IntTy::I32)),
             TyVariableKind::Float => TyKind::Scalar(Scalar::Float(FloatTy::F64)),
         }
@@ -231,6 +241,7 @@ pub(crate) struct TypeVariableData {
 pub(crate) struct InferenceTable {
     pub(super) var_unification_table: InPlaceUnificationTable<TypeVarId>,
     pub(super) type_variable_table: TypeVariableTable,
+    pub(super) revision: u32,
 }
 
 impl InferenceTable {
@@ -238,6 +249,7 @@ impl InferenceTable {
         InferenceTable {
             var_unification_table: InPlaceUnificationTable::new(),
             type_variable_table: TypeVariableTable { inner: Vec::new() },
+            revision: 0,
         }
     }
 
@@ -245,7 +257,7 @@ impl InferenceTable {
         self.type_variable_table.push(TypeVariableData { diverging });
         let key = self.var_unification_table.new_key(TypeVarValue::Unknown);
         assert_eq!(key.0 as usize, self.type_variable_table.inner.len() - 1);
-        TyKind::InferenceVar(InferenceVar::from_inner(key), kind).intern(&Interner)
+        TyKind::InferenceVar(to_inference_var(key), kind).intern(&Interner)
     }
 
     pub(crate) fn new_type_var(&mut self) -> Ty {
@@ -282,7 +294,9 @@ impl InferenceTable {
         substs2: &Substitution,
         depth: usize,
     ) -> bool {
-        substs1.0.iter().zip(substs2.0.iter()).all(|(t1, t2)| self.unify_inner(t1, t2, depth))
+        substs1.iter(&Interner).zip(substs2.iter(&Interner)).all(|(t1, t2)| {
+            self.unify_inner(t1.assert_ty_ref(&Interner), t2.assert_ty_ref(&Interner), depth)
+        })
     }
 
     fn unify_inner(&mut self, ty1: &Ty, ty2: &Ty, depth: usize) -> bool {
@@ -297,12 +311,12 @@ impl InferenceTable {
         let ty1 = self.resolve_ty_shallow(ty1);
         let ty2 = self.resolve_ty_shallow(ty2);
         if ty1.equals_ctor(&ty2) {
-            match (ty1.interned(&Interner), ty2.interned(&Interner)) {
+            match (ty1.kind(&Interner), ty2.kind(&Interner)) {
                 (TyKind::Adt(_, substs1), TyKind::Adt(_, substs2))
                 | (TyKind::FnDef(_, substs1), TyKind::FnDef(_, substs2))
                 | (
-                    TyKind::Function(FnPointer { substs: substs1, .. }),
-                    TyKind::Function(FnPointer { substs: substs2, .. }),
+                    TyKind::Function(FnPointer { substitution: FnSubst(substs1), .. }),
+                    TyKind::Function(FnPointer { substitution: FnSubst(substs2), .. }),
                 )
                 | (TyKind::Tuple(_, substs1), TyKind::Tuple(_, substs2))
                 | (TyKind::OpaqueType(_, substs1), TyKind::OpaqueType(_, substs2))
@@ -310,9 +324,11 @@ impl InferenceTable {
                 | (TyKind::Closure(.., substs1), TyKind::Closure(.., substs2)) => {
                     self.unify_substs(substs1, substs2, depth + 1)
                 }
-                (TyKind::Ref(_, ty1), TyKind::Ref(_, ty2))
+                (TyKind::Array(ty1, c1), TyKind::Array(ty2, c2)) if c1 == c2 => {
+                    self.unify_inner(ty1, ty2, depth + 1)
+                }
+                (TyKind::Ref(_, _, ty1), TyKind::Ref(_, _, ty2))
                 | (TyKind::Raw(_, ty1), TyKind::Raw(_, ty2))
-                | (TyKind::Array(ty1), TyKind::Array(ty2))
                 | (TyKind::Slice(ty1), TyKind::Slice(ty2)) => self.unify_inner(ty1, ty2, depth + 1),
                 _ => true, /* we checked equals_ctor already */
             }
@@ -322,8 +338,8 @@ impl InferenceTable {
     }
 
     pub(super) fn unify_inner_trivial(&mut self, ty1: &Ty, ty2: &Ty, depth: usize) -> bool {
-        match (ty1.interned(&Interner), ty2.interned(&Interner)) {
-            (TyKind::Unknown, _) | (_, TyKind::Unknown) => true,
+        match (ty1.kind(&Interner), ty2.kind(&Interner)) {
+            (TyKind::Error, _) | (_, TyKind::Error) => true,
 
             (TyKind::Placeholder(p1), TyKind::Placeholder(p2)) if *p1 == *p2 => true,
 
@@ -360,7 +376,14 @@ impl InferenceTable {
                 == self.type_variable_table.is_diverging(*tv2) =>
             {
                 // both type vars are unknown since we tried to resolve them
-                self.var_unification_table.union(tv1.to_inner(), tv2.to_inner());
+                if !self
+                    .var_unification_table
+                    .unioned(from_inference_var(*tv1), from_inference_var(*tv2))
+                {
+                    self.var_unification_table
+                        .union(from_inference_var(*tv1), from_inference_var(*tv2));
+                    self.revision += 1;
+                }
                 true
             }
 
@@ -395,9 +418,10 @@ impl InferenceTable {
             ) => {
                 // the type var is unknown since we tried to resolve it
                 self.var_unification_table.union_value(
-                    tv.to_inner(),
+                    from_inference_var(*tv),
                     TypeVarValue::Known(other.clone().intern(&Interner)),
                 );
+                self.revision += 1;
                 true
             }
 
@@ -447,9 +471,9 @@ impl InferenceTable {
             if i > 0 {
                 cov_mark::hit!(type_var_resolves_to_int_var);
             }
-            match ty.interned(&Interner) {
+            match ty.kind(&Interner) {
                 TyKind::InferenceVar(tv, _) => {
-                    let inner = tv.to_inner();
+                    let inner = from_inference_var(*tv);
                     match self.var_unification_table.inlined_probe_value(inner).known() {
                         Some(known_ty) => {
                             // The known_ty can't be a type var itself
@@ -470,55 +494,63 @@ impl InferenceTable {
     /// be resolved as far as possible, i.e. contain no type variables with
     /// known type.
     fn resolve_ty_as_possible_inner(&mut self, tv_stack: &mut Vec<TypeVarId>, ty: Ty) -> Ty {
-        ty.fold(&mut |ty| match ty.interned(&Interner) {
-            &TyKind::InferenceVar(tv, kind) => {
-                let inner = tv.to_inner();
-                if tv_stack.contains(&inner) {
-                    cov_mark::hit!(type_var_cycles_resolve_as_possible);
-                    // recursive type
-                    return self.type_variable_table.fallback_value(tv, kind);
-                }
-                if let Some(known_ty) =
-                    self.var_unification_table.inlined_probe_value(inner).known()
-                {
-                    // known_ty may contain other variables that are known by now
-                    tv_stack.push(inner);
-                    let result = self.resolve_ty_as_possible_inner(tv_stack, known_ty.clone());
-                    tv_stack.pop();
-                    result
-                } else {
-                    ty
+        fold_tys(
+            ty,
+            |ty, _| match ty.kind(&Interner) {
+                &TyKind::InferenceVar(tv, kind) => {
+                    let inner = from_inference_var(tv);
+                    if tv_stack.contains(&inner) {
+                        cov_mark::hit!(type_var_cycles_resolve_as_possible);
+                        // recursive type
+                        return self.type_variable_table.fallback_value(tv, kind);
+                    }
+                    if let Some(known_ty) =
+                        self.var_unification_table.inlined_probe_value(inner).known()
+                    {
+                        // known_ty may contain other variables that are known by now
+                        tv_stack.push(inner);
+                        let result = self.resolve_ty_as_possible_inner(tv_stack, known_ty.clone());
+                        tv_stack.pop();
+                        result
+                    } else {
+                        ty
+                    }
                 }
-            }
-            _ => ty,
-        })
+                _ => ty,
+            },
+            DebruijnIndex::INNERMOST,
+        )
     }
 
     /// Resolves the type completely; type variables without known type are
     /// replaced by TyKind::Unknown.
     fn resolve_ty_completely_inner(&mut self, tv_stack: &mut Vec<TypeVarId>, ty: Ty) -> Ty {
-        ty.fold(&mut |ty| match ty.interned(&Interner) {
-            &TyKind::InferenceVar(tv, kind) => {
-                let inner = tv.to_inner();
-                if tv_stack.contains(&inner) {
-                    cov_mark::hit!(type_var_cycles_resolve_completely);
-                    // recursive type
-                    return self.type_variable_table.fallback_value(tv, kind);
-                }
-                if let Some(known_ty) =
-                    self.var_unification_table.inlined_probe_value(inner).known()
-                {
-                    // known_ty may contain other variables that are known by now
-                    tv_stack.push(inner);
-                    let result = self.resolve_ty_completely_inner(tv_stack, known_ty.clone());
-                    tv_stack.pop();
-                    result
-                } else {
-                    self.type_variable_table.fallback_value(tv, kind)
+        fold_tys(
+            ty,
+            |ty, _| match ty.kind(&Interner) {
+                &TyKind::InferenceVar(tv, kind) => {
+                    let inner = from_inference_var(tv);
+                    if tv_stack.contains(&inner) {
+                        cov_mark::hit!(type_var_cycles_resolve_completely);
+                        // recursive type
+                        return self.type_variable_table.fallback_value(tv, kind);
+                    }
+                    if let Some(known_ty) =
+                        self.var_unification_table.inlined_probe_value(inner).known()
+                    {
+                        // known_ty may contain other variables that are known by now
+                        tv_stack.push(inner);
+                        let result = self.resolve_ty_completely_inner(tv_stack, known_ty.clone());
+                        tv_stack.pop();
+                        result
+                    } else {
+                        self.type_variable_table.fallback_value(tv, kind)
+                    }
                 }
-            }
-            _ => ty,
-        })
+                _ => ty,
+            },
+            DebruijnIndex::INNERMOST,
+        )
     }
 }
 
@@ -542,6 +574,14 @@ impl UnifyKey for TypeVarId {
     }
 }
 
+fn from_inference_var(var: InferenceVar) -> TypeVarId {
+    TypeVarId(var.index())
+}
+
+fn to_inference_var(TypeVarId(index): TypeVarId) -> InferenceVar {
+    index.into()
+}
+
 /// The value of a type variable: either we already know the type, or we don't
 /// know it yet.
 #[derive(Clone, PartialEq, Eq, Debug)]
diff --git a/crates/hir_ty/src/traits/chalk/interner.rs b/crates/hir_ty/src/interner.rs
index 94e94a26d..a1656115d 100644
--- a/crates/hir_ty/src/traits/chalk/interner.rs
+++ b/crates/hir_ty/src/interner.rs
@@ -1,61 +1,83 @@
 //! Implementation of the Chalk `Interner` trait, which allows customizing the
 //! representation of the various objects Chalk deals with (types, goals etc.).
 
-use super::tls;
+use crate::{chalk_db, tls, GenericArg};
 use base_db::salsa::InternId;
-use chalk_ir::{GenericArg, Goal, GoalData};
-use hir_def::TypeAliasId;
+use chalk_ir::{Goal, GoalData};
+use hir_def::{
+    intern::{impl_internable, InternStorage, Internable, Interned},
+    TypeAliasId,
+};
 use smallvec::SmallVec;
 use std::{fmt, sync::Arc};
 
 #[derive(Debug, Copy, Clone, Hash, PartialOrd, Ord, PartialEq, Eq)]
 pub struct Interner;
 
-pub(crate) type AssocTypeId = chalk_ir::AssocTypeId<Interner>;
-pub(crate) type AssociatedTyDatum = chalk_solve::rust_ir::AssociatedTyDatum<Interner>;
-pub(crate) type TraitId = chalk_ir::TraitId<Interner>;
-pub(crate) type TraitDatum = chalk_solve::rust_ir::TraitDatum<Interner>;
-pub(crate) type AdtId = chalk_ir::AdtId<Interner>;
-pub(crate) type StructDatum = chalk_solve::rust_ir::AdtDatum<Interner>;
-pub(crate) type ImplId = chalk_ir::ImplId<Interner>;
-pub(crate) type ImplDatum = chalk_solve::rust_ir::ImplDatum<Interner>;
-pub(crate) type AssociatedTyValueId = chalk_solve::rust_ir::AssociatedTyValueId<Interner>;
-pub(crate) type AssociatedTyValue = chalk_solve::rust_ir::AssociatedTyValue<Interner>;
-pub(crate) type FnDefDatum = chalk_solve::rust_ir::FnDefDatum<Interner>;
-pub(crate) type OpaqueTyId = chalk_ir::OpaqueTyId<Interner>;
-pub(crate) type OpaqueTyDatum = chalk_solve::rust_ir::OpaqueTyDatum<Interner>;
-pub(crate) type Variances = chalk_ir::Variances<Interner>;
+#[derive(PartialEq, Eq, Hash, Debug)]
+pub struct InternedWrapper<T>(T);
+
+impl<T> std::ops::Deref for InternedWrapper<T> {
+    type Target = T;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl_internable!(
+    InternedWrapper<Vec<chalk_ir::VariableKind<Interner>>>,
+    InternedWrapper<SmallVec<[GenericArg; 2]>>,
+    InternedWrapper<chalk_ir::TyData<Interner>>,
+    InternedWrapper<chalk_ir::LifetimeData<Interner>>,
+    InternedWrapper<chalk_ir::ConstData<Interner>>,
+    InternedWrapper<Vec<chalk_ir::CanonicalVarKind<Interner>>>,
+    InternedWrapper<Vec<chalk_ir::ProgramClause<Interner>>>,
+    InternedWrapper<Vec<chalk_ir::QuantifiedWhereClause<Interner>>>,
+    InternedWrapper<Vec<chalk_ir::Variance>>,
+);
 
 impl chalk_ir::interner::Interner for Interner {
-    type InternedType = Arc<chalk_ir::TyData<Self>>;
-    type InternedLifetime = chalk_ir::LifetimeData<Self>;
-    type InternedConst = Arc<chalk_ir::ConstData<Self>>;
+    type InternedType = Interned<InternedWrapper<chalk_ir::TyData<Interner>>>;
+    type InternedLifetime = Interned<InternedWrapper<chalk_ir::LifetimeData<Self>>>;
+    type InternedConst = Interned<InternedWrapper<chalk_ir::ConstData<Self>>>;
     type InternedConcreteConst = ();
     type InternedGenericArg = chalk_ir::GenericArgData<Self>;
     type InternedGoal = Arc<GoalData<Self>>;
     type InternedGoals = Vec<Goal<Self>>;
-    type InternedSubstitution = SmallVec<[GenericArg<Self>; 2]>;
-    type InternedProgramClause = Arc<chalk_ir::ProgramClauseData<Self>>;
-    type InternedProgramClauses = Arc<[chalk_ir::ProgramClause<Self>]>;
-    type InternedQuantifiedWhereClauses = Vec<chalk_ir::QuantifiedWhereClause<Self>>;
-    type InternedVariableKinds = Vec<chalk_ir::VariableKind<Self>>;
-    type InternedCanonicalVarKinds = Vec<chalk_ir::CanonicalVarKind<Self>>;
+    type InternedSubstitution = Interned<InternedWrapper<SmallVec<[GenericArg; 2]>>>;
+    type InternedProgramClause = chalk_ir::ProgramClauseData<Self>;
+    type InternedProgramClauses = Interned<InternedWrapper<Vec<chalk_ir::ProgramClause<Self>>>>;
+    type InternedQuantifiedWhereClauses =
+        Interned<InternedWrapper<Vec<chalk_ir::QuantifiedWhereClause<Self>>>>;
+    type InternedVariableKinds = Interned<InternedWrapper<Vec<chalk_ir::VariableKind<Interner>>>>;
+    type InternedCanonicalVarKinds =
+        Interned<InternedWrapper<Vec<chalk_ir::CanonicalVarKind<Self>>>>;
     type InternedConstraints = Vec<chalk_ir::InEnvironment<chalk_ir::Constraint<Self>>>;
-    type InternedVariances = Arc<[chalk_ir::Variance]>;
+    type InternedVariances = Interned<InternedWrapper<Vec<chalk_ir::Variance>>>;
     type DefId = InternId;
     type InternedAdtId = hir_def::AdtId;
     type Identifier = TypeAliasId;
     type FnAbi = ();
 
-    fn debug_adt_id(type_kind_id: AdtId, fmt: &mut fmt::Formatter<'_>) -> Option<fmt::Result> {
+    fn debug_adt_id(
+        type_kind_id: chalk_db::AdtId,
+        fmt: &mut fmt::Formatter<'_>,
+    ) -> Option<fmt::Result> {
         tls::with_current_program(|prog| Some(prog?.debug_struct_id(type_kind_id, fmt)))
     }
 
-    fn debug_trait_id(type_kind_id: TraitId, fmt: &mut fmt::Formatter<'_>) -> Option<fmt::Result> {
+    fn debug_trait_id(
+        type_kind_id: chalk_db::TraitId,
+        fmt: &mut fmt::Formatter<'_>,
+    ) -> Option<fmt::Result> {
         tls::with_current_program(|prog| Some(prog?.debug_trait_id(type_kind_id, fmt)))
     }
 
-    fn debug_assoc_type_id(id: AssocTypeId, fmt: &mut fmt::Formatter<'_>) -> Option<fmt::Result> {
+    fn debug_assoc_type_id(
+        id: chalk_db::AssocTypeId,
+        fmt: &mut fmt::Formatter<'_>,
+    ) -> Option<fmt::Result> {
         tls::with_current_program(|prog| Some(prog?.debug_assoc_type_id(id, fmt)))
     }
 
@@ -99,7 +121,7 @@ impl chalk_ir::interner::Interner for Interner {
     }
 
     fn debug_generic_arg(
-        parameter: &GenericArg<Interner>,
+        parameter: &GenericArg,
         fmt: &mut fmt::Formatter<'_>,
     ) -> Option<fmt::Result> {
         tls::with_current_program(|prog| Some(prog?.debug_generic_arg(parameter, fmt)))
@@ -192,59 +214,58 @@ impl chalk_ir::interner::Interner for Interner {
         tls::with_current_program(|prog| Some(prog?.debug_quantified_where_clauses(clauses, fmt)))
     }
 
-    fn intern_ty(&self, kind: chalk_ir::TyKind<Self>) -> Arc<chalk_ir::TyData<Self>> {
+    fn intern_ty(&self, kind: chalk_ir::TyKind<Self>) -> Self::InternedType {
         let flags = kind.compute_flags(self);
-        Arc::new(chalk_ir::TyData { kind, flags })
+        Interned::new(InternedWrapper(chalk_ir::TyData { kind, flags }))
     }
 
-    fn ty_data<'a>(&self, ty: &'a Arc<chalk_ir::TyData<Self>>) -> &'a chalk_ir::TyData<Self> {
-        ty
+    fn ty_data<'a>(&self, ty: &'a Self::InternedType) -> &'a chalk_ir::TyData<Self> {
+        &ty.0
     }
 
-    fn intern_lifetime(
-        &self,
-        lifetime: chalk_ir::LifetimeData<Self>,
-    ) -> chalk_ir::LifetimeData<Self> {
-        lifetime
+    fn intern_lifetime(&self, lifetime: chalk_ir::LifetimeData<Self>) -> Self::InternedLifetime {
+        Interned::new(InternedWrapper(lifetime))
     }
 
     fn lifetime_data<'a>(
         &self,
-        lifetime: &'a chalk_ir::LifetimeData<Self>,
+        lifetime: &'a Self::InternedLifetime,
     ) -> &'a chalk_ir::LifetimeData<Self> {
-        lifetime
+        &lifetime.0
     }
 
-    fn intern_const(&self, constant: chalk_ir::ConstData<Self>) -> Arc<chalk_ir::ConstData<Self>> {
-        Arc::new(constant)
+    fn intern_const(&self, constant: chalk_ir::ConstData<Self>) -> Self::InternedConst {
+        Interned::new(InternedWrapper(constant))
     }
 
-    fn const_data<'a>(
-        &self,
-        constant: &'a Arc<chalk_ir::ConstData<Self>>,
-    ) -> &'a chalk_ir::ConstData<Self> {
-        constant
+    fn const_data<'a>(&self, constant: &'a Self::InternedConst) -> &'a chalk_ir::ConstData<Self> {
+        &constant.0
     }
 
-    fn const_eq(&self, _ty: &Arc<chalk_ir::TyData<Self>>, _c1: &(), _c2: &()) -> bool {
+    fn const_eq(
+        &self,
+        _ty: &Self::InternedType,
+        _c1: &Self::InternedConcreteConst,
+        _c2: &Self::InternedConcreteConst,
+    ) -> bool {
         true
     }
 
     fn intern_generic_arg(
         &self,
         parameter: chalk_ir::GenericArgData<Self>,
-    ) -> chalk_ir::GenericArgData<Self> {
+    ) -> Self::InternedGenericArg {
         parameter
     }
 
     fn generic_arg_data<'a>(
         &self,
-        parameter: &'a chalk_ir::GenericArgData<Self>,
+        parameter: &'a Self::InternedGenericArg,
     ) -> &'a chalk_ir::GenericArgData<Self> {
         parameter
     }
 
-    fn intern_goal(&self, goal: GoalData<Self>) -> Arc<GoalData<Self>> {
+    fn intern_goal(&self, goal: GoalData<Self>) -> Self::InternedGoal {
         Arc::new(goal)
     }
 
@@ -255,38 +276,38 @@ impl chalk_ir::interner::Interner for Interner {
         data.into_iter().collect()
     }
 
-    fn goal_data<'a>(&self, goal: &'a Arc<GoalData<Self>>) -> &'a GoalData<Self> {
+    fn goal_data<'a>(&self, goal: &'a Self::InternedGoal) -> &'a GoalData<Self> {
         goal
     }
 
-    fn goals_data<'a>(&self, goals: &'a Vec<Goal<Interner>>) -> &'a [Goal<Interner>] {
+    fn goals_data<'a>(&self, goals: &'a Self::InternedGoals) -> &'a [Goal<Interner>] {
         goals
     }
 
     fn intern_substitution<E>(
         &self,
-        data: impl IntoIterator<Item = Result<GenericArg<Self>, E>>,
+        data: impl IntoIterator<Item = Result<GenericArg, E>>,
     ) -> Result<Self::InternedSubstitution, E> {
-        data.into_iter().collect()
+        Ok(Interned::new(InternedWrapper(data.into_iter().collect::<Result<_, _>>()?)))
     }
 
     fn substitution_data<'a>(
         &self,
         substitution: &'a Self::InternedSubstitution,
-    ) -> &'a [GenericArg<Self>] {
-        substitution
+    ) -> &'a [GenericArg] {
+        &substitution.as_ref().0
     }
 
     fn intern_program_clause(
         &self,
         data: chalk_ir::ProgramClauseData<Self>,
-    ) -> Arc<chalk_ir::ProgramClauseData<Self>> {
-        Arc::new(data)
+    ) -> Self::InternedProgramClause {
+        data
     }
 
     fn program_clause_data<'a>(
         &self,
-        clause: &'a Arc<chalk_ir::ProgramClauseData<Self>>,
+        clause: &'a Self::InternedProgramClause,
     ) -> &'a chalk_ir::ProgramClauseData<Self> {
         clause
     }
@@ -294,13 +315,13 @@ impl chalk_ir::interner::Interner for Interner {
     fn intern_program_clauses<E>(
         &self,
         data: impl IntoIterator<Item = Result<chalk_ir::ProgramClause<Self>, E>>,
-    ) -> Result<Arc<[chalk_ir::ProgramClause<Self>]>, E> {
-        data.into_iter().collect()
+    ) -> Result<Self::InternedProgramClauses, E> {
+        Ok(Interned::new(InternedWrapper(data.into_iter().collect::<Result<_, _>>()?)))
     }
 
     fn program_clauses_data<'a>(
         &self,
-        clauses: &'a Arc<[chalk_ir::ProgramClause<Self>]>,
+        clauses: &'a Self::InternedProgramClauses,
     ) -> &'a [chalk_ir::ProgramClause<Self>] {
         &clauses
     }
@@ -309,7 +330,7 @@ impl chalk_ir::interner::Interner for Interner {
         &self,
         data: impl IntoIterator<Item = Result<chalk_ir::QuantifiedWhereClause<Self>, E>>,
     ) -> Result<Self::InternedQuantifiedWhereClauses, E> {
-        data.into_iter().collect()
+        Ok(Interned::new(InternedWrapper(data.into_iter().collect::<Result<_, _>>()?)))
     }
 
     fn quantified_where_clauses_data<'a>(
@@ -323,21 +344,21 @@ impl chalk_ir::interner::Interner for Interner {
         &self,
         data: impl IntoIterator<Item = Result<chalk_ir::VariableKind<Self>, E>>,
     ) -> Result<Self::InternedVariableKinds, E> {
-        data.into_iter().collect()
+        Ok(Interned::new(InternedWrapper(data.into_iter().collect::<Result<_, _>>()?)))
     }
 
     fn variable_kinds_data<'a>(
         &self,
         parameter_kinds: &'a Self::InternedVariableKinds,
     ) -> &'a [chalk_ir::VariableKind<Self>] {
-        &parameter_kinds
+        &parameter_kinds.as_ref().0
     }
 
     fn intern_canonical_var_kinds<E>(
         &self,
         data: impl IntoIterator<Item = Result<chalk_ir::CanonicalVarKind<Self>, E>>,
     ) -> Result<Self::InternedCanonicalVarKinds, E> {
-        data.into_iter().collect()
+        Ok(Interned::new(InternedWrapper(data.into_iter().collect::<Result<_, _>>()?)))
     }
 
     fn canonical_var_kinds_data<'a>(
@@ -377,7 +398,7 @@ impl chalk_ir::interner::Interner for Interner {
         &self,
         data: impl IntoIterator<Item = Result<chalk_ir::Variance, E>>,
     ) -> Result<Self::InternedVariances, E> {
-        data.into_iter().collect()
+        Ok(Interned::new(InternedWrapper(data.into_iter().collect::<Result<_, _>>()?)))
     }
 
     fn variances_data<'a>(
@@ -391,3 +412,12 @@ impl chalk_ir::interner::Interner for Interner {
 impl chalk_ir::interner::HasInterner for Interner {
     type Interner = Self;
 }
+
+#[macro_export]
+macro_rules! has_interner {
+    ($t:ty) => {
+        impl HasInterner for $t {
+            type Interner = crate::Interner;
+        }
+    };
+}
diff --git a/crates/hir_ty/src/lib.rs b/crates/hir_ty/src/lib.rs
index 6f9c698e6..0505fa4ae 100644
--- a/crates/hir_ty/src/lib.rs
+++ b/crates/hir_ty/src/lib.rs
@@ -1,59 +1,68 @@
 //! The type system. We currently use this to infer types for completion, hover
 //! information and various assists.
+
 #[allow(unused)]
 macro_rules! eprintln {
     ($($tt:tt)*) => { stdx::eprintln!($($tt)*) };
 }
 
 mod autoderef;
-pub mod primitive;
-pub mod traits;
-pub mod method_resolution;
-mod op;
+mod builder;
+mod chalk_db;
+mod chalk_ext;
+mod infer;
+mod interner;
 mod lower;
-pub(crate) mod infer;
-pub(crate) mod utils;
-mod chalk_cast;
-
-pub mod display;
+mod mapping;
+mod op;
+mod tls;
+mod utils;
+mod walk;
 pub mod db;
 pub mod diagnostics;
+pub mod display;
+pub mod method_resolution;
+pub mod primitive;
+pub mod traits;
 
 #[cfg(test)]
 mod tests;
 #[cfg(test)]
 mod test_db;
 
-use std::{iter, mem, ops::Deref, sync::Arc};
+use std::sync::Arc;
 
-use base_db::salsa;
-use hir_def::{
-    builtin_type::BuiltinType, expr::ExprId, type_ref::Rawness, AssocContainerId, FunctionId,
-    GenericDefId, HasModule, LifetimeParamId, Lookup, TraitId, TypeAliasId, TypeParamId,
+use chalk_ir::{
+    fold::{Fold, Shift},
+    interner::HasInterner,
+    UintTy,
 };
-use itertools::Itertools;
-use smallvec::SmallVec;
+use hir_def::{expr::ExprId, type_ref::Rawness, TypeParamId};
 
-use crate::{
-    db::HirDatabase,
-    display::HirDisplay,
-    utils::{generics, make_mut_slice, Generics},
-};
+use crate::{db::HirDatabase, display::HirDisplay, utils::generics};
 
 pub use autoderef::autoderef;
-pub use infer::{could_unify, InferenceResult, InferenceVar};
+pub use builder::TyBuilder;
+pub use chalk_ext::*;
+pub use infer::{could_unify, InferenceResult};
+pub use interner::Interner;
 pub use lower::{
     associated_type_shorthand_candidates, callable_item_sig, CallableDefId, ImplTraitLoweringMode,
     TyDefId, TyLoweringContext, ValueTyDefId,
 };
-pub use traits::{AliasEq, DomainGoal, InEnvironment, TraitEnvironment};
+pub use mapping::{
+    const_from_placeholder_idx, from_assoc_type_id, from_chalk_trait_id, from_foreign_def_id,
+    from_placeholder_idx, lt_from_placeholder_idx, to_assoc_type_id, to_chalk_trait_id,
+    to_foreign_def_id, to_placeholder_idx,
+};
+pub use traits::TraitEnvironment;
+pub use utils::all_super_traits;
+pub use walk::TypeWalk;
 
 pub use chalk_ir::{
     cast::Cast, AdtId, BoundVar, DebruijnIndex, Mutability, Safety, Scalar, TyVariableKind,
 };
 
-pub use crate::traits::chalk::Interner;
-
 pub type ForeignDefId = chalk_ir::ForeignDefId<Interner>;
 pub type AssocTypeId = chalk_ir::AssocTypeId<Interner>;
 pub type FnDefId = chalk_ir::FnDefId<Interner>;
@@ -61,371 +70,56 @@ pub type ClosureId = chalk_ir::ClosureId<Interner>;
 pub type OpaqueTyId = chalk_ir::OpaqueTyId<Interner>;
 pub type PlaceholderIndex = chalk_ir::PlaceholderIndex;
 
+pub type VariableKind = chalk_ir::VariableKind<Interner>;
+pub type VariableKinds = chalk_ir::VariableKinds<Interner>;
 pub type CanonicalVarKinds = chalk_ir::CanonicalVarKinds<Interner>;
+pub type Binders<T> = chalk_ir::Binders<T>;
+pub type Substitution = chalk_ir::Substitution<Interner>;
+pub type GenericArg = chalk_ir::GenericArg<Interner>;
+pub type GenericArgData = chalk_ir::GenericArgData<Interner>;
+
+pub type Ty = chalk_ir::Ty<Interner>;
+pub type TyKind = chalk_ir::TyKind<Interner>;
+pub type DynTy = chalk_ir::DynTy<Interner>;
+pub type FnPointer = chalk_ir::FnPointer<Interner>;
+// pub type FnSubst = chalk_ir::FnSubst<Interner>;
+pub use chalk_ir::FnSubst;
+pub type ProjectionTy = chalk_ir::ProjectionTy<Interner>;
+pub type AliasTy = chalk_ir::AliasTy<Interner>;
+pub type OpaqueTy = chalk_ir::OpaqueTy<Interner>;
+pub type InferenceVar = chalk_ir::InferenceVar;
+
+pub type Lifetime = chalk_ir::Lifetime<Interner>;
+pub type LifetimeData = chalk_ir::LifetimeData<Interner>;
+pub type LifetimeOutlives = chalk_ir::LifetimeOutlives<Interner>;
+
+pub type Const = chalk_ir::Const<Interner>;
+pub type ConstData = chalk_ir::ConstData<Interner>;
+pub type ConstValue = chalk_ir::ConstValue<Interner>;
+pub type ConcreteConst = chalk_ir::ConcreteConst<Interner>;
 
 pub type ChalkTraitId = chalk_ir::TraitId<Interner>;
-
-#[derive(Clone, PartialEq, Eq, Debug, Hash)]
-pub enum Lifetime {
-    Parameter(LifetimeParamId),
-    Static,
-}
-
-#[derive(Clone, PartialEq, Eq, Debug, Hash)]
-pub struct OpaqueTy {
-    pub opaque_ty_id: OpaqueTyId,
-    pub substitution: Substitution,
-}
-
-impl TypeWalk for OpaqueTy {
-    fn walk(&self, f: &mut impl FnMut(&Ty)) {
-        self.substitution.walk(f);
-    }
-
-    fn walk_mut_binders(
-        &mut self,
-        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
-        binders: DebruijnIndex,
-    ) {
-        self.substitution.walk_mut_binders(f, binders);
-    }
-}
-
-/// A "projection" type corresponds to an (unnormalized)
-/// projection like `<P0 as Trait<P1..Pn>>::Foo`. Note that the
-/// trait and all its parameters are fully known.
-#[derive(Clone, PartialEq, Eq, Debug, Hash)]
-pub struct ProjectionTy {
-    pub associated_ty_id: AssocTypeId,
-    pub substitution: Substitution,
-}
-
-impl ProjectionTy {
-    pub fn trait_ref(&self, db: &dyn HirDatabase) -> TraitRef {
-        TraitRef {
-            trait_id: to_chalk_trait_id(self.trait_(db)),
-            substitution: self.substitution.clone(),
-        }
-    }
-
-    pub fn self_type_parameter(&self) -> &Ty {
-        &self.substitution[0]
-    }
-
-    fn trait_(&self, db: &dyn HirDatabase) -> TraitId {
-        match from_assoc_type_id(self.associated_ty_id).lookup(db.upcast()).container {
-            AssocContainerId::TraitId(it) => it,
-            _ => panic!("projection ty without parent trait"),
-        }
-    }
-}
-
-impl TypeWalk for ProjectionTy {
-    fn walk(&self, f: &mut impl FnMut(&Ty)) {
-        self.substitution.walk(f);
-    }
-
-    fn walk_mut_binders(
-        &mut self,
-        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
-        binders: DebruijnIndex,
-    ) {
-        self.substitution.walk_mut_binders(f, binders);
-    }
-}
-
-#[derive(Clone, PartialEq, Eq, Debug, Hash)]
-pub struct DynTy {
-    /// The unknown self type.
-    pub bounds: Binders<QuantifiedWhereClauses>,
-}
+pub type TraitRef = chalk_ir::TraitRef<Interner>;
+pub type QuantifiedWhereClause = Binders<WhereClause>;
+pub type QuantifiedWhereClauses = chalk_ir::QuantifiedWhereClauses<Interner>;
+pub type Canonical<T> = chalk_ir::Canonical<T>;
 
 pub type FnSig = chalk_ir::FnSig<Interner>;
 
-#[derive(Clone, PartialEq, Eq, Debug, Hash)]
-pub struct FnPointer {
-    pub num_args: usize,
-    pub sig: FnSig,
-    pub substs: Substitution,
-}
-
-#[derive(Clone, PartialEq, Eq, Debug, Hash)]
-pub enum AliasTy {
-    /// A "projection" type corresponds to an (unnormalized)
-    /// projection like `<P0 as Trait<P1..Pn>>::Foo`. Note that the
-    /// trait and all its parameters are fully known.
-    Projection(ProjectionTy),
-    /// An opaque type (`impl Trait`).
-    ///
-    /// This is currently only used for return type impl trait; each instance of
-    /// `impl Trait` in a return type gets its own ID.
-    Opaque(OpaqueTy),
-}
-
-impl TypeWalk for AliasTy {
-    fn walk(&self, f: &mut impl FnMut(&Ty)) {
-        match self {
-            AliasTy::Projection(it) => it.walk(f),
-            AliasTy::Opaque(it) => it.walk(f),
-        }
-    }
-
-    fn walk_mut_binders(
-        &mut self,
-        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
-        binders: DebruijnIndex,
-    ) {
-        match self {
-            AliasTy::Projection(it) => it.walk_mut_binders(f, binders),
-            AliasTy::Opaque(it) => it.walk_mut_binders(f, binders),
-        }
-    }
-}
-/// A type.
-///
-/// See also the `TyKind` enum in rustc (librustc/ty/sty.rs), which represents
-/// the same thing (but in a different way).
-///
-/// This should be cheap to clone.
-#[derive(Clone, PartialEq, Eq, Debug, Hash)]
-pub enum TyKind {
-    /// Structures, enumerations and unions.
-    Adt(AdtId<Interner>, Substitution),
-
-    /// Represents an associated item like `Iterator::Item`.  This is used
-    /// when we have tried to normalize a projection like `T::Item` but
-    /// couldn't find a better representation.  In that case, we generate
-    /// an **application type** like `(Iterator::Item)<T>`.
-    AssociatedType(AssocTypeId, Substitution),
-
-    /// a scalar type like `bool` or `u32`
-    Scalar(Scalar),
-
-    /// A tuple type.  For example, `(i32, bool)`.
-    Tuple(usize, Substitution),
-
-    /// An array with the given length. Written as `[T; n]`.
-    Array(Ty),
-
-    /// The pointee of an array slice.  Written as `[T]`.
-    Slice(Ty),
-
-    /// A raw pointer. Written as `*mut T` or `*const T`
-    Raw(Mutability, Ty),
-
-    /// A reference; a pointer with an associated lifetime. Written as
-    /// `&'a mut T` or `&'a T`.
-    Ref(Mutability, Ty),
+pub type InEnvironment<T> = chalk_ir::InEnvironment<T>;
+pub type DomainGoal = chalk_ir::DomainGoal<Interner>;
+pub type AliasEq = chalk_ir::AliasEq<Interner>;
+pub type Solution = chalk_solve::Solution<Interner>;
+pub type ConstrainedSubst = chalk_ir::ConstrainedSubst<Interner>;
+pub type Guidance = chalk_solve::Guidance<Interner>;
+pub type WhereClause = chalk_ir::WhereClause<Interner>;
 
-    /// This represents a placeholder for an opaque type in situations where we
-    /// don't know the hidden type (i.e. currently almost always). This is
-    /// analogous to the `AssociatedType` type constructor.
-    /// It is also used as the type of async block, with one type parameter
-    /// representing the Future::Output type.
-    OpaqueType(OpaqueTyId, Substitution),
-
-    /// The anonymous type of a function declaration/definition. Each
-    /// function has a unique type, which is output (for a function
-    /// named `foo` returning an `i32`) as `fn() -> i32 {foo}`.
-    ///
-    /// This includes tuple struct / enum variant constructors as well.
-    ///
-    /// For example the type of `bar` here:
-    ///
-    /// ```
-    /// fn foo() -> i32 { 1 }
-    /// let bar = foo; // bar: fn() -> i32 {foo}
-    /// ```
-    FnDef(FnDefId, Substitution),
-
-    /// The pointee of a string slice. Written as `str`.
-    Str,
-
-    /// The never type `!`.
-    Never,
-
-    /// The type of a specific closure.
-    ///
-    /// The closure signature is stored in a `FnPtr` type in the first type
-    /// parameter.
-    Closure(ClosureId, Substitution),
-
-    /// Represents a foreign type declared in external blocks.
-    ForeignType(ForeignDefId),
-
-    /// A pointer to a function.  Written as `fn() -> i32`.
-    ///
-    /// For example the type of `bar` here:
-    ///
-    /// ```
-    /// fn foo() -> i32 { 1 }
-    /// let bar: fn() -> i32 = foo;
-    /// ```
-    Function(FnPointer),
-
-    /// An "alias" type represents some form of type alias, such as:
-    /// - An associated type projection like `<T as Iterator>::Item`
-    /// - `impl Trait` types
-    /// - Named type aliases like `type Foo<X> = Vec<X>`
-    Alias(AliasTy),
-
-    /// A placeholder for a type parameter; for example, `T` in `fn f<T>(x: T)
-    /// {}` when we're type-checking the body of that function. In this
-    /// situation, we know this stands for *some* type, but don't know the exact
-    /// type.
-    Placeholder(PlaceholderIndex),
-
-    /// A bound type variable. This is used in various places: when representing
-    /// some polymorphic type like the type of function `fn f<T>`, the type
-    /// parameters get turned into variables; during trait resolution, inference
-    /// variables get turned into bound variables and back; and in `Dyn` the
-    /// `Self` type is represented with a bound variable as well.
-    BoundVar(BoundVar),
-
-    /// A type variable used during type checking.
-    InferenceVar(InferenceVar, TyVariableKind),
-
-    /// A trait object (`dyn Trait` or bare `Trait` in pre-2018 Rust).
-    ///
-    /// The predicates are quantified over the `Self` type, i.e. `Ty::Bound(0)`
-    /// represents the `Self` type inside the bounds. This is currently
-    /// implicit; Chalk has the `Binders` struct to make it explicit, but it
-    /// didn't seem worth the overhead yet.
-    Dyn(DynTy),
-
-    /// A placeholder for a type which could not be computed; this is propagated
-    /// to avoid useless error messages. Doubles as a placeholder where type
-    /// variables are inserted before type checking, since we want to try to
-    /// infer a better type here anyway -- for the IDE use case, we want to try
-    /// to infer as much as possible even in the presence of type errors.
-    Unknown,
-}
-
-#[derive(Clone, PartialEq, Eq, Debug, Hash)]
-pub struct Ty(Arc<TyKind>);
-
-impl TyKind {
-    pub fn intern(self, _interner: &Interner) -> Ty {
-        Ty(Arc::new(self))
-    }
-}
-
-impl Ty {
-    pub fn interned(&self, _interner: &Interner) -> &TyKind {
-        &self.0
-    }
-
-    pub fn interned_mut(&mut self) -> &mut TyKind {
-        Arc::make_mut(&mut self.0)
-    }
-
-    pub fn into_inner(self) -> TyKind {
-        Arc::try_unwrap(self.0).unwrap_or_else(|a| (*a).clone())
-    }
-}
-
-/// A list of substitutions for generic parameters.
-#[derive(Clone, PartialEq, Eq, Debug, Hash)]
-pub struct Substitution(SmallVec<[Ty; 2]>);
-
-impl TypeWalk for Substitution {
-    fn walk(&self, f: &mut impl FnMut(&Ty)) {
-        for t in self.0.iter() {
-            t.walk(f);
-        }
-    }
-
-    fn walk_mut_binders(
-        &mut self,
-        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
-        binders: DebruijnIndex,
-    ) {
-        for t in &mut self.0 {
-            t.walk_mut_binders(f, binders);
-        }
-    }
-}
-
-impl Substitution {
-    pub fn interned(&self, _: &Interner) -> &[Ty] {
-        &self.0
-    }
-
-    pub fn empty() -> Substitution {
-        Substitution(SmallVec::new())
-    }
-
-    pub fn single(ty: Ty) -> Substitution {
-        Substitution({
-            let mut v = SmallVec::new();
-            v.push(ty);
-            v
-        })
-    }
-
-    pub fn prefix(&self, n: usize) -> Substitution {
-        Substitution(self.0[..std::cmp::min(self.0.len(), n)].into())
-    }
-
-    pub fn suffix(&self, n: usize) -> Substitution {
-        Substitution(self.0[self.0.len() - std::cmp::min(self.0.len(), n)..].into())
-    }
-
-    pub fn as_single(&self) -> &Ty {
-        if self.0.len() != 1 {
-            panic!("expected substs of len 1, got {:?}", self);
-        }
-        &self.0[0]
-    }
-
-    pub fn from_iter(_interner: &Interner, elements: impl IntoIterator<Item = Ty>) -> Self {
-        Substitution(elements.into_iter().collect())
-    }
-
-    /// Return Substs that replace each parameter by itself (i.e. `Ty::Param`).
-    pub(crate) fn type_params_for_generics(
-        db: &dyn HirDatabase,
-        generic_params: &Generics,
-    ) -> Substitution {
-        Substitution(
-            generic_params
-                .iter()
-                .map(|(id, _)| TyKind::Placeholder(to_placeholder_idx(db, id)).intern(&Interner))
-                .collect(),
-        )
-    }
-
-    /// Return Substs that replace each parameter by itself (i.e. `Ty::Param`).
-    pub fn type_params(db: &dyn HirDatabase, def: impl Into<GenericDefId>) -> Substitution {
-        let params = generics(db.upcast(), def.into());
-        Substitution::type_params_for_generics(db, &params)
-    }
-
-    /// Return Substs that replace each parameter by a bound variable.
-    pub(crate) fn bound_vars(generic_params: &Generics, debruijn: DebruijnIndex) -> Substitution {
-        Substitution(
-            generic_params
-                .iter()
-                .enumerate()
-                .map(|(idx, _)| TyKind::BoundVar(BoundVar::new(debruijn, idx)).intern(&Interner))
-                .collect(),
-        )
-    }
-
-    pub fn build_for_def(db: &dyn HirDatabase, def: impl Into<GenericDefId>) -> SubstsBuilder {
-        let def = def.into();
-        let params = generics(db.upcast(), def);
-        let param_count = params.len();
-        Substitution::builder(param_count)
-    }
-
-    pub(crate) fn build_for_generics(generic_params: &Generics) -> SubstsBuilder {
-        Substitution::builder(generic_params.len())
-    }
-
-    fn builder(param_count: usize) -> SubstsBuilder {
-        SubstsBuilder { vec: Vec::with_capacity(param_count), param_count }
-    }
+// FIXME: get rid of this
+pub fn subst_prefix(s: &Substitution, n: usize) -> Substitution {
+    Substitution::from_iter(
+        &Interner,
+        s.as_slice(&Interner)[..std::cmp::min(s.len(&Interner), n)].iter().cloned(),
+    )
 }
 
 /// Return an index of a parameter in the generic type parameter list by it's id.
@@ -433,244 +127,39 @@ pub fn param_idx(db: &dyn HirDatabase, id: TypeParamId) -> Option<usize> {
     generics(db.upcast(), id.parent).param_idx(id)
 }
 
-#[derive(Debug, Clone)]
-pub struct SubstsBuilder {
-    vec: Vec<Ty>,
-    param_count: usize,
-}
-
-impl SubstsBuilder {
-    pub fn build(self) -> Substitution {
-        assert_eq!(self.vec.len(), self.param_count);
-        Substitution(self.vec.into())
-    }
-
-    pub fn push(mut self, ty: Ty) -> Self {
-        self.vec.push(ty);
-        self
-    }
-
-    fn remaining(&self) -> usize {
-        self.param_count - self.vec.len()
-    }
-
-    pub fn fill_with_bound_vars(self, debruijn: DebruijnIndex, starting_from: usize) -> Self {
-        self.fill(
-            (starting_from..)
-                .map(|idx| TyKind::BoundVar(BoundVar::new(debruijn, idx)).intern(&Interner)),
+pub(crate) fn wrap_empty_binders<T>(value: T) -> Binders<T>
+where
+    T: Fold<Interner, Result = T> + HasInterner<Interner = Interner>,
+{
+    Binders::empty(&Interner, value.shifted_in_from(&Interner, DebruijnIndex::ONE))
+}
+
+pub(crate) fn make_only_type_binders<T: HasInterner<Interner = Interner>>(
+    num_vars: usize,
+    value: T,
+) -> Binders<T> {
+    Binders::new(
+        VariableKinds::from_iter(
+            &Interner,
+            std::iter::repeat(chalk_ir::VariableKind::Ty(chalk_ir::TyVariableKind::General))
+                .take(num_vars),
+        ),
+        value,
+    )
+}
+
+// FIXME: get rid of this
+pub fn make_canonical<T: HasInterner<Interner = Interner>>(
+    value: T,
+    kinds: impl IntoIterator<Item = TyVariableKind>,
+) -> Canonical<T> {
+    let kinds = kinds.into_iter().map(|tk| {
+        chalk_ir::CanonicalVarKind::new(
+            chalk_ir::VariableKind::Ty(tk),
+            chalk_ir::UniverseIndex::ROOT,
         )
-    }
-
-    pub fn fill_with_unknown(self) -> Self {
-        self.fill(iter::repeat(TyKind::Unknown.intern(&Interner)))
-    }
-
-    pub fn fill(mut self, filler: impl Iterator<Item = Ty>) -> Self {
-        self.vec.extend(filler.take(self.remaining()));
-        assert_eq!(self.remaining(), 0);
-        self
-    }
-
-    pub fn use_parent_substs(mut self, parent_substs: &Substitution) -> Self {
-        assert!(self.vec.is_empty());
-        assert!(parent_substs.len() <= self.param_count);
-        self.vec.extend(parent_substs.iter().cloned());
-        self
-    }
-}
-
-impl Deref for Substitution {
-    type Target = [Ty];
-
-    fn deref(&self) -> &[Ty] {
-        &self.0
-    }
-}
-
-#[derive(Copy, Clone, PartialEq, Eq, Debug, Hash)]
-pub struct Binders<T> {
-    pub num_binders: usize,
-    pub value: T,
-}
-
-impl<T> Binders<T> {
-    pub fn new(num_binders: usize, value: T) -> Self {
-        Self { num_binders, value }
-    }
-
-    pub fn wrap_empty(value: T) -> Self
-    where
-        T: TypeWalk,
-    {
-        Self { num_binders: 0, value: value.shift_bound_vars(DebruijnIndex::ONE) }
-    }
-
-    pub fn as_ref(&self) -> Binders<&T> {
-        Binders { num_binders: self.num_binders, value: &self.value }
-    }
-
-    pub fn map<U>(self, f: impl FnOnce(T) -> U) -> Binders<U> {
-        Binders { num_binders: self.num_binders, value: f(self.value) }
-    }
-
-    pub fn filter_map<U>(self, f: impl FnOnce(T) -> Option<U>) -> Option<Binders<U>> {
-        Some(Binders { num_binders: self.num_binders, value: f(self.value)? })
-    }
-
-    pub fn skip_binders(&self) -> &T {
-        &self.value
-    }
-
-    pub fn into_value_and_skipped_binders(self) -> (T, usize) {
-        (self.value, self.num_binders)
-    }
-}
-
-impl<T: Clone> Binders<&T> {
-    pub fn cloned(&self) -> Binders<T> {
-        Binders { num_binders: self.num_binders, value: self.value.clone() }
-    }
-}
-
-impl<T: TypeWalk> Binders<T> {
-    /// Substitutes all variables.
-    pub fn subst(self, subst: &Substitution) -> T {
-        assert_eq!(subst.len(), self.num_binders);
-        self.value.subst_bound_vars(subst)
-    }
-}
-
-impl<T: TypeWalk> TypeWalk for Binders<T> {
-    fn walk(&self, f: &mut impl FnMut(&Ty)) {
-        self.value.walk(f);
-    }
-
-    fn walk_mut_binders(
-        &mut self,
-        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
-        binders: DebruijnIndex,
-    ) {
-        self.value.walk_mut_binders(f, binders.shifted_in())
-    }
-}
-
-/// A trait with type parameters. This includes the `Self`, so this represents a concrete type implementing the trait.
-#[derive(Clone, PartialEq, Eq, Debug, Hash)]
-pub struct TraitRef {
-    pub trait_id: ChalkTraitId,
-    pub substitution: Substitution,
-}
-
-impl TraitRef {
-    pub fn self_type_parameter(&self) -> &Ty {
-        &self.substitution[0]
-    }
-
-    pub fn hir_trait_id(&self) -> TraitId {
-        from_chalk_trait_id(self.trait_id)
-    }
-}
-
-impl TypeWalk for TraitRef {
-    fn walk(&self, f: &mut impl FnMut(&Ty)) {
-        self.substitution.walk(f);
-    }
-
-    fn walk_mut_binders(
-        &mut self,
-        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
-        binders: DebruijnIndex,
-    ) {
-        self.substitution.walk_mut_binders(f, binders);
-    }
-}
-
-/// Like `generics::WherePredicate`, but with resolved types: A condition on the
-/// parameters of a generic item.
-#[derive(Debug, Clone, PartialEq, Eq, Hash)]
-pub enum WhereClause {
-    /// The given trait needs to be implemented for its type parameters.
-    Implemented(TraitRef),
-    /// An associated type bindings like in `Iterator<Item = T>`.
-    AliasEq(AliasEq),
-}
-
-impl WhereClause {
-    pub fn is_implemented(&self) -> bool {
-        matches!(self, WhereClause::Implemented(_))
-    }
-
-    pub fn trait_ref(&self, db: &dyn HirDatabase) -> Option<TraitRef> {
-        match self {
-            WhereClause::Implemented(tr) => Some(tr.clone()),
-            WhereClause::AliasEq(AliasEq { alias: AliasTy::Projection(proj), .. }) => {
-                Some(proj.trait_ref(db))
-            }
-            WhereClause::AliasEq(_) => None,
-        }
-    }
-}
-
-impl TypeWalk for WhereClause {
-    fn walk(&self, f: &mut impl FnMut(&Ty)) {
-        match self {
-            WhereClause::Implemented(trait_ref) => trait_ref.walk(f),
-            WhereClause::AliasEq(alias_eq) => alias_eq.walk(f),
-        }
-    }
-
-    fn walk_mut_binders(
-        &mut self,
-        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
-        binders: DebruijnIndex,
-    ) {
-        match self {
-            WhereClause::Implemented(trait_ref) => trait_ref.walk_mut_binders(f, binders),
-            WhereClause::AliasEq(alias_eq) => alias_eq.walk_mut_binders(f, binders),
-        }
-    }
-}
-
-pub type QuantifiedWhereClause = Binders<WhereClause>;
-
-#[derive(Debug, Clone, PartialEq, Eq, Hash)]
-pub struct QuantifiedWhereClauses(Arc<[QuantifiedWhereClause]>);
-
-impl QuantifiedWhereClauses {
-    pub fn from_iter(
-        _interner: &Interner,
-        elements: impl IntoIterator<Item = QuantifiedWhereClause>,
-    ) -> Self {
-        QuantifiedWhereClauses(elements.into_iter().collect())
-    }
-
-    pub fn interned(&self) -> &Arc<[QuantifiedWhereClause]> {
-        &self.0
-    }
-}
-
-/// Basically a claim (currently not validated / checked) that the contained
-/// type / trait ref contains no inference variables; any inference variables it
-/// contained have been replaced by bound variables, and `kinds` tells us how
-/// many there are and whether they were normal or float/int variables. This is
-/// used to erase irrelevant differences between types before using them in
-/// queries.
-#[derive(Debug, Clone, PartialEq, Eq, Hash)]
-pub struct Canonical<T> {
-    pub value: T,
-    pub binders: CanonicalVarKinds,
-}
-
-impl<T> Canonical<T> {
-    pub fn new(value: T, kinds: impl IntoIterator<Item = TyVariableKind>) -> Self {
-        let kinds = kinds.into_iter().map(|tk| {
-            chalk_ir::CanonicalVarKind::new(
-                chalk_ir::VariableKind::Ty(tk),
-                chalk_ir::UniverseIndex::ROOT,
-            )
-        });
-        Self { value, binders: chalk_ir::CanonicalVarKinds::from_iter(&Interner, kinds) }
-    }
+    });
+    Canonical { value, binders: chalk_ir::CanonicalVarKinds::from_iter(&Interner, kinds) }
 }
 
 /// A function signature as seen by type inference: Several parameter types and
@@ -681,6 +170,8 @@ pub struct CallableSig {
     is_varargs: bool,
 }
 
+has_interner!(CallableSig);
+
 /// A polymorphic function signature.
 pub type PolyFnSig = Binders<CallableSig>;
 
@@ -692,23 +183,21 @@ impl CallableSig {
 
     pub fn from_fn_ptr(fn_ptr: &FnPointer) -> CallableSig {
         CallableSig {
-            // FIXME: what to do about lifetime params?
+            // FIXME: what to do about lifetime params? -> return PolyFnSig
             params_and_return: fn_ptr
-                .substs
+                .substitution
                 .clone()
-                .shift_bound_vars_out(DebruijnIndex::ONE)
-                .interned(&Interner)
+                .shifted_out_to(&Interner, DebruijnIndex::ONE)
+                .expect("unexpected lifetime vars in fn ptr")
+                .0
+                .as_slice(&Interner)
                 .iter()
-                .cloned()
+                .map(|arg| arg.assert_ty_ref(&Interner).clone())
                 .collect(),
             is_varargs: fn_ptr.sig.variadic,
         }
     }
 
-    pub fn from_substs(substs: &Substitution) -> CallableSig {
-        CallableSig { params_and_return: substs.iter().cloned().collect(), is_varargs: false }
-    }
-
     pub fn params(&self) -> &[Ty] {
         &self.params_and_return[0..self.params_and_return.len() - 1]
     }
@@ -718,516 +207,20 @@ impl CallableSig {
     }
 }
 
-impl TypeWalk for CallableSig {
-    fn walk(&self, f: &mut impl FnMut(&Ty)) {
-        for t in self.params_and_return.iter() {
-            t.walk(f);
-        }
-    }
-
-    fn walk_mut_binders(
-        &mut self,
-        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
-        binders: DebruijnIndex,
-    ) {
-        for t in make_mut_slice(&mut self.params_and_return) {
-            t.walk_mut_binders(f, binders);
-        }
-    }
-}
-
-impl Ty {
-    pub fn unit() -> Self {
-        TyKind::Tuple(0, Substitution::empty()).intern(&Interner)
-    }
-
-    pub fn adt_ty(adt: hir_def::AdtId, substs: Substitution) -> Ty {
-        TyKind::Adt(AdtId(adt), substs).intern(&Interner)
-    }
-
-    pub fn fn_ptr(sig: CallableSig) -> Self {
-        TyKind::Function(FnPointer {
-            num_args: sig.params().len(),
-            sig: FnSig { abi: (), safety: Safety::Safe, variadic: sig.is_varargs },
-            substs: Substitution::from_iter(&Interner, sig.params_and_return.iter().cloned()),
-        })
-        .intern(&Interner)
-    }
-
-    pub fn builtin(builtin: BuiltinType) -> Self {
-        match builtin {
-            BuiltinType::Char => TyKind::Scalar(Scalar::Char).intern(&Interner),
-            BuiltinType::Bool => TyKind::Scalar(Scalar::Bool).intern(&Interner),
-            BuiltinType::Str => TyKind::Str.intern(&Interner),
-            BuiltinType::Int(t) => {
-                TyKind::Scalar(Scalar::Int(primitive::int_ty_from_builtin(t))).intern(&Interner)
-            }
-            BuiltinType::Uint(t) => {
-                TyKind::Scalar(Scalar::Uint(primitive::uint_ty_from_builtin(t))).intern(&Interner)
-            }
-            BuiltinType::Float(t) => {
-                TyKind::Scalar(Scalar::Float(primitive::float_ty_from_builtin(t))).intern(&Interner)
-            }
-        }
-    }
-
-    pub fn as_reference(&self) -> Option<(&Ty, Mutability)> {
-        match self.interned(&Interner) {
-            TyKind::Ref(mutability, ty) => Some((ty, *mutability)),
-            _ => None,
-        }
-    }
-
-    pub fn as_reference_or_ptr(&self) -> Option<(&Ty, Rawness, Mutability)> {
-        match self.interned(&Interner) {
-            TyKind::Ref(mutability, ty) => Some((ty, Rawness::Ref, *mutability)),
-            TyKind::Raw(mutability, ty) => Some((ty, Rawness::RawPtr, *mutability)),
-            _ => None,
-        }
-    }
-
-    pub fn strip_references(&self) -> &Ty {
-        let mut t: &Ty = self;
-
-        while let TyKind::Ref(_mutability, ty) = t.interned(&Interner) {
-            t = ty;
-        }
-
-        t
-    }
-
-    pub fn as_adt(&self) -> Option<(hir_def::AdtId, &Substitution)> {
-        match self.interned(&Interner) {
-            TyKind::Adt(AdtId(adt), parameters) => Some((*adt, parameters)),
-            _ => None,
-        }
-    }
-
-    pub fn as_tuple(&self) -> Option<&Substitution> {
-        match self.interned(&Interner) {
-            TyKind::Tuple(_, substs) => Some(substs),
-            _ => None,
-        }
-    }
+impl Fold<Interner> for CallableSig {
+    type Result = CallableSig;
 
-    pub fn as_generic_def(&self, db: &dyn HirDatabase) -> Option<GenericDefId> {
-        match *self.interned(&Interner) {
-            TyKind::Adt(AdtId(adt), ..) => Some(adt.into()),
-            TyKind::FnDef(callable, ..) => {
-                Some(db.lookup_intern_callable_def(callable.into()).into())
-            }
-            TyKind::AssociatedType(type_alias, ..) => Some(from_assoc_type_id(type_alias).into()),
-            TyKind::ForeignType(type_alias, ..) => Some(from_foreign_def_id(type_alias).into()),
-            _ => None,
-        }
-    }
-
-    pub fn is_never(&self) -> bool {
-        matches!(self.interned(&Interner), TyKind::Never)
-    }
-
-    pub fn is_unknown(&self) -> bool {
-        matches!(self.interned(&Interner), TyKind::Unknown)
-    }
-
-    pub fn equals_ctor(&self, other: &Ty) -> bool {
-        match (self.interned(&Interner), other.interned(&Interner)) {
-            (TyKind::Adt(adt, ..), TyKind::Adt(adt2, ..)) => adt == adt2,
-            (TyKind::Slice(_), TyKind::Slice(_)) | (TyKind::Array(_), TyKind::Array(_)) => true,
-            (TyKind::FnDef(def_id, ..), TyKind::FnDef(def_id2, ..)) => def_id == def_id2,
-            (TyKind::OpaqueType(ty_id, ..), TyKind::OpaqueType(ty_id2, ..)) => ty_id == ty_id2,
-            (TyKind::AssociatedType(ty_id, ..), TyKind::AssociatedType(ty_id2, ..)) => {
-                ty_id == ty_id2
-            }
-            (TyKind::ForeignType(ty_id, ..), TyKind::ForeignType(ty_id2, ..)) => ty_id == ty_id2,
-            (TyKind::Closure(id1, _), TyKind::Closure(id2, _)) => id1 == id2,
-            (TyKind::Ref(mutability, ..), TyKind::Ref(mutability2, ..))
-            | (TyKind::Raw(mutability, ..), TyKind::Raw(mutability2, ..)) => {
-                mutability == mutability2
-            }
-            (
-                TyKind::Function(FnPointer { num_args, sig, .. }),
-                TyKind::Function(FnPointer { num_args: num_args2, sig: sig2, .. }),
-            ) => num_args == num_args2 && sig == sig2,
-            (TyKind::Tuple(cardinality, _), TyKind::Tuple(cardinality2, _)) => {
-                cardinality == cardinality2
-            }
-            (TyKind::Str, TyKind::Str) | (TyKind::Never, TyKind::Never) => true,
-            (TyKind::Scalar(scalar), TyKind::Scalar(scalar2)) => scalar == scalar2,
-            _ => false,
-        }
-    }
-
-    /// If this is a `dyn Trait` type, this returns the `Trait` part.
-    fn dyn_trait_ref(&self) -> Option<&TraitRef> {
-        match self.interned(&Interner) {
-            TyKind::Dyn(dyn_ty) => {
-                dyn_ty.bounds.value.interned().get(0).and_then(|b| match b.skip_binders() {
-                    WhereClause::Implemented(trait_ref) => Some(trait_ref),
-                    _ => None,
-                })
-            }
-            _ => None,
-        }
-    }
-
-    /// If this is a `dyn Trait`, returns that trait.
-    pub fn dyn_trait(&self) -> Option<TraitId> {
-        self.dyn_trait_ref().map(|it| it.trait_id).map(from_chalk_trait_id)
-    }
-
-    fn builtin_deref(&self) -> Option<Ty> {
-        match self.interned(&Interner) {
-            TyKind::Ref(.., ty) => Some(ty.clone()),
-            TyKind::Raw(.., ty) => Some(ty.clone()),
-            _ => None,
-        }
-    }
-
-    pub fn callable_def(&self, db: &dyn HirDatabase) -> Option<CallableDefId> {
-        match self.interned(&Interner) {
-            &TyKind::FnDef(def, ..) => Some(db.lookup_intern_callable_def(def.into())),
-            _ => None,
-        }
-    }
-
-    pub fn as_fn_def(&self, db: &dyn HirDatabase) -> Option<FunctionId> {
-        if let Some(CallableDefId::FunctionId(func)) = self.callable_def(db) {
-            Some(func)
-        } else {
-            None
-        }
-    }
-
-    pub fn callable_sig(&self, db: &dyn HirDatabase) -> Option<CallableSig> {
-        match self.interned(&Interner) {
-            TyKind::Function(fn_ptr) => Some(CallableSig::from_fn_ptr(fn_ptr)),
-            TyKind::FnDef(def, parameters) => {
-                let callable_def = db.lookup_intern_callable_def((*def).into());
-                let sig = db.callable_item_signature(callable_def);
-                Some(sig.subst(&parameters))
-            }
-            TyKind::Closure(.., substs) => {
-                let sig_param = &substs[0];
-                sig_param.callable_sig(db)
-            }
-            _ => None,
-        }
-    }
-
-    /// Returns the type parameters of this type if it has some (i.e. is an ADT
-    /// or function); so if `self` is `Option<u32>`, this returns the `u32`.
-    pub fn substs(&self) -> Option<&Substitution> {
-        match self.interned(&Interner) {
-            TyKind::Adt(_, substs)
-            | TyKind::FnDef(_, substs)
-            | TyKind::Function(FnPointer { substs, .. })
-            | TyKind::Tuple(_, substs)
-            | TyKind::OpaqueType(_, substs)
-            | TyKind::AssociatedType(_, substs)
-            | TyKind::Closure(.., substs) => Some(substs),
-            _ => None,
-        }
-    }
-
-    fn substs_mut(&mut self) -> Option<&mut Substitution> {
-        match self.interned_mut() {
-            TyKind::Adt(_, substs)
-            | TyKind::FnDef(_, substs)
-            | TyKind::Function(FnPointer { substs, .. })
-            | TyKind::Tuple(_, substs)
-            | TyKind::OpaqueType(_, substs)
-            | TyKind::AssociatedType(_, substs)
-            | TyKind::Closure(.., substs) => Some(substs),
-            _ => None,
-        }
-    }
-
-    pub fn impl_trait_bounds(&self, db: &dyn HirDatabase) -> Option<Vec<QuantifiedWhereClause>> {
-        match self.interned(&Interner) {
-            TyKind::OpaqueType(opaque_ty_id, ..) => {
-                match db.lookup_intern_impl_trait_id((*opaque_ty_id).into()) {
-                    ImplTraitId::AsyncBlockTypeImplTrait(def, _expr) => {
-                        let krate = def.module(db.upcast()).krate();
-                        if let Some(future_trait) = db
-                            .lang_item(krate, "future_trait".into())
-                            .and_then(|item| item.as_trait())
-                        {
-                            // This is only used by type walking.
-                            // Parameters will be walked outside, and projection predicate is not used.
-                            // So just provide the Future trait.
-                            let impl_bound = Binders::new(
-                                0,
-                                WhereClause::Implemented(TraitRef {
-                                    trait_id: to_chalk_trait_id(future_trait),
-                                    substitution: Substitution::empty(),
-                                }),
-                            );
-                            Some(vec![impl_bound])
-                        } else {
-                            None
-                        }
-                    }
-                    ImplTraitId::ReturnTypeImplTrait(..) => None,
-                }
-            }
-            TyKind::Alias(AliasTy::Opaque(opaque_ty)) => {
-                let predicates = match db.lookup_intern_impl_trait_id(opaque_ty.opaque_ty_id.into())
-                {
-                    ImplTraitId::ReturnTypeImplTrait(func, idx) => {
-                        db.return_type_impl_traits(func).map(|it| {
-                            let data = (*it)
-                                .as_ref()
-                                .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
-                            data.subst(&opaque_ty.substitution)
-                        })
-                    }
-                    // It always has an parameter for Future::Output type.
-                    ImplTraitId::AsyncBlockTypeImplTrait(..) => unreachable!(),
-                };
-
-                predicates.map(|it| it.value)
-            }
-            TyKind::Placeholder(idx) => {
-                let id = from_placeholder_idx(db, *idx);
-                let generic_params = db.generic_params(id.parent);
-                let param_data = &generic_params.types[id.local_id];
-                match param_data.provenance {
-                    hir_def::generics::TypeParamProvenance::ArgumentImplTrait => {
-                        let substs = Substitution::type_params(db, id.parent);
-                        let predicates = db
-                            .generic_predicates(id.parent)
-                            .into_iter()
-                            .map(|pred| pred.clone().subst(&substs))
-                            .filter(|wc| match &wc.skip_binders() {
-                                WhereClause::Implemented(tr) => tr.self_type_parameter() == self,
-                                WhereClause::AliasEq(AliasEq {
-                                    alias: AliasTy::Projection(proj),
-                                    ty: _,
-                                }) => proj.self_type_parameter() == self,
-                                _ => false,
-                            })
-                            .collect_vec();
-
-                        Some(predicates)
-                    }
-                    _ => None,
-                }
-            }
-            _ => None,
-        }
-    }
-
-    pub fn associated_type_parent_trait(&self, db: &dyn HirDatabase) -> Option<TraitId> {
-        match self.interned(&Interner) {
-            TyKind::AssociatedType(id, ..) => {
-                match from_assoc_type_id(*id).lookup(db.upcast()).container {
-                    AssocContainerId::TraitId(trait_id) => Some(trait_id),
-                    _ => None,
-                }
-            }
-            TyKind::Alias(AliasTy::Projection(projection_ty)) => {
-                match from_assoc_type_id(projection_ty.associated_ty_id)
-                    .lookup(db.upcast())
-                    .container
-                {
-                    AssocContainerId::TraitId(trait_id) => Some(trait_id),
-                    _ => None,
-                }
-            }
-            _ => None,
-        }
-    }
-}
-
-/// This allows walking structures that contain types to do something with those
-/// types, similar to Chalk's `Fold` trait.
-pub trait TypeWalk {
-    fn walk(&self, f: &mut impl FnMut(&Ty));
-    fn walk_mut(&mut self, f: &mut impl FnMut(&mut Ty)) {
-        self.walk_mut_binders(&mut |ty, _binders| f(ty), DebruijnIndex::INNERMOST);
-    }
-    /// Walk the type, counting entered binders.
-    ///
-    /// `TyKind::Bound` variables use DeBruijn indexing, which means that 0 refers
-    /// to the innermost binder, 1 to the next, etc.. So when we want to
-    /// substitute a certain bound variable, we can't just walk the whole type
-    /// and blindly replace each instance of a certain index; when we 'enter'
-    /// things that introduce new bound variables, we have to keep track of
-    /// that. Currently, the only thing that introduces bound variables on our
-    /// side are `TyKind::Dyn` and `TyKind::Opaque`, which each introduce a bound
-    /// variable for the self type.
-    fn walk_mut_binders(
-        &mut self,
-        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
-        binders: DebruijnIndex,
-    );
-
-    fn fold_binders(
-        mut self,
-        f: &mut impl FnMut(Ty, DebruijnIndex) -> Ty,
-        binders: DebruijnIndex,
-    ) -> Self
-    where
-        Self: Sized,
-    {
-        self.walk_mut_binders(
-            &mut |ty_mut, binders| {
-                let ty = mem::replace(ty_mut, TyKind::Unknown.intern(&Interner));
-                *ty_mut = f(ty, binders);
-            },
-            binders,
-        );
-        self
-    }
-
-    fn fold(mut self, f: &mut impl FnMut(Ty) -> Ty) -> Self
-    where
-        Self: Sized,
-    {
-        self.walk_mut(&mut |ty_mut| {
-            let ty = mem::replace(ty_mut, TyKind::Unknown.intern(&Interner));
-            *ty_mut = f(ty);
-        });
-        self
-    }
-
-    /// Substitutes `TyKind::Bound` vars with the given substitution.
-    fn subst_bound_vars(self, substs: &Substitution) -> Self
-    where
-        Self: Sized,
-    {
-        self.subst_bound_vars_at_depth(substs, DebruijnIndex::INNERMOST)
-    }
-
-    /// Substitutes `TyKind::Bound` vars with the given substitution.
-    fn subst_bound_vars_at_depth(mut self, substs: &Substitution, depth: DebruijnIndex) -> Self
-    where
-        Self: Sized,
-    {
-        self.walk_mut_binders(
-            &mut |ty, binders| {
-                if let &mut TyKind::BoundVar(bound) = ty.interned_mut() {
-                    if bound.debruijn >= binders {
-                        *ty = substs.0[bound.index].clone().shift_bound_vars(binders);
-                    }
-                }
-            },
-            depth,
-        );
-        self
-    }
-
-    /// Shifts up debruijn indices of `TyKind::Bound` vars by `n`.
-    fn shift_bound_vars(self, n: DebruijnIndex) -> Self
-    where
-        Self: Sized,
-    {
-        self.fold_binders(
-            &mut |ty, binders| match ty.interned(&Interner) {
-                TyKind::BoundVar(bound) if bound.debruijn >= binders => {
-                    TyKind::BoundVar(bound.shifted_in_from(n)).intern(&Interner)
-                }
-                _ => ty,
-            },
-            DebruijnIndex::INNERMOST,
-        )
-    }
-
-    /// Shifts debruijn indices of `TyKind::Bound` vars out (down) by `n`.
-    fn shift_bound_vars_out(self, n: DebruijnIndex) -> Self
+    fn fold_with<'i>(
+        self,
+        folder: &mut dyn chalk_ir::fold::Folder<'i, Interner>,
+        outer_binder: DebruijnIndex,
+    ) -> chalk_ir::Fallible<Self::Result>
     where
-        Self: Sized + std::fmt::Debug,
+        Interner: 'i,
     {
-        self.fold_binders(
-            &mut |ty, binders| match ty.interned(&Interner) {
-                TyKind::BoundVar(bound) if bound.debruijn >= binders => {
-                    TyKind::BoundVar(bound.shifted_out_to(n).unwrap_or(bound.clone()))
-                        .intern(&Interner)
-                }
-                _ => ty,
-            },
-            DebruijnIndex::INNERMOST,
-        )
-    }
-}
-
-impl TypeWalk for Ty {
-    fn walk(&self, f: &mut impl FnMut(&Ty)) {
-        match self.interned(&Interner) {
-            TyKind::Alias(AliasTy::Projection(p_ty)) => {
-                for t in p_ty.substitution.iter() {
-                    t.walk(f);
-                }
-            }
-            TyKind::Alias(AliasTy::Opaque(o_ty)) => {
-                for t in o_ty.substitution.iter() {
-                    t.walk(f);
-                }
-            }
-            TyKind::Dyn(dyn_ty) => {
-                for p in dyn_ty.bounds.value.interned().iter() {
-                    p.walk(f);
-                }
-            }
-            TyKind::Slice(ty) | TyKind::Array(ty) | TyKind::Ref(_, ty) | TyKind::Raw(_, ty) => {
-                ty.walk(f);
-            }
-            _ => {
-                if let Some(substs) = self.substs() {
-                    for t in substs.iter() {
-                        t.walk(f);
-                    }
-                }
-            }
-        }
-        f(self);
-    }
-
-    fn walk_mut_binders(
-        &mut self,
-        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
-        binders: DebruijnIndex,
-    ) {
-        match self.interned_mut() {
-            TyKind::Alias(AliasTy::Projection(p_ty)) => {
-                p_ty.substitution.walk_mut_binders(f, binders);
-            }
-            TyKind::Dyn(dyn_ty) => {
-                for p in make_mut_slice(&mut dyn_ty.bounds.value.0) {
-                    p.walk_mut_binders(f, binders.shifted_in());
-                }
-            }
-            TyKind::Alias(AliasTy::Opaque(o_ty)) => {
-                o_ty.substitution.walk_mut_binders(f, binders);
-            }
-            TyKind::Slice(ty) | TyKind::Array(ty) | TyKind::Ref(_, ty) | TyKind::Raw(_, ty) => {
-                ty.walk_mut_binders(f, binders);
-            }
-            _ => {
-                if let Some(substs) = self.substs_mut() {
-                    substs.walk_mut_binders(f, binders);
-                }
-            }
-        }
-        f(self, binders);
-    }
-}
-
-impl<T: TypeWalk> TypeWalk for Vec<T> {
-    fn walk(&self, f: &mut impl FnMut(&Ty)) {
-        for t in self {
-            t.walk(f);
-        }
-    }
-    fn walk_mut_binders(
-        &mut self,
-        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
-        binders: DebruijnIndex,
-    ) {
-        for t in self {
-            t.walk_mut_binders(f, binders);
-        }
+        let vec = self.params_and_return.to_vec();
+        let folded = vec.fold_with(folder, outer_binder)?;
+        Ok(CallableSig { params_and_return: folded.into(), is_varargs: self.is_varargs })
     }
 }
 
@@ -1242,45 +235,75 @@ pub struct ReturnTypeImplTraits {
     pub(crate) impl_traits: Vec<ReturnTypeImplTrait>,
 }
 
+has_interner!(ReturnTypeImplTraits);
+
 #[derive(Clone, PartialEq, Eq, Debug, Hash)]
 pub(crate) struct ReturnTypeImplTrait {
     pub(crate) bounds: Binders<Vec<QuantifiedWhereClause>>,
 }
 
-pub fn to_foreign_def_id(id: TypeAliasId) -> ForeignDefId {
-    chalk_ir::ForeignDefId(salsa::InternKey::as_intern_id(&id))
+pub fn static_lifetime() -> Lifetime {
+    LifetimeData::Static.intern(&Interner)
 }
 
-pub fn from_foreign_def_id(id: ForeignDefId) -> TypeAliasId {
-    salsa::InternKey::from_intern_id(id.0)
-}
-
-pub fn to_assoc_type_id(id: TypeAliasId) -> AssocTypeId {
-    chalk_ir::AssocTypeId(salsa::InternKey::as_intern_id(&id))
+pub fn dummy_usize_const() -> Const {
+    let usize_ty = chalk_ir::TyKind::Scalar(Scalar::Uint(UintTy::Usize)).intern(&Interner);
+    chalk_ir::ConstData {
+        ty: usize_ty,
+        value: chalk_ir::ConstValue::Concrete(chalk_ir::ConcreteConst { interned: () }),
+    }
+    .intern(&Interner)
 }
 
-pub fn from_assoc_type_id(id: AssocTypeId) -> TypeAliasId {
-    salsa::InternKey::from_intern_id(id.0)
-}
+pub(crate) fn fold_free_vars<T: HasInterner<Interner = Interner> + Fold<Interner>>(
+    t: T,
+    f: impl FnMut(BoundVar, DebruijnIndex) -> Ty,
+) -> T::Result {
+    use chalk_ir::{fold::Folder, Fallible};
+    struct FreeVarFolder<F>(F);
+    impl<'i, F: FnMut(BoundVar, DebruijnIndex) -> Ty + 'i> Folder<'i, Interner> for FreeVarFolder<F> {
+        fn as_dyn(&mut self) -> &mut dyn Folder<'i, Interner> {
+            self
+        }
 
-pub fn from_placeholder_idx(db: &dyn HirDatabase, idx: PlaceholderIndex) -> TypeParamId {
-    assert_eq!(idx.ui, chalk_ir::UniverseIndex::ROOT);
-    let interned_id = salsa::InternKey::from_intern_id(salsa::InternId::from(idx.idx));
-    db.lookup_intern_type_param_id(interned_id)
-}
+        fn interner(&self) -> &'i Interner {
+            &Interner
+        }
 
-pub fn to_placeholder_idx(db: &dyn HirDatabase, id: TypeParamId) -> PlaceholderIndex {
-    let interned_id = db.intern_type_param_id(id);
-    PlaceholderIndex {
-        ui: chalk_ir::UniverseIndex::ROOT,
-        idx: salsa::InternKey::as_intern_id(&interned_id).as_usize(),
+        fn fold_free_var_ty(
+            &mut self,
+            bound_var: BoundVar,
+            outer_binder: DebruijnIndex,
+        ) -> Fallible<Ty> {
+            Ok(self.0(bound_var, outer_binder))
+        }
     }
+    t.fold_with(&mut FreeVarFolder(f), DebruijnIndex::INNERMOST).expect("fold failed unexpectedly")
 }
 
-pub fn to_chalk_trait_id(id: TraitId) -> ChalkTraitId {
-    chalk_ir::TraitId(salsa::InternKey::as_intern_id(&id))
-}
+pub(crate) fn fold_tys<T: HasInterner<Interner = Interner> + Fold<Interner>>(
+    t: T,
+    f: impl FnMut(Ty, DebruijnIndex) -> Ty,
+    binders: DebruijnIndex,
+) -> T::Result {
+    use chalk_ir::{
+        fold::{Folder, SuperFold},
+        Fallible,
+    };
+    struct TyFolder<F>(F);
+    impl<'i, F: FnMut(Ty, DebruijnIndex) -> Ty + 'i> Folder<'i, Interner> for TyFolder<F> {
+        fn as_dyn(&mut self) -> &mut dyn Folder<'i, Interner> {
+            self
+        }
+
+        fn interner(&self) -> &'i Interner {
+            &Interner
+        }
 
-pub fn from_chalk_trait_id(id: ChalkTraitId) -> TraitId {
-    salsa::InternKey::from_intern_id(id.0)
+        fn fold_ty(&mut self, ty: Ty, outer_binder: DebruijnIndex) -> Fallible<Ty> {
+            let ty = ty.super_fold_with(self.as_dyn(), outer_binder)?;
+            Ok(self.0(ty, outer_binder))
+        }
+    }
+    t.fold_with(&mut TyFolder(f), binders).expect("fold failed unexpectedly")
 }
diff --git a/crates/hir_ty/src/lower.rs b/crates/hir_ty/src/lower.rs
index c87789d45..a035686bc 100644
--- a/crates/hir_ty/src/lower.rs
+++ b/crates/hir_ty/src/lower.rs
@@ -8,14 +8,14 @@
 use std::{iter, sync::Arc};
 
 use base_db::CrateId;
-use chalk_ir::{cast::Cast, Mutability, Safety};
+use chalk_ir::{cast::Cast, fold::Shift, interner::HasInterner, Mutability, Safety};
 use hir_def::{
     adt::StructKind,
     builtin_type::BuiltinType,
     generics::{TypeParamProvenance, WherePredicate, WherePredicateTypeTarget},
     path::{GenericArg, Path, PathSegment, PathSegments},
     resolver::{HasResolver, Resolver, TypeNs},
-    type_ref::{TypeBound, TypeRef},
+    type_ref::{TraitRef as HirTraitRef, TypeBound, TypeRef},
     AdtId, AssocContainerId, AssocItemId, ConstId, ConstParamId, EnumId, EnumVariantId, FunctionId,
     GenericDefId, HasModule, ImplId, LocalFieldId, Lookup, StaticId, StructId, TraitId,
     TypeAliasId, TypeParamId, UnionId, VariantId,
@@ -27,16 +27,16 @@ use stdx::impl_from;
 
 use crate::{
     db::HirDatabase,
-    to_assoc_type_id, to_chalk_trait_id, to_placeholder_idx,
-    traits::chalk::{Interner, ToChalk},
+    dummy_usize_const,
+    mapping::ToChalk,
+    static_lifetime, to_assoc_type_id, to_chalk_trait_id, to_placeholder_idx,
     utils::{
-        all_super_trait_refs, associated_type_by_name_including_super_traits, generics,
-        variant_data,
+        all_super_trait_refs, associated_type_by_name_including_super_traits, generics, Generics,
     },
     AliasEq, AliasTy, Binders, BoundVar, CallableSig, DebruijnIndex, DynTy, FnPointer, FnSig,
-    ImplTraitId, OpaqueTy, PolyFnSig, ProjectionTy, QuantifiedWhereClause, QuantifiedWhereClauses,
-    ReturnTypeImplTrait, ReturnTypeImplTraits, Substitution, TraitEnvironment, TraitRef, Ty,
-    TyKind, TypeWalk, WhereClause,
+    FnSubst, ImplTraitId, Interner, OpaqueTy, PolyFnSig, ProjectionTy, QuantifiedWhereClause,
+    QuantifiedWhereClauses, ReturnTypeImplTrait, ReturnTypeImplTraits, Substitution,
+    TraitEnvironment, TraitRef, TraitRefExt, Ty, TyBuilder, TyKind, WhereClause,
 };
 
 #[derive(Debug)]
@@ -146,7 +146,7 @@ impl<'a> TyLoweringContext<'a> {
         self.lower_ty_ext(type_ref).0
     }
 
-    fn lower_ty_ext(&self, type_ref: &TypeRef) -> (Ty, Option<TypeNs>) {
+    pub fn lower_ty_ext(&self, type_ref: &TypeRef) -> (Ty, Option<TypeNs>) {
         let mut res = None;
         let ty = match type_ref {
             TypeRef::Never => TyKind::Never.intern(&Interner),
@@ -166,7 +166,7 @@ impl<'a> TyLoweringContext<'a> {
             }
             TypeRef::Array(inner) => {
                 let inner_ty = self.lower_ty(inner);
-                TyKind::Array(inner_ty).intern(&Interner)
+                TyKind::Array(inner_ty, dummy_usize_const()).intern(&Interner)
             }
             TypeRef::Slice(inner) => {
                 let inner_ty = self.lower_ty(inner);
@@ -174,15 +174,19 @@ impl<'a> TyLoweringContext<'a> {
             }
             TypeRef::Reference(inner, _, mutability) => {
                 let inner_ty = self.lower_ty(inner);
-                TyKind::Ref(lower_to_chalk_mutability(*mutability), inner_ty).intern(&Interner)
+                let lifetime = static_lifetime();
+                TyKind::Ref(lower_to_chalk_mutability(*mutability), lifetime, inner_ty)
+                    .intern(&Interner)
             }
-            TypeRef::Placeholder => TyKind::Unknown.intern(&Interner),
+            TypeRef::Placeholder => TyKind::Error.intern(&Interner),
             TypeRef::Fn(params, is_varargs) => {
-                let substs = Substitution(params.iter().map(|tr| self.lower_ty(tr)).collect());
+                let substs = self.with_shifted_in(DebruijnIndex::ONE, |ctx| {
+                    Substitution::from_iter(&Interner, params.iter().map(|tr| ctx.lower_ty(tr)))
+                });
                 TyKind::Function(FnPointer {
-                    num_args: substs.len() - 1,
+                    num_binders: 0, // FIXME lower `for<'a> fn()` correctly
                     sig: FnSig { abi: (), safety: Safety::Safe, variadic: *is_varargs },
-                    substs,
+                    substitution: FnSubst(substs),
                 })
                 .intern(&Interner)
             }
@@ -195,8 +199,8 @@ impl<'a> TyLoweringContext<'a> {
                         bounds.iter().flat_map(|b| ctx.lower_type_bound(b, self_ty.clone(), false)),
                     )
                 });
-                let bounds = Binders::new(1, bounds);
-                TyKind::Dyn(DynTy { bounds }).intern(&Interner)
+                let bounds = crate::make_only_type_binders(1, bounds);
+                TyKind::Dyn(DynTy { bounds, lifetime: static_lifetime() }).intern(&Interner)
             }
             TypeRef::ImplTrait(bounds) => {
                 match self.impl_trait_mode {
@@ -208,9 +212,9 @@ impl<'a> TyLoweringContext<'a> {
                         // this dance is to make sure the data is in the right
                         // place even if we encounter more opaque types while
                         // lowering the bounds
-                        self.opaque_type_data
-                            .borrow_mut()
-                            .push(ReturnTypeImplTrait { bounds: Binders::new(1, Vec::new()) });
+                        self.opaque_type_data.borrow_mut().push(ReturnTypeImplTrait {
+                            bounds: crate::make_only_type_binders(1, Vec::new()),
+                        });
                         // We don't want to lower the bounds inside the binders
                         // we're currently in, because they don't end up inside
                         // those binders. E.g. when we have `impl Trait<impl
@@ -233,7 +237,7 @@ impl<'a> TyLoweringContext<'a> {
                         let impl_trait_id = ImplTraitId::ReturnTypeImplTrait(func, idx);
                         let opaque_ty_id = self.db.intern_impl_trait_id(impl_trait_id).into();
                         let generics = generics(self.db.upcast(), func.into());
-                        let parameters = Substitution::bound_vars(&generics, self.in_binders);
+                        let parameters = generics.bound_vars_subst(self.in_binders);
                         TyKind::Alias(AliasTy::Opaque(OpaqueTy {
                             opaque_ty_id,
                             substitution: parameters,
@@ -252,12 +256,12 @@ impl<'a> TyLoweringContext<'a> {
                                     data.provenance == TypeParamProvenance::ArgumentImplTrait
                                 })
                                 .nth(idx as usize)
-                                .map_or(TyKind::Unknown, |(id, _)| {
+                                .map_or(TyKind::Error, |(id, _)| {
                                     TyKind::Placeholder(to_placeholder_idx(self.db, id))
                                 });
                             param.intern(&Interner)
                         } else {
-                            TyKind::Unknown.intern(&Interner)
+                            TyKind::Error.intern(&Interner)
                         }
                     }
                     ImplTraitLoweringMode::Variable => {
@@ -279,11 +283,11 @@ impl<'a> TyLoweringContext<'a> {
                     }
                     ImplTraitLoweringMode::Disallowed => {
                         // FIXME: report error
-                        TyKind::Unknown.intern(&Interner)
+                        TyKind::Error.intern(&Interner)
                     }
                 }
             }
-            TypeRef::Error => TyKind::Unknown.intern(&Interner),
+            TypeRef::Error => TyKind::Error.intern(&Interner),
         };
         (ty, res)
     }
@@ -327,7 +331,7 @@ impl<'a> TyLoweringContext<'a> {
             (self.select_associated_type(res, segment), None)
         } else if remaining_segments.len() > 1 {
             // FIXME report error (ambiguous associated type)
-            (TyKind::Unknown.intern(&Interner), None)
+            (TyKind::Error.intern(&Interner), None)
         } else {
             (ty, res)
         }
@@ -371,21 +375,24 @@ impl<'a> TyLoweringContext<'a> {
                         }
                         None => {
                             // FIXME: report error (associated type not found)
-                            TyKind::Unknown.intern(&Interner)
+                            TyKind::Error.intern(&Interner)
                         }
                     }
                 } else if remaining_segments.len() > 1 {
                     // FIXME report error (ambiguous associated type)
-                    TyKind::Unknown.intern(&Interner)
+                    TyKind::Error.intern(&Interner)
                 } else {
                     let dyn_ty = DynTy {
-                        bounds: Binders::new(
+                        bounds: crate::make_only_type_binders(
                             1,
                             QuantifiedWhereClauses::from_iter(
                                 &Interner,
-                                Some(Binders::wrap_empty(WhereClause::Implemented(trait_ref))),
+                                Some(crate::wrap_empty_binders(WhereClause::Implemented(
+                                    trait_ref,
+                                ))),
                             ),
                         ),
+                        lifetime: static_lifetime(),
                     };
                     TyKind::Dyn(dyn_ty).intern(&Interner)
                 };
@@ -410,26 +417,18 @@ impl<'a> TyLoweringContext<'a> {
             TypeNs::SelfType(impl_id) => {
                 let generics = generics(self.db.upcast(), impl_id.into());
                 let substs = match self.type_param_mode {
-                    TypeParamLoweringMode::Placeholder => {
-                        Substitution::type_params_for_generics(self.db, &generics)
-                    }
-                    TypeParamLoweringMode::Variable => {
-                        Substitution::bound_vars(&generics, self.in_binders)
-                    }
+                    TypeParamLoweringMode::Placeholder => generics.type_params_subst(self.db),
+                    TypeParamLoweringMode::Variable => generics.bound_vars_subst(self.in_binders),
                 };
-                self.db.impl_self_ty(impl_id).subst(&substs)
+                self.db.impl_self_ty(impl_id).substitute(&Interner, &substs)
             }
             TypeNs::AdtSelfType(adt) => {
                 let generics = generics(self.db.upcast(), adt.into());
                 let substs = match self.type_param_mode {
-                    TypeParamLoweringMode::Placeholder => {
-                        Substitution::type_params_for_generics(self.db, &generics)
-                    }
-                    TypeParamLoweringMode::Variable => {
-                        Substitution::bound_vars(&generics, self.in_binders)
-                    }
+                    TypeParamLoweringMode::Placeholder => generics.type_params_subst(self.db),
+                    TypeParamLoweringMode::Variable => generics.bound_vars_subst(self.in_binders),
                 };
-                self.db.ty(adt.into()).subst(&substs)
+                self.db.ty(adt.into()).substitute(&Interner, &substs)
             }
 
             TypeNs::AdtId(it) => self.lower_path_inner(resolved_segment, it.into(), infer_args),
@@ -440,7 +439,7 @@ impl<'a> TyLoweringContext<'a> {
                 self.lower_path_inner(resolved_segment, it.into(), infer_args)
             }
             // FIXME: report error
-            TypeNs::EnumVariantId(_) => return (TyKind::Unknown.intern(&Interner), None),
+            TypeNs::EnumVariantId(_) => return (TyKind::Error.intern(&Interner), None),
         };
         self.lower_ty_relative_path(ty, Some(resolution), remaining_segments)
     }
@@ -454,7 +453,7 @@ impl<'a> TyLoweringContext<'a> {
         let (resolution, remaining_index) =
             match self.resolver.resolve_path_in_type_ns(self.db.upcast(), path.mod_path()) {
                 Some(it) => it,
-                None => return (TyKind::Unknown.intern(&Interner), None),
+                None => return (TyKind::Error.intern(&Interner), None),
             };
         let (resolved_segment, remaining_segments) = match remaining_index {
             None => (
@@ -477,19 +476,20 @@ impl<'a> TyLoweringContext<'a> {
                             TypeParamLoweringMode::Placeholder => {
                                 // if we're lowering to placeholders, we have to put
                                 // them in now
-                                let s = Substitution::type_params(
-                                    self.db,
+                                let generics = generics(
+                                    self.db.upcast(),
                                     self.resolver.generic_def().expect(
                                         "there should be generics if there's a generic param",
                                     ),
                                 );
-                                t.substitution.clone().subst_bound_vars(&s)
+                                let s = generics.type_params_subst(self.db);
+                                s.apply(t.substitution.clone(), &Interner)
                             }
                             TypeParamLoweringMode::Variable => t.substitution.clone(),
                         };
                         // We need to shift in the bound vars, since
                         // associated_type_shorthand_candidates does not do that
-                        let substs = substs.shift_bound_vars(self.in_binders);
+                        let substs = substs.shifted_in_from(&Interner, self.in_binders);
                         // FIXME handle type parameters on the segment
                         return Some(
                             TyKind::Alias(AliasTy::Projection(ProjectionTy {
@@ -504,9 +504,9 @@ impl<'a> TyLoweringContext<'a> {
                 },
             );
 
-            ty.unwrap_or(TyKind::Unknown.intern(&Interner))
+            ty.unwrap_or(TyKind::Error.intern(&Interner))
         } else {
-            TyKind::Unknown.intern(&Interner)
+            TyKind::Error.intern(&Interner)
         }
     }
 
@@ -522,7 +522,7 @@ impl<'a> TyLoweringContext<'a> {
             TyDefId::TypeAliasId(it) => Some(it.into()),
         };
         let substs = self.substs_from_path_segment(segment, generic_def, infer_args, None);
-        self.db.ty(typeable).subst(&substs)
+        self.db.ty(typeable).substitute(&Interner, &substs)
     }
 
     /// Collect generic arguments from a path into a `Substs`. See also
@@ -575,13 +575,13 @@ impl<'a> TyLoweringContext<'a> {
             def_generics.map_or((0, 0, 0, 0), |g| g.provenance_split());
         let total_len = parent_params + self_params + type_params + impl_trait_params;
 
-        substs.extend(iter::repeat(TyKind::Unknown.intern(&Interner)).take(parent_params));
+        substs.extend(iter::repeat(TyKind::Error.intern(&Interner)).take(parent_params));
 
         let fill_self_params = || {
             substs.extend(
                 explicit_self_ty
                     .into_iter()
-                    .chain(iter::repeat(TyKind::Unknown.intern(&Interner)))
+                    .chain(iter::repeat(TyKind::Error.intern(&Interner)))
                     .take(self_params),
             )
         };
@@ -625,8 +625,8 @@ impl<'a> TyLoweringContext<'a> {
 
                 for default_ty in defaults.iter().skip(substs.len()) {
                     // each default can depend on the previous parameters
-                    let substs_so_far = Substitution(substs.clone().into());
-                    substs.push(default_ty.clone().subst(&substs_so_far));
+                    let substs_so_far = Substitution::from_iter(&Interner, substs.clone());
+                    substs.push(default_ty.clone().substitute(&Interner, &substs_so_far));
                 }
             }
         }
@@ -634,11 +634,11 @@ impl<'a> TyLoweringContext<'a> {
         // add placeholders for args that were not provided
         // FIXME: emit diagnostics in contexts where this is not allowed
         for _ in substs.len()..total_len {
-            substs.push(TyKind::Unknown.intern(&Interner));
+            substs.push(TyKind::Error.intern(&Interner));
         }
         assert_eq!(substs.len(), total_len);
 
-        Substitution(substs.into())
+        Substitution::from_iter(&Interner, substs)
     }
 
     fn lower_trait_ref_from_path(
@@ -667,14 +667,10 @@ impl<'a> TyLoweringContext<'a> {
 
     fn lower_trait_ref(
         &self,
-        type_ref: &TypeRef,
+        trait_ref: &HirTraitRef,
         explicit_self_ty: Option<Ty>,
     ) -> Option<TraitRef> {
-        let path = match type_ref {
-            TypeRef::Path(path) => path,
-            _ => return None,
-        };
-        self.lower_trait_ref_from_path(path, explicit_self_ty)
+        self.lower_trait_ref_from_path(&trait_ref.path, explicit_self_ty)
     }
 
     fn trait_ref_substs_from_path(
@@ -730,7 +726,7 @@ impl<'a> TyLoweringContext<'a> {
         let trait_ref = match bound {
             TypeBound::Path(path) => {
                 bindings = self.lower_trait_ref_from_path(path, Some(self_ty));
-                bindings.clone().map(WhereClause::Implemented).map(|b| Binders::wrap_empty(b))
+                bindings.clone().map(WhereClause::Implemented).map(|b| crate::wrap_empty_binders(b))
             }
             TypeBound::Lifetime(_) => None,
             TypeBound::Error => None,
@@ -777,7 +773,7 @@ impl<'a> TyLoweringContext<'a> {
                     let ty = self.lower_ty(type_ref);
                     let alias_eq =
                         AliasEq { alias: AliasTy::Projection(projection_ty.clone()), ty };
-                    preds.push(Binders::wrap_empty(WhereClause::AliasEq(alias_eq)));
+                    preds.push(crate::wrap_empty_binders(WhereClause::AliasEq(alias_eq)));
                 }
                 for bound in &binding.bounds {
                     preds.extend(self.lower_type_bound(
@@ -797,7 +793,7 @@ impl<'a> TyLoweringContext<'a> {
         let predicates = self.with_shifted_in(DebruijnIndex::ONE, |ctx| {
             bounds.iter().flat_map(|b| ctx.lower_type_bound(b, self_ty.clone(), false)).collect()
         });
-        ReturnTypeImplTrait { bounds: Binders::new(1, predicates) }
+        ReturnTypeImplTrait { bounds: crate::make_only_type_binders(1, predicates) }
     }
 }
 
@@ -825,58 +821,57 @@ pub fn associated_type_shorthand_candidates<R>(
     res: TypeNs,
     mut cb: impl FnMut(&Name, &TraitRef, TypeAliasId) -> Option<R>,
 ) -> Option<R> {
-    let traits_from_env: Vec<_> = match res {
-        TypeNs::SelfType(impl_id) => match db.impl_trait(impl_id) {
-            None => vec![],
-            // FIXME: how to correctly handle higher-ranked bounds here?
-            Some(trait_ref) => vec![trait_ref.value.shift_bound_vars_out(DebruijnIndex::ONE)],
-        },
+    let mut search = |t| {
+        for t in all_super_trait_refs(db, t) {
+            let data = db.trait_data(t.hir_trait_id());
+
+            for (name, assoc_id) in &data.items {
+                if let AssocItemId::TypeAliasId(alias) = assoc_id {
+                    if let Some(result) = cb(name, &t, *alias) {
+                        return Some(result);
+                    }
+                }
+            }
+        }
+        None
+    };
+
+    match res {
+        TypeNs::SelfType(impl_id) => search(
+            // we're _in_ the impl -- the binders get added back later. Correct,
+            // but it would be nice to make this more explicit
+            db.impl_trait(impl_id)?.into_value_and_skipped_binders().0,
+        ),
         TypeNs::GenericParam(param_id) => {
             let predicates = db.generic_predicates_for_param(param_id);
-            let mut traits_: Vec<_> = predicates
-                .iter()
-                .filter_map(|pred| match &pred.value.value {
-                    // FIXME: how to correctly handle higher-ranked bounds here?
-                    WhereClause::Implemented(tr) => {
-                        Some(tr.clone().shift_bound_vars_out(DebruijnIndex::ONE))
-                    }
-                    _ => None,
-                })
-                .collect();
+            let res = predicates.iter().find_map(|pred| match pred.skip_binders().skip_binders() {
+                // FIXME: how to correctly handle higher-ranked bounds here?
+                WhereClause::Implemented(tr) => search(
+                    tr.clone()
+                        .shifted_out_to(&Interner, DebruijnIndex::ONE)
+                        .expect("FIXME unexpected higher-ranked trait bound"),
+                ),
+                _ => None,
+            });
+            if let res @ Some(_) = res {
+                return res;
+            }
             // Handle `Self::Type` referring to own associated type in trait definitions
             if let GenericDefId::TraitId(trait_id) = param_id.parent {
                 let generics = generics(db.upcast(), trait_id.into());
                 if generics.params.types[param_id.local_id].provenance
                     == TypeParamProvenance::TraitSelf
                 {
-                    let trait_ref = TraitRef {
-                        trait_id: to_chalk_trait_id(trait_id),
-                        substitution: Substitution::bound_vars(&generics, DebruijnIndex::INNERMOST),
-                    };
-                    traits_.push(trait_ref);
+                    let trait_ref = TyBuilder::trait_ref(db, trait_id)
+                        .fill_with_bound_vars(DebruijnIndex::INNERMOST, 0)
+                        .build();
+                    return search(trait_ref);
                 }
             }
-            traits_
-        }
-        _ => vec![],
-    };
-
-    for t in traits_from_env.into_iter().flat_map(move |t| all_super_trait_refs(db, t)) {
-        let data = db.trait_data(t.hir_trait_id());
-
-        for (name, assoc_id) in &data.items {
-            match assoc_id {
-                AssocItemId::TypeAliasId(alias) => {
-                    if let Some(result) = cb(name, &t, *alias) {
-                        return Some(result);
-                    }
-                }
-                AssocItemId::FunctionId(_) | AssocItemId::ConstId(_) => {}
-            }
+            None
         }
+        _ => None,
     }
-
-    None
 }
 
 /// Build the type of all specific fields of a struct or enum variant.
@@ -884,7 +879,7 @@ pub(crate) fn field_types_query(
     db: &dyn HirDatabase,
     variant_id: VariantId,
 ) -> Arc<ArenaMap<LocalFieldId, Binders<Ty>>> {
-    let var_data = variant_data(db.upcast(), variant_id);
+    let var_data = variant_id.variant_data(db.upcast());
     let (resolver, def): (_, GenericDefId) = match variant_id {
         VariantId::StructId(it) => (it.resolver(db.upcast()), it.into()),
         VariantId::UnionId(it) => (it.resolver(db.upcast()), it.into()),
@@ -895,7 +890,7 @@ pub(crate) fn field_types_query(
     let ctx =
         TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
     for (field_id, field_data) in var_data.fields().iter() {
-        res.insert(field_id, Binders::new(generics.len(), ctx.lower_ty(&field_data.type_ref)))
+        res.insert(field_id, make_binders(&generics, ctx.lower_ty(&field_data.type_ref)))
     }
     Arc::new(res)
 }
@@ -929,9 +924,7 @@ pub(crate) fn generic_predicates_for_param_query(
             },
             WherePredicate::Lifetime { .. } => false,
         })
-        .flat_map(|pred| {
-            ctx.lower_where_predicate(pred, true).map(|p| Binders::new(generics.len(), p))
-        })
+        .flat_map(|pred| ctx.lower_where_predicate(pred, true).map(|p| make_binders(&generics, p)))
         .collect()
 }
 
@@ -955,10 +948,10 @@ pub(crate) fn trait_environment_query(
     for pred in resolver.where_predicates_in_scope() {
         for pred in ctx.lower_where_predicate(pred, false) {
             if let WhereClause::Implemented(tr) = &pred.skip_binders() {
-                traits_in_scope.push((tr.self_type_parameter().clone(), tr.hir_trait_id()));
+                traits_in_scope
+                    .push((tr.self_type_parameter(&Interner).clone(), tr.hir_trait_id()));
             }
-            let program_clause: chalk_ir::ProgramClause<Interner> =
-                pred.clone().to_chalk(db).cast(&Interner);
+            let program_clause: chalk_ir::ProgramClause<Interner> = pred.clone().cast(&Interner);
             clauses.push(program_clause.into_from_env_clause(&Interner));
         }
     }
@@ -978,10 +971,10 @@ pub(crate) fn trait_environment_query(
         // function default implementations (and hypothetical code
         // inside consts or type aliases)
         cov_mark::hit!(trait_self_implements_self);
-        let substs = Substitution::type_params(db, trait_id);
+        let substs = TyBuilder::type_params_subst(db, trait_id);
         let trait_ref = TraitRef { trait_id: to_chalk_trait_id(trait_id), substitution: substs };
         let pred = WhereClause::Implemented(trait_ref);
-        let program_clause: chalk_ir::ProgramClause<Interner> = pred.to_chalk(db).cast(&Interner);
+        let program_clause: chalk_ir::ProgramClause<Interner> = pred.cast(&Interner);
         clauses.push(program_clause.into_from_env_clause(&Interner));
     }
 
@@ -1001,9 +994,7 @@ pub(crate) fn generic_predicates_query(
     let generics = generics(db.upcast(), def);
     resolver
         .where_predicates_in_scope()
-        .flat_map(|pred| {
-            ctx.lower_where_predicate(pred, false).map(|p| Binders::new(generics.len(), p))
-        })
+        .flat_map(|pred| ctx.lower_where_predicate(pred, false).map(|p| make_binders(&generics, p)))
         .collect()
 }
 
@@ -1022,25 +1013,21 @@ pub(crate) fn generic_defaults_query(
         .enumerate()
         .map(|(idx, (_, p))| {
             let mut ty =
-                p.default.as_ref().map_or(TyKind::Unknown.intern(&Interner), |t| ctx.lower_ty(t));
+                p.default.as_ref().map_or(TyKind::Error.intern(&Interner), |t| ctx.lower_ty(t));
 
             // Each default can only refer to previous parameters.
-            ty.walk_mut_binders(
-                &mut |ty, binders| match ty.interned_mut() {
-                    TyKind::BoundVar(BoundVar { debruijn, index }) if *debruijn == binders => {
-                        if *index >= idx {
-                            // type variable default referring to parameter coming
-                            // after it. This is forbidden (FIXME: report
-                            // diagnostic)
-                            *ty = TyKind::Unknown.intern(&Interner);
-                        }
-                    }
-                    _ => {}
-                },
-                DebruijnIndex::INNERMOST,
-            );
+            ty = crate::fold_free_vars(ty, |bound, binders| {
+                if bound.index >= idx && bound.debruijn == DebruijnIndex::INNERMOST {
+                    // type variable default referring to parameter coming
+                    // after it. This is forbidden (FIXME: report
+                    // diagnostic)
+                    TyKind::Error.intern(&Interner)
+                } else {
+                    bound.shifted_in_from(binders).to_ty(&Interner)
+                }
+            });
 
-            Binders::new(idx, ty)
+            crate::make_only_type_binders(idx, ty)
         })
         .collect();
 
@@ -1053,23 +1040,22 @@ fn fn_sig_for_fn(db: &dyn HirDatabase, def: FunctionId) -> PolyFnSig {
     let ctx_params = TyLoweringContext::new(db, &resolver)
         .with_impl_trait_mode(ImplTraitLoweringMode::Variable)
         .with_type_param_mode(TypeParamLoweringMode::Variable);
-    let params = data.params.iter().map(|tr| (&ctx_params).lower_ty(tr)).collect::<Vec<_>>();
+    let params = data.params.iter().map(|tr| ctx_params.lower_ty(tr)).collect::<Vec<_>>();
     let ctx_ret = TyLoweringContext::new(db, &resolver)
         .with_impl_trait_mode(ImplTraitLoweringMode::Opaque)
         .with_type_param_mode(TypeParamLoweringMode::Variable);
-    let ret = (&ctx_ret).lower_ty(&data.ret_type);
+    let ret = ctx_ret.lower_ty(&data.ret_type);
     let generics = generics(db.upcast(), def.into());
-    let num_binders = generics.len();
-    Binders::new(num_binders, CallableSig::from_params_and_return(params, ret, data.is_varargs))
+    make_binders(&generics, CallableSig::from_params_and_return(params, ret, data.is_varargs()))
 }
 
 /// Build the declared type of a function. This should not need to look at the
 /// function body.
 fn type_for_fn(db: &dyn HirDatabase, def: FunctionId) -> Binders<Ty> {
     let generics = generics(db.upcast(), def.into());
-    let substs = Substitution::bound_vars(&generics, DebruijnIndex::INNERMOST);
-    Binders::new(
-        substs.len(),
+    let substs = generics.bound_vars_subst(DebruijnIndex::INNERMOST);
+    make_binders(
+        &generics,
         TyKind::FnDef(CallableDefId::FunctionId(def).to_chalk(db), substs).intern(&Interner),
     )
 }
@@ -1082,7 +1068,7 @@ fn type_for_const(db: &dyn HirDatabase, def: ConstId) -> Binders<Ty> {
     let ctx =
         TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
 
-    Binders::new(generics.len(), ctx.lower_ty(&data.type_ref))
+    make_binders(&generics, ctx.lower_ty(&data.type_ref))
 }
 
 /// Build the declared type of a static.
@@ -1091,7 +1077,7 @@ fn type_for_static(db: &dyn HirDatabase, def: StaticId) -> Binders<Ty> {
     let resolver = def.resolver(db.upcast());
     let ctx = TyLoweringContext::new(db, &resolver);
 
-    Binders::new(0, ctx.lower_ty(&data.type_ref))
+    Binders::empty(&Interner, ctx.lower_ty(&data.type_ref))
 }
 
 fn fn_sig_for_struct_constructor(db: &dyn HirDatabase, def: StructId) -> PolyFnSig {
@@ -1101,8 +1087,8 @@ fn fn_sig_for_struct_constructor(db: &dyn HirDatabase, def: StructId) -> PolyFnS
     let ctx =
         TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
     let params = fields.iter().map(|(_, field)| ctx.lower_ty(&field.type_ref)).collect::<Vec<_>>();
-    let ret = type_for_adt(db, def.into());
-    Binders::new(ret.num_binders, CallableSig::from_params_and_return(params, ret.value, false))
+    let (ret, binders) = type_for_adt(db, def.into()).into_value_and_skipped_binders();
+    Binders::new(binders, CallableSig::from_params_and_return(params, ret, false))
 }
 
 /// Build the type of a tuple struct constructor.
@@ -1112,9 +1098,9 @@ fn type_for_struct_constructor(db: &dyn HirDatabase, def: StructId) -> Binders<T
         return type_for_adt(db, def.into());
     }
     let generics = generics(db.upcast(), def.into());
-    let substs = Substitution::bound_vars(&generics, DebruijnIndex::INNERMOST);
-    Binders::new(
-        substs.len(),
+    let substs = generics.bound_vars_subst(DebruijnIndex::INNERMOST);
+    make_binders(
+        &generics,
         TyKind::FnDef(CallableDefId::StructId(def).to_chalk(db), substs).intern(&Interner),
     )
 }
@@ -1127,8 +1113,8 @@ fn fn_sig_for_enum_variant_constructor(db: &dyn HirDatabase, def: EnumVariantId)
     let ctx =
         TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
     let params = fields.iter().map(|(_, field)| ctx.lower_ty(&field.type_ref)).collect::<Vec<_>>();
-    let ret = type_for_adt(db, def.parent.into());
-    Binders::new(ret.num_binders, CallableSig::from_params_and_return(params, ret.value, false))
+    let (ret, binders) = type_for_adt(db, def.parent.into()).into_value_and_skipped_binders();
+    Binders::new(binders, CallableSig::from_params_and_return(params, ret, false))
 }
 
 /// Build the type of a tuple enum variant constructor.
@@ -1139,17 +1125,18 @@ fn type_for_enum_variant_constructor(db: &dyn HirDatabase, def: EnumVariantId) -
         return type_for_adt(db, def.parent.into());
     }
     let generics = generics(db.upcast(), def.parent.into());
-    let substs = Substitution::bound_vars(&generics, DebruijnIndex::INNERMOST);
-    Binders::new(
-        substs.len(),
+    let substs = generics.bound_vars_subst(DebruijnIndex::INNERMOST);
+    make_binders(
+        &generics,
         TyKind::FnDef(CallableDefId::EnumVariantId(def).to_chalk(db), substs).intern(&Interner),
     )
 }
 
 fn type_for_adt(db: &dyn HirDatabase, adt: AdtId) -> Binders<Ty> {
     let generics = generics(db.upcast(), adt.into());
-    let substs = Substitution::bound_vars(&generics, DebruijnIndex::INNERMOST);
-    Binders::new(substs.len(), Ty::adt_ty(adt, substs))
+    let b = TyBuilder::adt(db, adt);
+    let ty = b.fill_with_bound_vars(DebruijnIndex::INNERMOST, 0).build();
+    make_binders(&generics, ty)
 }
 
 fn type_for_type_alias(db: &dyn HirDatabase, t: TypeAliasId) -> Binders<Ty> {
@@ -1158,11 +1145,11 @@ fn type_for_type_alias(db: &dyn HirDatabase, t: TypeAliasId) -> Binders<Ty> {
     let ctx =
         TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
     if db.type_alias_data(t).is_extern {
-        Binders::new(0, TyKind::ForeignType(crate::to_foreign_def_id(t)).intern(&Interner))
+        Binders::empty(&Interner, TyKind::Foreign(crate::to_foreign_def_id(t)).intern(&Interner))
     } else {
         let type_ref = &db.type_alias_data(t).type_ref;
-        let inner = ctx.lower_ty(type_ref.as_ref().unwrap_or(&TypeRef::Error));
-        Binders::new(generics.len(), inner)
+        let inner = ctx.lower_ty(type_ref.as_deref().unwrap_or(&TypeRef::Error));
+        make_binders(&generics, inner)
     }
 }
 
@@ -1221,19 +1208,21 @@ impl_from!(FunctionId, StructId, UnionId, EnumVariantId, ConstId, StaticId for V
 /// namespace.
 pub(crate) fn ty_query(db: &dyn HirDatabase, def: TyDefId) -> Binders<Ty> {
     match def {
-        TyDefId::BuiltinType(it) => Binders::new(0, Ty::builtin(it)),
+        TyDefId::BuiltinType(it) => Binders::empty(&Interner, TyBuilder::builtin(it)),
         TyDefId::AdtId(it) => type_for_adt(db, it),
         TyDefId::TypeAliasId(it) => type_for_type_alias(db, it),
     }
 }
 
 pub(crate) fn ty_recover(db: &dyn HirDatabase, _cycle: &[String], def: &TyDefId) -> Binders<Ty> {
-    let num_binders = match *def {
-        TyDefId::BuiltinType(_) => 0,
-        TyDefId::AdtId(it) => generics(db.upcast(), it.into()).len(),
-        TyDefId::TypeAliasId(it) => generics(db.upcast(), it.into()).len(),
+    let generics = match *def {
+        TyDefId::BuiltinType(_) => {
+            return Binders::empty(&Interner, TyKind::Error.intern(&Interner))
+        }
+        TyDefId::AdtId(it) => generics(db.upcast(), it.into()),
+        TyDefId::TypeAliasId(it) => generics(db.upcast(), it.into()),
     };
-    Binders::new(num_binders, TyKind::Unknown.intern(&Interner))
+    make_binders(&generics, TyKind::Error.intern(&Interner))
 }
 
 pub(crate) fn value_ty_query(db: &dyn HirDatabase, def: ValueTyDefId) -> Binders<Ty> {
@@ -1253,7 +1242,7 @@ pub(crate) fn impl_self_ty_query(db: &dyn HirDatabase, impl_id: ImplId) -> Binde
     let generics = generics(db.upcast(), impl_id.into());
     let ctx =
         TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
-    Binders::new(generics.len(), ctx.lower_ty(&impl_data.target_type))
+    make_binders(&generics, ctx.lower_ty(&impl_data.self_ty))
 }
 
 pub(crate) fn const_param_ty_query(db: &dyn HirDatabase, def: ConstParamId) -> Ty {
@@ -1271,7 +1260,7 @@ pub(crate) fn impl_self_ty_recover(
     impl_id: &ImplId,
 ) -> Binders<Ty> {
     let generics = generics(db.upcast(), (*impl_id).into());
-    Binders::new(generics.len(), TyKind::Unknown.intern(&Interner))
+    make_binders(&generics, TyKind::Error.intern(&Interner))
 }
 
 pub(crate) fn impl_trait_query(db: &dyn HirDatabase, impl_id: ImplId) -> Option<Binders<TraitRef>> {
@@ -1279,9 +1268,9 @@ pub(crate) fn impl_trait_query(db: &dyn HirDatabase, impl_id: ImplId) -> Option<
     let resolver = impl_id.resolver(db.upcast());
     let ctx =
         TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
-    let self_ty = db.impl_self_ty(impl_id);
+    let (self_ty, binders) = db.impl_self_ty(impl_id).into_value_and_skipped_binders();
     let target_trait = impl_data.target_trait.as_ref()?;
-    Some(Binders::new(self_ty.num_binders, ctx.lower_trait_ref(target_trait, Some(self_ty.value))?))
+    Some(Binders::new(binders, ctx.lower_trait_ref(target_trait, Some(self_ty))?))
 }
 
 pub(crate) fn return_type_impl_traits(
@@ -1296,13 +1285,12 @@ pub(crate) fn return_type_impl_traits(
         .with_type_param_mode(TypeParamLoweringMode::Variable);
     let _ret = (&ctx_ret).lower_ty(&data.ret_type);
     let generics = generics(db.upcast(), def.into());
-    let num_binders = generics.len();
     let return_type_impl_traits =
         ReturnTypeImplTraits { impl_traits: ctx_ret.opaque_type_data.into_inner() };
     if return_type_impl_traits.impl_traits.is_empty() {
         None
     } else {
-        Some(Arc::new(Binders::new(num_binders, return_type_impl_traits)))
+        Some(Arc::new(make_binders(&generics, return_type_impl_traits)))
     }
 }
 
@@ -1312,3 +1300,7 @@ pub(crate) fn lower_to_chalk_mutability(m: hir_def::type_ref::Mutability) -> Mut
         hir_def::type_ref::Mutability::Mut => Mutability::Mut,
     }
 }
+
+fn make_binders<T: HasInterner<Interner = Interner>>(generics: &Generics, value: T) -> Binders<T> {
+    crate::make_only_type_binders(generics.len(), value)
+}
diff --git a/crates/hir_ty/src/mapping.rs b/crates/hir_ty/src/mapping.rs
new file mode 100644
index 000000000..5e86fafe5
--- /dev/null
+++ b/crates/hir_ty/src/mapping.rs
@@ -0,0 +1,154 @@
+//! This module contains the implementations of the `ToChalk` trait, which
+//! handles conversion between our data types and their corresponding types in
+//! Chalk (in both directions); plus some helper functions for more specialized
+//! conversions.
+
+use chalk_solve::rust_ir;
+
+use base_db::salsa::{self, InternKey};
+use hir_def::{ConstParamId, LifetimeParamId, TraitId, TypeAliasId, TypeParamId};
+
+use crate::{
+    chalk_db, db::HirDatabase, AssocTypeId, CallableDefId, ChalkTraitId, FnDefId, ForeignDefId,
+    Interner, OpaqueTyId, PlaceholderIndex,
+};
+
+pub(crate) trait ToChalk {
+    type Chalk;
+    fn to_chalk(self, db: &dyn HirDatabase) -> Self::Chalk;
+    fn from_chalk(db: &dyn HirDatabase, chalk: Self::Chalk) -> Self;
+}
+
+pub(crate) fn from_chalk<T, ChalkT>(db: &dyn HirDatabase, chalk: ChalkT) -> T
+where
+    T: ToChalk<Chalk = ChalkT>,
+{
+    T::from_chalk(db, chalk)
+}
+
+impl ToChalk for hir_def::ImplId {
+    type Chalk = chalk_db::ImplId;
+
+    fn to_chalk(self, _db: &dyn HirDatabase) -> chalk_db::ImplId {
+        chalk_ir::ImplId(self.as_intern_id())
+    }
+
+    fn from_chalk(_db: &dyn HirDatabase, impl_id: chalk_db::ImplId) -> hir_def::ImplId {
+        InternKey::from_intern_id(impl_id.0)
+    }
+}
+
+impl ToChalk for CallableDefId {
+    type Chalk = FnDefId;
+
+    fn to_chalk(self, db: &dyn HirDatabase) -> FnDefId {
+        db.intern_callable_def(self).into()
+    }
+
+    fn from_chalk(db: &dyn HirDatabase, fn_def_id: FnDefId) -> CallableDefId {
+        db.lookup_intern_callable_def(fn_def_id.into())
+    }
+}
+
+pub(crate) struct TypeAliasAsValue(pub(crate) TypeAliasId);
+
+impl ToChalk for TypeAliasAsValue {
+    type Chalk = chalk_db::AssociatedTyValueId;
+
+    fn to_chalk(self, _db: &dyn HirDatabase) -> chalk_db::AssociatedTyValueId {
+        rust_ir::AssociatedTyValueId(self.0.as_intern_id())
+    }
+
+    fn from_chalk(
+        _db: &dyn HirDatabase,
+        assoc_ty_value_id: chalk_db::AssociatedTyValueId,
+    ) -> TypeAliasAsValue {
+        TypeAliasAsValue(TypeAliasId::from_intern_id(assoc_ty_value_id.0))
+    }
+}
+
+impl From<FnDefId> for crate::db::InternedCallableDefId {
+    fn from(fn_def_id: FnDefId) -> Self {
+        InternKey::from_intern_id(fn_def_id.0)
+    }
+}
+
+impl From<crate::db::InternedCallableDefId> for FnDefId {
+    fn from(callable_def_id: crate::db::InternedCallableDefId) -> Self {
+        chalk_ir::FnDefId(callable_def_id.as_intern_id())
+    }
+}
+
+impl From<OpaqueTyId> for crate::db::InternedOpaqueTyId {
+    fn from(id: OpaqueTyId) -> Self {
+        InternKey::from_intern_id(id.0)
+    }
+}
+
+impl From<crate::db::InternedOpaqueTyId> for OpaqueTyId {
+    fn from(id: crate::db::InternedOpaqueTyId) -> Self {
+        chalk_ir::OpaqueTyId(id.as_intern_id())
+    }
+}
+
+impl From<chalk_ir::ClosureId<Interner>> for crate::db::InternedClosureId {
+    fn from(id: chalk_ir::ClosureId<Interner>) -> Self {
+        Self::from_intern_id(id.0)
+    }
+}
+
+impl From<crate::db::InternedClosureId> for chalk_ir::ClosureId<Interner> {
+    fn from(id: crate::db::InternedClosureId) -> Self {
+        chalk_ir::ClosureId(id.as_intern_id())
+    }
+}
+
+pub fn to_foreign_def_id(id: TypeAliasId) -> ForeignDefId {
+    chalk_ir::ForeignDefId(salsa::InternKey::as_intern_id(&id))
+}
+
+pub fn from_foreign_def_id(id: ForeignDefId) -> TypeAliasId {
+    salsa::InternKey::from_intern_id(id.0)
+}
+
+pub fn to_assoc_type_id(id: TypeAliasId) -> AssocTypeId {
+    chalk_ir::AssocTypeId(salsa::InternKey::as_intern_id(&id))
+}
+
+pub fn from_assoc_type_id(id: AssocTypeId) -> TypeAliasId {
+    salsa::InternKey::from_intern_id(id.0)
+}
+
+pub fn from_placeholder_idx(db: &dyn HirDatabase, idx: PlaceholderIndex) -> TypeParamId {
+    assert_eq!(idx.ui, chalk_ir::UniverseIndex::ROOT);
+    let interned_id = salsa::InternKey::from_intern_id(salsa::InternId::from(idx.idx));
+    db.lookup_intern_type_param_id(interned_id)
+}
+
+pub fn to_placeholder_idx(db: &dyn HirDatabase, id: TypeParamId) -> PlaceholderIndex {
+    let interned_id = db.intern_type_param_id(id);
+    PlaceholderIndex {
+        ui: chalk_ir::UniverseIndex::ROOT,
+        idx: salsa::InternKey::as_intern_id(&interned_id).as_usize(),
+    }
+}
+
+pub fn lt_from_placeholder_idx(db: &dyn HirDatabase, idx: PlaceholderIndex) -> LifetimeParamId {
+    assert_eq!(idx.ui, chalk_ir::UniverseIndex::ROOT);
+    let interned_id = salsa::InternKey::from_intern_id(salsa::InternId::from(idx.idx));
+    db.lookup_intern_lifetime_param_id(interned_id)
+}
+
+pub fn const_from_placeholder_idx(db: &dyn HirDatabase, idx: PlaceholderIndex) -> ConstParamId {
+    assert_eq!(idx.ui, chalk_ir::UniverseIndex::ROOT);
+    let interned_id = salsa::InternKey::from_intern_id(salsa::InternId::from(idx.idx));
+    db.lookup_intern_const_param_id(interned_id)
+}
+
+pub fn to_chalk_trait_id(id: TraitId) -> ChalkTraitId {
+    chalk_ir::TraitId(salsa::InternKey::as_intern_id(&id))
+}
+
+pub fn from_chalk_trait_id(id: ChalkTraitId) -> TraitId {
+    salsa::InternKey::from_intern_id(id.0)
+}
diff --git a/crates/hir_ty/src/method_resolution.rs b/crates/hir_ty/src/method_resolution.rs
index bf7d5eded..3693e3284 100644
--- a/crates/hir_ty/src/method_resolution.rs
+++ b/crates/hir_ty/src/method_resolution.rs
@@ -8,8 +8,8 @@ use arrayvec::ArrayVec;
 use base_db::CrateId;
 use chalk_ir::{cast::Cast, Mutability, UniverseIndex};
 use hir_def::{
-    lang_item::LangItemTarget, AssocContainerId, AssocItemId, FunctionId, GenericDefId, HasModule,
-    ImplId, Lookup, ModuleId, TraitId,
+    lang_item::LangItemTarget, nameres::DefMap, AssocContainerId, AssocItemId, FunctionId,
+    GenericDefId, HasModule, ImplId, Lookup, ModuleId, TraitId,
 };
 use hir_expand::name::Name;
 use rustc_hash::{FxHashMap, FxHashSet};
@@ -19,52 +19,91 @@ use crate::{
     db::HirDatabase,
     from_foreign_def_id,
     primitive::{self, FloatTy, IntTy, UintTy},
-    to_chalk_trait_id,
+    static_lifetime,
     utils::all_super_traits,
-    AdtId, Canonical, CanonicalVarKinds, DebruijnIndex, FnPointer, FnSig, ForeignDefId,
-    InEnvironment, Interner, Scalar, Substitution, TraitEnvironment, TraitRef, Ty, TyKind,
-    TypeWalk,
+    AdtId, Canonical, CanonicalVarKinds, DebruijnIndex, ForeignDefId, InEnvironment, Interner,
+    Scalar, Substitution, TraitEnvironment, TraitRefExt, Ty, TyBuilder, TyExt, TyKind,
 };
 
 /// This is used as a key for indexing impls.
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
 pub enum TyFingerprint {
+    // These are lang item impls:
     Str,
     Slice,
     Array,
     Never,
     RawPtr(Mutability),
     Scalar(Scalar),
+    // These can have user-defined impls:
     Adt(hir_def::AdtId),
     Dyn(TraitId),
-    Tuple(usize),
     ForeignType(ForeignDefId),
-    FnPtr(usize, FnSig),
+    // These only exist for trait impls
+    Unit,
+    Unnameable,
+    Function(u32),
 }
 
 impl TyFingerprint {
-    /// Creates a TyFingerprint for looking up an impl. Only certain types can
-    /// have impls: if we have some `struct S`, we can have an `impl S`, but not
-    /// `impl &S`. Hence, this will return `None` for reference types and such.
-    pub fn for_impl(ty: &Ty) -> Option<TyFingerprint> {
-        let fp = match *ty.interned(&Interner) {
+    /// Creates a TyFingerprint for looking up an inherent impl. Only certain
+    /// types can have inherent impls: if we have some `struct S`, we can have
+    /// an `impl S`, but not `impl &S`. Hence, this will return `None` for
+    /// reference types and such.
+    pub fn for_inherent_impl(ty: &Ty) -> Option<TyFingerprint> {
+        let fp = match ty.kind(&Interner) {
             TyKind::Str => TyFingerprint::Str,
             TyKind::Never => TyFingerprint::Never,
             TyKind::Slice(..) => TyFingerprint::Slice,
             TyKind::Array(..) => TyFingerprint::Array,
-            TyKind::Scalar(scalar) => TyFingerprint::Scalar(scalar),
-            TyKind::Adt(AdtId(adt), _) => TyFingerprint::Adt(adt),
-            TyKind::Tuple(cardinality, _) => TyFingerprint::Tuple(cardinality),
-            TyKind::Raw(mutability, ..) => TyFingerprint::RawPtr(mutability),
-            TyKind::ForeignType(alias_id, ..) => TyFingerprint::ForeignType(alias_id),
-            TyKind::Function(FnPointer { num_args, sig, .. }) => {
-                TyFingerprint::FnPtr(num_args, sig)
-            }
+            TyKind::Scalar(scalar) => TyFingerprint::Scalar(*scalar),
+            TyKind::Adt(AdtId(adt), _) => TyFingerprint::Adt(*adt),
+            TyKind::Raw(mutability, ..) => TyFingerprint::RawPtr(*mutability),
+            TyKind::Foreign(alias_id, ..) => TyFingerprint::ForeignType(*alias_id),
             TyKind::Dyn(_) => ty.dyn_trait().map(|trait_| TyFingerprint::Dyn(trait_))?,
             _ => return None,
         };
         Some(fp)
     }
+
+    /// Creates a TyFingerprint for looking up a trait impl.
+    pub fn for_trait_impl(ty: &Ty) -> Option<TyFingerprint> {
+        let fp = match ty.kind(&Interner) {
+            TyKind::Str => TyFingerprint::Str,
+            TyKind::Never => TyFingerprint::Never,
+            TyKind::Slice(..) => TyFingerprint::Slice,
+            TyKind::Array(..) => TyFingerprint::Array,
+            TyKind::Scalar(scalar) => TyFingerprint::Scalar(*scalar),
+            TyKind::Adt(AdtId(adt), _) => TyFingerprint::Adt(*adt),
+            TyKind::Raw(mutability, ..) => TyFingerprint::RawPtr(*mutability),
+            TyKind::Foreign(alias_id, ..) => TyFingerprint::ForeignType(*alias_id),
+            TyKind::Dyn(_) => ty.dyn_trait().map(|trait_| TyFingerprint::Dyn(trait_))?,
+            TyKind::Ref(_, _, ty) => return TyFingerprint::for_trait_impl(ty),
+            TyKind::Tuple(_, subst) => {
+                let first_ty = subst.interned().get(0).map(|arg| arg.assert_ty_ref(&Interner));
+                if let Some(ty) = first_ty {
+                    return TyFingerprint::for_trait_impl(ty);
+                } else {
+                    TyFingerprint::Unit
+                }
+            }
+            TyKind::AssociatedType(_, _)
+            | TyKind::OpaqueType(_, _)
+            | TyKind::FnDef(_, _)
+            | TyKind::Closure(_, _)
+            | TyKind::Generator(..)
+            | TyKind::GeneratorWitness(..) => TyFingerprint::Unnameable,
+            TyKind::Function(fn_ptr) => {
+                TyFingerprint::Function(fn_ptr.substitution.0.len(&Interner) as u32)
+            }
+            TyKind::Alias(_)
+            | TyKind::Placeholder(_)
+            | TyKind::BoundVar(_)
+            | TyKind::InferenceVar(_, _)
+            | TyKind::Error => return None,
+        };
+        Some(fp)
+    }
 }
 
 pub(crate) const ALL_INT_FPS: [TyFingerprint; 12] = [
@@ -100,25 +139,38 @@ impl TraitImpls {
         let mut impls = Self { map: FxHashMap::default() };
 
         let crate_def_map = db.crate_def_map(krate);
-        for (_module_id, module_data) in crate_def_map.modules() {
-            for impl_id in module_data.scope.impls() {
-                let target_trait = match db.impl_trait(impl_id) {
-                    Some(tr) => tr.value.hir_trait_id(),
-                    None => continue,
-                };
-                let self_ty = db.impl_self_ty(impl_id);
-                let self_ty_fp = TyFingerprint::for_impl(&self_ty.value);
-                impls
-                    .map
-                    .entry(target_trait)
-                    .or_default()
-                    .entry(self_ty_fp)
-                    .or_default()
-                    .push(impl_id);
+        collect_def_map(db, &crate_def_map, &mut impls);
+
+        return Arc::new(impls);
+
+        fn collect_def_map(db: &dyn HirDatabase, def_map: &DefMap, impls: &mut TraitImpls) {
+            for (_module_id, module_data) in def_map.modules() {
+                for impl_id in module_data.scope.impls() {
+                    let target_trait = match db.impl_trait(impl_id) {
+                        Some(tr) => tr.skip_binders().hir_trait_id(),
+                        None => continue,
+                    };
+                    let self_ty = db.impl_self_ty(impl_id);
+                    let self_ty_fp = TyFingerprint::for_trait_impl(self_ty.skip_binders());
+                    impls
+                        .map
+                        .entry(target_trait)
+                        .or_default()
+                        .entry(self_ty_fp)
+                        .or_default()
+                        .push(impl_id);
+                }
+
+                // To better support custom derives, collect impls in all unnamed const items.
+                // const _: () = { ... };
+                for konst in module_data.scope.unnamed_consts() {
+                    let body = db.body(konst.into());
+                    for (_, block_def_map) in body.blocks(db.upcast()) {
+                        collect_def_map(db, &block_def_map, impls);
+                    }
+                }
             }
         }
-
-        Arc::new(impls)
     }
 
     pub(crate) fn trait_impls_in_deps_query(db: &dyn HirDatabase, krate: CrateId) -> Arc<Self> {
@@ -144,10 +196,13 @@ impl TraitImpls {
     }
 
     /// Queries all trait impls for the given type.
-    pub fn for_self_ty(&self, fp: TyFingerprint) -> impl Iterator<Item = ImplId> + '_ {
+    pub fn for_self_ty_without_blanket_impls(
+        &self,
+        fp: TyFingerprint,
+    ) -> impl Iterator<Item = ImplId> + '_ {
         self.map
             .values()
-            .flat_map(move |impls| impls.get(&None).into_iter().chain(impls.get(&Some(fp))))
+            .flat_map(move |impls| impls.get(&Some(fp)).into_iter())
             .flat_map(|it| it.iter().copied())
     }
 
@@ -202,17 +257,22 @@ impl InherentImpls {
                 }
 
                 let self_ty = db.impl_self_ty(impl_id);
-                if let Some(fp) = TyFingerprint::for_impl(&self_ty.value) {
+                let fp = TyFingerprint::for_inherent_impl(self_ty.skip_binders());
+                if let Some(fp) = fp {
                     map.entry(fp).or_default().push(impl_id);
                 }
+                // `fp` should only be `None` in error cases (either erroneous code or incomplete name resolution)
             }
         }
 
+        // NOTE: We're not collecting inherent impls from unnamed consts here, we intentionally only
+        // support trait impls there.
+
         Arc::new(Self { map })
     }
 
     pub fn for_self_ty(&self, self_ty: &Ty) -> &[ImplId] {
-        match TyFingerprint::for_impl(self_ty) {
+        match TyFingerprint::for_inherent_impl(self_ty) {
             Some(fp) => self.map.get(&fp).map(|vec| vec.as_ref()).unwrap_or(&[]),
             None => &[],
         }
@@ -223,15 +283,14 @@ impl InherentImpls {
     }
 }
 
-impl Ty {
-    pub fn def_crates(
-        &self,
-        db: &dyn HirDatabase,
-        cur_crate: CrateId,
-    ) -> Option<ArrayVec<CrateId, 2>> {
-        // Types like slice can have inherent impls in several crates, (core and alloc).
-        // The corresponding impls are marked with lang items, so we can use them to find the required crates.
-        macro_rules! lang_item_crate {
+pub fn def_crates(
+    db: &dyn HirDatabase,
+    ty: &Ty,
+    cur_crate: CrateId,
+) -> Option<ArrayVec<CrateId, 2>> {
+    // Types like slice can have inherent impls in several crates, (core and alloc).
+    // The corresponding impls are marked with lang items, so we can use them to find the required crates.
+    macro_rules! lang_item_crate {
             ($($name:expr),+ $(,)?) => {{
                 let mut v = ArrayVec::<LangItemTarget, 2>::new();
                 $(
@@ -241,51 +300,50 @@ impl Ty {
             }};
         }
 
-        let mod_to_crate_ids = |module: ModuleId| Some(std::iter::once(module.krate()).collect());
+    let mod_to_crate_ids = |module: ModuleId| Some(std::iter::once(module.krate()).collect());
 
-        let lang_item_targets = match self.interned(&Interner) {
-            TyKind::Adt(AdtId(def_id), _) => {
-                return mod_to_crate_ids(def_id.module(db.upcast()));
-            }
-            TyKind::ForeignType(id) => {
-                return mod_to_crate_ids(
-                    from_foreign_def_id(*id).lookup(db.upcast()).module(db.upcast()),
-                );
-            }
-            TyKind::Scalar(Scalar::Bool) => lang_item_crate!("bool"),
-            TyKind::Scalar(Scalar::Char) => lang_item_crate!("char"),
-            TyKind::Scalar(Scalar::Float(f)) => match f {
-                // There are two lang items: one in libcore (fXX) and one in libstd (fXX_runtime)
-                FloatTy::F32 => lang_item_crate!("f32", "f32_runtime"),
-                FloatTy::F64 => lang_item_crate!("f64", "f64_runtime"),
-            },
-            &TyKind::Scalar(Scalar::Int(t)) => {
-                lang_item_crate!(primitive::int_ty_to_string(t))
-            }
-            &TyKind::Scalar(Scalar::Uint(t)) => {
-                lang_item_crate!(primitive::uint_ty_to_string(t))
-            }
-            TyKind::Str => lang_item_crate!("str_alloc", "str"),
-            TyKind::Slice(_) => lang_item_crate!("slice_alloc", "slice"),
-            TyKind::Raw(Mutability::Not, _) => lang_item_crate!("const_ptr"),
-            TyKind::Raw(Mutability::Mut, _) => lang_item_crate!("mut_ptr"),
-            TyKind::Dyn(_) => {
-                return self.dyn_trait().and_then(|trait_| {
-                    mod_to_crate_ids(GenericDefId::TraitId(trait_).module(db.upcast()))
-                });
-            }
-            _ => return None,
-        };
-        let res = lang_item_targets
-            .into_iter()
-            .filter_map(|it| match it {
-                LangItemTarget::ImplDefId(it) => Some(it),
-                _ => None,
-            })
-            .map(|it| it.lookup(db.upcast()).container.krate())
-            .collect();
-        Some(res)
-    }
+    let lang_item_targets = match ty.kind(&Interner) {
+        TyKind::Adt(AdtId(def_id), _) => {
+            return mod_to_crate_ids(def_id.module(db.upcast()));
+        }
+        TyKind::Foreign(id) => {
+            return mod_to_crate_ids(
+                from_foreign_def_id(*id).lookup(db.upcast()).module(db.upcast()),
+            );
+        }
+        TyKind::Scalar(Scalar::Bool) => lang_item_crate!("bool"),
+        TyKind::Scalar(Scalar::Char) => lang_item_crate!("char"),
+        TyKind::Scalar(Scalar::Float(f)) => match f {
+            // There are two lang items: one in libcore (fXX) and one in libstd (fXX_runtime)
+            FloatTy::F32 => lang_item_crate!("f32", "f32_runtime"),
+            FloatTy::F64 => lang_item_crate!("f64", "f64_runtime"),
+        },
+        &TyKind::Scalar(Scalar::Int(t)) => {
+            lang_item_crate!(primitive::int_ty_to_string(t))
+        }
+        &TyKind::Scalar(Scalar::Uint(t)) => {
+            lang_item_crate!(primitive::uint_ty_to_string(t))
+        }
+        TyKind::Str => lang_item_crate!("str_alloc", "str"),
+        TyKind::Slice(_) => lang_item_crate!("slice_alloc", "slice"),
+        TyKind::Raw(Mutability::Not, _) => lang_item_crate!("const_ptr"),
+        TyKind::Raw(Mutability::Mut, _) => lang_item_crate!("mut_ptr"),
+        TyKind::Dyn(_) => {
+            return ty.dyn_trait().and_then(|trait_| {
+                mod_to_crate_ids(GenericDefId::TraitId(trait_).module(db.upcast()))
+            });
+        }
+        _ => return None,
+    };
+    let res = lang_item_targets
+        .into_iter()
+        .filter_map(|it| match it {
+            LangItemTarget::ImplDefId(it) => Some(it),
+            _ => None,
+        })
+        .map(|it| it.lookup(db.upcast()).container.krate())
+        .collect();
+    Some(res)
 }
 
 /// Look up the method with the given name, returning the actual autoderefed
@@ -454,7 +512,8 @@ fn iterate_method_candidates_with_autoref(
     }
     let refed = Canonical {
         binders: deref_chain[0].binders.clone(),
-        value: TyKind::Ref(Mutability::Not, deref_chain[0].value.clone()).intern(&Interner),
+        value: TyKind::Ref(Mutability::Not, static_lifetime(), deref_chain[0].value.clone())
+            .intern(&Interner),
     };
     if iterate_method_candidates_by_receiver(
         &refed,
@@ -471,7 +530,8 @@ fn iterate_method_candidates_with_autoref(
     }
     let ref_muted = Canonical {
         binders: deref_chain[0].binders.clone(),
-        value: TyKind::Ref(Mutability::Mut, deref_chain[0].value.clone()).intern(&Interner),
+        value: TyKind::Ref(Mutability::Mut, static_lifetime(), deref_chain[0].value.clone())
+            .intern(&Interner),
     };
     if iterate_method_candidates_by_receiver(
         &ref_muted,
@@ -563,7 +623,7 @@ fn iterate_trait_method_candidates(
     // if ty is `dyn Trait`, the trait doesn't need to be in scope
     let inherent_trait =
         self_ty.value.dyn_trait().into_iter().flat_map(|t| all_super_traits(db.upcast(), t));
-    let env_traits = if let TyKind::Placeholder(_) = self_ty.value.interned(&Interner) {
+    let env_traits = if let TyKind::Placeholder(_) = self_ty.value.kind(&Interner) {
         // if we have `T: Trait` in the param env, the trait doesn't need to be in scope
         env.traits_in_scope_from_clauses(&self_ty.value)
             .flat_map(|t| all_super_traits(db.upcast(), t))
@@ -593,6 +653,7 @@ fn iterate_trait_method_candidates(
                 }
             }
             known_implemented = true;
+            // FIXME: we shouldn't be ignoring the binders here
             if callback(&self_ty.value, *item) {
                 return true;
             }
@@ -610,7 +671,7 @@ fn iterate_inherent_methods(
     visible_from_module: Option<ModuleId>,
     callback: &mut dyn FnMut(&Ty, AssocItemId) -> bool,
 ) -> bool {
-    let def_crates = match self_ty.value.def_crates(db, krate) {
+    let def_crates = match def_crates(db, &self_ty.value, krate) {
         Some(k) => k,
         None => return false,
     };
@@ -675,7 +736,7 @@ fn is_valid_candidate(
                 }
             }
             if let Some(receiver_ty) = receiver_ty {
-                if !data.has_self_param {
+                if !data.has_self_param() {
                     return false;
                 }
                 let transformed_receiver_ty = match transform_receiver_ty(db, m, self_ty) {
@@ -710,48 +771,44 @@ pub(crate) fn inherent_impl_substs(
 ) -> Option<Substitution> {
     // we create a var for each type parameter of the impl; we need to keep in
     // mind here that `self_ty` might have vars of its own
-    let vars = Substitution::build_for_def(db, impl_id)
-        .fill_with_bound_vars(DebruijnIndex::INNERMOST, self_ty.binders.len(&Interner))
+    let self_ty_vars = self_ty.binders.len(&Interner);
+    let vars = TyBuilder::subst_for_def(db, impl_id)
+        .fill_with_bound_vars(DebruijnIndex::INNERMOST, self_ty_vars)
         .build();
-    let self_ty_with_vars = db.impl_self_ty(impl_id).subst(&vars);
+    let self_ty_with_vars = db.impl_self_ty(impl_id).substitute(&Interner, &vars);
     let mut kinds = self_ty.binders.interned().to_vec();
     kinds.extend(
         iter::repeat(chalk_ir::WithKind::new(
             chalk_ir::VariableKind::Ty(chalk_ir::TyVariableKind::General),
             UniverseIndex::ROOT,
         ))
-        .take(vars.len()),
+        .take(vars.len(&Interner)),
     );
     let tys = Canonical {
         binders: CanonicalVarKinds::from_iter(&Interner, kinds),
         value: (self_ty_with_vars, self_ty.value.clone()),
     };
-    let substs = super::infer::unify(&tys);
+    let substs = super::infer::unify(&tys)?;
     // We only want the substs for the vars we added, not the ones from self_ty.
     // Also, if any of the vars we added are still in there, we replace them by
     // Unknown. I think this can only really happen if self_ty contained
     // Unknown, and in that case we want the result to contain Unknown in those
     // places again.
-    substs.map(|s| fallback_bound_vars(s.suffix(vars.len()), self_ty.binders.len(&Interner)))
+    let suffix =
+        Substitution::from_iter(&Interner, substs.iter(&Interner).cloned().skip(self_ty_vars));
+    Some(fallback_bound_vars(suffix, self_ty_vars))
 }
 
 /// This replaces any 'free' Bound vars in `s` (i.e. those with indices past
 /// num_vars_to_keep) by `TyKind::Unknown`.
 fn fallback_bound_vars(s: Substitution, num_vars_to_keep: usize) -> Substitution {
-    s.fold_binders(
-        &mut |ty, binders| {
-            if let TyKind::BoundVar(bound) = ty.interned(&Interner) {
-                if bound.index >= num_vars_to_keep && bound.debruijn >= binders {
-                    TyKind::Unknown.intern(&Interner)
-                } else {
-                    ty
-                }
-            } else {
-                ty
-            }
-        },
-        DebruijnIndex::INNERMOST,
-    )
+    crate::fold_free_vars(s, |bound, binders| {
+        if bound.index >= num_vars_to_keep && bound.debruijn == DebruijnIndex::INNERMOST {
+            TyKind::Error.intern(&Interner)
+        } else {
+            bound.shifted_in_from(binders).to_ty(&Interner)
+        }
+    })
 }
 
 fn transform_receiver_ty(
@@ -760,13 +817,13 @@ fn transform_receiver_ty(
     self_ty: &Canonical<Ty>,
 ) -> Option<Ty> {
     let substs = match function_id.lookup(db.upcast()).container {
-        AssocContainerId::TraitId(_) => Substitution::build_for_def(db, function_id)
+        AssocContainerId::TraitId(_) => TyBuilder::subst_for_def(db, function_id)
             .push(self_ty.value.clone())
             .fill_with_unknown()
             .build(),
         AssocContainerId::ImplId(impl_id) => {
             let impl_substs = inherent_impl_substs(db, impl_id, &self_ty)?;
-            Substitution::build_for_def(db, function_id)
+            TyBuilder::subst_for_def(db, function_id)
                 .use_parent_substs(&impl_substs)
                 .fill_with_unknown()
                 .build()
@@ -774,7 +831,7 @@ fn transform_receiver_ty(
         AssocContainerId::ModuleId(_) => unreachable!(),
     };
     let sig = db.callable_item_signature(function_id.into());
-    Some(sig.value.params()[0].clone().subst_bound_vars(&substs))
+    Some(sig.map(|s| s.params()[0].clone()).substitute(&Interner, &substs))
 }
 
 pub fn implements_trait(
@@ -800,7 +857,7 @@ pub fn implements_trait_unique(
     let goal = generic_implements_goal(db, env, trait_, ty.clone());
     let solution = db.trait_solve(krate, goal);
 
-    matches!(solution, Some(crate::traits::Solution::Unique(_)))
+    matches!(solution, Some(crate::Solution::Unique(_)))
 }
 
 /// This creates Substs for a trait with the given Self type and type variables
@@ -812,7 +869,7 @@ fn generic_implements_goal(
     self_ty: Canonical<Ty>,
 ) -> Canonical<InEnvironment<super::DomainGoal>> {
     let mut kinds = self_ty.binders.interned().to_vec();
-    let substs = super::Substitution::build_for_def(db, trait_)
+    let trait_ref = TyBuilder::trait_ref(db, trait_)
         .push(self_ty.value)
         .fill_with_bound_vars(DebruijnIndex::INNERMOST, kinds.len())
         .build();
@@ -821,13 +878,12 @@ fn generic_implements_goal(
             chalk_ir::VariableKind::Ty(chalk_ir::TyVariableKind::General),
             UniverseIndex::ROOT,
         ))
-        .take(substs.len() - 1),
+        .take(trait_ref.substitution.len(&Interner) - 1),
     );
-    let trait_ref = TraitRef { trait_id: to_chalk_trait_id(trait_), substitution: substs };
     let obligation = trait_ref.cast(&Interner);
     Canonical {
         binders: CanonicalVarKinds::from_iter(&Interner, kinds),
-        value: InEnvironment::new(env.env.clone(), obligation),
+        value: InEnvironment::new(&env.env, obligation),
     }
 }
 
@@ -838,8 +894,8 @@ fn autoderef_method_receiver(
 ) -> Vec<Canonical<Ty>> {
     let mut deref_chain: Vec<_> = autoderef::autoderef(db, Some(krate), ty).collect();
     // As a last step, we can do array unsizing (that's the only unsizing that rustc does for method receivers!)
-    if let Some(TyKind::Array(parameters)) =
-        deref_chain.last().map(|ty| ty.value.interned(&Interner))
+    if let Some(TyKind::Array(parameters, _)) =
+        deref_chain.last().map(|ty| ty.value.kind(&Interner))
     {
         let kinds = deref_chain.last().unwrap().binders.clone();
         let unsized_ty = TyKind::Slice(parameters.clone()).intern(&Interner);
diff --git a/crates/hir_ty/src/op.rs b/crates/hir_ty/src/op.rs
index 527c5cbbd..0222de2bc 100644
--- a/crates/hir_ty/src/op.rs
+++ b/crates/hir_ty/src/op.rs
@@ -2,29 +2,63 @@
 use chalk_ir::TyVariableKind;
 use hir_def::expr::{ArithOp, BinaryOp, CmpOp};
 
-use crate::{Interner, Scalar, Ty, TyKind};
+use crate::{Interner, Scalar, Ty, TyBuilder, TyKind};
 
 pub(super) fn binary_op_return_ty(op: BinaryOp, lhs_ty: Ty, rhs_ty: Ty) -> Ty {
     match op {
         BinaryOp::LogicOp(_) | BinaryOp::CmpOp(_) => TyKind::Scalar(Scalar::Bool).intern(&Interner),
-        BinaryOp::Assignment { .. } => Ty::unit(),
+        BinaryOp::Assignment { .. } => TyBuilder::unit(),
         BinaryOp::ArithOp(ArithOp::Shl) | BinaryOp::ArithOp(ArithOp::Shr) => {
-            match lhs_ty.interned(&Interner) {
+            // all integer combinations are valid here
+            if matches!(
+                lhs_ty.kind(&Interner),
                 TyKind::Scalar(Scalar::Int(_))
-                | TyKind::Scalar(Scalar::Uint(_))
-                | TyKind::Scalar(Scalar::Float(_)) => lhs_ty,
-                TyKind::InferenceVar(_, TyVariableKind::Integer)
-                | TyKind::InferenceVar(_, TyVariableKind::Float) => lhs_ty,
-                _ => TyKind::Unknown.intern(&Interner),
+                    | TyKind::Scalar(Scalar::Uint(_))
+                    | TyKind::InferenceVar(_, TyVariableKind::Integer)
+            ) && matches!(
+                rhs_ty.kind(&Interner),
+                TyKind::Scalar(Scalar::Int(_))
+                    | TyKind::Scalar(Scalar::Uint(_))
+                    | TyKind::InferenceVar(_, TyVariableKind::Integer)
+            ) {
+                lhs_ty
+            } else {
+                TyKind::Error.intern(&Interner)
             }
         }
-        BinaryOp::ArithOp(_) => match rhs_ty.interned(&Interner) {
-            TyKind::Scalar(Scalar::Int(_))
-            | TyKind::Scalar(Scalar::Uint(_))
-            | TyKind::Scalar(Scalar::Float(_)) => rhs_ty,
-            TyKind::InferenceVar(_, TyVariableKind::Integer)
-            | TyKind::InferenceVar(_, TyVariableKind::Float) => rhs_ty,
-            _ => TyKind::Unknown.intern(&Interner),
+        BinaryOp::ArithOp(_) => match (lhs_ty.kind(&Interner), rhs_ty.kind(&Interner)) {
+            // (int, int) | (uint, uint) | (float, float)
+            (TyKind::Scalar(Scalar::Int(_)), TyKind::Scalar(Scalar::Int(_)))
+            | (TyKind::Scalar(Scalar::Uint(_)), TyKind::Scalar(Scalar::Uint(_)))
+            | (TyKind::Scalar(Scalar::Float(_)), TyKind::Scalar(Scalar::Float(_))) => rhs_ty,
+            // ({int}, int) | ({int}, uint)
+            (TyKind::InferenceVar(_, TyVariableKind::Integer), TyKind::Scalar(Scalar::Int(_)))
+            | (TyKind::InferenceVar(_, TyVariableKind::Integer), TyKind::Scalar(Scalar::Uint(_))) => {
+                rhs_ty
+            }
+            // (int, {int}) | (uint, {int})
+            (TyKind::Scalar(Scalar::Int(_)), TyKind::InferenceVar(_, TyVariableKind::Integer))
+            | (TyKind::Scalar(Scalar::Uint(_)), TyKind::InferenceVar(_, TyVariableKind::Integer)) => {
+                lhs_ty
+            }
+            // ({float} | float)
+            (TyKind::InferenceVar(_, TyVariableKind::Float), TyKind::Scalar(Scalar::Float(_))) => {
+                rhs_ty
+            }
+            // (float, {float})
+            (TyKind::Scalar(Scalar::Float(_)), TyKind::InferenceVar(_, TyVariableKind::Float)) => {
+                lhs_ty
+            }
+            // ({int}, {int}) | ({float}, {float})
+            (
+                TyKind::InferenceVar(_, TyVariableKind::Integer),
+                TyKind::InferenceVar(_, TyVariableKind::Integer),
+            )
+            | (
+                TyKind::InferenceVar(_, TyVariableKind::Float),
+                TyKind::InferenceVar(_, TyVariableKind::Float),
+            ) => rhs_ty,
+            _ => TyKind::Error.intern(&Interner),
         },
     }
 }
@@ -33,24 +67,24 @@ pub(super) fn binary_op_rhs_expectation(op: BinaryOp, lhs_ty: Ty) -> Ty {
     match op {
         BinaryOp::LogicOp(..) => TyKind::Scalar(Scalar::Bool).intern(&Interner),
         BinaryOp::Assignment { op: None } => lhs_ty,
-        BinaryOp::CmpOp(CmpOp::Eq { .. }) => match lhs_ty.interned(&Interner) {
+        BinaryOp::CmpOp(CmpOp::Eq { .. }) => match lhs_ty.kind(&Interner) {
             TyKind::Scalar(_) | TyKind::Str => lhs_ty,
             TyKind::InferenceVar(_, TyVariableKind::Integer)
             | TyKind::InferenceVar(_, TyVariableKind::Float) => lhs_ty,
-            _ => TyKind::Unknown.intern(&Interner),
+            _ => TyKind::Error.intern(&Interner),
         },
         BinaryOp::ArithOp(ArithOp::Shl) | BinaryOp::ArithOp(ArithOp::Shr) => {
-            TyKind::Unknown.intern(&Interner)
+            TyKind::Error.intern(&Interner)
         }
         BinaryOp::CmpOp(CmpOp::Ord { .. })
         | BinaryOp::Assignment { op: Some(_) }
-        | BinaryOp::ArithOp(_) => match lhs_ty.interned(&Interner) {
+        | BinaryOp::ArithOp(_) => match lhs_ty.kind(&Interner) {
             TyKind::Scalar(Scalar::Int(_))
             | TyKind::Scalar(Scalar::Uint(_))
             | TyKind::Scalar(Scalar::Float(_)) => lhs_ty,
             TyKind::InferenceVar(_, TyVariableKind::Integer)
             | TyKind::InferenceVar(_, TyVariableKind::Float) => lhs_ty,
-            _ => TyKind::Unknown.intern(&Interner),
+            _ => TyKind::Error.intern(&Interner),
         },
     }
 }
diff --git a/crates/hir_ty/src/primitive.rs b/crates/hir_ty/src/primitive.rs
index 2449addfb..d7f48c69a 100644
--- a/crates/hir_ty/src/primitive.rs
+++ b/crates/hir_ty/src/primitive.rs
@@ -1,7 +1,4 @@
-//! Defines primitive types, which have a couple of peculiarities:
-//!
-//! * during type inference, they can be uncertain (ie, `let x = 92;`)
-//! * they don't belong to any particular crate.
+//! A few helper functions for dealing with primitives.
 
 pub use chalk_ir::{FloatTy, IntTy, UintTy};
 pub use hir_def::builtin_type::{BuiltinFloat, BuiltinInt, BuiltinUint};
diff --git a/crates/hir_ty/src/tests.rs b/crates/hir_ty/src/tests.rs
index ad283c1e0..ccfb88c52 100644
--- a/crates/hir_ty/src/tests.rs
+++ b/crates/hir_ty/src/tests.rs
@@ -288,7 +288,7 @@ fn visit_module(
     }
 
     fn visit_body(db: &TestDB, body: &Body, cb: &mut dyn FnMut(DefWithBodyId)) {
-        for def_map in body.block_scopes.iter().filter_map(|block| db.block_def_map(*block)) {
+        for (_, def_map) in body.blocks(db) {
             for (mod_id, _) in def_map.modules() {
                 visit_module(db, &def_map, mod_id, cb);
             }
diff --git a/crates/hir_ty/src/tests/macros.rs b/crates/hir_ty/src/tests/macros.rs
index 3eb01dbd0..b8e373ed8 100644
--- a/crates/hir_ty/src/tests/macros.rs
+++ b/crates/hir_ty/src/tests/macros.rs
@@ -373,6 +373,32 @@ fn recursive_inner_item_macro_rules() {
 }
 
 #[test]
+fn infer_macro_defining_block_with_items() {
+    check_infer(
+        r#"
+        macro_rules! foo {
+            () => {{
+                fn bar() -> usize { 0 }
+                bar()
+            }};
+        }
+        fn main() {
+            let _a = foo!();
+        }
+    "#,
+        expect![[r#"
+            !15..18 '{0}': usize
+            !16..17 '0': usize
+            !0..24 '{fnbar...bar()}': usize
+            !18..21 'bar': fn bar() -> usize
+            !18..23 'bar()': usize
+            98..122 '{     ...!(); }': ()
+            108..110 '_a': usize
+        "#]],
+    );
+}
+
+#[test]
 fn infer_type_value_macro_having_same_name() {
     check_infer(
         r#"
@@ -1039,11 +1065,11 @@ fn macro_in_arm() {
         }
         "#,
         expect![[r#"
+            !0..2 '()': ()
             51..110 '{     ...  }; }': ()
             61..62 'x': u32
             65..107 'match ...     }': u32
             71..73 '()': ()
-            84..91 'unit!()': ()
             95..100 '92u32': u32
         "#]],
     );
diff --git a/crates/hir_ty/src/tests/method_resolution.rs b/crates/hir_ty/src/tests/method_resolution.rs
index 61f18b0d2..4b2c82b41 100644
--- a/crates/hir_ty/src/tests/method_resolution.rs
+++ b/crates/hir_ty/src/tests/method_resolution.rs
@@ -1292,3 +1292,25 @@ mod b {
         "#]],
     )
 }
+
+#[test]
+fn impl_in_unnamed_const() {
+    check_types(
+        r#"
+struct S;
+
+trait Tr {
+    fn method(&self) -> u16;
+}
+
+const _: () = {
+    impl Tr for S {}
+};
+
+fn f() {
+    S.method();
+  //^^^^^^^^^^ u16
+}
+    "#,
+    );
+}
diff --git a/crates/hir_ty/src/tests/patterns.rs b/crates/hir_ty/src/tests/patterns.rs
index 85a28e76b..f514b3efe 100644
--- a/crates/hir_ty/src/tests/patterns.rs
+++ b/crates/hir_ty/src/tests/patterns.rs
@@ -1,6 +1,6 @@
 use expect_test::expect;
 
-use super::{check_infer, check_infer_with_mismatches};
+use super::{check_infer, check_infer_with_mismatches, check_types};
 
 #[test]
 fn infer_pattern() {
@@ -825,3 +825,29 @@ fn foo(foo: Foo) {
         "#]],
     );
 }
+
+#[test]
+fn macro_pat() {
+    check_types(
+        r#"
+macro_rules! pat {
+    ($name:ident) => { Enum::Variant1($name) }
+}
+
+enum Enum {
+    Variant1(u8),
+    Variant2,
+}
+
+fn f(e: Enum) {
+    match e {
+        pat!(bind) => {
+            bind;
+          //^^^^ u8
+        }
+        Enum::Variant2 => {}
+    }
+}
+    "#,
+    )
+}
diff --git a/crates/hir_ty/src/tests/regression.rs b/crates/hir_ty/src/tests/regression.rs
index b69f86050..9cd9f473d 100644
--- a/crates/hir_ty/src/tests/regression.rs
+++ b/crates/hir_ty/src/tests/regression.rs
@@ -974,3 +974,41 @@ fn param_overrides_fn() {
         "#,
     )
 }
+
+#[test]
+fn lifetime_from_chalk_during_deref() {
+    check_types(
+        r#"
+        #[lang = "deref"]
+        pub trait Deref {
+            type Target;
+        }
+
+        struct Box<T: ?Sized> {}
+        impl<T> Deref for Box<T> {
+            type Target = T;
+
+            fn deref(&self) -> &Self::Target {
+                loop {}
+            }
+        }
+
+        trait Iterator {
+            type Item;
+        }
+
+        pub struct Iter<'a, T: 'a> {
+            inner: Box<dyn IterTrait<'a, T, Item = &'a T> + 'a>,
+        }
+
+        trait IterTrait<'a, T: 'a>: Iterator<Item = &'a T> {
+            fn clone_box(&self);
+        }
+
+        fn clone_iter<T>(s: Iter<T>) {
+            s.inner.clone_box();
+          //^^^^^^^^^^^^^^^^^^^ ()
+        }
+        "#,
+    )
+}
diff --git a/crates/hir_ty/src/tests/simple.rs b/crates/hir_ty/src/tests/simple.rs
index 361cd6302..5948d0bc2 100644
--- a/crates/hir_ty/src/tests/simple.rs
+++ b/crates/hir_ty/src/tests/simple.rs
@@ -1765,6 +1765,24 @@ fn main() {
 }
 
 #[test]
+fn shadowing_primitive_with_inner_items() {
+    check_types(
+        r#"
+struct i32;
+struct Foo;
+
+impl i32 { fn foo(&self) -> Foo { Foo } }
+
+fn main() {
+    fn inner() {}
+    let x: i32 = i32;
+    x.foo();
+        //^ Foo
+}"#,
+    );
+}
+
+#[test]
 fn not_shadowing_primitive_by_module() {
     check_types(
         r#"
@@ -2564,3 +2582,36 @@ fn f() {
     "#,
     )
 }
+
+#[test]
+fn infer_type_alias_variant() {
+    check_infer(
+        r#"
+type Qux = Foo;
+enum Foo {
+    Bar(i32),
+    Baz { baz: f32 }
+}
+
+fn f() {
+    match Foo::Bar(3) {
+        Qux::Bar(bar) => (),
+        Qux::Baz { baz } => (),
+    }
+}
+    "#,
+        expect![[r#"
+            72..166 '{     ...   } }': ()
+            78..164 'match ...     }': ()
+            84..92 'Foo::Bar': Bar(i32) -> Foo
+            84..95 'Foo::Bar(3)': Foo
+            93..94 '3': i32
+            106..119 'Qux::Bar(bar)': Foo
+            115..118 'bar': i32
+            123..125 '()': ()
+            135..151 'Qux::B... baz }': Foo
+            146..149 'baz': f32
+            155..157 '()': ()
+        "#]],
+    )
+}
diff --git a/crates/hir_ty/src/tests/traits.rs b/crates/hir_ty/src/tests/traits.rs
index 2ba97f814..ffc7c8ef4 100644
--- a/crates/hir_ty/src/tests/traits.rs
+++ b/crates/hir_ty/src/tests/traits.rs
@@ -263,15 +263,14 @@ mod ops {
 fn infer_from_bound_1() {
     check_infer(
         r#"
-        trait Trait<T> {}
-        struct S<T>(T);
-        impl<U> Trait<U> for S<U> {}
-        fn foo<T: Trait<u32>>(t: T) {}
-        fn test() {
-            let s = S(unknown);
-            foo(s);
-        }
-        "#,
+trait Trait<T> {}
+struct S<T>(T);
+impl<U> Trait<U> for S<U> {}
+fn foo<T: Trait<u32>>(t: T) {}
+fn test() {
+    let s = S(unknown);
+    foo(s);
+}"#,
         expect![[r#"
             85..86 't': T
             91..93 '{}': ()
@@ -291,15 +290,14 @@ fn infer_from_bound_1() {
 fn infer_from_bound_2() {
     check_infer(
         r#"
-        trait Trait<T> {}
-        struct S<T>(T);
-        impl<U> Trait<U> for S<U> {}
-        fn foo<U, T: Trait<U>>(t: T) -> U {}
-        fn test() {
-            let s = S(unknown);
-            let x: u32 = foo(s);
-        }
-        "#,
+trait Trait<T> {}
+struct S<T>(T);
+impl<U> Trait<U> for S<U> {}
+fn foo<U, T: Trait<U>>(t: T) -> U {}
+fn test() {
+    let s = S(unknown);
+    let x: u32 = foo(s);
+}"#,
         expect![[r#"
             86..87 't': T
             97..99 '{}': ()
@@ -321,13 +319,12 @@ fn trait_default_method_self_bound_implements_trait() {
     cov_mark::check!(trait_self_implements_self);
     check_infer(
         r#"
-        trait Trait {
-            fn foo(&self) -> i64;
-            fn bar(&self) -> {
-                let x = self.foo();
-            }
-        }
-        "#,
+trait Trait {
+    fn foo(&self) -> i64;
+    fn bar(&self) -> {
+        let x = self.foo();
+    }
+}"#,
         expect![[r#"
             26..30 'self': &Self
             52..56 'self': &Self
@@ -343,15 +340,14 @@ fn trait_default_method_self_bound_implements_trait() {
 fn trait_default_method_self_bound_implements_super_trait() {
     check_infer(
         r#"
-        trait SuperTrait {
-            fn foo(&self) -> i64;
-        }
-        trait Trait: SuperTrait {
-            fn bar(&self) -> {
-                let x = self.foo();
-            }
-        }
-        "#,
+trait SuperTrait {
+    fn foo(&self) -> i64;
+}
+trait Trait: SuperTrait {
+    fn bar(&self) -> {
+        let x = self.foo();
+    }
+}"#,
         expect![[r#"
             31..35 'self': &Self
             85..89 'self': &Self
@@ -367,18 +363,17 @@ fn trait_default_method_self_bound_implements_super_trait() {
 fn infer_project_associated_type() {
     check_infer(
         r#"
-        trait Iterable {
-            type Item;
-        }
-        struct S;
-        impl Iterable for S { type Item = u32; }
-        fn test<T: Iterable>() {
-            let x: <S as Iterable>::Item = 1;
-            let y: <T as Iterable>::Item = no_matter;
-            let z: T::Item = no_matter;
-            let a: <T>::Item = no_matter;
-        }
-        "#,
+trait Iterable {
+    type Item;
+}
+struct S;
+impl Iterable for S { type Item = u32; }
+fn test<T: Iterable>() {
+    let x: <S as Iterable>::Item = 1;
+    let y: <T as Iterable>::Item = no_matter;
+    let z: T::Item = no_matter;
+    let a: <T>::Item = no_matter;
+}"#,
         expect![[r#"
             108..261 '{     ...ter; }': ()
             118..119 'x': u32
@@ -397,20 +392,19 @@ fn infer_project_associated_type() {
 fn infer_return_associated_type() {
     check_infer(
         r#"
-        trait Iterable {
-            type Item;
-        }
-        struct S;
-        impl Iterable for S { type Item = u32; }
-        fn foo1<T: Iterable>(t: T) -> T::Item {}
-        fn foo2<T: Iterable>(t: T) -> <T as Iterable>::Item {}
-        fn foo3<T: Iterable>(t: T) -> <T>::Item {}
-        fn test() {
-            let x = foo1(S);
-            let y = foo2(S);
-            let z = foo3(S);
-        }
-        "#,
+trait Iterable {
+    type Item;
+}
+struct S;
+impl Iterable for S { type Item = u32; }
+fn foo1<T: Iterable>(t: T) -> T::Item {}
+fn foo2<T: Iterable>(t: T) -> <T as Iterable>::Item {}
+fn foo3<T: Iterable>(t: T) -> <T>::Item {}
+fn test() {
+    let x = foo1(S);
+    let y = foo2(S);
+    let z = foo3(S);
+}"#,
         expect![[r#"
             106..107 't': T
             123..125 '{}': ()
@@ -439,13 +433,12 @@ fn infer_return_associated_type() {
 fn infer_associated_type_bound() {
     check_infer(
         r#"
-        trait Iterable {
-            type Item;
-        }
-        fn test<T: Iterable<Item=u32>>() {
-            let y: T::Item = unknown;
-        }
-        "#,
+trait Iterable {
+    type Item;
+}
+fn test<T: Iterable<Item=u32>>() {
+    let y: T::Item = unknown;
+}"#,
         expect![[r#"
             67..100 '{     ...own; }': ()
             77..78 'y': u32
@@ -458,9 +451,8 @@ fn infer_associated_type_bound() {
 fn infer_const_body() {
     check_infer(
         r#"
-        const A: u32 = 1 + 1;
-        static B: u64 = { let x = 1; x };
-        "#,
+const A: u32 = 1 + 1;
+static B: u64 = { let x = 1; x };"#,
         expect![[r#"
             15..16 '1': u32
             15..20 '1 + 1': u32
@@ -477,13 +469,12 @@ fn infer_const_body() {
 fn tuple_struct_fields() {
     check_infer(
         r#"
-        struct S(i32, u64);
-        fn test() -> u64 {
-            let a = S(4, 6);
-            let b = a.0;
-            a.1
-        }
-        "#,
+struct S(i32, u64);
+fn test() -> u64 {
+    let a = S(4, 6);
+    let b = a.0;
+    a.1
+}"#,
         expect![[r#"
             37..86 '{     ... a.1 }': u64
             47..48 'a': S
@@ -504,13 +495,12 @@ fn tuple_struct_fields() {
 fn tuple_struct_with_fn() {
     check_infer(
         r#"
-        struct S(fn(u32) -> u64);
-        fn test() -> u64 {
-            let a = S(|i| 2*i);
-            let b = a.0(4);
-            a.0(2)
-        }
-        "#,
+struct S(fn(u32) -> u64);
+fn test() -> u64 {
+    let a = S(|i| 2*i);
+    let b = a.0(4);
+    a.0(2)
+}"#,
         expect![[r#"
             43..101 '{     ...0(2) }': u64
             53..54 'a': S
@@ -949,27 +939,26 @@ fn test<T: ApplyL>(t: T) {
 fn argument_impl_trait() {
     check_infer_with_mismatches(
         r#"
-        trait Trait<T> {
-            fn foo(&self) -> T;
-            fn foo2(&self) -> i64;
-        }
-        fn bar(x: impl Trait<u16>) {}
-        struct S<T>(T);
-        impl<T> Trait<T> for S<T> {}
-
-        fn test(x: impl Trait<u64>, y: &impl Trait<u32>) {
-            x;
-            y;
-            let z = S(1);
-            bar(z);
-            x.foo();
-            y.foo();
-            z.foo();
-            x.foo2();
-            y.foo2();
-            z.foo2();
-        }
-        "#,
+trait Trait<T> {
+    fn foo(&self) -> T;
+    fn foo2(&self) -> i64;
+}
+fn bar(x: impl Trait<u16>) {}
+struct S<T>(T);
+impl<T> Trait<T> for S<T> {}
+
+fn test(x: impl Trait<u64>, y: &impl Trait<u32>) {
+    x;
+    y;
+    let z = S(1);
+    bar(z);
+    x.foo();
+    y.foo();
+    z.foo();
+    x.foo2();
+    y.foo2();
+    z.foo2();
+}"#,
         expect![[r#"
             29..33 'self': &Self
             54..58 'self': &Self
@@ -1007,30 +996,29 @@ fn argument_impl_trait() {
 fn argument_impl_trait_type_args_1() {
     check_infer_with_mismatches(
         r#"
-        trait Trait {}
-        trait Foo {
-            // this function has an implicit Self param, an explicit type param,
-            // and an implicit impl Trait param!
-            fn bar<T>(x: impl Trait) -> T { loop {} }
-        }
-        fn foo<T>(x: impl Trait) -> T { loop {} }
-        struct S;
-        impl Trait for S {}
-        struct F;
-        impl Foo for F {}
-
-        fn test() {
-            Foo::bar(S);
-            <F as Foo>::bar(S);
-            F::bar(S);
-            Foo::bar::<u32>(S);
-            <F as Foo>::bar::<u32>(S);
-
-            foo(S);
-            foo::<u32>(S);
-            foo::<u32, i32>(S); // we should ignore the extraneous i32
-        }
-        "#,
+trait Trait {}
+trait Foo {
+    // this function has an implicit Self param, an explicit type param,
+    // and an implicit impl Trait param!
+    fn bar<T>(x: impl Trait) -> T { loop {} }
+}
+fn foo<T>(x: impl Trait) -> T { loop {} }
+struct S;
+impl Trait for S {}
+struct F;
+impl Foo for F {}
+
+fn test() {
+    Foo::bar(S);
+    <F as Foo>::bar(S);
+    F::bar(S);
+    Foo::bar::<u32>(S);
+    <F as Foo>::bar::<u32>(S);
+
+    foo(S);
+    foo::<u32>(S);
+    foo::<u32, i32>(S); // we should ignore the extraneous i32
+}"#,
         expect![[r#"
             155..156 'x': impl Trait
             175..186 '{ loop {} }': T
@@ -1073,21 +1061,20 @@ fn argument_impl_trait_type_args_1() {
 fn argument_impl_trait_type_args_2() {
     check_infer_with_mismatches(
         r#"
-        trait Trait {}
-        struct S;
-        impl Trait for S {}
-        struct F<T>;
-        impl<T> F<T> {
-            fn foo<U>(self, x: impl Trait) -> (T, U) { loop {} }
-        }
+trait Trait {}
+struct S;
+impl Trait for S {}
+struct F<T>;
+impl<T> F<T> {
+    fn foo<U>(self, x: impl Trait) -> (T, U) { loop {} }
+}
 
-        fn test() {
-            F.foo(S);
-            F::<u32>.foo(S);
-            F::<u32>.foo::<i32>(S);
-            F::<u32>.foo::<i32, u32>(S); // extraneous argument should be ignored
-        }
-        "#,
+fn test() {
+    F.foo(S);
+    F::<u32>.foo(S);
+    F::<u32>.foo::<i32>(S);
+    F::<u32>.foo::<i32, u32>(S); // extraneous argument should be ignored
+}"#,
         expect![[r#"
             87..91 'self': F<T>
             93..94 'x': impl Trait
@@ -1115,15 +1102,14 @@ fn argument_impl_trait_type_args_2() {
 fn argument_impl_trait_to_fn_pointer() {
     check_infer_with_mismatches(
         r#"
-        trait Trait {}
-        fn foo(x: impl Trait) { loop {} }
-        struct S;
-        impl Trait for S {}
+trait Trait {}
+fn foo(x: impl Trait) { loop {} }
+struct S;
+impl Trait for S {}
 
-        fn test() {
-            let f: fn(S) -> () = foo;
-        }
-        "#,
+fn test() {
+    let f: fn(S) -> () = foo;
+}"#,
         expect![[r#"
             22..23 'x': impl Trait
             37..48 '{ loop {} }': ()
@@ -1140,24 +1126,23 @@ fn argument_impl_trait_to_fn_pointer() {
 fn impl_trait() {
     check_infer(
         r#"
-        trait Trait<T> {
-            fn foo(&self) -> T;
-            fn foo2(&self) -> i64;
-        }
-        fn bar() -> impl Trait<u64> {}
+trait Trait<T> {
+    fn foo(&self) -> T;
+    fn foo2(&self) -> i64;
+}
+fn bar() -> impl Trait<u64> {}
 
-        fn test(x: impl Trait<u64>, y: &impl Trait<u64>) {
-            x;
-            y;
-            let z = bar();
-            x.foo();
-            y.foo();
-            z.foo();
-            x.foo2();
-            y.foo2();
-            z.foo2();
-        }
-        "#,
+fn test(x: impl Trait<u64>, y: &impl Trait<u64>) {
+    x;
+    y;
+    let z = bar();
+    x.foo();
+    y.foo();
+    z.foo();
+    x.foo2();
+    y.foo2();
+    z.foo2();
+}"#,
         expect![[r#"
             29..33 'self': &Self
             54..58 'self': &Self
@@ -1191,16 +1176,15 @@ fn simple_return_pos_impl_trait() {
     cov_mark::check!(lower_rpit);
     check_infer(
         r#"
-        trait Trait<T> {
-            fn foo(&self) -> T;
-        }
-        fn bar() -> impl Trait<u64> { loop {} }
+trait Trait<T> {
+    fn foo(&self) -> T;
+}
+fn bar() -> impl Trait<u64> { loop {} }
 
-        fn test() {
-            let a = bar();
-            a.foo();
-        }
-        "#,
+fn test() {
+    let a = bar();
+    a.foo();
+}"#,
         expect![[r#"
             29..33 'self': &Self
             71..82 '{ loop {} }': !
@@ -1220,25 +1204,24 @@ fn simple_return_pos_impl_trait() {
 fn more_return_pos_impl_trait() {
     check_infer(
         r#"
-        trait Iterator {
-            type Item;
-            fn next(&mut self) -> Self::Item;
-        }
-        trait Trait<T> {
-            fn foo(&self) -> T;
-        }
-        fn bar() -> (impl Iterator<Item = impl Trait<u32>>, impl Trait<u64>) { loop {} }
-        fn baz<T>(t: T) -> (impl Iterator<Item = impl Trait<T>>, impl Trait<T>) { loop {} }
-
-        fn test() {
-            let (a, b) = bar();
-            a.next().foo();
-            b.foo();
-            let (c, d) = baz(1u128);
-            c.next().foo();
-            d.foo();
-        }
-        "#,
+trait Iterator {
+    type Item;
+    fn next(&mut self) -> Self::Item;
+}
+trait Trait<T> {
+    fn foo(&self) -> T;
+}
+fn bar() -> (impl Iterator<Item = impl Trait<u32>>, impl Trait<u64>) { loop {} }
+fn baz<T>(t: T) -> (impl Iterator<Item = impl Trait<T>>, impl Trait<T>) { loop {} }
+
+fn test() {
+    let (a, b) = bar();
+    a.next().foo();
+    b.foo();
+    let (c, d) = baz(1u128);
+    c.next().foo();
+    d.foo();
+}"#,
         expect![[r#"
             49..53 'self': &mut Self
             101..105 'self': &Self
@@ -1279,24 +1262,23 @@ fn more_return_pos_impl_trait() {
 fn dyn_trait() {
     check_infer(
         r#"
-        trait Trait<T> {
-            fn foo(&self) -> T;
-            fn foo2(&self) -> i64;
-        }
-        fn bar() -> dyn Trait<u64> {}
+trait Trait<T> {
+    fn foo(&self) -> T;
+    fn foo2(&self) -> i64;
+}
+fn bar() -> dyn Trait<u64> {}
 
-        fn test(x: dyn Trait<u64>, y: &dyn Trait<u64>) {
-            x;
-            y;
-            let z = bar();
-            x.foo();
-            y.foo();
-            z.foo();
-            x.foo2();
-            y.foo2();
-            z.foo2();
-        }
-        "#,
+fn test(x: dyn Trait<u64>, y: &dyn Trait<u64>) {
+    x;
+    y;
+    let z = bar();
+    x.foo();
+    y.foo();
+    z.foo();
+    x.foo2();
+    y.foo2();
+    z.foo2();
+}"#,
         expect![[r#"
             29..33 'self': &Self
             54..58 'self': &Self
@@ -1329,22 +1311,21 @@ fn dyn_trait() {
 fn dyn_trait_in_impl() {
     check_infer(
         r#"
-        trait Trait<T, U> {
-            fn foo(&self) -> (T, U);
-        }
-        struct S<T, U> {}
-        impl<T, U> S<T, U> {
-            fn bar(&self) -> &dyn Trait<T, U> { loop {} }
-        }
-        trait Trait2<T, U> {
-            fn baz(&self) -> (T, U);
-        }
-        impl<T, U> Trait2<T, U> for dyn Trait<T, U> { }
+trait Trait<T, U> {
+    fn foo(&self) -> (T, U);
+}
+struct S<T, U> {}
+impl<T, U> S<T, U> {
+    fn bar(&self) -> &dyn Trait<T, U> { loop {} }
+}
+trait Trait2<T, U> {
+    fn baz(&self) -> (T, U);
+}
+impl<T, U> Trait2<T, U> for dyn Trait<T, U> { }
 
-        fn test(s: S<u32, i32>) {
-            s.bar().baz();
-        }
-        "#,
+fn test(s: S<u32, i32>) {
+    s.bar().baz();
+}"#,
         expect![[r#"
             32..36 'self': &Self
             102..106 'self': &S<T, U>
@@ -1365,20 +1346,19 @@ fn dyn_trait_in_impl() {
 fn dyn_trait_bare() {
     check_infer(
         r#"
-        trait Trait {
-            fn foo(&self) -> u64;
-        }
-        fn bar() -> Trait {}
+trait Trait {
+    fn foo(&self) -> u64;
+}
+fn bar() -> Trait {}
 
-        fn test(x: Trait, y: &Trait) -> u64 {
-            x;
-            y;
-            let z = bar();
-            x.foo();
-            y.foo();
-            z.foo();
-        }
-        "#,
+fn test(x: Trait, y: &Trait) -> u64 {
+    x;
+    y;
+    let z = bar();
+    x.foo();
+    y.foo();
+    z.foo();
+}"#,
         expect![[r#"
             26..30 'self': &Self
             60..62 '{}': ()
@@ -1404,17 +1384,24 @@ fn dyn_trait_bare() {
 fn weird_bounds() {
     check_infer(
         r#"
-        trait Trait {}
-        fn test(a: impl Trait + 'lifetime, b: impl 'lifetime, c: impl (Trait), d: impl ('lifetime), e: impl ?Sized, f: impl Trait + ?Sized) {}
-        "#,
+trait Trait {}
+fn test(
+    a: impl Trait + 'lifetime,
+    b: impl 'lifetime,
+    c: impl (Trait),
+    d: impl ('lifetime),
+    e: impl ?Sized,
+    f: impl Trait + ?Sized
+) {}
+"#,
         expect![[r#"
-            23..24 'a': impl Trait
-            50..51 'b': impl
-            69..70 'c': impl Trait
-            86..87 'd': impl
-            107..108 'e': impl
-            123..124 'f': impl Trait
-            147..149 '{}': ()
+            28..29 'a': impl Trait
+            59..60 'b': impl
+            82..83 'c': impl Trait
+            103..104 'd': impl
+            128..129 'e': impl
+            148..149 'f': impl Trait
+            173..175 '{}': ()
         "#]],
     );
 }
@@ -1439,27 +1426,26 @@ fn test(x: (impl Trait + UnknownTrait)) {
 fn assoc_type_bindings() {
     check_infer(
         r#"
-        trait Trait {
-            type Type;
-        }
+trait Trait {
+    type Type;
+}
 
-        fn get<T: Trait>(t: T) -> <T as Trait>::Type {}
-        fn get2<U, T: Trait<Type = U>>(t: T) -> U {}
-        fn set<T: Trait<Type = u64>>(t: T) -> T {t}
-
-        struct S<T>;
-        impl<T> Trait for S<T> { type Type = T; }
-
-        fn test<T: Trait<Type = u32>>(x: T, y: impl Trait<Type = i64>) {
-            get(x);
-            get2(x);
-            get(y);
-            get2(y);
-            get(set(S));
-            get2(set(S));
-            get2(S::<str>);
-        }
-        "#,
+fn get<T: Trait>(t: T) -> <T as Trait>::Type {}
+fn get2<U, T: Trait<Type = U>>(t: T) -> U {}
+fn set<T: Trait<Type = u64>>(t: T) -> T {t}
+
+struct S<T>;
+impl<T> Trait for S<T> { type Type = T; }
+
+fn test<T: Trait<Type = u32>>(x: T, y: impl Trait<Type = i64>) {
+    get(x);
+    get2(x);
+    get(y);
+    get2(y);
+    get(set(S));
+    get2(set(S));
+    get2(S::<str>);
+}"#,
         expect![[r#"
             49..50 't': T
             77..79 '{}': ()
@@ -1546,18 +1532,17 @@ mod iter {
 fn projection_eq_within_chalk() {
     check_infer(
         r#"
-        trait Trait1 {
-            type Type;
-        }
-        trait Trait2<T> {
-            fn foo(self) -> T;
-        }
-        impl<T, U> Trait2<T> for U where U: Trait1<Type = T> {}
+trait Trait1 {
+    type Type;
+}
+trait Trait2<T> {
+    fn foo(self) -> T;
+}
+impl<T, U> Trait2<T> for U where U: Trait1<Type = T> {}
 
-        fn test<T: Trait1<Type = u32>>(x: T) {
-            x.foo();
-        }
-        "#,
+fn test<T: Trait1<Type = u32>>(x: T) {
+    x.foo();
+}"#,
         expect![[r#"
             61..65 'self': Self
             163..164 'x': T
@@ -1589,19 +1574,18 @@ fn test<T: foo::Trait>(x: T) {
 fn super_trait_method_resolution() {
     check_infer(
         r#"
-        mod foo {
-            trait SuperTrait {
-                fn foo(&self) -> u32 {}
-            }
-        }
-        trait Trait1: foo::SuperTrait {}
-        trait Trait2 where Self: foo::SuperTrait {}
+mod foo {
+    trait SuperTrait {
+        fn foo(&self) -> u32 {}
+    }
+}
+trait Trait1: foo::SuperTrait {}
+trait Trait2 where Self: foo::SuperTrait {}
 
-        fn test<T: Trait1, U: Trait2>(x: T, y: U) {
-            x.foo();
-            y.foo();
-        }
-        "#,
+fn test<T: Trait1, U: Trait2>(x: T, y: U) {
+    x.foo();
+    y.foo();
+}"#,
         expect![[r#"
             49..53 'self': &Self
             62..64 '{}': ()
@@ -1620,17 +1604,16 @@ fn super_trait_method_resolution() {
 fn super_trait_impl_trait_method_resolution() {
     check_infer(
         r#"
-        mod foo {
-            trait SuperTrait {
-                fn foo(&self) -> u32 {}
-            }
-        }
-        trait Trait1: foo::SuperTrait {}
+mod foo {
+    trait SuperTrait {
+        fn foo(&self) -> u32 {}
+    }
+}
+trait Trait1: foo::SuperTrait {}
 
-        fn test(x: &impl Trait1) {
-            x.foo();
-        }
-        "#,
+fn test(x: &impl Trait1) {
+    x.foo();
+}"#,
         expect![[r#"
             49..53 'self': &Self
             62..64 '{}': ()
@@ -1667,20 +1650,19 @@ fn super_trait_cycle() {
 fn super_trait_assoc_type_bounds() {
     check_infer(
         r#"
-        trait SuperTrait { type Type; }
-        trait Trait where Self: SuperTrait {}
+trait SuperTrait { type Type; }
+trait Trait where Self: SuperTrait {}
 
-        fn get2<U, T: Trait<Type = U>>(t: T) -> U {}
-        fn set<T: Trait<Type = u64>>(t: T) -> T {t}
+fn get2<U, T: Trait<Type = U>>(t: T) -> U {}
+fn set<T: Trait<Type = u64>>(t: T) -> T {t}
 
-        struct S<T>;
-        impl<T> SuperTrait for S<T> { type Type = T; }
-        impl<T> Trait for S<T> {}
+struct S<T>;
+impl<T> SuperTrait for S<T> { type Type = T; }
+impl<T> Trait for S<T> {}
 
-        fn test() {
-            get2(set(S));
-        }
-        "#,
+fn test() {
+    get2(set(S));
+}"#,
         expect![[r#"
             102..103 't': T
             113..115 '{}': ()
@@ -1701,16 +1683,15 @@ fn super_trait_assoc_type_bounds() {
 fn fn_trait() {
     check_infer_with_mismatches(
         r#"
-        trait FnOnce<Args> {
-            type Output;
+trait FnOnce<Args> {
+    type Output;
 
-            fn call_once(self, args: Args) -> <Self as FnOnce<Args>>::Output;
-        }
+    fn call_once(self, args: Args) -> <Self as FnOnce<Args>>::Output;
+}
 
-        fn test<F: FnOnce(u32, u64) -> u128>(f: F) {
-            f.call_once((1, 2));
-        }
-        "#,
+fn test<F: FnOnce(u32, u64) -> u128>(f: F) {
+    f.call_once((1, 2));
+}"#,
         expect![[r#"
             56..60 'self': Self
             62..66 'args': Args
@@ -1729,37 +1710,36 @@ fn fn_trait() {
 fn fn_ptr_and_item() {
     check_infer_with_mismatches(
         r#"
-        #[lang="fn_once"]
-        trait FnOnce<Args> {
-            type Output;
+#[lang="fn_once"]
+trait FnOnce<Args> {
+    type Output;
 
-            fn call_once(self, args: Args) -> Self::Output;
-        }
+    fn call_once(self, args: Args) -> Self::Output;
+}
 
-        trait Foo<T> {
-            fn foo(&self) -> T;
-        }
+trait Foo<T> {
+    fn foo(&self) -> T;
+}
 
-        struct Bar<T>(T);
+struct Bar<T>(T);
 
-        impl<A1, R, F: FnOnce(A1) -> R> Foo<(A1, R)> for Bar<F> {
-            fn foo(&self) -> (A1, R) { loop {} }
-        }
+impl<A1, R, F: FnOnce(A1) -> R> Foo<(A1, R)> for Bar<F> {
+    fn foo(&self) -> (A1, R) { loop {} }
+}
 
-        enum Opt<T> { None, Some(T) }
-        impl<T> Opt<T> {
-            fn map<U, F: FnOnce(T) -> U>(self, f: F) -> Opt<U> { loop {} }
-        }
+enum Opt<T> { None, Some(T) }
+impl<T> Opt<T> {
+    fn map<U, F: FnOnce(T) -> U>(self, f: F) -> Opt<U> { loop {} }
+}
 
-        fn test() {
-            let bar: Bar<fn(u8) -> u32>;
-            bar.foo();
+fn test() {
+    let bar: Bar<fn(u8) -> u32>;
+    bar.foo();
 
-            let opt: Opt<u8>;
-            let f: fn(u8) -> u32;
-            opt.map(f);
-        }
-        "#,
+    let opt: Opt<u8>;
+    let f: fn(u8) -> u32;
+    opt.map(f);
+}"#,
         expect![[r#"
             74..78 'self': Self
             80..84 'args': Args
@@ -1790,46 +1770,45 @@ fn fn_ptr_and_item() {
 fn fn_trait_deref_with_ty_default() {
     check_infer(
         r#"
-        #[lang = "deref"]
-        trait Deref {
-            type Target;
+#[lang = "deref"]
+trait Deref {
+    type Target;
 
-            fn deref(&self) -> &Self::Target;
-        }
+    fn deref(&self) -> &Self::Target;
+}
 
-        #[lang="fn_once"]
-        trait FnOnce<Args> {
-            type Output;
+#[lang="fn_once"]
+trait FnOnce<Args> {
+    type Output;
 
-            fn call_once(self, args: Args) -> Self::Output;
-        }
+    fn call_once(self, args: Args) -> Self::Output;
+}
 
-        struct Foo;
+struct Foo;
 
-        impl Foo {
-            fn foo(&self) -> usize {}
-        }
+impl Foo {
+    fn foo(&self) -> usize {}
+}
 
-        struct Lazy<T, F = fn() -> T>(F);
+struct Lazy<T, F = fn() -> T>(F);
 
-        impl<T, F> Lazy<T, F> {
-            pub fn new(f: F) -> Lazy<T, F> {}
-        }
+impl<T, F> Lazy<T, F> {
+    pub fn new(f: F) -> Lazy<T, F> {}
+}
 
-        impl<T, F: FnOnce() -> T> Deref for Lazy<T, F> {
-            type Target = T;
-        }
+impl<T, F: FnOnce() -> T> Deref for Lazy<T, F> {
+    type Target = T;
+}
 
-        fn test() {
-            let lazy1: Lazy<Foo, _> = Lazy::new(|| Foo);
-            let r1 = lazy1.foo();
+fn test() {
+    let lazy1: Lazy<Foo, _> = Lazy::new(|| Foo);
+    let r1 = lazy1.foo();
 
-            fn make_foo_fn() -> Foo {}
-            let make_foo_fn_ptr: fn() -> Foo = make_foo_fn;
-            let lazy2: Lazy<Foo, _> = Lazy::new(make_foo_fn_ptr);
-            let r2 = lazy2.foo();
-        }
-        "#,
+    fn make_foo_fn() -> Foo {}
+    let make_foo_fn_ptr: fn() -> Foo = make_foo_fn;
+    let lazy2: Lazy<Foo, _> = Lazy::new(make_foo_fn_ptr);
+    let r2 = lazy2.foo();
+}"#,
         expect![[r#"
             64..68 'self': &Self
             165..169 'self': Self
@@ -1865,23 +1844,22 @@ fn fn_trait_deref_with_ty_default() {
 fn closure_1() {
     check_infer_with_mismatches(
         r#"
-        #[lang = "fn_once"]
-        trait FnOnce<Args> {
-            type Output;
-        }
+#[lang = "fn_once"]
+trait FnOnce<Args> {
+    type Output;
+}
 
-        enum Option<T> { Some(T), None }
-        impl<T> Option<T> {
-            fn map<U, F: FnOnce(T) -> U>(self, f: F) -> Option<U> { loop {} }
-        }
+enum Option<T> { Some(T), None }
+impl<T> Option<T> {
+    fn map<U, F: FnOnce(T) -> U>(self, f: F) -> Option<U> { loop {} }
+}
 
-        fn test() {
-            let x = Option::Some(1u32);
-            x.map(|v| v + 1);
-            x.map(|_v| 1u64);
-            let y: Option<i64> = x.map(|_v| 1);
-        }
-        "#,
+fn test() {
+    let x = Option::Some(1u32);
+    x.map(|v| v + 1);
+    x.map(|_v| 1u64);
+    let y: Option<i64> = x.map(|_v| 1);
+}"#,
         expect![[r#"
             147..151 'self': Option<T>
             153..154 'f': F
@@ -1919,38 +1897,63 @@ fn closure_1() {
 fn closure_2() {
     check_infer_with_mismatches(
         r#"
-        trait FnOnce<Args> {
-            type Output;
-        }
+#[lang = "add"]
+pub trait Add<Rhs = Self> {
+    type Output;
+    fn add(self, rhs: Rhs) -> Self::Output;
+}
 
-        fn test<F: FnOnce(u32) -> u64>(f: F) {
-            f(1);
-            let g = |v| v + 1;
-            g(1u64);
-            let h = |v| 1u128 + v;
-        }
-        "#,
+trait FnOnce<Args> {
+    type Output;
+}
+
+impl Add for u64 {
+    type Output = Self;
+    fn add(self, rhs: u64) -> Self::Output {0}
+}
+
+impl Add for u128 {
+    type Output = Self;
+    fn add(self, rhs: u128) -> Self::Output {0}
+}
+
+fn test<F: FnOnce(u32) -> u64>(f: F) {
+    f(1);
+    let g = |v| v + 1;
+    g(1u64);
+    let h = |v| 1u128 + v;
+}"#,
         expect![[r#"
-            72..73 'f': F
-            78..154 '{     ...+ v; }': ()
-            84..85 'f': F
-            84..88 'f(1)': {unknown}
-            86..87 '1': i32
-            98..99 'g': |u64| -> i32
-            102..111 '|v| v + 1': |u64| -> i32
-            103..104 'v': u64
-            106..107 'v': u64
-            106..111 'v + 1': i32
-            110..111 '1': i32
-            117..118 'g': |u64| -> i32
-            117..124 'g(1u64)': i32
-            119..123 '1u64': u64
-            134..135 'h': |u128| -> u128
-            138..151 '|v| 1u128 + v': |u128| -> u128
-            139..140 'v': u128
-            142..147 '1u128': u128
-            142..151 '1u128 + v': u128
-            150..151 'v': u128
+            72..76 'self': Self
+            78..81 'rhs': Rhs
+            203..207 'self': u64
+            209..212 'rhs': u64
+            235..238 '{0}': u64
+            236..237 '0': u64
+            297..301 'self': u128
+            303..306 'rhs': u128
+            330..333 '{0}': u128
+            331..332 '0': u128
+            368..369 'f': F
+            374..450 '{     ...+ v; }': ()
+            380..381 'f': F
+            380..384 'f(1)': {unknown}
+            382..383 '1': i32
+            394..395 'g': |u64| -> u64
+            398..407 '|v| v + 1': |u64| -> u64
+            399..400 'v': u64
+            402..403 'v': u64
+            402..407 'v + 1': u64
+            406..407 '1': u64
+            413..414 'g': |u64| -> u64
+            413..420 'g(1u64)': u64
+            415..419 '1u64': u64
+            430..431 'h': |u128| -> u128
+            434..447 '|v| 1u128 + v': |u128| -> u128
+            435..436 'v': u128
+            438..443 '1u128': u128
+            438..447 '1u128 + v': u128
+            446..447 'v': u128
         "#]],
     );
 }
@@ -1959,29 +1962,28 @@ fn closure_2() {
 fn closure_as_argument_inference_order() {
     check_infer_with_mismatches(
         r#"
-        #[lang = "fn_once"]
-        trait FnOnce<Args> {
-            type Output;
-        }
+#[lang = "fn_once"]
+trait FnOnce<Args> {
+    type Output;
+}
 
-        fn foo1<T, U, F: FnOnce(T) -> U>(x: T, f: F) -> U { loop {} }
-        fn foo2<T, U, F: FnOnce(T) -> U>(f: F, x: T) -> U { loop {} }
+fn foo1<T, U, F: FnOnce(T) -> U>(x: T, f: F) -> U { loop {} }
+fn foo2<T, U, F: FnOnce(T) -> U>(f: F, x: T) -> U { loop {} }
 
-        struct S;
-        impl S {
-            fn method(self) -> u64;
+struct S;
+impl S {
+    fn method(self) -> u64;
 
-            fn foo1<T, U, F: FnOnce(T) -> U>(self, x: T, f: F) -> U { loop {} }
-            fn foo2<T, U, F: FnOnce(T) -> U>(self, f: F, x: T) -> U { loop {} }
-        }
+    fn foo1<T, U, F: FnOnce(T) -> U>(self, x: T, f: F) -> U { loop {} }
+    fn foo2<T, U, F: FnOnce(T) -> U>(self, f: F, x: T) -> U { loop {} }
+}
 
-        fn test() {
-            let x1 = foo1(S, |s| s.method());
-            let x2 = foo2(|s| s.method(), S);
-            let x3 = S.foo1(S, |s| s.method());
-            let x4 = S.foo2(|s| s.method(), S);
-        }
-        "#,
+fn test() {
+    let x1 = foo1(S, |s| s.method());
+    let x2 = foo2(|s| s.method(), S);
+    let x3 = S.foo1(S, |s| s.method());
+    let x4 = S.foo2(|s| s.method(), S);
+}"#,
         expect![[r#"
             94..95 'x': T
             100..101 'f': F
@@ -2110,27 +2112,26 @@ fn test<T, U>() where T::Item: Trait2, T: Trait<U::Item>, U: Trait<()> {
 fn unselected_projection_on_impl_self() {
     check_infer(
         r#"
-        //- /main.rs
-        trait Trait {
-            type Item;
+//- /main.rs
+trait Trait {
+    type Item;
 
-            fn f(&self, x: Self::Item);
-        }
+    fn f(&self, x: Self::Item);
+}
 
-        struct S;
+struct S;
 
-        impl Trait for S {
-            type Item = u32;
-            fn f(&self, x: Self::Item) { let y = x; }
-        }
+impl Trait for S {
+    type Item = u32;
+    fn f(&self, x: Self::Item) { let y = x; }
+}
 
-        struct S2;
+struct S2;
 
-        impl Trait for S2 {
-            type Item = i32;
-            fn f(&self, x: <Self>::Item) { let y = x; }
-        }
-        "#,
+impl Trait for S2 {
+    type Item = i32;
+    fn f(&self, x: <Self>::Item) { let y = x; }
+}"#,
         expect![[r#"
             40..44 'self': &Self
             46..47 'x': Trait::Item<Self>
@@ -2366,58 +2367,57 @@ fn test<I: Iterator<Item: Iterator<Item = u32>>>() {
 fn proc_macro_server_types() {
     check_infer(
         r#"
-        macro_rules! with_api {
-            ($S:ident, $self:ident, $m:ident) => {
-                $m! {
-                    TokenStream {
-                        fn new() -> $S::TokenStream;
-                    },
-                    Group {
-                    },
-                }
-            };
+macro_rules! with_api {
+    ($S:ident, $self:ident, $m:ident) => {
+        $m! {
+            TokenStream {
+                fn new() -> $S::TokenStream;
+            },
+            Group {
+            },
         }
-        macro_rules! associated_item {
-            (type TokenStream) =>
-                (type TokenStream: 'static;);
-            (type Group) =>
-                (type Group: 'static;);
-            ($($item:tt)*) => ($($item)*;)
-        }
-        macro_rules! declare_server_traits {
-            ($($name:ident {
-                $(fn $method:ident($($arg:ident: $arg_ty:ty),* $(,)?) $(-> $ret_ty:ty)?;)*
-            }),* $(,)?) => {
-                pub trait Types {
-                    $(associated_item!(type $name);)*
-                }
-
-                $(pub trait $name: Types {
-                    $(associated_item!(fn $method($($arg: $arg_ty),*) $(-> $ret_ty)?);)*
-                })*
-
-                pub trait Server: Types $(+ $name)* {}
-                impl<S: Types $(+ $name)*> Server for S {}
-            }
+    };
+}
+macro_rules! associated_item {
+    (type TokenStream) =>
+        (type TokenStream: 'static;);
+    (type Group) =>
+        (type Group: 'static;);
+    ($($item:tt)*) => ($($item)*;)
+}
+macro_rules! declare_server_traits {
+    ($($name:ident {
+        $(fn $method:ident($($arg:ident: $arg_ty:ty),* $(,)?) $(-> $ret_ty:ty)?;)*
+    }),* $(,)?) => {
+        pub trait Types {
+            $(associated_item!(type $name);)*
         }
 
-        with_api!(Self, self_, declare_server_traits);
-        struct G {}
-        struct T {}
-        struct Rustc;
-        impl Types for Rustc {
-            type TokenStream = T;
-            type Group = G;
-        }
+        $(pub trait $name: Types {
+            $(associated_item!(fn $method($($arg: $arg_ty),*) $(-> $ret_ty)?);)*
+        })*
 
-        fn make<T>() -> T { loop {} }
-        impl TokenStream for Rustc {
-            fn new() -> Self::TokenStream {
-                let group: Self::Group = make();
-                make()
-            }
-        }
-        "#,
+        pub trait Server: Types $(+ $name)* {}
+        impl<S: Types $(+ $name)*> Server for S {}
+    }
+}
+
+with_api!(Self, self_, declare_server_traits);
+struct G {}
+struct T {}
+struct Rustc;
+impl Types for Rustc {
+    type TokenStream = T;
+    type Group = G;
+}
+
+fn make<T>() -> T { loop {} }
+impl TokenStream for Rustc {
+    fn new() -> Self::TokenStream {
+        let group: Self::Group = make();
+        make()
+    }
+}"#,
         expect![[r#"
             1061..1072 '{ loop {} }': T
             1063..1070 'loop {}': !
@@ -2436,23 +2436,22 @@ fn proc_macro_server_types() {
 fn unify_impl_trait() {
     check_infer_with_mismatches(
         r#"
-        trait Trait<T> {}
+trait Trait<T> {}
 
-        fn foo(x: impl Trait<u32>) { loop {} }
-        fn bar<T>(x: impl Trait<T>) -> T { loop {} }
+fn foo(x: impl Trait<u32>) { loop {} }
+fn bar<T>(x: impl Trait<T>) -> T { loop {} }
 
-        struct S<T>(T);
-        impl<T> Trait<T> for S<T> {}
+struct S<T>(T);
+impl<T> Trait<T> for S<T> {}
 
-        fn default<T>() -> T { loop {} }
+fn default<T>() -> T { loop {} }
 
-        fn test() -> impl Trait<i32> {
-            let s1 = S(default());
-            foo(s1);
-            let x: i32 = bar(S(default()));
-            S(default())
-        }
-        "#,
+fn test() -> impl Trait<i32> {
+    let s1 = S(default());
+    foo(s1);
+    let x: i32 = bar(S(default()));
+    S(default())
+}"#,
         expect![[r#"
             26..27 'x': impl Trait<u32>
             46..57 '{ loop {} }': ()
@@ -2493,30 +2492,29 @@ fn unify_impl_trait() {
 fn assoc_types_from_bounds() {
     check_infer(
         r#"
-        //- /main.rs
-        #[lang = "fn_once"]
-        trait FnOnce<Args> {
-            type Output;
-        }
+//- /main.rs
+#[lang = "fn_once"]
+trait FnOnce<Args> {
+    type Output;
+}
 
-        trait T {
-            type O;
-        }
+trait T {
+    type O;
+}
 
-        impl T for () {
-            type O = ();
-        }
+impl T for () {
+    type O = ();
+}
 
-        fn f<X, F>(_v: F)
-        where
-            X: T,
-            F: FnOnce(&X::O),
-        { }
+fn f<X, F>(_v: F)
+where
+    X: T,
+    F: FnOnce(&X::O),
+{ }
 
-        fn main() {
-            f::<(), _>(|z| { z; });
-        }
-        "#,
+fn main() {
+    f::<(), _>(|z| { z; });
+}"#,
         expect![[r#"
             133..135 '_v': F
             178..181 '{ }': ()
@@ -2602,76 +2600,75 @@ fn test() {
 fn iterator_chain() {
     check_infer_with_mismatches(
         r#"
-        //- /main.rs
-        #[lang = "fn_once"]
-        trait FnOnce<Args> {
-            type Output;
-        }
-        #[lang = "fn_mut"]
-        trait FnMut<Args>: FnOnce<Args> { }
+//- /main.rs
+#[lang = "fn_once"]
+trait FnOnce<Args> {
+    type Output;
+}
+#[lang = "fn_mut"]
+trait FnMut<Args>: FnOnce<Args> { }
 
-        enum Option<T> { Some(T), None }
-        use Option::*;
+enum Option<T> { Some(T), None }
+use Option::*;
 
-        pub trait Iterator {
-            type Item;
+pub trait Iterator {
+    type Item;
 
-            fn filter_map<B, F>(self, f: F) -> FilterMap<Self, F>
-            where
-                F: FnMut(Self::Item) -> Option<B>,
-            { loop {} }
+    fn filter_map<B, F>(self, f: F) -> FilterMap<Self, F>
+    where
+        F: FnMut(Self::Item) -> Option<B>,
+    { loop {} }
 
-            fn for_each<F>(self, f: F)
-            where
-                F: FnMut(Self::Item),
-            { loop {} }
-        }
+    fn for_each<F>(self, f: F)
+    where
+        F: FnMut(Self::Item),
+    { loop {} }
+}
 
-        pub trait IntoIterator {
-            type Item;
-            type IntoIter: Iterator<Item = Self::Item>;
-            fn into_iter(self) -> Self::IntoIter;
-        }
+pub trait IntoIterator {
+    type Item;
+    type IntoIter: Iterator<Item = Self::Item>;
+    fn into_iter(self) -> Self::IntoIter;
+}
 
-        pub struct FilterMap<I, F> { }
-        impl<B, I: Iterator, F> Iterator for FilterMap<I, F>
-        where
-            F: FnMut(I::Item) -> Option<B>,
-        {
-            type Item = B;
-        }
+pub struct FilterMap<I, F> { }
+impl<B, I: Iterator, F> Iterator for FilterMap<I, F>
+where
+    F: FnMut(I::Item) -> Option<B>,
+{
+    type Item = B;
+}
 
-        #[stable(feature = "rust1", since = "1.0.0")]
-        impl<I: Iterator> IntoIterator for I {
-            type Item = I::Item;
-            type IntoIter = I;
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<I: Iterator> IntoIterator for I {
+    type Item = I::Item;
+    type IntoIter = I;
 
-            fn into_iter(self) -> I {
-                self
-            }
-        }
+    fn into_iter(self) -> I {
+        self
+    }
+}
 
-        struct Vec<T> {}
-        impl<T> Vec<T> {
-            fn new() -> Self { loop {} }
-        }
+struct Vec<T> {}
+impl<T> Vec<T> {
+    fn new() -> Self { loop {} }
+}
 
-        impl<T> IntoIterator for Vec<T> {
-            type Item = T;
-            type IntoIter = IntoIter<T>;
-        }
+impl<T> IntoIterator for Vec<T> {
+    type Item = T;
+    type IntoIter = IntoIter<T>;
+}
 
-        pub struct IntoIter<T> { }
-        impl<T> Iterator for IntoIter<T> {
-            type Item = T;
-        }
+pub struct IntoIter<T> { }
+impl<T> Iterator for IntoIter<T> {
+    type Item = T;
+}
 
-        fn main() {
-            Vec::<i32>::new().into_iter()
-            .filter_map(|x| if x > 0 { Some(x as u32) } else { None })
-            .for_each(|y| { y; });
-        }
-        "#,
+fn main() {
+    Vec::<i32>::new().into_iter()
+    .filter_map(|x| if x > 0 { Some(x as u32) } else { None })
+    .for_each(|y| { y; });
+}"#,
         expect![[r#"
             226..230 'self': Self
             232..233 'f': F
@@ -2753,14 +2750,13 @@ fn main() {
 fn trait_object_no_coercion() {
     check_infer_with_mismatches(
         r#"
-        trait Foo {}
+trait Foo {}
 
-        fn foo(x: &dyn Foo) {}
+fn foo(x: &dyn Foo) {}
 
-        fn test(x: &dyn Foo) {
-            foo(x);
-        }
-        "#,
+fn test(x: &dyn Foo) {
+    foo(x);
+}"#,
         expect![[r#"
             21..22 'x': &dyn Foo
             34..36 '{}': ()
@@ -2777,23 +2773,22 @@ fn trait_object_no_coercion() {
 fn builtin_copy() {
     check_infer_with_mismatches(
         r#"
-        #[lang = "copy"]
-        trait Copy {}
+#[lang = "copy"]
+trait Copy {}
 
-        struct IsCopy;
-        impl Copy for IsCopy {}
-        struct NotCopy;
+struct IsCopy;
+impl Copy for IsCopy {}
+struct NotCopy;
 
-        trait Test { fn test(&self) -> bool; }
-        impl<T: Copy> Test for T {}
+trait Test { fn test(&self) -> bool; }
+impl<T: Copy> Test for T {}
 
-        fn test() {
-            IsCopy.test();
-            NotCopy.test();
-            (IsCopy, IsCopy).test();
-            (IsCopy, NotCopy).test();
-        }
-        "#,
+fn test() {
+    IsCopy.test();
+    NotCopy.test();
+    (IsCopy, IsCopy).test();
+    (IsCopy, NotCopy).test();
+}"#,
         expect![[r#"
             110..114 'self': &Self
             166..267 '{     ...t(); }': ()
@@ -2817,24 +2812,23 @@ fn builtin_copy() {
 fn builtin_fn_def_copy() {
     check_infer_with_mismatches(
         r#"
-        #[lang = "copy"]
-        trait Copy {}
+#[lang = "copy"]
+trait Copy {}
 
-        fn foo() {}
-        fn bar<T: Copy>(T) -> T {}
-        struct Struct(usize);
-        enum Enum { Variant(usize) }
+fn foo() {}
+fn bar<T: Copy>(T) -> T {}
+struct Struct(usize);
+enum Enum { Variant(usize) }
 
-        trait Test { fn test(&self) -> bool; }
-        impl<T: Copy> Test for T {}
+trait Test { fn test(&self) -> bool; }
+impl<T: Copy> Test for T {}
 
-        fn test() {
-            foo.test();
-            bar.test();
-            Struct.test();
-            Enum::Variant.test();
-        }
-        "#,
+fn test() {
+    foo.test();
+    bar.test();
+    Struct.test();
+    Enum::Variant.test();
+}"#,
         expect![[r#"
             41..43 '{}': ()
             60..61 'T': {unknown}
@@ -2858,18 +2852,17 @@ fn builtin_fn_def_copy() {
 fn builtin_fn_ptr_copy() {
     check_infer_with_mismatches(
         r#"
-        #[lang = "copy"]
-        trait Copy {}
+#[lang = "copy"]
+trait Copy {}
 
-        trait Test { fn test(&self) -> bool; }
-        impl<T: Copy> Test for T {}
+trait Test { fn test(&self) -> bool; }
+impl<T: Copy> Test for T {}
 
-        fn test(f1: fn(), f2: fn(usize) -> u8, f3: fn(u8, u8) -> &u8) {
-            f1.test();
-            f2.test();
-            f3.test();
-        }
-        "#,
+fn test(f1: fn(), f2: fn(usize) -> u8, f3: fn(u8, u8) -> &u8) {
+    f1.test();
+    f2.test();
+    f3.test();
+}"#,
         expect![[r#"
             54..58 'self': &Self
             108..110 'f1': fn()
@@ -2890,19 +2883,18 @@ fn builtin_fn_ptr_copy() {
 fn builtin_sized() {
     check_infer_with_mismatches(
         r#"
-        #[lang = "sized"]
-        trait Sized {}
+#[lang = "sized"]
+trait Sized {}
 
-        trait Test { fn test(&self) -> bool; }
-        impl<T: Sized> Test for T {}
+trait Test { fn test(&self) -> bool; }
+impl<T: Sized> Test for T {}
 
-        fn test() {
-            1u8.test();
-            (*"foo").test(); // not Sized
-            (1u8, 1u8).test();
-            (1u8, *"foo").test(); // not Sized
-        }
-        "#,
+fn test() {
+    1u8.test();
+    (*"foo").test(); // not Sized
+    (1u8, 1u8).test();
+    (1u8, *"foo").test(); // not Sized
+}"#,
         expect![[r#"
             56..60 'self': &Self
             113..228 '{     ...ized }': ()
@@ -2972,19 +2964,18 @@ impl<A: Step> iter::Iterator for ops::Range<A> {
 fn infer_closure_arg() {
     check_infer(
         r#"
-        //- /lib.rs
+//- /lib.rs
 
-        enum Option<T> {
-            None,
-            Some(T)
-        }
+enum Option<T> {
+    None,
+    Some(T)
+}
 
-        fn foo() {
-            let s = Option::None;
-            let f = |x: Option<i32>| {};
-            (&f)(s)
-        }
-        "#,
+fn foo() {
+    let s = Option::None;
+    let f = |x: Option<i32>| {};
+    (&f)(s)
+}"#,
         expect![[r#"
             52..126 '{     ...)(s) }': ()
             62..63 's': Option<i32>
@@ -3053,46 +3044,45 @@ fn infer_box_fn_arg() {
     // The type mismatch is a bug
     check_infer_with_mismatches(
         r#"
-        //- /lib.rs deps:std
+//- /lib.rs deps:std
 
-        #[lang = "fn_once"]
-        pub trait FnOnce<Args> {
-            type Output;
+#[lang = "fn_once"]
+pub trait FnOnce<Args> {
+    type Output;
 
-            extern "rust-call" fn call_once(self, args: Args) -> Self::Output;
-        }
+    extern "rust-call" fn call_once(self, args: Args) -> Self::Output;
+}
 
-        #[lang = "deref"]
-        pub trait Deref {
-            type Target: ?Sized;
+#[lang = "deref"]
+pub trait Deref {
+    type Target: ?Sized;
 
-            fn deref(&self) -> &Self::Target;
-        }
+    fn deref(&self) -> &Self::Target;
+}
 
-        #[lang = "owned_box"]
-        pub struct Box<T: ?Sized> {
-            inner: *mut T,
-        }
+#[lang = "owned_box"]
+pub struct Box<T: ?Sized> {
+    inner: *mut T,
+}
 
-        impl<T: ?Sized> Deref for Box<T> {
-            type Target = T;
+impl<T: ?Sized> Deref for Box<T> {
+    type Target = T;
 
-            fn deref(&self) -> &T {
-                &self.inner
-            }
-        }
+    fn deref(&self) -> &T {
+        &self.inner
+    }
+}
 
-        enum Option<T> {
-            None,
-            Some(T)
-        }
+enum Option<T> {
+    None,
+    Some(T)
+}
 
-        fn foo() {
-            let s = Option::None;
-            let f: Box<dyn FnOnce(&Option<i32>)> = box (|ps| {});
-            f(&s);
-        }
-        "#,
+fn foo() {
+    let s = Option::None;
+    let f: Box<dyn FnOnce(&Option<i32>)> = box (|ps| {});
+    f(&s);
+}"#,
         expect![[r#"
             100..104 'self': Self
             106..110 'args': Args
@@ -3258,8 +3248,7 @@ fn f() {
         ().method();
       //^^^^^^^^^^^ u8
     }
-}
-        "#,
+}"#,
         expect![[r#"
             46..50 'self': &Self
             58..63 '{ 0 }': u8
@@ -3313,8 +3302,7 @@ fn f() {
     fn inner() -> S {
         let s = inner();
     }
-}
-        "#,
+}"#,
         expect![[r#"
             17..73 '{     ...   } }': ()
             39..71 '{     ...     }': ()
@@ -3349,8 +3337,7 @@ fn test() {
     let x = A;
     let y = A;
     let r = x.do_op(y);
-}
-        "#,
+}"#,
         expect![[r#"
             63..67 'self': Self
             69..72 'rhs': RHS
@@ -3370,3 +3357,120 @@ fn test() {
         "#]],
     )
 }
+
+#[test]
+fn qualified_path_as_qualified_trait() {
+    check_infer(
+        r#"
+mod foo {
+
+    pub trait Foo {
+        type Target;
+    }
+    pub trait Bar {
+        type Output;
+        fn boo() -> Self::Output {
+            loop {}
+        }
+    }
+}
+
+struct F;
+impl foo::Foo for F {
+    type Target = ();
+}
+impl foo::Bar for F {
+    type Output = <F as foo::Foo>::Target;
+}
+
+fn foo() {
+    use foo::Bar;
+    let x = <F as Bar>::boo();
+}"#,
+        expect![[r#"
+            132..163 '{     ...     }': Bar::Output<Self>
+            146..153 'loop {}': !
+            151..153 '{}': ()
+            306..358 '{     ...o(); }': ()
+            334..335 'x': ()
+            338..353 '<F as Bar>::boo': fn boo<F>() -> <F as Bar>::Output
+            338..355 '<F as ...:boo()': ()
+        "#]],
+    );
+}
+
+#[test]
+fn renamed_extern_crate_in_block() {
+    check_types(
+        r#"
+//- /lib.rs crate:lib deps:serde
+use serde::Deserialize;
+
+struct Foo {}
+
+const _ : () = {
+    extern crate serde as _serde;
+    impl _serde::Deserialize for Foo {
+        fn deserialize() -> u8 { 0 }
+    }
+};
+
+fn foo() {
+    Foo::deserialize();
+  //^^^^^^^^^^^^^^^^^^ u8
+}
+
+//- /serde.rs crate:serde
+
+pub trait Deserialize {
+    fn deserialize() -> u8;
+}"#,
+    );
+}
+
+#[test]
+fn bin_op_adt_with_rhs_primitive() {
+    check_infer_with_mismatches(
+        r#"
+#[lang = "add"]
+pub trait Add<Rhs = Self> {
+    type Output;
+    fn add(self, rhs: Rhs) -> Self::Output;
+}
+
+struct Wrapper(u32);
+impl Add<u32> for Wrapper {
+    type Output = Self;
+    fn add(self, rhs: u32) -> Wrapper {
+        Wrapper(rhs)
+    }
+}
+fn main(){
+    let wrapped = Wrapper(10);
+    let num: u32 = 2;
+    let res = wrapped + num;
+
+}"#,
+        expect![[r#"
+            72..76 'self': Self
+            78..81 'rhs': Rhs
+            192..196 'self': Wrapper
+            198..201 'rhs': u32
+            219..247 '{     ...     }': Wrapper
+            229..236 'Wrapper': Wrapper(u32) -> Wrapper
+            229..241 'Wrapper(rhs)': Wrapper
+            237..240 'rhs': u32
+            259..345 '{     ...um;  }': ()
+            269..276 'wrapped': Wrapper
+            279..286 'Wrapper': Wrapper(u32) -> Wrapper
+            279..290 'Wrapper(10)': Wrapper
+            287..289 '10': u32
+            300..303 'num': u32
+            311..312 '2': u32
+            322..325 'res': Wrapper
+            328..335 'wrapped': Wrapper
+            328..341 'wrapped + num': Wrapper
+            338..341 'num': u32
+        "#]],
+    )
+}
diff --git a/crates/hir_ty/src/traits/chalk/tls.rs b/crates/hir_ty/src/tls.rs
index 8892a63a9..87c671a42 100644
--- a/crates/hir_ty/src/traits/chalk/tls.rs
+++ b/crates/hir_ty/src/tls.rs
@@ -4,8 +4,10 @@ use std::fmt;
 use chalk_ir::{AliasTy, GenericArg, Goal, Goals, Lifetime, ProgramClauseImplication};
 use itertools::Itertools;
 
-use super::{from_chalk, Interner};
-use crate::{db::HirDatabase, from_assoc_type_id, CallableDefId};
+use crate::{
+    chalk_db, db::HirDatabase, from_assoc_type_id, from_chalk_trait_id, mapping::from_chalk,
+    CallableDefId, Interner,
+};
 use hir_def::{AdtId, AssocContainerId, Lookup, TypeAliasId};
 
 pub(crate) use unsafe_tls::{set_current_program, with_current_program};
@@ -15,7 +17,7 @@ pub(crate) struct DebugContext<'a>(&'a dyn HirDatabase);
 impl DebugContext<'_> {
     pub(crate) fn debug_struct_id(
         &self,
-        id: super::AdtId,
+        id: chalk_db::AdtId,
         f: &mut fmt::Formatter<'_>,
     ) -> Result<(), fmt::Error> {
         let name = match id.0 {
@@ -28,17 +30,17 @@ impl DebugContext<'_> {
 
     pub(crate) fn debug_trait_id(
         &self,
-        id: super::TraitId,
+        id: chalk_db::TraitId,
         fmt: &mut fmt::Formatter<'_>,
     ) -> Result<(), fmt::Error> {
-        let trait_: hir_def::TraitId = from_chalk(self.0, id);
+        let trait_: hir_def::TraitId = from_chalk_trait_id(id);
         let trait_data = self.0.trait_data(trait_);
         write!(fmt, "{}", trait_data.name)
     }
 
     pub(crate) fn debug_assoc_type_id(
         &self,
-        id: super::AssocTypeId,
+        id: chalk_db::AssocTypeId,
         fmt: &mut fmt::Formatter<'_>,
     ) -> Result<(), fmt::Error> {
         let type_alias: TypeAliasId = from_assoc_type_id(id);
diff --git a/crates/hir_ty/src/traits.rs b/crates/hir_ty/src/traits.rs
index ccee0e5ad..9936d0803 100644
--- a/crates/hir_ty/src/traits.rs
+++ b/crates/hir_ty/src/traits.rs
@@ -1,28 +1,26 @@
 //! Trait solving using Chalk.
+
 use std::env::var;
 
-use base_db::CrateId;
 use chalk_ir::cast::Cast;
 use chalk_solve::{logging_db::LoggingRustIrDatabase, Solver};
+
+use base_db::CrateId;
 use hir_def::{lang_item::LangItemTarget, TraitId};
 use stdx::panic_context;
 
 use crate::{
-    db::HirDatabase, AliasTy, Canonical, DebruijnIndex, HirDisplay, Substitution, Ty, TyKind,
-    TypeWalk, WhereClause,
+    db::HirDatabase, AliasEq, AliasTy, Canonical, DomainGoal, Guidance, HirDisplay, InEnvironment,
+    Interner, Solution, TraitRefExt, Ty, TyKind, WhereClause,
 };
 
-use self::chalk::{from_chalk, Interner, ToChalk};
-
-pub(crate) mod chalk;
-
 /// This controls how much 'time' we give the Chalk solver before giving up.
 const CHALK_SOLVER_FUEL: i32 = 100;
 
 #[derive(Debug, Copy, Clone)]
-struct ChalkContext<'a> {
-    db: &'a dyn HirDatabase,
-    krate: CrateId,
+pub(crate) struct ChalkContext<'a> {
+    pub(crate) db: &'a dyn HirDatabase,
+    pub(crate) krate: CrateId,
 }
 
 fn create_chalk_solver() -> chalk_recursive::RecursiveSolver<Interner> {
@@ -70,55 +68,6 @@ impl Default for TraitEnvironment {
     }
 }
 
-/// Something (usually a goal), along with an environment.
-#[derive(Clone, Debug, PartialEq, Eq, Hash)]
-pub struct InEnvironment<T> {
-    pub environment: chalk_ir::Environment<Interner>,
-    pub goal: T,
-}
-
-impl<T> InEnvironment<T> {
-    pub fn new(environment: chalk_ir::Environment<Interner>, value: T) -> InEnvironment<T> {
-        InEnvironment { environment, goal: value }
-    }
-}
-
-/// Something that needs to be proven (by Chalk) during type checking, e.g. that
-/// a certain type implements a certain trait. Proving the Obligation might
-/// result in additional information about inference variables.
-#[derive(Clone, Debug, PartialEq, Eq, Hash)]
-pub enum DomainGoal {
-    Holds(WhereClause),
-}
-
-#[derive(Clone, Debug, PartialEq, Eq, Hash)]
-pub struct AliasEq {
-    pub alias: AliasTy,
-    pub ty: Ty,
-}
-
-impl TypeWalk for AliasEq {
-    fn walk(&self, f: &mut impl FnMut(&Ty)) {
-        self.ty.walk(f);
-        match &self.alias {
-            AliasTy::Projection(projection_ty) => projection_ty.walk(f),
-            AliasTy::Opaque(opaque) => opaque.walk(f),
-        }
-    }
-
-    fn walk_mut_binders(
-        &mut self,
-        f: &mut impl FnMut(&mut Ty, DebruijnIndex),
-        binders: DebruijnIndex,
-    ) {
-        self.ty.walk_mut_binders(f, binders);
-        match &mut self.alias {
-            AliasTy::Projection(projection_ty) => projection_ty.walk_mut_binders(f, binders),
-            AliasTy::Opaque(opaque) => opaque.walk_mut_binders(f, binders),
-        }
-    }
-}
-
 /// Solve a trait goal using Chalk.
 pub(crate) fn trait_solve_query(
     db: &dyn HirDatabase,
@@ -130,6 +79,7 @@ pub(crate) fn trait_solve_query(
             db.trait_data(it.hir_trait_id()).name.to_string()
         }
         DomainGoal::Holds(WhereClause::AliasEq(_)) => "alias_eq".to_string(),
+        _ => "??".to_string(),
     });
     log::info!("trait_solve_query({})", goal.value.goal.display(db));
 
@@ -138,19 +88,18 @@ pub(crate) fn trait_solve_query(
         ..
     })) = &goal.value.goal
     {
-        if let TyKind::BoundVar(_) = &projection_ty.substitution[0].interned(&Interner) {
+        if let TyKind::BoundVar(_) = projection_ty.self_type_parameter(&Interner).kind(&Interner) {
             // Hack: don't ask Chalk to normalize with an unknown self type, it'll say that's impossible
             return Some(Solution::Ambig(Guidance::Unknown));
         }
     }
 
-    let canonical = goal.to_chalk(db).cast(&Interner);
+    let canonical = goal.cast(&Interner);
 
     // We currently don't deal with universes (I think / hope they're not yet
     // relevant for our use cases?)
     let u_canonical = chalk_ir::UCanonical { canonical, universes: 1 };
-    let solution = solve(db, krate, &u_canonical);
-    solution.map(|solution| solution_from_chalk(db, solution))
+    solve(db, krate, &u_canonical)
 }
 
 fn solve(
@@ -197,7 +146,7 @@ fn solve(
     // don't set the TLS for Chalk unless Chalk debugging is active, to make
     // extra sure we only use it for debugging
     let solution =
-        if is_chalk_debug() { chalk::tls::set_current_program(db, solve) } else { solve() };
+        if is_chalk_debug() { crate::tls::set_current_program(db, solve) } else { solve() };
 
     solution
 }
@@ -218,69 +167,6 @@ fn is_chalk_print() -> bool {
     std::env::var("CHALK_PRINT").is_ok()
 }
 
-fn solution_from_chalk(
-    db: &dyn HirDatabase,
-    solution: chalk_solve::Solution<Interner>,
-) -> Solution {
-    let convert_subst = |subst: chalk_ir::Canonical<chalk_ir::Substitution<Interner>>| {
-        let result = from_chalk(db, subst);
-        SolutionVariables(result)
-    };
-    match solution {
-        chalk_solve::Solution::Unique(constr_subst) => {
-            let subst = chalk_ir::Canonical {
-                value: constr_subst.value.subst,
-                binders: constr_subst.binders,
-            };
-            Solution::Unique(convert_subst(subst))
-        }
-        chalk_solve::Solution::Ambig(chalk_solve::Guidance::Definite(subst)) => {
-            Solution::Ambig(Guidance::Definite(convert_subst(subst)))
-        }
-        chalk_solve::Solution::Ambig(chalk_solve::Guidance::Suggested(subst)) => {
-            Solution::Ambig(Guidance::Suggested(convert_subst(subst)))
-        }
-        chalk_solve::Solution::Ambig(chalk_solve::Guidance::Unknown) => {
-            Solution::Ambig(Guidance::Unknown)
-        }
-    }
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct SolutionVariables(pub Canonical<Substitution>);
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-/// A (possible) solution for a proposed goal.
-pub enum Solution {
-    /// The goal indeed holds, and there is a unique value for all existential
-    /// variables.
-    Unique(SolutionVariables),
-
-    /// The goal may be provable in multiple ways, but regardless we may have some guidance
-    /// for type inference. In this case, we don't return any lifetime
-    /// constraints, since we have not "committed" to any particular solution
-    /// yet.
-    Ambig(Guidance),
-}
-
-#[derive(Clone, Debug, PartialEq, Eq)]
-/// When a goal holds ambiguously (e.g., because there are multiple possible
-/// solutions), we issue a set of *guidance* back to type inference.
-pub enum Guidance {
-    /// The existential variables *must* have the given values if the goal is
-    /// ever to hold, but that alone isn't enough to guarantee the goal will
-    /// actually hold.
-    Definite(SolutionVariables),
-
-    /// There are multiple plausible values for the existentials, but the ones
-    /// here are suggested as the preferred choice heuristically. These should
-    /// be used for inference fallback only.
-    Suggested(SolutionVariables),
-
-    /// There's no useful information to feed back to type inference
-    Unknown,
-}
-
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
 pub enum FnTrait {
     FnOnce,
diff --git a/crates/hir_ty/src/traits/chalk/mapping.rs b/crates/hir_ty/src/traits/chalk/mapping.rs
deleted file mode 100644
index aef6b8a15..000000000
--- a/crates/hir_ty/src/traits/chalk/mapping.rs
+++ /dev/null
@@ -1,560 +0,0 @@
-//! This module contains the implementations of the `ToChalk` trait, which
-//! handles conversion between our data types and their corresponding types in
-//! Chalk (in both directions); plus some helper functions for more specialized
-//! conversions.
-
-use chalk_ir::{cast::Cast, fold::shift::Shift, interner::HasInterner, LifetimeData};
-use chalk_solve::rust_ir;
-
-use base_db::salsa::InternKey;
-use hir_def::{GenericDefId, TypeAliasId};
-
-use crate::{
-    db::HirDatabase,
-    primitive::UintTy,
-    traits::{Canonical, DomainGoal},
-    AliasTy, CallableDefId, FnPointer, InEnvironment, OpaqueTy, ProjectionTy,
-    QuantifiedWhereClause, Scalar, Substitution, TraitRef, Ty, TypeWalk, WhereClause,
-};
-
-use super::interner::*;
-use super::*;
-
-impl ToChalk for Ty {
-    type Chalk = chalk_ir::Ty<Interner>;
-    fn to_chalk(self, db: &dyn HirDatabase) -> chalk_ir::Ty<Interner> {
-        match self.into_inner() {
-            TyKind::Ref(m, ty) => ref_to_chalk(db, m, ty),
-            TyKind::Array(ty) => array_to_chalk(db, ty),
-            TyKind::Function(FnPointer { sig, substs, .. }) => {
-                let substitution = chalk_ir::FnSubst(substs.to_chalk(db).shifted_in(&Interner));
-                chalk_ir::TyKind::Function(chalk_ir::FnPointer {
-                    num_binders: 0,
-                    sig,
-                    substitution,
-                })
-                .intern(&Interner)
-            }
-            TyKind::AssociatedType(assoc_type_id, substs) => {
-                let substitution = substs.to_chalk(db);
-                chalk_ir::TyKind::AssociatedType(assoc_type_id, substitution).intern(&Interner)
-            }
-
-            TyKind::OpaqueType(id, substs) => {
-                let substitution = substs.to_chalk(db);
-                chalk_ir::TyKind::OpaqueType(id, substitution).intern(&Interner)
-            }
-
-            TyKind::ForeignType(id) => chalk_ir::TyKind::Foreign(id).intern(&Interner),
-
-            TyKind::Scalar(scalar) => chalk_ir::TyKind::Scalar(scalar).intern(&Interner),
-
-            TyKind::Tuple(cardinality, substs) => {
-                let substitution = substs.to_chalk(db);
-                chalk_ir::TyKind::Tuple(cardinality, substitution).intern(&Interner)
-            }
-            TyKind::Raw(mutability, ty) => {
-                let ty = ty.to_chalk(db);
-                chalk_ir::TyKind::Raw(mutability, ty).intern(&Interner)
-            }
-            TyKind::Slice(ty) => chalk_ir::TyKind::Slice(ty.to_chalk(db)).intern(&Interner),
-            TyKind::Str => chalk_ir::TyKind::Str.intern(&Interner),
-            TyKind::FnDef(id, substs) => {
-                let substitution = substs.to_chalk(db);
-                chalk_ir::TyKind::FnDef(id, substitution).intern(&Interner)
-            }
-            TyKind::Never => chalk_ir::TyKind::Never.intern(&Interner),
-
-            TyKind::Closure(closure_id, substs) => {
-                let substitution = substs.to_chalk(db);
-                chalk_ir::TyKind::Closure(closure_id, substitution).intern(&Interner)
-            }
-
-            TyKind::Adt(adt_id, substs) => {
-                let substitution = substs.to_chalk(db);
-                chalk_ir::TyKind::Adt(adt_id, substitution).intern(&Interner)
-            }
-            TyKind::Alias(AliasTy::Projection(proj_ty)) => {
-                let associated_ty_id = proj_ty.associated_ty_id;
-                let substitution = proj_ty.substitution.to_chalk(db);
-                chalk_ir::AliasTy::Projection(chalk_ir::ProjectionTy {
-                    associated_ty_id,
-                    substitution,
-                })
-                .cast(&Interner)
-                .intern(&Interner)
-            }
-            TyKind::Alias(AliasTy::Opaque(opaque_ty)) => {
-                let opaque_ty_id = opaque_ty.opaque_ty_id;
-                let substitution = opaque_ty.substitution.to_chalk(db);
-                chalk_ir::AliasTy::Opaque(chalk_ir::OpaqueTy { opaque_ty_id, substitution })
-                    .cast(&Interner)
-                    .intern(&Interner)
-            }
-            TyKind::Placeholder(idx) => idx.to_ty::<Interner>(&Interner),
-            TyKind::BoundVar(idx) => chalk_ir::TyKind::BoundVar(idx).intern(&Interner),
-            TyKind::InferenceVar(..) => panic!("uncanonicalized infer ty"),
-            TyKind::Dyn(dyn_ty) => {
-                let where_clauses = chalk_ir::QuantifiedWhereClauses::from_iter(
-                    &Interner,
-                    dyn_ty.bounds.value.interned().iter().cloned().map(|p| p.to_chalk(db)),
-                );
-                let bounded_ty = chalk_ir::DynTy {
-                    bounds: make_binders(where_clauses, 1),
-                    lifetime: LifetimeData::Static.intern(&Interner),
-                };
-                chalk_ir::TyKind::Dyn(bounded_ty).intern(&Interner)
-            }
-            TyKind::Unknown => chalk_ir::TyKind::Error.intern(&Interner),
-        }
-    }
-    fn from_chalk(db: &dyn HirDatabase, chalk: chalk_ir::Ty<Interner>) -> Self {
-        match chalk.data(&Interner).kind.clone() {
-            chalk_ir::TyKind::Error => TyKind::Unknown,
-            chalk_ir::TyKind::Array(ty, _size) => TyKind::Array(from_chalk(db, ty)),
-            chalk_ir::TyKind::Placeholder(idx) => TyKind::Placeholder(idx),
-            chalk_ir::TyKind::Alias(chalk_ir::AliasTy::Projection(proj)) => {
-                let associated_ty = proj.associated_ty_id;
-                let parameters = from_chalk(db, proj.substitution);
-                TyKind::Alias(AliasTy::Projection(ProjectionTy {
-                    associated_ty_id: associated_ty,
-                    substitution: parameters,
-                }))
-            }
-            chalk_ir::TyKind::Alias(chalk_ir::AliasTy::Opaque(opaque_ty)) => {
-                let opaque_ty_id = opaque_ty.opaque_ty_id;
-                let parameters = from_chalk(db, opaque_ty.substitution);
-                TyKind::Alias(AliasTy::Opaque(OpaqueTy { opaque_ty_id, substitution: parameters }))
-            }
-            chalk_ir::TyKind::Function(chalk_ir::FnPointer {
-                num_binders,
-                sig,
-                substitution,
-                ..
-            }) => {
-                assert_eq!(num_binders, 0);
-                let substs: Substitution = from_chalk(
-                    db,
-                    substitution.0.shifted_out(&Interner).expect("fn ptr should have no binders"),
-                );
-                TyKind::Function(FnPointer { num_args: (substs.len() - 1), sig, substs })
-            }
-            chalk_ir::TyKind::BoundVar(idx) => TyKind::BoundVar(idx),
-            chalk_ir::TyKind::InferenceVar(_iv, _kind) => TyKind::Unknown,
-            chalk_ir::TyKind::Dyn(where_clauses) => {
-                assert_eq!(where_clauses.bounds.binders.len(&Interner), 1);
-                let bounds = where_clauses
-                    .bounds
-                    .skip_binders()
-                    .iter(&Interner)
-                    .map(|c| from_chalk(db, c.clone()));
-                TyKind::Dyn(crate::DynTy {
-                    bounds: crate::Binders::new(
-                        1,
-                        crate::QuantifiedWhereClauses::from_iter(&Interner, bounds),
-                    ),
-                })
-            }
-
-            chalk_ir::TyKind::Adt(adt_id, subst) => TyKind::Adt(adt_id, from_chalk(db, subst)),
-            chalk_ir::TyKind::AssociatedType(type_id, subst) => {
-                TyKind::AssociatedType(type_id, from_chalk(db, subst))
-            }
-
-            chalk_ir::TyKind::OpaqueType(opaque_type_id, subst) => {
-                TyKind::OpaqueType(opaque_type_id, from_chalk(db, subst))
-            }
-
-            chalk_ir::TyKind::Scalar(scalar) => TyKind::Scalar(scalar),
-            chalk_ir::TyKind::Tuple(cardinality, subst) => {
-                TyKind::Tuple(cardinality, from_chalk(db, subst))
-            }
-            chalk_ir::TyKind::Raw(mutability, ty) => TyKind::Raw(mutability, from_chalk(db, ty)),
-            chalk_ir::TyKind::Slice(ty) => TyKind::Slice(from_chalk(db, ty)),
-            chalk_ir::TyKind::Ref(mutability, _lifetime, ty) => {
-                TyKind::Ref(mutability, from_chalk(db, ty))
-            }
-            chalk_ir::TyKind::Str => TyKind::Str,
-            chalk_ir::TyKind::Never => TyKind::Never,
-
-            chalk_ir::TyKind::FnDef(fn_def_id, subst) => {
-                TyKind::FnDef(fn_def_id, from_chalk(db, subst))
-            }
-
-            chalk_ir::TyKind::Closure(id, subst) => TyKind::Closure(id, from_chalk(db, subst)),
-
-            chalk_ir::TyKind::Foreign(foreign_def_id) => TyKind::ForeignType(foreign_def_id),
-            chalk_ir::TyKind::Generator(_, _) => unimplemented!(), // FIXME
-            chalk_ir::TyKind::GeneratorWitness(_, _) => unimplemented!(), // FIXME
-        }
-        .intern(&Interner)
-    }
-}
-
-/// We currently don't model lifetimes, but Chalk does. So, we have to insert a
-/// fake lifetime here, because Chalks built-in logic may expect it to be there.
-fn ref_to_chalk(
-    db: &dyn HirDatabase,
-    mutability: chalk_ir::Mutability,
-    ty: Ty,
-) -> chalk_ir::Ty<Interner> {
-    let arg = ty.to_chalk(db);
-    let lifetime = LifetimeData::Static.intern(&Interner);
-    chalk_ir::TyKind::Ref(mutability, lifetime, arg).intern(&Interner)
-}
-
-/// We currently don't model constants, but Chalk does. So, we have to insert a
-/// fake constant here, because Chalks built-in logic may expect it to be there.
-fn array_to_chalk(db: &dyn HirDatabase, ty: Ty) -> chalk_ir::Ty<Interner> {
-    let arg = ty.to_chalk(db);
-    let usize_ty = chalk_ir::TyKind::Scalar(Scalar::Uint(UintTy::Usize)).intern(&Interner);
-    let const_ = chalk_ir::ConstData {
-        ty: usize_ty,
-        value: chalk_ir::ConstValue::Concrete(chalk_ir::ConcreteConst { interned: () }),
-    }
-    .intern(&Interner);
-    chalk_ir::TyKind::Array(arg, const_).intern(&Interner)
-}
-
-impl ToChalk for Substitution {
-    type Chalk = chalk_ir::Substitution<Interner>;
-
-    fn to_chalk(self, db: &dyn HirDatabase) -> chalk_ir::Substitution<Interner> {
-        chalk_ir::Substitution::from_iter(&Interner, self.iter().map(|ty| ty.clone().to_chalk(db)))
-    }
-
-    fn from_chalk(
-        db: &dyn HirDatabase,
-        parameters: chalk_ir::Substitution<Interner>,
-    ) -> Substitution {
-        let tys = parameters
-            .iter(&Interner)
-            .map(|p| match p.ty(&Interner) {
-                Some(ty) => from_chalk(db, ty.clone()),
-                None => unimplemented!(),
-            })
-            .collect();
-        Substitution(tys)
-    }
-}
-
-impl ToChalk for TraitRef {
-    type Chalk = chalk_ir::TraitRef<Interner>;
-
-    fn to_chalk(self: TraitRef, db: &dyn HirDatabase) -> chalk_ir::TraitRef<Interner> {
-        let trait_id = self.trait_id;
-        let substitution = self.substitution.to_chalk(db);
-        chalk_ir::TraitRef { trait_id, substitution }
-    }
-
-    fn from_chalk(db: &dyn HirDatabase, trait_ref: chalk_ir::TraitRef<Interner>) -> Self {
-        let trait_id = trait_ref.trait_id;
-        let substs = from_chalk(db, trait_ref.substitution);
-        TraitRef { trait_id, substitution: substs }
-    }
-}
-
-impl ToChalk for hir_def::TraitId {
-    type Chalk = TraitId;
-
-    fn to_chalk(self, _db: &dyn HirDatabase) -> TraitId {
-        chalk_ir::TraitId(self.as_intern_id())
-    }
-
-    fn from_chalk(_db: &dyn HirDatabase, trait_id: TraitId) -> hir_def::TraitId {
-        InternKey::from_intern_id(trait_id.0)
-    }
-}
-
-impl ToChalk for hir_def::ImplId {
-    type Chalk = ImplId;
-
-    fn to_chalk(self, _db: &dyn HirDatabase) -> ImplId {
-        chalk_ir::ImplId(self.as_intern_id())
-    }
-
-    fn from_chalk(_db: &dyn HirDatabase, impl_id: ImplId) -> hir_def::ImplId {
-        InternKey::from_intern_id(impl_id.0)
-    }
-}
-
-impl ToChalk for CallableDefId {
-    type Chalk = FnDefId;
-
-    fn to_chalk(self, db: &dyn HirDatabase) -> FnDefId {
-        db.intern_callable_def(self).into()
-    }
-
-    fn from_chalk(db: &dyn HirDatabase, fn_def_id: FnDefId) -> CallableDefId {
-        db.lookup_intern_callable_def(fn_def_id.into())
-    }
-}
-
-pub(crate) struct TypeAliasAsValue(pub(crate) TypeAliasId);
-
-impl ToChalk for TypeAliasAsValue {
-    type Chalk = AssociatedTyValueId;
-
-    fn to_chalk(self, _db: &dyn HirDatabase) -> AssociatedTyValueId {
-        rust_ir::AssociatedTyValueId(self.0.as_intern_id())
-    }
-
-    fn from_chalk(
-        _db: &dyn HirDatabase,
-        assoc_ty_value_id: AssociatedTyValueId,
-    ) -> TypeAliasAsValue {
-        TypeAliasAsValue(TypeAliasId::from_intern_id(assoc_ty_value_id.0))
-    }
-}
-
-impl ToChalk for WhereClause {
-    type Chalk = chalk_ir::WhereClause<Interner>;
-
-    fn to_chalk(self, db: &dyn HirDatabase) -> chalk_ir::WhereClause<Interner> {
-        match self {
-            WhereClause::Implemented(trait_ref) => {
-                chalk_ir::WhereClause::Implemented(trait_ref.to_chalk(db))
-            }
-            WhereClause::AliasEq(alias_eq) => chalk_ir::WhereClause::AliasEq(alias_eq.to_chalk(db)),
-        }
-    }
-
-    fn from_chalk(
-        db: &dyn HirDatabase,
-        where_clause: chalk_ir::WhereClause<Interner>,
-    ) -> WhereClause {
-        match where_clause {
-            chalk_ir::WhereClause::Implemented(tr) => WhereClause::Implemented(from_chalk(db, tr)),
-            chalk_ir::WhereClause::AliasEq(alias_eq) => {
-                WhereClause::AliasEq(from_chalk(db, alias_eq))
-            }
-
-            chalk_ir::WhereClause::LifetimeOutlives(_) => {
-                // we shouldn't get these from Chalk
-                panic!("encountered LifetimeOutlives from Chalk")
-            }
-
-            chalk_ir::WhereClause::TypeOutlives(_) => {
-                // we shouldn't get these from Chalk
-                panic!("encountered TypeOutlives from Chalk")
-            }
-        }
-    }
-}
-
-impl ToChalk for ProjectionTy {
-    type Chalk = chalk_ir::ProjectionTy<Interner>;
-
-    fn to_chalk(self, db: &dyn HirDatabase) -> chalk_ir::ProjectionTy<Interner> {
-        chalk_ir::ProjectionTy {
-            associated_ty_id: self.associated_ty_id,
-            substitution: self.substitution.to_chalk(db),
-        }
-    }
-
-    fn from_chalk(
-        db: &dyn HirDatabase,
-        projection_ty: chalk_ir::ProjectionTy<Interner>,
-    ) -> ProjectionTy {
-        ProjectionTy {
-            associated_ty_id: projection_ty.associated_ty_id,
-            substitution: from_chalk(db, projection_ty.substitution),
-        }
-    }
-}
-impl ToChalk for OpaqueTy {
-    type Chalk = chalk_ir::OpaqueTy<Interner>;
-
-    fn to_chalk(self, db: &dyn HirDatabase) -> Self::Chalk {
-        chalk_ir::OpaqueTy {
-            opaque_ty_id: self.opaque_ty_id,
-            substitution: self.substitution.to_chalk(db),
-        }
-    }
-
-    fn from_chalk(db: &dyn HirDatabase, chalk: Self::Chalk) -> Self {
-        OpaqueTy {
-            opaque_ty_id: chalk.opaque_ty_id,
-            substitution: from_chalk(db, chalk.substitution),
-        }
-    }
-}
-
-impl ToChalk for AliasTy {
-    type Chalk = chalk_ir::AliasTy<Interner>;
-
-    fn to_chalk(self, db: &dyn HirDatabase) -> Self::Chalk {
-        match self {
-            AliasTy::Projection(projection_ty) => {
-                chalk_ir::AliasTy::Projection(projection_ty.to_chalk(db))
-            }
-            AliasTy::Opaque(opaque_ty) => chalk_ir::AliasTy::Opaque(opaque_ty.to_chalk(db)),
-        }
-    }
-
-    fn from_chalk(db: &dyn HirDatabase, chalk: Self::Chalk) -> Self {
-        match chalk {
-            chalk_ir::AliasTy::Projection(projection_ty) => {
-                AliasTy::Projection(from_chalk(db, projection_ty))
-            }
-            chalk_ir::AliasTy::Opaque(opaque_ty) => AliasTy::Opaque(from_chalk(db, opaque_ty)),
-        }
-    }
-}
-
-impl ToChalk for AliasEq {
-    type Chalk = chalk_ir::AliasEq<Interner>;
-
-    fn to_chalk(self, db: &dyn HirDatabase) -> chalk_ir::AliasEq<Interner> {
-        chalk_ir::AliasEq { alias: self.alias.to_chalk(db), ty: self.ty.to_chalk(db) }
-    }
-
-    fn from_chalk(db: &dyn HirDatabase, alias_eq: chalk_ir::AliasEq<Interner>) -> Self {
-        AliasEq { alias: from_chalk(db, alias_eq.alias), ty: from_chalk(db, alias_eq.ty) }
-    }
-}
-
-impl ToChalk for DomainGoal {
-    type Chalk = chalk_ir::DomainGoal<Interner>;
-
-    fn to_chalk(self, db: &dyn HirDatabase) -> chalk_ir::DomainGoal<Interner> {
-        match self {
-            DomainGoal::Holds(WhereClause::Implemented(tr)) => tr.to_chalk(db).cast(&Interner),
-            DomainGoal::Holds(WhereClause::AliasEq(alias_eq)) => {
-                alias_eq.to_chalk(db).cast(&Interner)
-            }
-        }
-    }
-
-    fn from_chalk(_db: &dyn HirDatabase, _goal: chalk_ir::DomainGoal<Interner>) -> Self {
-        unimplemented!()
-    }
-}
-
-impl<T> ToChalk for Canonical<T>
-where
-    T: ToChalk,
-    T::Chalk: HasInterner<Interner = Interner>,
-{
-    type Chalk = chalk_ir::Canonical<T::Chalk>;
-
-    fn to_chalk(self, db: &dyn HirDatabase) -> chalk_ir::Canonical<T::Chalk> {
-        let value = self.value.to_chalk(db);
-        chalk_ir::Canonical { value, binders: self.binders }
-    }
-
-    fn from_chalk(db: &dyn HirDatabase, canonical: chalk_ir::Canonical<T::Chalk>) -> Canonical<T> {
-        Canonical { binders: canonical.binders, value: from_chalk(db, canonical.value) }
-    }
-}
-
-impl<T: ToChalk> ToChalk for InEnvironment<T>
-where
-    T::Chalk: chalk_ir::interner::HasInterner<Interner = Interner>,
-{
-    type Chalk = chalk_ir::InEnvironment<T::Chalk>;
-
-    fn to_chalk(self, db: &dyn HirDatabase) -> chalk_ir::InEnvironment<T::Chalk> {
-        chalk_ir::InEnvironment { environment: self.environment, goal: self.goal.to_chalk(db) }
-    }
-
-    fn from_chalk(
-        _db: &dyn HirDatabase,
-        _in_env: chalk_ir::InEnvironment<T::Chalk>,
-    ) -> InEnvironment<T> {
-        unimplemented!()
-    }
-}
-
-impl<T: ToChalk> ToChalk for crate::Binders<T>
-where
-    T::Chalk: chalk_ir::interner::HasInterner<Interner = Interner>,
-{
-    type Chalk = chalk_ir::Binders<T::Chalk>;
-
-    fn to_chalk(self, db: &dyn HirDatabase) -> chalk_ir::Binders<T::Chalk> {
-        chalk_ir::Binders::new(
-            chalk_ir::VariableKinds::from_iter(
-                &Interner,
-                std::iter::repeat(chalk_ir::VariableKind::Ty(chalk_ir::TyVariableKind::General))
-                    .take(self.num_binders),
-            ),
-            self.value.to_chalk(db),
-        )
-    }
-
-    fn from_chalk(db: &dyn HirDatabase, binders: chalk_ir::Binders<T::Chalk>) -> crate::Binders<T> {
-        let (v, b) = binders.into_value_and_skipped_binders();
-        crate::Binders::new(b.len(&Interner), from_chalk(db, v))
-    }
-}
-
-pub(super) fn make_binders<T>(value: T, num_vars: usize) -> chalk_ir::Binders<T>
-where
-    T: HasInterner<Interner = Interner>,
-{
-    chalk_ir::Binders::new(
-        chalk_ir::VariableKinds::from_iter(
-            &Interner,
-            std::iter::repeat(chalk_ir::VariableKind::Ty(chalk_ir::TyVariableKind::General))
-                .take(num_vars),
-        ),
-        value,
-    )
-}
-
-pub(super) fn convert_where_clauses(
-    db: &dyn HirDatabase,
-    def: GenericDefId,
-    substs: &Substitution,
-) -> Vec<chalk_ir::QuantifiedWhereClause<Interner>> {
-    let generic_predicates = db.generic_predicates(def);
-    let mut result = Vec::with_capacity(generic_predicates.len());
-    for pred in generic_predicates.iter() {
-        result.push(pred.clone().subst(substs).to_chalk(db));
-    }
-    result
-}
-
-pub(super) fn generic_predicate_to_inline_bound(
-    db: &dyn HirDatabase,
-    pred: &QuantifiedWhereClause,
-    self_ty: &Ty,
-) -> Option<chalk_ir::Binders<rust_ir::InlineBound<Interner>>> {
-    // An InlineBound is like a GenericPredicate, except the self type is left out.
-    // We don't have a special type for this, but Chalk does.
-    let self_ty_shifted_in = self_ty.clone().shift_bound_vars(DebruijnIndex::ONE);
-    match &pred.value {
-        WhereClause::Implemented(trait_ref) => {
-            if trait_ref.self_type_parameter() != &self_ty_shifted_in {
-                // we can only convert predicates back to type bounds if they
-                // have the expected self type
-                return None;
-            }
-            let args_no_self = trait_ref.substitution[1..]
-                .iter()
-                .map(|ty| ty.clone().to_chalk(db).cast(&Interner))
-                .collect();
-            let trait_bound = rust_ir::TraitBound { trait_id: trait_ref.trait_id, args_no_self };
-            Some(make_binders(rust_ir::InlineBound::TraitBound(trait_bound), pred.num_binders))
-        }
-        WhereClause::AliasEq(AliasEq { alias: AliasTy::Projection(projection_ty), ty }) => {
-            if projection_ty.self_type_parameter() != &self_ty_shifted_in {
-                return None;
-            }
-            let trait_ = projection_ty.trait_(db);
-            let args_no_self = projection_ty.substitution[1..]
-                .iter()
-                .map(|ty| ty.clone().to_chalk(db).cast(&Interner))
-                .collect();
-            let alias_eq_bound = rust_ir::AliasEqBound {
-                value: ty.clone().to_chalk(db),
-                trait_bound: rust_ir::TraitBound { trait_id: trait_.to_chalk(db), args_no_self },
-                associated_ty_id: projection_ty.associated_ty_id,
-                parameters: Vec::new(), // FIXME we don't support generic associated types yet
-            };
-            Some(make_binders(rust_ir::InlineBound::AliasEqBound(alias_eq_bound), pred.num_binders))
-        }
-        _ => None,
-    }
-}
diff --git a/crates/hir_ty/src/utils.rs b/crates/hir_ty/src/utils.rs
index 42d7af146..2f04ee57a 100644
--- a/crates/hir_ty/src/utils.rs
+++ b/crates/hir_ty/src/utils.rs
@@ -1,22 +1,21 @@
 //! Helper functions for working with def, which don't need to be a separate
 //! query, but can't be computed directly from `*Data` (ie, which need a `db`).
-use std::sync::Arc;
 
-use chalk_ir::DebruijnIndex;
+use chalk_ir::{fold::Shift, BoundVar, DebruijnIndex};
 use hir_def::{
-    adt::VariantData,
     db::DefDatabase,
     generics::{
         GenericParams, TypeParamData, TypeParamProvenance, WherePredicate, WherePredicateTypeTarget,
     },
+    intern::Interned,
     path::Path,
     resolver::{HasResolver, TypeNs},
     type_ref::TypeRef,
-    AssocContainerId, GenericDefId, Lookup, TraitId, TypeAliasId, TypeParamId, VariantId,
+    AssocContainerId, GenericDefId, Lookup, TraitId, TypeAliasId, TypeParamId,
 };
 use hir_expand::name::{name, Name};
 
-use crate::{db::HirDatabase, TraitRef, TypeWalk, WhereClause};
+use crate::{db::HirDatabase, Interner, Substitution, TraitRef, TraitRefExt, TyKind, WhereClause};
 
 fn direct_super_traits(db: &dyn DefDatabase, trait_: TraitId) -> Vec<TraitId> {
     let resolver = trait_.resolver(db);
@@ -32,11 +31,10 @@ fn direct_super_traits(db: &dyn DefDatabase, trait_: TraitId) -> Vec<TraitId> {
         .filter_map(|pred| match pred {
             WherePredicate::ForLifetime { target, bound, .. }
             | WherePredicate::TypeBound { target, bound } => match target {
-                WherePredicateTypeTarget::TypeRef(TypeRef::Path(p))
-                    if p == &Path::from(name![Self]) =>
-                {
-                    bound.as_path()
-                }
+                WherePredicateTypeTarget::TypeRef(type_ref) => match &**type_ref {
+                    TypeRef::Path(p) if p == &Path::from(name![Self]) => bound.as_path(),
+                    _ => None,
+                },
                 WherePredicateTypeTarget::TypeParam(local_id) if Some(*local_id) == trait_self => {
                     bound.as_path()
                 }
@@ -66,19 +64,21 @@ fn direct_super_trait_refs(db: &dyn HirDatabase, trait_ref: &TraitRef) -> Vec<Tr
         .filter_map(|pred| {
             pred.as_ref().filter_map(|pred| match pred.skip_binders() {
                 // FIXME: how to correctly handle higher-ranked bounds here?
-                WhereClause::Implemented(tr) => {
-                    Some(tr.clone().shift_bound_vars_out(DebruijnIndex::ONE))
-                }
+                WhereClause::Implemented(tr) => Some(
+                    tr.clone()
+                        .shifted_out_to(&Interner, DebruijnIndex::ONE)
+                        .expect("FIXME unexpected higher-ranked trait bound"),
+                ),
                 _ => None,
             })
         })
-        .map(|pred| pred.subst(&trait_ref.substitution))
+        .map(|pred| pred.substitute(&Interner, &trait_ref.substitution))
         .collect()
 }
 
 /// Returns an iterator over the whole super trait hierarchy (including the
 /// trait itself).
-pub(super) fn all_super_traits(db: &dyn DefDatabase, trait_: TraitId) -> Vec<TraitId> {
+pub fn all_super_traits(db: &dyn DefDatabase, trait_: TraitId) -> Vec<TraitId> {
     // we need to take care a bit here to avoid infinite loops in case of cycles
     // (i.e. if we have `trait A: B; trait B: A;`)
     let mut result = vec![trait_];
@@ -103,6 +103,8 @@ pub(super) fn all_super_traits(db: &dyn DefDatabase, trait_: TraitId) -> Vec<Tra
 /// we have `Self: Trait<u32, i32>` and `Trait<T, U>: OtherTrait<U>` we'll get
 /// `Self: OtherTrait<i32>`.
 pub(super) fn all_super_trait_refs(db: &dyn HirDatabase, trait_ref: TraitRef) -> Vec<TraitRef> {
+    // FIXME: replace by Chalk's `super_traits`, maybe make this a query
+
     // we need to take care a bit here to avoid infinite loops in case of cycles
     // (i.e. if we have `trait A: B; trait B: A;`)
     let mut result = vec![trait_ref];
@@ -132,25 +134,6 @@ pub(super) fn associated_type_by_name_including_super_traits(
     })
 }
 
-pub(super) fn variant_data(db: &dyn DefDatabase, var: VariantId) -> Arc<VariantData> {
-    match var {
-        VariantId::StructId(it) => db.struct_data(it).variant_data.clone(),
-        VariantId::UnionId(it) => db.union_data(it).variant_data.clone(),
-        VariantId::EnumVariantId(it) => {
-            db.enum_data(it.parent).variants[it.local_id].variant_data.clone()
-        }
-    }
-}
-
-/// Helper for mutating `Arc<[T]>` (i.e. `Arc::make_mut` for Arc slices).
-/// The underlying values are cloned if there are other strong references.
-pub(crate) fn make_mut_slice<T: Clone>(a: &mut Arc<[T]>) -> &mut [T] {
-    if Arc::get_mut(a).is_none() {
-        *a = a.iter().cloned().collect();
-    }
-    Arc::get_mut(a).unwrap()
-}
-
 pub(crate) fn generics(db: &dyn DefDatabase, def: GenericDefId) -> Generics {
     let parent_generics = parent_generic_def(db, def).map(|def| Box::new(generics(db, def)));
     Generics { def, params: db.generic_params(def), parent_generics }
@@ -159,7 +142,7 @@ pub(crate) fn generics(db: &dyn DefDatabase, def: GenericDefId) -> Generics {
 #[derive(Debug)]
 pub(crate) struct Generics {
     def: GenericDefId,
-    pub(crate) params: Arc<GenericParams>,
+    pub(crate) params: Interned<GenericParams>,
     parent_generics: Option<Box<Generics>>,
 }
 
@@ -249,6 +232,26 @@ impl Generics {
             self.parent_generics.as_ref().and_then(|g| g.find_param(param))
         }
     }
+
+    /// Returns a Substitution that replaces each parameter by a bound variable.
+    pub(crate) fn bound_vars_subst(&self, debruijn: DebruijnIndex) -> Substitution {
+        Substitution::from_iter(
+            &Interner,
+            self.iter()
+                .enumerate()
+                .map(|(idx, _)| TyKind::BoundVar(BoundVar::new(debruijn, idx)).intern(&Interner)),
+        )
+    }
+
+    /// Returns a Substitution that replaces each parameter by itself (i.e. `Ty::Param`).
+    pub(crate) fn type_params_subst(&self, db: &dyn HirDatabase) -> Substitution {
+        Substitution::from_iter(
+            &Interner,
+            self.iter().map(|(id, _)| {
+                TyKind::Placeholder(crate::to_placeholder_idx(db, id)).intern(&Interner)
+            }),
+        )
+    }
 }
 
 fn parent_generic_def(db: &dyn DefDatabase, def: GenericDefId) -> Option<GenericDefId> {
diff --git a/crates/hir_ty/src/walk.rs b/crates/hir_ty/src/walk.rs
new file mode 100644
index 000000000..6ef1d5336
--- /dev/null
+++ b/crates/hir_ty/src/walk.rs
@@ -0,0 +1,150 @@
+//! The `TypeWalk` trait (probably to be replaced by Chalk's `Fold` and
+//! `Visit`).
+
+use chalk_ir::interner::HasInterner;
+
+use crate::{
+    AliasEq, AliasTy, Binders, CallableSig, FnSubst, GenericArg, GenericArgData, Interner,
+    OpaqueTy, ProjectionTy, Substitution, TraitRef, Ty, TyKind, WhereClause,
+};
+
+/// This allows walking structures that contain types to do something with those
+/// types, similar to Chalk's `Fold` trait.
+pub trait TypeWalk {
+    fn walk(&self, f: &mut impl FnMut(&Ty));
+}
+
+impl TypeWalk for Ty {
+    fn walk(&self, f: &mut impl FnMut(&Ty)) {
+        match self.kind(&Interner) {
+            TyKind::Alias(AliasTy::Projection(p_ty)) => {
+                for t in p_ty.substitution.iter(&Interner) {
+                    t.walk(f);
+                }
+            }
+            TyKind::Alias(AliasTy::Opaque(o_ty)) => {
+                for t in o_ty.substitution.iter(&Interner) {
+                    t.walk(f);
+                }
+            }
+            TyKind::Dyn(dyn_ty) => {
+                for p in dyn_ty.bounds.skip_binders().interned().iter() {
+                    p.walk(f);
+                }
+            }
+            TyKind::Slice(ty)
+            | TyKind::Array(ty, _)
+            | TyKind::Ref(_, _, ty)
+            | TyKind::Raw(_, ty) => {
+                ty.walk(f);
+            }
+            TyKind::Function(fn_pointer) => {
+                fn_pointer.substitution.0.walk(f);
+            }
+            TyKind::Adt(_, substs)
+            | TyKind::FnDef(_, substs)
+            | TyKind::Tuple(_, substs)
+            | TyKind::OpaqueType(_, substs)
+            | TyKind::AssociatedType(_, substs)
+            | TyKind::Closure(.., substs) => {
+                substs.walk(f);
+            }
+            _ => {}
+        }
+        f(self);
+    }
+}
+
+impl<T: TypeWalk> TypeWalk for Vec<T> {
+    fn walk(&self, f: &mut impl FnMut(&Ty)) {
+        for t in self {
+            t.walk(f);
+        }
+    }
+}
+
+impl TypeWalk for OpaqueTy {
+    fn walk(&self, f: &mut impl FnMut(&Ty)) {
+        self.substitution.walk(f);
+    }
+}
+
+impl TypeWalk for ProjectionTy {
+    fn walk(&self, f: &mut impl FnMut(&Ty)) {
+        self.substitution.walk(f);
+    }
+}
+
+impl TypeWalk for AliasTy {
+    fn walk(&self, f: &mut impl FnMut(&Ty)) {
+        match self {
+            AliasTy::Projection(it) => it.walk(f),
+            AliasTy::Opaque(it) => it.walk(f),
+        }
+    }
+}
+
+impl TypeWalk for GenericArg {
+    fn walk(&self, f: &mut impl FnMut(&Ty)) {
+        match &self.interned() {
+            GenericArgData::Ty(ty) => {
+                ty.walk(f);
+            }
+            _ => {}
+        }
+    }
+}
+
+impl TypeWalk for Substitution {
+    fn walk(&self, f: &mut impl FnMut(&Ty)) {
+        for t in self.iter(&Interner) {
+            t.walk(f);
+        }
+    }
+}
+
+impl<T: TypeWalk + HasInterner<Interner = Interner>> TypeWalk for Binders<T> {
+    fn walk(&self, f: &mut impl FnMut(&Ty)) {
+        self.skip_binders().walk(f);
+    }
+}
+
+impl TypeWalk for TraitRef {
+    fn walk(&self, f: &mut impl FnMut(&Ty)) {
+        self.substitution.walk(f);
+    }
+}
+
+impl TypeWalk for WhereClause {
+    fn walk(&self, f: &mut impl FnMut(&Ty)) {
+        match self {
+            WhereClause::Implemented(trait_ref) => trait_ref.walk(f),
+            WhereClause::AliasEq(alias_eq) => alias_eq.walk(f),
+            _ => {}
+        }
+    }
+}
+
+impl TypeWalk for CallableSig {
+    fn walk(&self, f: &mut impl FnMut(&Ty)) {
+        for t in self.params_and_return.iter() {
+            t.walk(f);
+        }
+    }
+}
+
+impl TypeWalk for AliasEq {
+    fn walk(&self, f: &mut impl FnMut(&Ty)) {
+        self.ty.walk(f);
+        match &self.alias {
+            AliasTy::Projection(projection_ty) => projection_ty.walk(f),
+            AliasTy::Opaque(opaque) => opaque.walk(f),
+        }
+    }
+}
+
+impl TypeWalk for FnSubst<Interner> {
+    fn walk(&self, f: &mut impl FnMut(&Ty)) {
+        self.0.walk(f)
+    }
+}
diff --git a/crates/ide/src/annotations.rs b/crates/ide/src/annotations.rs
index 64bc926f1..5ebe7fd0e 100644
--- a/crates/ide/src/annotations.rs
+++ b/crates/ide/src/annotations.rs
@@ -19,6 +19,8 @@ use crate::{
 //
 // Provides user with annotations above items for looking up references or impl blocks
 // and running/debugging binaries.
+//
+// image::https://user-images.githubusercontent.com/48062697/113020672-b7c34f00-917a-11eb-8f6e-858735660a0e.png[]
 #[derive(Debug)]
 pub struct Annotation {
     pub range: TextRange,
diff --git a/crates/ide/src/diagnostics.rs b/crates/ide/src/diagnostics.rs
index 22697a537..1c911a8b2 100644
--- a/crates/ide/src/diagnostics.rs
+++ b/crates/ide/src/diagnostics.rs
@@ -20,12 +20,12 @@ use itertools::Itertools;
 use rustc_hash::FxHashSet;
 use syntax::{
     ast::{self, AstNode},
-    SyntaxNode, SyntaxNodePtr, TextRange,
+    SyntaxNode, SyntaxNodePtr, TextRange, TextSize,
 };
 use text_edit::TextEdit;
 use unlinked_file::UnlinkedFile;
 
-use crate::{FileId, Label, SourceChange};
+use crate::{Assist, AssistId, AssistKind, FileId, Label, SourceChange};
 
 use self::fixes::DiagnosticWithFix;
 
@@ -35,7 +35,7 @@ pub struct Diagnostic {
     pub message: String,
     pub range: TextRange,
     pub severity: Severity,
-    pub fix: Option<Fix>,
+    pub fix: Option<Assist>,
     pub unused: bool,
     pub code: Option<DiagnosticCode>,
 }
@@ -56,7 +56,7 @@ impl Diagnostic {
         }
     }
 
-    fn with_fix(self, fix: Option<Fix>) -> Self {
+    fn with_fix(self, fix: Option<Assist>) -> Self {
         Self { fix, ..self }
     }
 
@@ -69,21 +69,6 @@ impl Diagnostic {
     }
 }
 
-#[derive(Debug)]
-pub struct Fix {
-    pub label: Label,
-    pub source_change: SourceChange,
-    /// Allows to trigger the fix only when the caret is in the range given
-    pub fix_trigger_range: TextRange,
-}
-
-impl Fix {
-    fn new(label: &str, source_change: SourceChange, fix_trigger_range: TextRange) -> Self {
-        let label = Label::new(label);
-        Self { label, source_change, fix_trigger_range }
-    }
-}
-
 #[derive(Debug, Copy, Clone)]
 pub enum Severity {
     Error,
@@ -99,6 +84,7 @@ pub struct DiagnosticsConfig {
 pub(crate) fn diagnostics(
     db: &RootDatabase,
     config: &DiagnosticsConfig,
+    resolve: bool,
     file_id: FileId,
 ) -> Vec<Diagnostic> {
     let _p = profile::span("diagnostics");
@@ -122,25 +108,25 @@ pub(crate) fn diagnostics(
     let res = RefCell::new(res);
     let sink_builder = DiagnosticSinkBuilder::new()
         .on::<hir::diagnostics::UnresolvedModule, _>(|d| {
-            res.borrow_mut().push(diagnostic_with_fix(d, &sema));
+            res.borrow_mut().push(diagnostic_with_fix(d, &sema, resolve));
         })
         .on::<hir::diagnostics::MissingFields, _>(|d| {
-            res.borrow_mut().push(diagnostic_with_fix(d, &sema));
+            res.borrow_mut().push(diagnostic_with_fix(d, &sema, resolve));
         })
         .on::<hir::diagnostics::MissingOkOrSomeInTailExpr, _>(|d| {
-            res.borrow_mut().push(diagnostic_with_fix(d, &sema));
+            res.borrow_mut().push(diagnostic_with_fix(d, &sema, resolve));
         })
         .on::<hir::diagnostics::NoSuchField, _>(|d| {
-            res.borrow_mut().push(diagnostic_with_fix(d, &sema));
+            res.borrow_mut().push(diagnostic_with_fix(d, &sema, resolve));
         })
         .on::<hir::diagnostics::RemoveThisSemicolon, _>(|d| {
-            res.borrow_mut().push(diagnostic_with_fix(d, &sema));
+            res.borrow_mut().push(diagnostic_with_fix(d, &sema, resolve));
         })
         .on::<hir::diagnostics::IncorrectCase, _>(|d| {
-            res.borrow_mut().push(warning_with_fix(d, &sema));
+            res.borrow_mut().push(warning_with_fix(d, &sema, resolve));
         })
         .on::<hir::diagnostics::ReplaceFilterMapNextWithFindMap, _>(|d| {
-            res.borrow_mut().push(warning_with_fix(d, &sema));
+            res.borrow_mut().push(warning_with_fix(d, &sema, resolve));
         })
         .on::<hir::diagnostics::InactiveCode, _>(|d| {
             // If there's inactive code somewhere in a macro, don't propagate to the call-site.
@@ -159,15 +145,16 @@ pub(crate) fn diagnostics(
             );
         })
         .on::<UnlinkedFile, _>(|d| {
+            // Limit diagnostic to the first few characters in the file. This matches how VS Code
+            // renders it with the full span, but on other editors, and is less invasive.
+            let range = sema.diagnostics_display_range(d.display_source()).range;
+            let range = range.intersect(TextRange::up_to(TextSize::of("..."))).unwrap_or(range);
+
             // Override severity and mark as unused.
             res.borrow_mut().push(
-                Diagnostic::hint(
-                    sema.diagnostics_display_range(d.display_source()).range,
-                    d.message(),
-                )
-                .with_unused(true)
-                .with_fix(d.fix(&sema))
-                .with_code(Some(d.code())),
+                Diagnostic::hint(range, d.message())
+                    .with_fix(d.fix(&sema, resolve))
+                    .with_code(Some(d.code())),
             );
         })
         .on::<hir::diagnostics::UnresolvedProcMacro, _>(|d| {
@@ -222,15 +209,23 @@ pub(crate) fn diagnostics(
     res.into_inner()
 }
 
-fn diagnostic_with_fix<D: DiagnosticWithFix>(d: &D, sema: &Semantics<RootDatabase>) -> Diagnostic {
+fn diagnostic_with_fix<D: DiagnosticWithFix>(
+    d: &D,
+    sema: &Semantics<RootDatabase>,
+    resolve: bool,
+) -> Diagnostic {
     Diagnostic::error(sema.diagnostics_display_range(d.display_source()).range, d.message())
-        .with_fix(d.fix(&sema))
+        .with_fix(d.fix(&sema, resolve))
         .with_code(Some(d.code()))
 }
 
-fn warning_with_fix<D: DiagnosticWithFix>(d: &D, sema: &Semantics<RootDatabase>) -> Diagnostic {
+fn warning_with_fix<D: DiagnosticWithFix>(
+    d: &D,
+    sema: &Semantics<RootDatabase>,
+    resolve: bool,
+) -> Diagnostic {
     Diagnostic::hint(sema.diagnostics_display_range(d.display_source()).range, d.message())
-        .with_fix(d.fix(&sema))
+        .with_fix(d.fix(&sema, resolve))
         .with_code(Some(d.code()))
 }
 
@@ -260,7 +255,8 @@ fn check_unnecessary_braces_in_use_statement(
 
         acc.push(
             Diagnostic::hint(use_range, "Unnecessary braces in use statement".to_string())
-                .with_fix(Some(Fix::new(
+                .with_fix(Some(fix(
+                    "remove_braces",
                     "Remove unnecessary braces",
                     SourceChange::from_text_edit(file_id, edit),
                     use_range,
@@ -283,6 +279,23 @@ fn text_edit_for_remove_unnecessary_braces_with_self_in_use_statement(
     None
 }
 
+fn fix(id: &'static str, label: &str, source_change: SourceChange, target: TextRange) -> Assist {
+    let mut res = unresolved_fix(id, label, target);
+    res.source_change = Some(source_change);
+    res
+}
+
+fn unresolved_fix(id: &'static str, label: &str, target: TextRange) -> Assist {
+    assert!(!id.contains(' '));
+    Assist {
+        id: AssistId(id, AssistKind::QuickFix),
+        label: Label::new(label),
+        group: None,
+        target,
+        source_change: None,
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use expect_test::{expect, Expect};
@@ -301,16 +314,17 @@ mod tests {
 
         let (analysis, file_position) = fixture::position(ra_fixture_before);
         let diagnostic = analysis
-            .diagnostics(&DiagnosticsConfig::default(), file_position.file_id)
+            .diagnostics(&DiagnosticsConfig::default(), true, file_position.file_id)
             .unwrap()
             .pop()
             .unwrap();
         let fix = diagnostic.fix.unwrap();
         let actual = {
-            let file_id = *fix.source_change.source_file_edits.keys().next().unwrap();
+            let source_change = fix.source_change.unwrap();
+            let file_id = *source_change.source_file_edits.keys().next().unwrap();
             let mut actual = analysis.file_text(file_id).unwrap().to_string();
 
-            for edit in fix.source_change.source_file_edits.values() {
+            for edit in source_change.source_file_edits.values() {
                 edit.apply(&mut actual);
             }
             actual
@@ -318,9 +332,9 @@ mod tests {
 
         assert_eq_text!(&after, &actual);
         assert!(
-            fix.fix_trigger_range.contains_inclusive(file_position.offset),
+            fix.target.contains_inclusive(file_position.offset),
             "diagnostic fix range {:?} does not touch cursor position {:?}",
-            fix.fix_trigger_range,
+            fix.target,
             file_position.offset
         );
     }
@@ -329,7 +343,7 @@ mod tests {
     fn check_no_fix(ra_fixture: &str) {
         let (analysis, file_position) = fixture::position(ra_fixture);
         let diagnostic = analysis
-            .diagnostics(&DiagnosticsConfig::default(), file_position.file_id)
+            .diagnostics(&DiagnosticsConfig::default(), true, file_position.file_id)
             .unwrap()
             .pop()
             .unwrap();
@@ -343,7 +357,7 @@ mod tests {
         let diagnostics = files
             .into_iter()
             .flat_map(|file_id| {
-                analysis.diagnostics(&DiagnosticsConfig::default(), file_id).unwrap()
+                analysis.diagnostics(&DiagnosticsConfig::default(), true, file_id).unwrap()
             })
             .collect::<Vec<_>>();
         assert_eq!(diagnostics.len(), 0, "unexpected diagnostics:\n{:#?}", diagnostics);
@@ -351,7 +365,8 @@ mod tests {
 
     fn check_expect(ra_fixture: &str, expect: Expect) {
         let (analysis, file_id) = fixture::file(ra_fixture);
-        let diagnostics = analysis.diagnostics(&DiagnosticsConfig::default(), file_id).unwrap();
+        let diagnostics =
+            analysis.diagnostics(&DiagnosticsConfig::default(), true, file_id).unwrap();
         expect.assert_debug_eq(&diagnostics)
     }
 
@@ -664,24 +679,31 @@ fn test_fn() {
                         range: 0..8,
                         severity: Error,
                         fix: Some(
-                            Fix {
+                            Assist {
+                                id: AssistId(
+                                    "create_module",
+                                    QuickFix,
+                                ),
                                 label: "Create module",
-                                source_change: SourceChange {
-                                    source_file_edits: {},
-                                    file_system_edits: [
-                                        CreateFile {
-                                            dst: AnchoredPathBuf {
-                                                anchor: FileId(
-                                                    0,
-                                                ),
-                                                path: "foo.rs",
+                                group: None,
+                                target: 0..8,
+                                source_change: Some(
+                                    SourceChange {
+                                        source_file_edits: {},
+                                        file_system_edits: [
+                                            CreateFile {
+                                                dst: AnchoredPathBuf {
+                                                    anchor: FileId(
+                                                        0,
+                                                    ),
+                                                    path: "foo.rs",
+                                                },
+                                                initial_contents: "",
                                             },
-                                            initial_contents: "",
-                                        },
-                                    ],
-                                    is_snippet: false,
-                                },
-                                fix_trigger_range: 0..8,
+                                        ],
+                                        is_snippet: false,
+                                    },
+                                ),
                             },
                         ),
                         unused: false,
@@ -703,7 +725,7 @@ fn test_fn() {
             expect![[r#"
                 [
                     Diagnostic {
-                        message: "unresolved macro call",
+                        message: "unresolved macro `foo::bar!`",
                         range: 5..8,
                         severity: Error,
                         fix: None,
@@ -889,10 +911,11 @@ struct Foo {
 
         let (analysis, file_id) = fixture::file(r#"mod foo;"#);
 
-        let diagnostics = analysis.diagnostics(&config, file_id).unwrap();
+        let diagnostics = analysis.diagnostics(&config, true, file_id).unwrap();
         assert!(diagnostics.is_empty());
 
-        let diagnostics = analysis.diagnostics(&DiagnosticsConfig::default(), file_id).unwrap();
+        let diagnostics =
+            analysis.diagnostics(&DiagnosticsConfig::default(), true, file_id).unwrap();
         assert!(!diagnostics.is_empty());
     }
 
@@ -998,8 +1021,9 @@ impl TestStruct {
         let expected = r#"fn foo() {}"#;
 
         let (analysis, file_position) = fixture::position(input);
-        let diagnostics =
-            analysis.diagnostics(&DiagnosticsConfig::default(), file_position.file_id).unwrap();
+        let diagnostics = analysis
+            .diagnostics(&DiagnosticsConfig::default(), true, file_position.file_id)
+            .unwrap();
         assert_eq!(diagnostics.len(), 1);
 
         check_fix(input, expected);
diff --git a/crates/ide/src/diagnostics/field_shorthand.rs b/crates/ide/src/diagnostics/field_shorthand.rs
index 5c89e2170..2b1787f9b 100644
--- a/crates/ide/src/diagnostics/field_shorthand.rs
+++ b/crates/ide/src/diagnostics/field_shorthand.rs
@@ -5,7 +5,7 @@ use ide_db::{base_db::FileId, source_change::SourceChange};
 use syntax::{ast, match_ast, AstNode, SyntaxNode};
 use text_edit::TextEdit;
 
-use crate::{Diagnostic, Fix};
+use crate::{diagnostics::fix, Diagnostic};
 
 pub(super) fn check(acc: &mut Vec<Diagnostic>, file_id: FileId, node: &SyntaxNode) {
     match_ast! {
@@ -47,7 +47,8 @@ fn check_expr_field_shorthand(
         let field_range = record_field.syntax().text_range();
         acc.push(
             Diagnostic::hint(field_range, "Shorthand struct initialization".to_string()).with_fix(
-                Some(Fix::new(
+                Some(fix(
+                    "use_expr_field_shorthand",
                     "Use struct shorthand initialization",
                     SourceChange::from_text_edit(file_id, edit),
                     field_range,
@@ -86,7 +87,8 @@ fn check_pat_field_shorthand(
 
         let field_range = record_pat_field.syntax().text_range();
         acc.push(Diagnostic::hint(field_range, "Shorthand struct pattern".to_string()).with_fix(
-            Some(Fix::new(
+            Some(fix(
+                "use_pat_field_shorthand",
                 "Use struct field shorthand",
                 SourceChange::from_text_edit(file_id, edit),
                 field_range,
diff --git a/crates/ide/src/diagnostics/fixes.rs b/crates/ide/src/diagnostics/fixes.rs
index 5fb3e2d91..7be8b3459 100644
--- a/crates/ide/src/diagnostics/fixes.rs
+++ b/crates/ide/src/diagnostics/fixes.rs
@@ -20,20 +20,30 @@ use syntax::{
 };
 use text_edit::TextEdit;
 
-use crate::{diagnostics::Fix, references::rename::rename_with_semantics, FilePosition};
+use crate::{
+    diagnostics::{fix, unresolved_fix},
+    references::rename::rename_with_semantics,
+    Assist, FilePosition,
+};
 
 /// A [Diagnostic] that potentially has a fix available.
 ///
 /// [Diagnostic]: hir::diagnostics::Diagnostic
 pub(crate) trait DiagnosticWithFix: Diagnostic {
-    fn fix(&self, sema: &Semantics<RootDatabase>) -> Option<Fix>;
+    /// `resolve` determines if the diagnostic should fill in the `edit` field
+    /// of the assist.
+    ///
+    /// If `resolve` is false, the edit will be computed later, on demand, and
+    /// can be omitted.
+    fn fix(&self, sema: &Semantics<RootDatabase>, _resolve: bool) -> Option<Assist>;
 }
 
 impl DiagnosticWithFix for UnresolvedModule {
-    fn fix(&self, sema: &Semantics<RootDatabase>) -> Option<Fix> {
+    fn fix(&self, sema: &Semantics<RootDatabase>, _resolve: bool) -> Option<Assist> {
         let root = sema.db.parse_or_expand(self.file)?;
         let unresolved_module = self.decl.to_node(&root);
-        Some(Fix::new(
+        Some(fix(
+            "create_module",
             "Create module",
             FileSystemEdit::CreateFile {
                 dst: AnchoredPathBuf {
@@ -49,7 +59,7 @@ impl DiagnosticWithFix for UnresolvedModule {
 }
 
 impl DiagnosticWithFix for NoSuchField {
-    fn fix(&self, sema: &Semantics<RootDatabase>) -> Option<Fix> {
+    fn fix(&self, sema: &Semantics<RootDatabase>, _resolve: bool) -> Option<Assist> {
         let root = sema.db.parse_or_expand(self.file)?;
         missing_record_expr_field_fix(
             &sema,
@@ -60,7 +70,7 @@ impl DiagnosticWithFix for NoSuchField {
 }
 
 impl DiagnosticWithFix for MissingFields {
-    fn fix(&self, sema: &Semantics<RootDatabase>) -> Option<Fix> {
+    fn fix(&self, sema: &Semantics<RootDatabase>, _resolve: bool) -> Option<Assist> {
         // Note that although we could add a diagnostics to
         // fill the missing tuple field, e.g :
         // `struct A(usize);`
@@ -86,7 +96,8 @@ impl DiagnosticWithFix for MissingFields {
                 .into_text_edit(&mut builder);
             builder.finish()
         };
-        Some(Fix::new(
+        Some(fix(
+            "fill_missing_fields",
             "Fill struct fields",
             SourceChange::from_text_edit(self.file.original_file(sema.db), edit),
             sema.original_range(&field_list_parent.syntax()).range,
@@ -95,7 +106,7 @@ impl DiagnosticWithFix for MissingFields {
 }
 
 impl DiagnosticWithFix for MissingOkOrSomeInTailExpr {
-    fn fix(&self, sema: &Semantics<RootDatabase>) -> Option<Fix> {
+    fn fix(&self, sema: &Semantics<RootDatabase>, _resolve: bool) -> Option<Assist> {
         let root = sema.db.parse_or_expand(self.file)?;
         let tail_expr = self.expr.to_node(&root);
         let tail_expr_range = tail_expr.syntax().text_range();
@@ -103,12 +114,12 @@ impl DiagnosticWithFix for MissingOkOrSomeInTailExpr {
         let edit = TextEdit::replace(tail_expr_range, replacement);
         let source_change = SourceChange::from_text_edit(self.file.original_file(sema.db), edit);
         let name = if self.required == "Ok" { "Wrap with Ok" } else { "Wrap with Some" };
-        Some(Fix::new(name, source_change, tail_expr_range))
+        Some(fix("wrap_tail_expr", name, source_change, tail_expr_range))
     }
 }
 
 impl DiagnosticWithFix for RemoveThisSemicolon {
-    fn fix(&self, sema: &Semantics<RootDatabase>) -> Option<Fix> {
+    fn fix(&self, sema: &Semantics<RootDatabase>, _resolve: bool) -> Option<Assist> {
         let root = sema.db.parse_or_expand(self.file)?;
 
         let semicolon = self
@@ -123,12 +134,12 @@ impl DiagnosticWithFix for RemoveThisSemicolon {
         let edit = TextEdit::delete(semicolon);
         let source_change = SourceChange::from_text_edit(self.file.original_file(sema.db), edit);
 
-        Some(Fix::new("Remove this semicolon", source_change, semicolon))
+        Some(fix("remove_semicolon", "Remove this semicolon", source_change, semicolon))
     }
 }
 
 impl DiagnosticWithFix for IncorrectCase {
-    fn fix(&self, sema: &Semantics<RootDatabase>) -> Option<Fix> {
+    fn fix(&self, sema: &Semantics<RootDatabase>, resolve: bool) -> Option<Assist> {
         let root = sema.db.parse_or_expand(self.file)?;
         let name_node = self.ident.to_node(&root);
 
@@ -136,16 +147,19 @@ impl DiagnosticWithFix for IncorrectCase {
         let frange = name_node.original_file_range(sema.db);
         let file_position = FilePosition { file_id: frange.file_id, offset: frange.range.start() };
 
-        let rename_changes =
-            rename_with_semantics(sema, file_position, &self.suggested_text).ok()?;
-
         let label = format!("Rename to {}", self.suggested_text);
-        Some(Fix::new(&label, rename_changes, frange.range))
+        let mut res = unresolved_fix("change_case", &label, frange.range);
+        if resolve {
+            let source_change = rename_with_semantics(sema, file_position, &self.suggested_text);
+            res.source_change = Some(source_change.ok().unwrap_or_default());
+        }
+
+        Some(res)
     }
 }
 
 impl DiagnosticWithFix for ReplaceFilterMapNextWithFindMap {
-    fn fix(&self, sema: &Semantics<RootDatabase>) -> Option<Fix> {
+    fn fix(&self, sema: &Semantics<RootDatabase>, _resolve: bool) -> Option<Assist> {
         let root = sema.db.parse_or_expand(self.file)?;
         let next_expr = self.next_expr.to_node(&root);
         let next_call = ast::MethodCallExpr::cast(next_expr.syntax().clone())?;
@@ -163,7 +177,8 @@ impl DiagnosticWithFix for ReplaceFilterMapNextWithFindMap {
 
         let source_change = SourceChange::from_text_edit(self.file.original_file(sema.db), edit);
 
-        Some(Fix::new(
+        Some(fix(
+            "replace_with_find_map",
             "Replace filter_map(..).next() with find_map()",
             source_change,
             trigger_range,
@@ -175,7 +190,7 @@ fn missing_record_expr_field_fix(
     sema: &Semantics<RootDatabase>,
     usage_file_id: FileId,
     record_expr_field: &ast::RecordExprField,
-) -> Option<Fix> {
+) -> Option<Assist> {
     let record_lit = ast::RecordExpr::cast(record_expr_field.syntax().parent()?.parent()?)?;
     let def_id = sema.resolve_variant(record_lit)?;
     let module;
@@ -233,7 +248,12 @@ fn missing_record_expr_field_fix(
         def_file_id,
         TextEdit::insert(last_field_syntax.text_range().end(), new_field),
     );
-    return Some(Fix::new("Create field", source_change, record_expr_field.syntax().text_range()));
+    return Some(fix(
+        "create_field",
+        "Create field",
+        source_change,
+        record_expr_field.syntax().text_range(),
+    ));
 
     fn record_field_list(field_def_list: ast::FieldList) -> Option<ast::RecordFieldList> {
         match field_def_list {
diff --git a/crates/ide/src/diagnostics/unlinked_file.rs b/crates/ide/src/diagnostics/unlinked_file.rs
index e174fb767..7d39f4fbe 100644
--- a/crates/ide/src/diagnostics/unlinked_file.rs
+++ b/crates/ide/src/diagnostics/unlinked_file.rs
@@ -16,9 +16,10 @@ use syntax::{
 };
 use text_edit::TextEdit;
 
-use crate::Fix;
-
-use super::fixes::DiagnosticWithFix;
+use crate::{
+    diagnostics::{fix, fixes::DiagnosticWithFix},
+    Assist,
+};
 
 // Diagnostic: unlinked-file
 //
@@ -49,7 +50,7 @@ impl Diagnostic for UnlinkedFile {
 }
 
 impl DiagnosticWithFix for UnlinkedFile {
-    fn fix(&self, sema: &hir::Semantics<RootDatabase>) -> Option<Fix> {
+    fn fix(&self, sema: &hir::Semantics<RootDatabase>, _resolve: bool) -> Option<Assist> {
         // If there's an existing module that could add a `mod` item to include the unlinked file,
         // suggest that as a fix.
 
@@ -100,7 +101,7 @@ fn make_fix(
     parent_file_id: FileId,
     new_mod_name: &str,
     added_file_id: FileId,
-) -> Option<Fix> {
+) -> Option<Assist> {
     fn is_outline_mod(item: &ast::Item) -> bool {
         matches!(item, ast::Item::Module(m) if m.item_list().is_none())
     }
@@ -152,7 +153,8 @@ fn make_fix(
 
     let edit = builder.finish();
     let trigger_range = db.parse(added_file_id).tree().syntax().text_range();
-    Some(Fix::new(
+    Some(fix(
+        "add_mod_declaration",
         &format!("Insert `{}`", mod_decl),
         SourceChange::from_text_edit(parent_file_id, edit),
         trigger_range,
diff --git a/crates/ide/src/doc_links.rs b/crates/ide/src/doc_links.rs
index 9301cdeff..c5dc14a23 100644
--- a/crates/ide/src/doc_links.rs
+++ b/crates/ide/src/doc_links.rs
@@ -1,6 +1,9 @@
 //! Extracts, resolves and rewrites links and intra-doc links in markdown documentation.
 
-use std::{convert::TryFrom, iter::once, ops::Range};
+use std::{
+    convert::{TryFrom, TryInto},
+    iter::once,
+};
 
 use itertools::Itertools;
 use pulldown_cmark::{BrokenLink, CowStr, Event, InlineStr, LinkType, Options, Parser, Tag};
@@ -16,8 +19,7 @@ use ide_db::{
     RootDatabase,
 };
 use syntax::{
-    ast, match_ast, AstNode, AstToken, SyntaxKind::*, SyntaxNode, SyntaxToken, TextRange, TextSize,
-    TokenAtOffset, T,
+    ast, match_ast, AstNode, SyntaxKind::*, SyntaxNode, SyntaxToken, TextRange, TokenAtOffset, T,
 };
 
 use crate::{FilePosition, Semantics};
@@ -26,12 +28,7 @@ pub(crate) type DocumentationLink = String;
 
 /// Rewrite documentation links in markdown to point to an online host (e.g. docs.rs)
 pub(crate) fn rewrite_links(db: &RootDatabase, markdown: &str, definition: &Definition) -> String {
-    let mut cb = |link: BrokenLink| {
-        Some((
-            /*url*/ link.reference.to_owned().into(),
-            /*title*/ link.reference.to_owned().into(),
-        ))
-    };
+    let mut cb = broken_link_clone_cb;
     let doc = Parser::new_with_broken_link_callback(markdown, Options::empty(), Some(&mut cb));
 
     let doc = map_links(doc, |target, title: &str| {
@@ -98,76 +95,52 @@ pub(crate) fn remove_links(markdown: &str) -> String {
     out
 }
 
+/// Retrieve a link to documentation for the given symbol.
+pub(crate) fn external_docs(
+    db: &RootDatabase,
+    position: &FilePosition,
+) -> Option<DocumentationLink> {
+    let sema = Semantics::new(db);
+    let file = sema.parse(position.file_id).syntax().clone();
+    let token = pick_best(file.token_at_offset(position.offset))?;
+    let token = sema.descend_into_macros(token);
+
+    let node = token.parent()?;
+    let definition = match_ast! {
+        match node {
+            ast::NameRef(name_ref) => NameRefClass::classify(&sema, &name_ref).map(|d| d.referenced(sema.db)),
+            ast::Name(name) => NameClass::classify(&sema, &name).map(|d| d.referenced_or_defined(sema.db)),
+            _ => None,
+        }
+    };
+
+    get_doc_link(db, definition?)
+}
+
+/// Extracts all links from a given markdown text.
 pub(crate) fn extract_definitions_from_markdown(
     markdown: &str,
-) -> Vec<(Range<usize>, String, Option<hir::Namespace>)> {
-    let mut res = vec![];
-    let mut cb = |link: BrokenLink| {
-        // These allocations are actually unnecessary but the lifetimes on BrokenLinkCallback are wrong
-        // this is fixed in the repo but not on the crates.io release yet
-        Some((
-            /*url*/ link.reference.to_owned().into(),
-            /*title*/ link.reference.to_owned().into(),
-        ))
-    };
-    let doc = Parser::new_with_broken_link_callback(markdown, Options::empty(), Some(&mut cb));
-    for (event, range) in doc.into_offset_iter() {
+) -> Vec<(TextRange, String, Option<hir::Namespace>)> {
+    Parser::new_with_broken_link_callback(
+        markdown,
+        Options::empty(),
+        Some(&mut broken_link_clone_cb),
+    )
+    .into_offset_iter()
+    .filter_map(|(event, range)| {
         if let Event::Start(Tag::Link(_, target, title)) = event {
             let link = if target.is_empty() { title } else { target };
             let (link, ns) = parse_intra_doc_link(&link);
-            res.push((range, link.to_string(), ns));
-        }
-    }
-    res
-}
-
-/// Extracts a link from a comment at the given position returning the spanning range, link and
-/// optionally it's namespace.
-pub(crate) fn extract_positioned_link_from_comment(
-    position: TextSize,
-    comment: &ast::Comment,
-) -> Option<(TextRange, String, Option<hir::Namespace>)> {
-    let doc_comment = comment.doc_comment()?;
-    let comment_start =
-        comment.syntax().text_range().start() + TextSize::from(comment.prefix().len() as u32);
-    let def_links = extract_definitions_from_markdown(doc_comment);
-    let (range, def_link, ns) =
-        def_links.into_iter().find_map(|(Range { start, end }, def_link, ns)| {
-            let range = TextRange::at(
-                comment_start + TextSize::from(start as u32),
-                TextSize::from((end - start) as u32),
-            );
-            range.contains(position).then(|| (range, def_link, ns))
-        })?;
-    Some((range, def_link, ns))
-}
-
-/// Turns a syntax node into it's [`Definition`] if it can hold docs.
-pub(crate) fn doc_owner_to_def(
-    sema: &Semantics<RootDatabase>,
-    item: &SyntaxNode,
-) -> Option<Definition> {
-    let res: hir::ModuleDef = match_ast! {
-        match item {
-            ast::SourceFile(_it) => sema.scope(item).module()?.into(),
-            ast::Fn(it) => sema.to_def(&it)?.into(),
-            ast::Struct(it) => sema.to_def(&it)?.into(),
-            ast::Enum(it) => sema.to_def(&it)?.into(),
-            ast::Union(it) => sema.to_def(&it)?.into(),
-            ast::Trait(it) => sema.to_def(&it)?.into(),
-            ast::Const(it) => sema.to_def(&it)?.into(),
-            ast::Static(it) => sema.to_def(&it)?.into(),
-            ast::TypeAlias(it) => sema.to_def(&it)?.into(),
-            ast::Variant(it) => sema.to_def(&it)?.into(),
-            ast::Trait(it) => sema.to_def(&it)?.into(),
-            ast::Impl(it) => return sema.to_def(&it).map(Definition::SelfType),
-            ast::Macro(it) => return sema.to_def(&it).map(Definition::Macro),
-            ast::TupleField(it) => return sema.to_def(&it).map(Definition::Field),
-            ast::RecordField(it) => return sema.to_def(&it).map(Definition::Field),
-            _ => return None,
+            Some((
+                TextRange::new(range.start.try_into().ok()?, range.end.try_into().ok()?),
+                link.to_string(),
+                ns,
+            ))
+        } else {
+            None
         }
-    };
-    Some(Definition::ModuleDef(res))
+    })
+    .collect()
 }
 
 pub(crate) fn resolve_doc_path_for_def(
@@ -178,15 +151,15 @@ pub(crate) fn resolve_doc_path_for_def(
 ) -> Option<hir::ModuleDef> {
     match def {
         Definition::ModuleDef(def) => match def {
-            ModuleDef::Module(it) => it.resolve_doc_path(db, &link, ns),
-            ModuleDef::Function(it) => it.resolve_doc_path(db, &link, ns),
-            ModuleDef::Adt(it) => it.resolve_doc_path(db, &link, ns),
-            ModuleDef::Variant(it) => it.resolve_doc_path(db, &link, ns),
-            ModuleDef::Const(it) => it.resolve_doc_path(db, &link, ns),
-            ModuleDef::Static(it) => it.resolve_doc_path(db, &link, ns),
-            ModuleDef::Trait(it) => it.resolve_doc_path(db, &link, ns),
-            ModuleDef::TypeAlias(it) => it.resolve_doc_path(db, &link, ns),
-            ModuleDef::BuiltinType(_) => None,
+            hir::ModuleDef::Module(it) => it.resolve_doc_path(db, &link, ns),
+            hir::ModuleDef::Function(it) => it.resolve_doc_path(db, &link, ns),
+            hir::ModuleDef::Adt(it) => it.resolve_doc_path(db, &link, ns),
+            hir::ModuleDef::Variant(it) => it.resolve_doc_path(db, &link, ns),
+            hir::ModuleDef::Const(it) => it.resolve_doc_path(db, &link, ns),
+            hir::ModuleDef::Static(it) => it.resolve_doc_path(db, &link, ns),
+            hir::ModuleDef::Trait(it) => it.resolve_doc_path(db, &link, ns),
+            hir::ModuleDef::TypeAlias(it) => it.resolve_doc_path(db, &link, ns),
+            hir::ModuleDef::BuiltinType(_) => None,
         },
         Definition::Macro(it) => it.resolve_doc_path(db, &link, ns),
         Definition::Field(it) => it.resolve_doc_path(db, &link, ns),
@@ -197,6 +170,42 @@ pub(crate) fn resolve_doc_path_for_def(
     }
 }
 
+pub(crate) fn doc_attributes(
+    sema: &Semantics<RootDatabase>,
+    node: &SyntaxNode,
+) -> Option<(hir::AttrsWithOwner, Definition)> {
+    match_ast! {
+        match node {
+            ast::SourceFile(it)  => sema.to_def(&it).map(|def| (def.attrs(sema.db), Definition::ModuleDef(hir::ModuleDef::Module(def)))),
+            ast::Module(it)      => sema.to_def(&it).map(|def| (def.attrs(sema.db), Definition::ModuleDef(hir::ModuleDef::Module(def)))),
+            ast::Fn(it)          => sema.to_def(&it).map(|def| (def.attrs(sema.db), Definition::ModuleDef(hir::ModuleDef::Function(def)))),
+            ast::Struct(it)      => sema.to_def(&it).map(|def| (def.attrs(sema.db), Definition::ModuleDef(hir::ModuleDef::Adt(hir::Adt::Struct(def))))),
+            ast::Union(it)       => sema.to_def(&it).map(|def| (def.attrs(sema.db), Definition::ModuleDef(hir::ModuleDef::Adt(hir::Adt::Union(def))))),
+            ast::Enum(it)        => sema.to_def(&it).map(|def| (def.attrs(sema.db), Definition::ModuleDef(hir::ModuleDef::Adt(hir::Adt::Enum(def))))),
+            ast::Variant(it)     => sema.to_def(&it).map(|def| (def.attrs(sema.db), Definition::ModuleDef(hir::ModuleDef::Variant(def)))),
+            ast::Trait(it)       => sema.to_def(&it).map(|def| (def.attrs(sema.db), Definition::ModuleDef(hir::ModuleDef::Trait(def)))),
+            ast::Static(it)      => sema.to_def(&it).map(|def| (def.attrs(sema.db), Definition::ModuleDef(hir::ModuleDef::Static(def)))),
+            ast::Const(it)       => sema.to_def(&it).map(|def| (def.attrs(sema.db), Definition::ModuleDef(hir::ModuleDef::Const(def)))),
+            ast::TypeAlias(it)   => sema.to_def(&it).map(|def| (def.attrs(sema.db), Definition::ModuleDef(hir::ModuleDef::TypeAlias(def)))),
+            ast::Impl(it)        => sema.to_def(&it).map(|def| (def.attrs(sema.db), Definition::SelfType(def))),
+            ast::RecordField(it) => sema.to_def(&it).map(|def| (def.attrs(sema.db), Definition::Field(def))),
+            ast::TupleField(it)  => sema.to_def(&it).map(|def| (def.attrs(sema.db), Definition::Field(def))),
+            ast::Macro(it)       => sema.to_def(&it).map(|def| (def.attrs(sema.db), Definition::Macro(def))),
+            // ast::Use(it) => sema.to_def(&it).map(|def| (Box::new(it) as _, def.attrs(sema.db))),
+            _ => return None
+        }
+    }
+}
+
+fn broken_link_clone_cb<'a, 'b>(link: BrokenLink<'a>) -> Option<(CowStr<'b>, CowStr<'b>)> {
+    // These allocations are actually unnecessary but the lifetimes on BrokenLinkCallback are wrong
+    // this is fixed in the repo but not on the crates.io release yet
+    Some((
+        /*url*/ link.reference.to_owned().into(),
+        /*title*/ link.reference.to_owned().into(),
+    ))
+}
+
 // FIXME:
 // BUG: For Option::Some
 // Returns https://doc.rust-lang.org/nightly/core/prelude/v1/enum.Option.html#variant.Some
@@ -214,7 +223,7 @@ fn get_doc_link(db: &RootDatabase, definition: Definition) -> Option<String> {
                 .and_then(|assoc| match assoc.container(db) {
                     AssocItemContainer::Trait(t) => Some(t.into()),
                     AssocItemContainer::Impl(impld) => {
-                        impld.target_ty(db).as_adt().map(|adt| adt.into())
+                        impld.self_ty(db).as_adt().map(|adt| adt.into())
                     }
                 })
                 .unwrap_or_else(|| f.clone().into()),
@@ -328,28 +337,6 @@ fn rewrite_url_link(db: &RootDatabase, def: ModuleDef, target: &str) -> Option<S
         .map(|url| url.into_string())
 }
 
-/// Retrieve a link to documentation for the given symbol.
-pub(crate) fn external_docs(
-    db: &RootDatabase,
-    position: &FilePosition,
-) -> Option<DocumentationLink> {
-    let sema = Semantics::new(db);
-    let file = sema.parse(position.file_id).syntax().clone();
-    let token = pick_best(file.token_at_offset(position.offset))?;
-    let token = sema.descend_into_macros(token);
-
-    let node = token.parent()?;
-    let definition = match_ast! {
-        match node {
-            ast::NameRef(name_ref) => NameRefClass::classify(&sema, &name_ref).map(|d| d.referenced(sema.db)),
-            ast::Name(name) => NameClass::classify(&sema, &name).map(|d| d.referenced_or_defined(sema.db)),
-            _ => None,
-        }
-    };
-
-    get_doc_link(db, definition?)
-}
-
 /// Rewrites a markdown document, applying 'callback' to each link.
 fn map_links<'e>(
     events: impl Iterator<Item = Event<'e>>,
diff --git a/crates/ide/src/expand_macro.rs b/crates/ide/src/expand_macro.rs
index ffb3a6f7d..be0ee03bf 100644
--- a/crates/ide/src/expand_macro.rs
+++ b/crates/ide/src/expand_macro.rs
@@ -1,3 +1,5 @@
+use std::iter;
+
 use hir::Semantics;
 use ide_db::RootDatabase;
 use syntax::{
@@ -23,6 +25,8 @@ pub struct ExpandedMacro {
 //
 // | VS Code | **Rust Analyzer: Expand macro recursively**
 // |===
+//
+// image::https://user-images.githubusercontent.com/48062697/113020648-b3973180-917a-11eb-84a9-ecb921293dc5.gif[]
 pub(crate) fn expand_macro(db: &RootDatabase, position: FilePosition) -> Option<ExpandedMacro> {
     let sema = Semantics::new(db);
     let file = sema.parse(position.file_id);
@@ -89,24 +93,42 @@ fn insert_whitespaces(syn: SyntaxNode) -> String {
         let is_last =
             |f: fn(SyntaxKind) -> bool, default| -> bool { last.map(f).unwrap_or(default) };
 
-        res += &match token.kind() {
-            k if is_text(k) && is_next(|it| !it.is_punct(), true) => token.text().to_string() + " ",
+        match token.kind() {
+            k if is_text(k) && is_next(|it| !it.is_punct(), true) => {
+                res.push_str(token.text());
+                res.push(' ');
+            }
             L_CURLY if is_next(|it| it != R_CURLY, true) => {
                 indent += 1;
-                let leading_space = if is_last(is_text, false) { " " } else { "" };
-                format!("{}{{\n{}", leading_space, "  ".repeat(indent))
+                if is_last(is_text, false) {
+                    res.push(' ');
+                }
+                res.push_str("{\n");
+                res.extend(iter::repeat(" ").take(2 * indent));
             }
             R_CURLY if is_last(|it| it != L_CURLY, true) => {
                 indent = indent.saturating_sub(1);
-                format!("\n{}}}", "  ".repeat(indent))
+                res.push('\n');
+                res.extend(iter::repeat(" ").take(2 * indent));
+                res.push_str("}");
             }
-            R_CURLY => format!("}}\n{}", "  ".repeat(indent)),
-            T![;] => format!(";\n{}", "  ".repeat(indent)),
-            T![->] => " -> ".to_string(),
-            T![=] => " = ".to_string(),
-            T![=>] => " => ".to_string(),
-            _ => token.text().to_string(),
-        };
+            R_CURLY => {
+                res.push_str("}\n");
+                res.extend(iter::repeat(" ").take(2 * indent));
+            }
+            LIFETIME_IDENT if is_next(|it| it == IDENT, true) => {
+                res.push_str(token.text());
+                res.push(' ');
+            }
+            T![;] => {
+                res.push_str(";\n");
+                res.extend(iter::repeat(" ").take(2 * indent));
+            }
+            T![->] => res.push_str(" -> "),
+            T![=] => res.push_str(" = "),
+            T![=>] => res.push_str(" => "),
+            _ => res.push_str(token.text()),
+        }
 
         last = Some(token.kind());
     }
diff --git a/crates/ide/src/extend_selection.rs b/crates/ide/src/extend_selection.rs
index 5201ce587..7032889ac 100644
--- a/crates/ide/src/extend_selection.rs
+++ b/crates/ide/src/extend_selection.rs
@@ -24,6 +24,8 @@ use crate::FileRange;
 //
 // | VS Code | kbd:[Alt+Shift+→], kbd:[Alt+Shift+←]
 // |===
+//
+// image::https://user-images.githubusercontent.com/48062697/113020651-b42fc800-917a-11eb-8a4f-cf1a07859fac.gif[]
 pub(crate) fn extend_selection(db: &RootDatabase, frange: FileRange) -> TextRange {
     let sema = Semantics::new(db);
     let src = sema.parse(frange.file_id);
diff --git a/crates/ide/src/file_structure.rs b/crates/ide/src/file_structure.rs
index 2c898eae8..19071d6be 100644
--- a/crates/ide/src/file_structure.rs
+++ b/crates/ide/src/file_structure.rs
@@ -35,6 +35,9 @@ pub enum StructureNodeKind {
 //
 // | VS Code | kbd:[Ctrl+Shift+O]
 // |===
+//
+// image::https://user-images.githubusercontent.com/48062697/113020654-b42fc800-917a-11eb-8388-e7dc4d92b02e.gif[]
+
 pub(crate) fn file_structure(file: &SourceFile) -> Vec<StructureNode> {
     let mut res = Vec::new();
     let mut stack = Vec::new();
diff --git a/crates/ide/src/folding_ranges.rs b/crates/ide/src/folding_ranges.rs
index 4b1b24562..2b9ed123c 100644
--- a/crates/ide/src/folding_ranges.rs
+++ b/crates/ide/src/folding_ranges.rs
@@ -17,6 +17,9 @@ pub enum FoldKind {
     Block,
     ArgList,
     Region,
+    Consts,
+    Statics,
+    Array,
 }
 
 #[derive(Debug)]
@@ -30,6 +33,8 @@ pub(crate) fn folding_ranges(file: &SourceFile) -> Vec<Fold> {
     let mut visited_comments = FxHashSet::default();
     let mut visited_imports = FxHashSet::default();
     let mut visited_mods = FxHashSet::default();
+    let mut visited_consts = FxHashSet::default();
+    let mut visited_statics = FxHashSet::default();
     // regions can be nested, here is a LIFO buffer
     let mut regions_starts: Vec<TextSize> = vec![];
 
@@ -91,6 +96,19 @@ pub(crate) fn folding_ranges(file: &SourceFile) -> Vec<Fold> {
                         res.push(Fold { range, kind: FoldKind::Mods })
                     }
                 }
+
+                // Fold groups of consts
+                if node.kind() == CONST && !visited_consts.contains(&node) {
+                    if let Some(range) = contiguous_range_for_group(&node, &mut visited_consts) {
+                        res.push(Fold { range, kind: FoldKind::Consts })
+                    }
+                }
+                // Fold groups of consts
+                if node.kind() == STATIC && !visited_statics.contains(&node) {
+                    if let Some(range) = contiguous_range_for_group(&node, &mut visited_statics) {
+                        res.push(Fold { range, kind: FoldKind::Statics })
+                    }
+                }
             }
         }
     }
@@ -102,6 +120,7 @@ fn fold_kind(kind: SyntaxKind) -> Option<FoldKind> {
     match kind {
         COMMENT => Some(FoldKind::Comment),
         ARG_LIST | PARAM_LIST => Some(FoldKind::ArgList),
+        ARRAY_EXPR => Some(FoldKind::Array),
         ASSOC_ITEM_LIST
         | RECORD_FIELD_LIST
         | RECORD_PAT_FIELD_LIST
@@ -250,6 +269,9 @@ mod tests {
                 FoldKind::Block => "block",
                 FoldKind::ArgList => "arglist",
                 FoldKind::Region => "region",
+                FoldKind::Consts => "consts",
+                FoldKind::Statics => "statics",
+                FoldKind::Array => "array",
             };
             assert_eq!(kind, &attr.unwrap());
         }
@@ -446,6 +468,20 @@ fn foo<fold arglist>(
     }
 
     #[test]
+    fn fold_multiline_array() {
+        check(
+            r#"
+const FOO: [usize; 4] = <fold array>[
+    1,
+    2,
+    3,
+    4,
+]</fold>;
+"#,
+        )
+    }
+
+    #[test]
     fn fold_region() {
         check(
             r#"
@@ -457,4 +493,24 @@ calling_function(x,y);
 "#,
         )
     }
+
+    #[test]
+    fn fold_consecutive_const() {
+        check(
+            r#"
+<fold consts>const FIRST_CONST: &str = "first";
+const SECOND_CONST: &str = "second";</fold>
+            "#,
+        )
+    }
+
+    #[test]
+    fn fold_consecutive_static() {
+        check(
+            r#"
+<fold statics>static FIRST_STATIC: &str = "first";
+static SECOND_STATIC: &str = "second";</fold>
+            "#,
+        )
+    }
 }
diff --git a/crates/ide/src/goto_definition.rs b/crates/ide/src/goto_definition.rs
index a2c97061f..a04333e63 100644
--- a/crates/ide/src/goto_definition.rs
+++ b/crates/ide/src/goto_definition.rs
@@ -1,5 +1,5 @@
 use either::Either;
-use hir::Semantics;
+use hir::{InFile, Semantics};
 use ide_db::{
     defs::{NameClass, NameRefClass},
     RootDatabase,
@@ -8,7 +8,7 @@ use syntax::{ast, match_ast, AstNode, AstToken, SyntaxKind::*, SyntaxToken, Toke
 
 use crate::{
     display::TryToNav,
-    doc_links::{doc_owner_to_def, extract_positioned_link_from_comment, resolve_doc_path_for_def},
+    doc_links::{doc_attributes, extract_definitions_from_markdown, resolve_doc_path_for_def},
     FilePosition, NavigationTarget, RangeInfo,
 };
 
@@ -21,6 +21,8 @@ use crate::{
 //
 // | VS Code | kbd:[F12]
 // |===
+//
+// image::https://user-images.githubusercontent.com/48062697/113065563-025fbe00-91b1-11eb-83e4-a5a703610b23.gif[]
 pub(crate) fn goto_definition(
     db: &RootDatabase,
     position: FilePosition,
@@ -30,9 +32,16 @@ pub(crate) fn goto_definition(
     let original_token = pick_best(file.token_at_offset(position.offset))?;
     let token = sema.descend_into_macros(original_token.clone());
     let parent = token.parent()?;
-    if let Some(comment) = ast::Comment::cast(token) {
-        let (_, link, ns) = extract_positioned_link_from_comment(position.offset, &comment)?;
-        let def = doc_owner_to_def(&sema, &parent)?;
+    if let Some(_) = ast::Comment::cast(token) {
+        let (attributes, def) = doc_attributes(&sema, &parent)?;
+
+        let (docs, doc_mapping) = attributes.docs_with_rangemap(db)?;
+        let (_, link, ns) =
+            extract_definitions_from_markdown(docs.as_str()).into_iter().find(|(range, ..)| {
+                doc_mapping.map(range.clone()).map_or(false, |InFile { file_id, value: range }| {
+                    file_id == position.file_id.into() && range.contains(position.offset)
+                })
+            })?;
         let nav = resolve_doc_path_for_def(db, def, &link, ns)?.try_to_nav(db)?;
         return Some(RangeInfo::new(original_token.text_range(), vec![nav]));
     }
@@ -101,6 +110,13 @@ mod tests {
         assert_eq!(expected, FileRange { file_id: nav.file_id, range: nav.focus_or_full_range() });
     }
 
+    fn check_unresolved(ra_fixture: &str) {
+        let (analysis, position) = fixture::position(ra_fixture);
+        let navs = analysis.goto_definition(position).unwrap().expect("no definition found").info;
+
+        assert!(navs.is_empty(), "didn't expect this to resolve anywhere: {:?}", navs)
+    }
+
     #[test]
     fn goto_def_for_extern_crate() {
         check(
@@ -918,6 +934,16 @@ fn f() -> impl Iterator<Item$0 = u8> {}
     }
 
     #[test]
+    fn unknown_assoc_ty() {
+        check_unresolved(
+            r#"
+trait Iterator { type Item; }
+fn f() -> impl Iterator<Invalid$0 = u8> {}
+"#,
+        )
+    }
+
+    #[test]
     fn goto_def_for_assoc_ty_in_path_multiple() {
         check(
             r#"
@@ -1143,4 +1169,51 @@ fn fn_macro() {}
             "#,
         )
     }
+
+    #[test]
+    fn goto_intra_doc_links() {
+        check(
+            r#"
+
+pub mod theitem {
+    /// This is the item. Cool!
+    pub struct TheItem;
+             //^^^^^^^
+}
+
+/// Gives you a [`TheItem$0`].
+///
+/// [`TheItem`]: theitem::TheItem
+pub fn gimme() -> theitem::TheItem {
+    theitem::TheItem
+}
+"#,
+        );
+    }
+
+    #[test]
+    fn goto_ident_from_pat_macro() {
+        check(
+            r#"
+macro_rules! pat {
+    ($name:ident) => { Enum::Variant1($name) }
+}
+
+enum Enum {
+    Variant1(u8),
+    Variant2,
+}
+
+fn f(e: Enum) {
+    match e {
+        pat!(bind) => {
+           //^^^^
+            bind$0
+        }
+        Enum::Variant2 => {}
+    }
+}
+"#,
+        );
+    }
 }
diff --git a/crates/ide/src/goto_implementation.rs b/crates/ide/src/goto_implementation.rs
index f4d7c14a6..05130a237 100644
--- a/crates/ide/src/goto_implementation.rs
+++ b/crates/ide/src/goto_implementation.rs
@@ -16,6 +16,8 @@ use crate::{display::TryToNav, FilePosition, NavigationTarget, RangeInfo};
 //
 // | VS Code | kbd:[Ctrl+F12]
 // |===
+//
+// image::https://user-images.githubusercontent.com/48062697/113065566-02f85480-91b1-11eb-9288-aaad8abd8841.gif[]
 pub(crate) fn goto_implementation(
     db: &RootDatabase,
     position: FilePosition,
diff --git a/crates/ide/src/goto_type_definition.rs b/crates/ide/src/goto_type_definition.rs
index 2d38cb112..9d34b109b 100644
--- a/crates/ide/src/goto_type_definition.rs
+++ b/crates/ide/src/goto_type_definition.rs
@@ -12,6 +12,8 @@ use crate::{display::TryToNav, FilePosition, NavigationTarget, RangeInfo};
 //
 // | VS Code | **Go to Type Definition*
 // |===
+//
+// image::https://user-images.githubusercontent.com/48062697/113020657-b560f500-917a-11eb-9007-0f809733a338.gif[]
 pub(crate) fn goto_type_definition(
     db: &RootDatabase,
     position: FilePosition,
diff --git a/crates/ide/src/hover.rs b/crates/ide/src/hover.rs
index 3c951c507..9de653739 100644
--- a/crates/ide/src/hover.rs
+++ b/crates/ide/src/hover.rs
@@ -1,6 +1,6 @@
 use either::Either;
 use hir::{
-    AsAssocItem, AssocItemContainer, GenericParam, HasAttrs, HasSource, HirDisplay, Module,
+    AsAssocItem, AssocItemContainer, GenericParam, HasAttrs, HasSource, HirDisplay, InFile, Module,
     ModuleDef, Semantics,
 };
 use ide_db::{
@@ -16,8 +16,8 @@ use syntax::{ast, match_ast, AstNode, AstToken, SyntaxKind::*, SyntaxToken, Toke
 use crate::{
     display::{macro_label, TryToNav},
     doc_links::{
-        doc_owner_to_def, extract_positioned_link_from_comment, remove_links,
-        resolve_doc_path_for_def, rewrite_links,
+        doc_attributes, extract_definitions_from_markdown, remove_links, resolve_doc_path_for_def,
+        rewrite_links,
     },
     markdown_remove::remove_markdown,
     markup::Markup,
@@ -82,6 +82,8 @@ pub struct HoverResult {
 //
 // Shows additional information, like type of an expression or documentation for definition when "focusing" code.
 // Focusing is usually hovering with a mouse, but can also be triggered with a shortcut.
+//
+// image::https://user-images.githubusercontent.com/48062697/113020658-b5f98b80-917a-11eb-9f88-3dbc27320c95.gif[]
 pub(crate) fn hover(
     db: &RootDatabase,
     position: FilePosition,
@@ -114,11 +116,19 @@ pub(crate) fn hover(
             ),
 
             _ => ast::Comment::cast(token.clone())
-                .and_then(|comment| {
+                .and_then(|_| {
+                    let (attributes, def) = doc_attributes(&sema, &node)?;
+                    let (docs, doc_mapping) = attributes.docs_with_rangemap(db)?;
                     let (idl_range, link, ns) =
-                        extract_positioned_link_from_comment(position.offset, &comment)?;
+                        extract_definitions_from_markdown(docs.as_str()).into_iter().find_map(|(range, link, ns)| {
+                            let InFile { file_id, value: range } = doc_mapping.map(range.clone())?;
+                            if file_id == position.file_id.into() && range.contains(position.offset) {
+                                Some((range, link, ns))
+                            } else {
+                                None
+                            }
+                        })?;
                     range = Some(idl_range);
-                    let def = doc_owner_to_def(&sema, &node)?;
                     resolve_doc_path_for_def(db, def, &link, ns)
                 })
                 .map(Definition::ModuleDef),
@@ -195,7 +205,7 @@ fn show_implementations_action(db: &RootDatabase, def: Definition) -> Option<Hov
     let adt = match def {
         Definition::ModuleDef(ModuleDef::Trait(it)) => return it.try_to_nav(db).map(to_action),
         Definition::ModuleDef(ModuleDef::Adt(it)) => Some(it),
-        Definition::SelfType(it) => it.target_ty(db).as_adt(),
+        Definition::SelfType(it) => it.self_ty(db).as_adt(),
         _ => None,
     }?;
     adt.try_to_nav(db).map(to_action)
@@ -318,7 +328,7 @@ fn definition_owner_name(db: &RootDatabase, def: &Definition) -> Option<String>
         Definition::ModuleDef(md) => match md {
             ModuleDef::Function(f) => match f.as_assoc_item(db)?.container(db) {
                 AssocItemContainer::Trait(t) => Some(t.name(db)),
-                AssocItemContainer::Impl(i) => i.target_ty(db).as_adt().map(|adt| adt.name(db)),
+                AssocItemContainer::Impl(i) => i.self_ty(db).as_adt().map(|adt| adt.name(db)),
             },
             ModuleDef::Variant(e) => Some(e.parent_enum(db).name(db)),
             _ => None,
@@ -376,7 +386,7 @@ fn hover_for_definition(
         },
         Definition::Local(it) => hover_for_local(it, db),
         Definition::SelfType(impl_def) => {
-            impl_def.target_ty(db).as_adt().and_then(|adt| from_hir_fmt(db, adt, mod_path))
+            impl_def.self_ty(db).as_adt().and_then(|adt| from_hir_fmt(db, adt, mod_path))
         }
         Definition::GenericParam(it) => from_hir_fmt(db, it, None),
         Definition::Label(it) => Some(Markup::fenced_block(&it.name(db))),
@@ -470,6 +480,7 @@ fn find_std_module(famous_defs: &FamousDefs, name: &str) -> Option<hir::Module>
 
 fn pick_best(tokens: TokenAtOffset<SyntaxToken>) -> Option<SyntaxToken> {
     return tokens.max_by_key(priority);
+
     fn priority(n: &SyntaxToken) -> usize {
         match n.kind() {
             IDENT | INT_NUMBER | LIFETIME_IDENT | T![self] | T![super] | T![crate] => 3,
@@ -3811,24 +3822,139 @@ fn main() {
     fn hover_intra_doc_links() {
         check(
             r#"
-/// This is the [`foo`](foo$0) function.
-fn foo() {}
+
+pub mod theitem {
+    /// This is the item. Cool!
+    pub struct TheItem;
+}
+
+/// Gives you a [`TheItem$0`].
+///
+/// [`TheItem`]: theitem::TheItem
+pub fn gimme() -> theitem::TheItem {
+    theitem::TheItem
+}
 "#,
             expect![[r#"
-                *[`foo`](foo)*
+                *[`TheItem`]*
 
                 ```rust
-                test
+                test::theitem
                 ```
 
                 ```rust
-                fn foo()
+                pub struct TheItem
                 ```
 
                 ---
 
-                This is the [`foo`](https://docs.rs/test/*/test/fn.foo.html) function.
+                This is the item. Cool!
+            "#]],
+        );
+    }
+
+    #[test]
+    fn hover_generic_assoc() {
+        check(
+            r#"
+fn foo<T: A>() where T::Assoc$0: {}
+
+trait A {
+    type Assoc;
+}"#,
+            expect![[r#"
+                *Assoc*
+
+                ```rust
+                test
+                ```
+
+                ```rust
+                type Assoc
+                ```
+            "#]],
+        );
+        check(
+            r#"
+fn foo<T: A>() {
+    let _: <T>::Assoc$0;
+}
+
+trait A {
+    type Assoc;
+}"#,
+            expect![[r#"
+                *Assoc*
+
+                ```rust
+                test
+                ```
+
+                ```rust
+                type Assoc
+                ```
+            "#]],
+        );
+        check(
+            r#"
+trait A where
+    Self::Assoc$0: ,
+{
+    type Assoc;
+}"#,
+            expect![[r#"
+                *Assoc*
+
+                ```rust
+                test
+                ```
+
+                ```rust
+                type Assoc
+                ```
             "#]],
         );
     }
+
+    #[test]
+    fn string_shadowed_with_inner_items() {
+        check(
+            r#"
+//- /main.rs crate:main deps:alloc
+
+/// Custom `String` type.
+struct String;
+
+fn f() {
+    let _: String$0;
+
+    fn inner() {}
+}
+
+//- /alloc.rs crate:alloc
+#[prelude_import]
+pub use string::*;
+
+mod string {
+    /// This is `alloc::String`.
+    pub struct String;
+}
+            "#,
+            expect![[r#"
+                *String*
+
+                ```rust
+                main
+                ```
+
+                ```rust
+                struct String
+                ```
+
+                ---
+
+                Custom `String` type.
+            "#]],
+        )
+    }
 }
diff --git a/crates/ide/src/inlay_hints.rs b/crates/ide/src/inlay_hints.rs
index 25f96222c..d5ef054d8 100644
--- a/crates/ide/src/inlay_hints.rs
+++ b/crates/ide/src/inlay_hints.rs
@@ -52,6 +52,8 @@ pub struct InlayHint {
 //
 // | VS Code | **Rust Analyzer: Toggle inlay hints*
 // |===
+//
+// image::https://user-images.githubusercontent.com/48062697/113020660-b5f98b80-917a-11eb-8d70-3be3fd558cdd.png[]
 pub(crate) fn inlay_hints(
     db: &RootDatabase,
     file_id: FileId,
@@ -232,7 +234,7 @@ fn hint_iterator(
             hir::AssocItem::TypeAlias(alias) if alias.name(db) == known::Item => Some(alias),
             _ => None,
         })?;
-        if let Some(ty) = ty.normalize_trait_assoc_type(db, iter_trait, &[], assoc_type_item) {
+        if let Some(ty) = ty.normalize_trait_assoc_type(db, &[], assoc_type_item) {
             const LABEL_START: &str = "impl Iterator<Item = ";
             const LABEL_END: &str = ">";
 
diff --git a/crates/ide/src/join_lines.rs b/crates/ide/src/join_lines.rs
index 4b25135cd..fe2a349e6 100644
--- a/crates/ide/src/join_lines.rs
+++ b/crates/ide/src/join_lines.rs
@@ -19,6 +19,8 @@ use text_edit::{TextEdit, TextEditBuilder};
 //
 // | VS Code | **Rust Analyzer: Join lines**
 // |===
+//
+// image::https://user-images.githubusercontent.com/48062697/113020661-b6922200-917a-11eb-87c4-b75acc028f11.gif[]
 pub(crate) fn join_lines(file: &SourceFile, range: TextRange) -> TextEdit {
     let range = if range.is_empty() {
         let syntax = file.syntax();
@@ -86,8 +88,11 @@ fn remove_newline(edit: &mut TextEditBuilder, token: &SyntaxToken, offset: TextS
     }
 
     // The node is between two other nodes
-    let prev = token.prev_sibling_or_token().unwrap();
-    let next = token.next_sibling_or_token().unwrap();
+    let (prev, next) = match (token.prev_sibling_or_token(), token.next_sibling_or_token()) {
+        (Some(prev), Some(next)) => (prev, next),
+        _ => return,
+    };
+
     if is_trailing_comma(prev.kind(), next.kind()) {
         // Removes: trailing comma, newline (incl. surrounding whitespace)
         edit.delete(TextRange::new(prev.text_range().start(), token.text_range().end()));
@@ -827,4 +832,15 @@ $0hello world
 "#,
         );
     }
+    #[test]
+    fn join_last_line_empty() {
+        check_join_lines(
+            r#"
+fn main() {$0}
+"#,
+            r#"
+fn main() {$0}
+"#,
+        );
+    }
 }
diff --git a/crates/ide/src/lib.rs b/crates/ide/src/lib.rs
index 3f73c0632..b24c664ba 100644
--- a/crates/ide/src/lib.rs
+++ b/crates/ide/src/lib.rs
@@ -69,7 +69,7 @@ use crate::display::ToNav;
 pub use crate::{
     annotations::{Annotation, AnnotationConfig, AnnotationKind},
     call_hierarchy::CallItem,
-    diagnostics::{Diagnostic, DiagnosticsConfig, Fix, Severity},
+    diagnostics::{Diagnostic, DiagnosticsConfig, Severity},
     display::navigation_target::NavigationTarget,
     expand_macro::ExpandedMacro,
     file_structure::{StructureNode, StructureNodeKind},
@@ -82,7 +82,7 @@ pub use crate::{
     references::{rename::RenameError, ReferenceSearchResult},
     runnables::{Runnable, RunnableKind, TestId},
     syntax_highlighting::{
-        tags::{Highlight, HlMod, HlMods, HlPunct, HlTag},
+        tags::{Highlight, HlMod, HlMods, HlOperator, HlPunct, HlTag},
         HlRange,
     },
 };
@@ -526,9 +526,39 @@ impl Analysis {
     pub fn diagnostics(
         &self,
         config: &DiagnosticsConfig,
+        resolve: bool,
         file_id: FileId,
     ) -> Cancelable<Vec<Diagnostic>> {
-        self.with_db(|db| diagnostics::diagnostics(db, config, file_id))
+        self.with_db(|db| diagnostics::diagnostics(db, config, resolve, file_id))
+    }
+
+    /// Convenience function to return assists + quick fixes for diagnostics
+    pub fn assists_with_fixes(
+        &self,
+        assist_config: &AssistConfig,
+        diagnostics_config: &DiagnosticsConfig,
+        resolve: bool,
+        frange: FileRange,
+    ) -> Cancelable<Vec<Assist>> {
+        let include_fixes = match &assist_config.allowed {
+            Some(it) => it.iter().any(|&it| it == AssistKind::None || it == AssistKind::QuickFix),
+            None => true,
+        };
+
+        self.with_db(|db| {
+            let mut res = Assist::get(db, assist_config, resolve, frange);
+            ssr::add_ssr_assist(db, &mut res, resolve, frange);
+
+            if include_fixes {
+                res.extend(
+                    diagnostics::diagnostics(db, diagnostics_config, resolve, frange.file_id)
+                        .into_iter()
+                        .filter_map(|it| it.fix)
+                        .filter(|it| it.target.intersect(frange.range).is_some()),
+                );
+            }
+            res
+        })
     }
 
     /// Returns the edit required to rename reference at the position to the new
diff --git a/crates/ide/src/matching_brace.rs b/crates/ide/src/matching_brace.rs
index 4241a6dac..261dcc255 100644
--- a/crates/ide/src/matching_brace.rs
+++ b/crates/ide/src/matching_brace.rs
@@ -14,6 +14,8 @@ use syntax::{
 //
 // | VS Code | **Rust Analyzer: Find matching brace**
 // |===
+//
+// image::https://user-images.githubusercontent.com/48062697/113065573-04298180-91b1-11eb-8dec-d4e2a202f304.gif[]
 pub(crate) fn matching_brace(file: &SourceFile, offset: TextSize) -> Option<TextSize> {
     const BRACES: &[SyntaxKind] =
         &[T!['{'], T!['}'], T!['['], T![']'], T!['('], T![')'], T![<], T![>], T![|], T![|]];
diff --git a/crates/ide/src/move_item.rs b/crates/ide/src/move_item.rs
index 05fa8fc13..246f10a0a 100644
--- a/crates/ide/src/move_item.rs
+++ b/crates/ide/src/move_item.rs
@@ -1,13 +1,15 @@
-use std::iter::once;
+use std::{iter::once, mem};
 
 use hir::Semantics;
 use ide_db::{base_db::FileRange, RootDatabase};
 use itertools::Itertools;
 use syntax::{
-    algo, ast, match_ast, AstNode, NodeOrToken, SyntaxElement, SyntaxKind, SyntaxNode, TextRange,
+    algo, ast, match_ast, AstNode, SyntaxElement, SyntaxKind, SyntaxNode, SyntaxToken, TextRange,
+    TokenAtOffset,
 };
 use text_edit::{TextEdit, TextEditBuilder};
 
+#[derive(Copy, Clone, Debug)]
 pub enum Direction {
     Up,
     Down,
@@ -23,6 +25,8 @@ pub enum Direction {
 // | VS Code | **Rust Analyzer: Move item up**
 // | VS Code | **Rust Analyzer: Move item down**
 // |===
+//
+// image::https://user-images.githubusercontent.com/48062697/113065576-04298180-91b1-11eb-91ce-4505e99ed598.gif[]
 pub(crate) fn move_item(
     db: &RootDatabase,
     range: FileRange,
@@ -31,14 +35,19 @@ pub(crate) fn move_item(
     let sema = Semantics::new(db);
     let file = sema.parse(range.file_id);
 
-    let item = file.syntax().covering_element(range.range);
+    let item = if range.range.is_empty() {
+        SyntaxElement::Token(pick_best(file.syntax().token_at_offset(range.range.start()))?)
+    } else {
+        file.syntax().covering_element(range.range)
+    };
+
     find_ancestors(item, direction, range.range)
 }
 
 fn find_ancestors(item: SyntaxElement, direction: Direction, range: TextRange) -> Option<TextEdit> {
     let root = match item {
-        NodeOrToken::Node(node) => node,
-        NodeOrToken::Token(token) => token.parent()?,
+        SyntaxElement::Node(node) => node,
+        SyntaxElement::Token(token) => token.parent()?,
     };
 
     let movable = [
@@ -51,6 +60,11 @@ fn find_ancestors(item: SyntaxElement, direction: Direction, range: TextRange) -
         SyntaxKind::PARAM,
         SyntaxKind::LET_STMT,
         SyntaxKind::EXPR_STMT,
+        SyntaxKind::IF_EXPR,
+        SyntaxKind::FOR_EXPR,
+        SyntaxKind::LOOP_EXPR,
+        SyntaxKind::WHILE_EXPR,
+        SyntaxKind::RETURN_EXPR,
         SyntaxKind::MATCH_EXPR,
         SyntaxKind::MACRO_CALL,
         SyntaxKind::TYPE_ALIAS,
@@ -83,12 +97,12 @@ fn move_in_direction(
 ) -> Option<TextEdit> {
     match_ast! {
         match node {
-            ast::ArgList(it) => swap_sibling_in_list(it.args(), range, direction),
-            ast::GenericParamList(it) => swap_sibling_in_list(it.generic_params(), range, direction),
-            ast::GenericArgList(it) => swap_sibling_in_list(it.generic_args(), range, direction),
-            ast::VariantList(it) => swap_sibling_in_list(it.variants(), range, direction),
-            ast::TypeBoundList(it) => swap_sibling_in_list(it.bounds(), range, direction),
-            _ => Some(replace_nodes(node, &match direction {
+            ast::ArgList(it) => swap_sibling_in_list(node, it.args(), range, direction),
+            ast::GenericParamList(it) => swap_sibling_in_list(node, it.generic_params(), range, direction),
+            ast::GenericArgList(it) => swap_sibling_in_list(node, it.generic_args(), range, direction),
+            ast::VariantList(it) => swap_sibling_in_list(node, it.variants(), range, direction),
+            ast::TypeBoundList(it) => swap_sibling_in_list(node, it.bounds(), range, direction),
+            _ => Some(replace_nodes(range, node, &match direction {
                 Direction::Up => node.prev_sibling(),
                 Direction::Down => node.next_sibling(),
             }?))
@@ -97,30 +111,77 @@ fn move_in_direction(
 }
 
 fn swap_sibling_in_list<A: AstNode + Clone, I: Iterator<Item = A>>(
+    node: &SyntaxNode,
     list: I,
     range: TextRange,
     direction: Direction,
 ) -> Option<TextEdit> {
-    let (l, r) = list
+    let list_lookup = list
         .tuple_windows()
         .filter(|(l, r)| match direction {
             Direction::Up => r.syntax().text_range().contains_range(range),
             Direction::Down => l.syntax().text_range().contains_range(range),
         })
-        .next()?;
-
-    Some(replace_nodes(l.syntax(), r.syntax()))
+        .next();
+
+    if let Some((l, r)) = list_lookup {
+        Some(replace_nodes(range, l.syntax(), r.syntax()))
+    } else {
+        // Cursor is beyond any movable list item (for example, on curly brace in enum).
+        // It's not necessary, that parent of list is movable (arg list's parent is not, for example),
+        // and we have to continue tree traversal to find suitable node.
+        find_ancestors(SyntaxElement::Node(node.parent()?), direction, range)
+    }
 }
 
-fn replace_nodes(first: &SyntaxNode, second: &SyntaxNode) -> TextEdit {
+fn replace_nodes<'a>(
+    range: TextRange,
+    mut first: &'a SyntaxNode,
+    mut second: &'a SyntaxNode,
+) -> TextEdit {
+    let cursor_offset = if range.is_empty() {
+        // FIXME: `applySnippetTextEdits` does not support non-empty selection ranges
+        if first.text_range().contains_range(range) {
+            Some(range.start() - first.text_range().start())
+        } else if second.text_range().contains_range(range) {
+            mem::swap(&mut first, &mut second);
+            Some(range.start() - first.text_range().start())
+        } else {
+            None
+        }
+    } else {
+        None
+    };
+
+    let first_with_cursor = match cursor_offset {
+        Some(offset) => {
+            let mut item_text = first.text().to_string();
+            item_text.insert_str(offset.into(), "$0");
+            item_text
+        }
+        None => first.text().to_string(),
+    };
+
     let mut edit = TextEditBuilder::default();
 
     algo::diff(first, second).into_text_edit(&mut edit);
-    algo::diff(second, first).into_text_edit(&mut edit);
+    edit.replace(second.text_range(), first_with_cursor);
 
     edit.finish()
 }
 
+fn pick_best(tokens: TokenAtOffset<SyntaxToken>) -> Option<SyntaxToken> {
+    return tokens.max_by_key(priority);
+
+    fn priority(n: &SyntaxToken) -> usize {
+        match n.kind() {
+            SyntaxKind::IDENT | SyntaxKind::LIFETIME_IDENT => 2,
+            kind if kind.is_trivia() => 0,
+            _ => 1,
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use crate::fixture;
@@ -154,7 +215,7 @@ fn main() {
             expect![[r#"
 fn main() {
     match true {
-        false => {
+        false =>$0 {
             println!("Test");
         },
         true => {
@@ -188,7 +249,7 @@ fn main() {
         false => {
             println!("Test");
         },
-        true => {
+        true =>$0 {
             println!("Hello, world");
         }
     };
@@ -240,7 +301,7 @@ fn main() {
             "#,
             expect![[r#"
 fn main() {
-    let test2 = 456;
+    let test2$0 = 456;
     let test = 123;
 }
             "#]],
@@ -259,7 +320,108 @@ fn main() {
             "#,
             expect![[r#"
 fn main() {
-    println!("All I want to say is...");
+    println!("All I want to say is...");$0
+    println!("Hello, world");
+}
+            "#]],
+            Direction::Up,
+        );
+        check(
+            r#"
+fn main() {
+    println!("Hello, world");
+
+    if true {
+        println!("Test");
+    }$0$0
+}
+            "#,
+            expect![[r#"
+fn main() {
+    if true {
+        println!("Test");
+    }$0
+
+    println!("Hello, world");
+}
+            "#]],
+            Direction::Up,
+        );
+        check(
+            r#"
+fn main() {
+    println!("Hello, world");
+
+    for i in 0..10 {
+        println!("Test");
+    }$0$0
+}
+            "#,
+            expect![[r#"
+fn main() {
+    for i in 0..10 {
+        println!("Test");
+    }$0
+
+    println!("Hello, world");
+}
+            "#]],
+            Direction::Up,
+        );
+        check(
+            r#"
+fn main() {
+    println!("Hello, world");
+
+    loop {
+        println!("Test");
+    }$0$0
+}
+            "#,
+            expect![[r#"
+fn main() {
+    loop {
+        println!("Test");
+    }$0
+
+    println!("Hello, world");
+}
+            "#]],
+            Direction::Up,
+        );
+        check(
+            r#"
+fn main() {
+    println!("Hello, world");
+
+    while true {
+        println!("Test");
+    }$0$0
+}
+            "#,
+            expect![[r#"
+fn main() {
+    while true {
+        println!("Test");
+    }$0
+
+    println!("Hello, world");
+}
+            "#]],
+            Direction::Up,
+        );
+        check(
+            r#"
+fn main() {
+    println!("Hello, world");
+
+    return 123;$0$0
+}
+            "#,
+            expect![[r#"
+fn main() {
+    return 123;$0
+
     println!("Hello, world");
 }
             "#]],
@@ -295,7 +457,7 @@ fn main() {}
 fn foo() {}$0$0
             "#,
             expect![[r#"
-fn foo() {}
+fn foo() {}$0
 
 fn main() {}
             "#]],
@@ -316,7 +478,7 @@ impl Wow for Yay $0$0{}
             expect![[r#"
 struct Yay;
 
-impl Wow for Yay {}
+impl Wow for Yay $0{}
 
 trait Wow {}
             "#]],
@@ -332,7 +494,7 @@ use std::vec::Vec;
 use std::collections::HashMap$0$0;
             "#,
             expect![[r#"
-use std::collections::HashMap;
+use std::collections::HashMap$0;
 use std::vec::Vec;
             "#]],
             Direction::Up,
@@ -367,7 +529,7 @@ fn main() {
     }
 
     #[test]
-    fn test_moves_param_up() {
+    fn test_moves_param() {
         check(
             r#"
 fn test(one: i32, two$0$0: u32) {}
@@ -377,7 +539,7 @@ fn main() {
 }
             "#,
             expect![[r#"
-fn test(two: u32, one: i32) {}
+fn test(two$0: u32, one: i32) {}
 
 fn main() {
     test(123, 456);
@@ -385,6 +547,15 @@ fn main() {
             "#]],
             Direction::Up,
         );
+        check(
+            r#"
+fn f($0$0arg: u8, arg2: u16) {}
+            "#,
+            expect![[r#"
+fn f(arg2: u16, $0arg: u8) {}
+            "#]],
+            Direction::Down,
+        );
     }
 
     #[test]
@@ -401,7 +572,7 @@ fn main() {
 fn test(one: i32, two: u32) {}
 
 fn main() {
-    test(456, 123);
+    test(456$0, 123);
 }
             "#]],
             Direction::Up,
@@ -422,7 +593,7 @@ fn main() {
 fn test(one: i32, two: u32) {}
 
 fn main() {
-    test(456, 123);
+    test(456, 123$0);
 }
             "#]],
             Direction::Down,
@@ -459,7 +630,7 @@ struct Test<A, B$0$0>(A, B);
 fn main() {}
             "#,
             expect![[r#"
-struct Test<B, A>(A, B);
+struct Test<B$0, A>(A, B);
 
 fn main() {}
             "#]],
@@ -481,7 +652,7 @@ fn main() {
 struct Test<A, B>(A, B);
 
 fn main() {
-    let t = Test::<&str, i32>(123, "yay");
+    let t = Test::<&str$0, i32>(123, "yay");
 }
             "#]],
             Direction::Up,
@@ -501,7 +672,7 @@ fn main() {}
             "#,
             expect![[r#"
 enum Hello {
-    Two,
+    Two$0,
     One
 }
 
@@ -528,7 +699,7 @@ trait One {}
 
 trait Two {}
 
-fn test<T: Two + One>(t: T) {}
+fn test<T: Two$0 + One>(t: T) {}
 
 fn main() {}
             "#]],
@@ -574,7 +745,7 @@ trait Yay {
 impl Yay for Test {
     type One = i32;
 
-    fn inner() {
+    fn inner() {$0
         println!("Mmmm");
     }
 
@@ -601,7 +772,7 @@ fn test() {
             "#,
             expect![[r#"
 fn test() {
-    mod hi {
+    mod hi {$0
         fn inner() {}
     }
 
@@ -615,6 +786,115 @@ fn test() {
     }
 
     #[test]
+    fn test_cursor_at_item_start() {
+        check(
+            r#"
+$0$0#[derive(Debug)]
+enum FooBar {
+    Foo,
+    Bar,
+}
+
+fn main() {}
+            "#,
+            expect![[r#"
+fn main() {}
+
+$0#[derive(Debug)]
+enum FooBar {
+    Foo,
+    Bar,
+}
+            "#]],
+            Direction::Down,
+        );
+        check(
+            r#"
+$0$0enum FooBar {
+    Foo,
+    Bar,
+}
+
+fn main() {}
+            "#,
+            expect![[r#"
+fn main() {}
+
+$0enum FooBar {
+    Foo,
+    Bar,
+}
+            "#]],
+            Direction::Down,
+        );
+        check(
+            r#"
+struct Test;
+
+trait SomeTrait {}
+
+$0$0impl SomeTrait for Test {}
+
+fn main() {}
+            "#,
+            expect![[r#"
+struct Test;
+
+$0impl SomeTrait for Test {}
+
+trait SomeTrait {}
+
+fn main() {}
+            "#]],
+            Direction::Up,
+        );
+    }
+
+    #[test]
+    fn test_cursor_at_item_end() {
+        check(
+            r#"
+enum FooBar {
+    Foo,
+    Bar,
+}$0$0
+
+fn main() {}
+            "#,
+            expect![[r#"
+fn main() {}
+
+enum FooBar {
+    Foo,
+    Bar,
+}$0
+            "#]],
+            Direction::Down,
+        );
+        check(
+            r#"
+struct Test;
+
+trait SomeTrait {}
+
+impl SomeTrait for Test {}$0$0
+
+fn main() {}
+            "#,
+            expect![[r#"
+struct Test;
+
+impl SomeTrait for Test {}$0
+
+trait SomeTrait {}
+
+fn main() {}
+            "#]],
+            Direction::Up,
+        );
+    }
+
+    #[test]
     fn handles_empty_file() {
         check(r#"$0$0"#, expect![[r#""#]], Direction::Up);
     }
diff --git a/crates/ide/src/parent_module.rs b/crates/ide/src/parent_module.rs
index 22b0d6ecb..99365c8a7 100644
--- a/crates/ide/src/parent_module.rs
+++ b/crates/ide/src/parent_module.rs
@@ -18,6 +18,8 @@ use crate::NavigationTarget;
 //
 // | VS Code | **Rust Analyzer: Locate parent module**
 // |===
+//
+// image::https://user-images.githubusercontent.com/48062697/113065580-04c21800-91b1-11eb-9a32-00086161c0bd.gif[]
 
 /// This returns `Vec` because a module may be included from several places.
 pub(crate) fn parent_module(db: &RootDatabase, position: FilePosition) -> Vec<NavigationTarget> {
diff --git a/crates/ide/src/references.rs b/crates/ide/src/references.rs
index 95ed8a045..11ca7ec6b 100644
--- a/crates/ide/src/references.rs
+++ b/crates/ide/src/references.rs
@@ -48,6 +48,8 @@ pub struct Declaration {
 //
 // | VS Code | kbd:[Shift+Alt+F12]
 // |===
+//
+// image::https://user-images.githubusercontent.com/48062697/113020670-b7c34f00-917a-11eb-8003-370ac5f2b3cb.gif[]
 pub(crate) fn find_all_refs(
     sema: &Semantics<RootDatabase>,
     position: FilePosition,
diff --git a/crates/ide/src/references/rename.rs b/crates/ide/src/references/rename.rs
index 26d6dc9c9..2408a0181 100644
--- a/crates/ide/src/references/rename.rs
+++ b/crates/ide/src/references/rename.rs
@@ -70,6 +70,8 @@ pub(crate) fn prepare_rename(
 //
 // | VS Code | kbd:[F2]
 // |===
+//
+// image::https://user-images.githubusercontent.com/48062697/113065582-055aae80-91b1-11eb-8ade-2b58e6d81883.gif[]
 pub(crate) fn rename(
     db: &RootDatabase,
     position: FilePosition,
@@ -307,7 +309,7 @@ fn rename_to_self(sema: &Semantics<RootDatabase>, local: hir::Local) -> RenameRe
         hir::AssocItemContainer::Impl(impl_) => impl_,
     };
     let first_param_ty = first_param.ty();
-    let impl_ty = impl_.target_ty(sema.db);
+    let impl_ty = impl_.self_ty(sema.db);
     let (ty, self_param) = if impl_ty.remove_ref().is_some() {
         // if the impl is a ref to the type we can just match the `&T` with self directly
         (first_param_ty.clone(), "self")
diff --git a/crates/ide/src/runnables.rs b/crates/ide/src/runnables.rs
index 7e4c5a078..3eb9e27ee 100644
--- a/crates/ide/src/runnables.rs
+++ b/crates/ide/src/runnables.rs
@@ -98,6 +98,7 @@ impl Runnable {
 //
 // | VS Code | **Rust Analyzer: Run**
 // |===
+// image::https://user-images.githubusercontent.com/48062697/113065583-055aae80-91b1-11eb-958f-d67efcaf6a2f.gif[]
 pub(crate) fn runnables(db: &RootDatabase, file_id: FileId) -> Vec<Runnable> {
     let sema = Semantics::new(db);
 
@@ -298,7 +299,7 @@ fn module_def_doctest(sema: &Semantics<RootDatabase>, def: hir::ModuleDef) -> Op
             // FIXME: this also looks very wrong
             if let Some(assoc_def) = assoc_def {
                 if let hir::AssocItemContainer::Impl(imp) = assoc_def.container(sema.db) {
-                    let ty = imp.target_ty(sema.db);
+                    let ty = imp.self_ty(sema.db);
                     if let Some(adt) = ty.as_adt() {
                         let name = adt.name(sema.db);
                         let idx = path.rfind(':').map_or(0, |idx| idx + 1);
diff --git a/crates/ide/src/status.rs b/crates/ide/src/status.rs
index 137c38c0d..49fde1945 100644
--- a/crates/ide/src/status.rs
+++ b/crates/ide/src/status.rs
@@ -31,6 +31,7 @@ fn macro_syntax_tree_stats(db: &RootDatabase) -> SyntaxTreeStats {
 //
 // | VS Code | **Rust Analyzer: Status**
 // |===
+// image::https://user-images.githubusercontent.com/48062697/113065584-05f34500-91b1-11eb-98cc-5c196f76be7f.gif[]
 pub(crate) fn status(db: &RootDatabase, file_id: Option<FileId>) -> String {
     let mut buf = String::new();
     format_to!(buf, "{}\n", FileTextQuery.in_db(db).entries::<FilesStats>());
diff --git a/crates/ide/src/syntax_highlighting.rs b/crates/ide/src/syntax_highlighting.rs
index 67a10766b..9df8d21af 100644
--- a/crates/ide/src/syntax_highlighting.rs
+++ b/crates/ide/src/syntax_highlighting.rs
@@ -48,6 +48,9 @@ pub struct HlRange {
 //
 // The general rule is that a reference to an entity gets colored the same way as the entity itself.
 // We also give special modifier for `mut` and `&mut` local variables.
+//
+// image::https://user-images.githubusercontent.com/48062697/113164457-06cfb980-9239-11eb-819b-0f93e646acf8.png[]
+// image::https://user-images.githubusercontent.com/48062697/113187625-f7f50100-9250-11eb-825e-91c58f236071.png[]
 pub(crate) fn highlight(
     db: &RootDatabase,
     file_id: FileId,
diff --git a/crates/ide/src/syntax_highlighting/highlight.rs b/crates/ide/src/syntax_highlighting/highlight.rs
index b0cfdd8b7..8cc877c1c 100644
--- a/crates/ide/src/syntax_highlighting/highlight.rs
+++ b/crates/ide/src/syntax_highlighting/highlight.rs
@@ -1,6 +1,6 @@
 //! Computes color for a single element.
 
-use hir::{AsAssocItem, Semantics, VariantDef};
+use hir::{AsAssocItem, AssocItemContainer, Semantics, VariantDef};
 use ide_db::{
     defs::{Definition, NameClass, NameRefClass},
     RootDatabase, SymbolKind,
@@ -12,7 +12,10 @@ use syntax::{
     SyntaxNode, SyntaxToken, T,
 };
 
-use crate::{syntax_highlighting::tags::HlPunct, Highlight, HlMod, HlTag};
+use crate::{
+    syntax_highlighting::tags::{HlOperator, HlPunct},
+    Highlight, HlMod, HlTag,
+};
 
 pub(super) fn element(
     sema: &Semantics<RootDatabase>,
@@ -132,7 +135,7 @@ pub(super) fn element(
         INT_NUMBER | FLOAT_NUMBER => HlTag::NumericLiteral.into(),
         BYTE => HlTag::ByteLiteral.into(),
         CHAR => HlTag::CharLiteral.into(),
-        QUESTION => Highlight::new(HlTag::Operator) | HlMod::ControlFlow,
+        QUESTION => Highlight::new(HlTag::Operator(HlOperator::Other)) | HlMod::ControlFlow,
         LIFETIME => {
             let lifetime = element.into_node().and_then(ast::Lifetime::cast).unwrap();
 
@@ -146,8 +149,11 @@ pub(super) fn element(
             }
         }
         p if p.is_punct() => match p {
+            T![&] if element.parent().and_then(ast::BinExpr::cast).is_some() => {
+                HlTag::Operator(HlOperator::Bitwise).into()
+            }
             T![&] => {
-                let h = HlTag::Operator.into();
+                let h = HlTag::Operator(HlOperator::Other).into();
                 let is_unsafe = element
                     .parent()
                     .and_then(ast::RefExpr::cast)
@@ -159,13 +165,18 @@ pub(super) fn element(
                     h
                 }
             }
-            T![::] | T![->] | T![=>] | T![..] | T![=] | T![@] | T![.] => HlTag::Operator.into(),
+            T![::] | T![->] | T![=>] | T![..] | T![=] | T![@] | T![.] => {
+                HlTag::Operator(HlOperator::Other).into()
+            }
             T![!] if element.parent().and_then(ast::MacroCall::cast).is_some() => {
                 HlTag::Symbol(SymbolKind::Macro).into()
             }
             T![!] if element.parent().and_then(ast::NeverType::cast).is_some() => {
                 HlTag::BuiltinType.into()
             }
+            T![!] if element.parent().and_then(ast::PrefixExpr::cast).is_some() => {
+                HlTag::Operator(HlOperator::Logical).into()
+            }
             T![*] if element.parent().and_then(ast::PtrType::cast).is_some() => {
                 HlTag::Keyword.into()
             }
@@ -175,9 +186,9 @@ pub(super) fn element(
                 let expr = prefix_expr.expr()?;
                 let ty = sema.type_of_expr(&expr)?;
                 if ty.is_raw_ptr() {
-                    HlTag::Operator | HlMod::Unsafe
+                    HlTag::Operator(HlOperator::Other) | HlMod::Unsafe
                 } else if let Some(ast::PrefixOp::Deref) = prefix_expr.op_kind() {
-                    HlTag::Operator.into()
+                    HlTag::Operator(HlOperator::Other).into()
                 } else {
                     HlTag::Punctuation(HlPunct::Other).into()
                 }
@@ -188,19 +199,43 @@ pub(super) fn element(
                 let expr = prefix_expr.expr()?;
                 match expr {
                     ast::Expr::Literal(_) => HlTag::NumericLiteral,
-                    _ => HlTag::Operator,
+                    _ => HlTag::Operator(HlOperator::Other),
                 }
                 .into()
             }
             _ if element.parent().and_then(ast::PrefixExpr::cast).is_some() => {
-                HlTag::Operator.into()
+                HlTag::Operator(HlOperator::Other).into()
+            }
+            T![+] | T![-] | T![*] | T![/] | T![+=] | T![-=] | T![*=] | T![/=]
+                if element.parent().and_then(ast::BinExpr::cast).is_some() =>
+            {
+                HlTag::Operator(HlOperator::Arithmetic).into()
+            }
+            T![|] | T![&] | T![!] | T![^] | T![|=] | T![&=] | T![^=]
+                if element.parent().and_then(ast::BinExpr::cast).is_some() =>
+            {
+                HlTag::Operator(HlOperator::Bitwise).into()
+            }
+            T![&&] | T![||] if element.parent().and_then(ast::BinExpr::cast).is_some() => {
+                HlTag::Operator(HlOperator::Logical).into()
+            }
+            T![>] | T![<] | T![==] | T![>=] | T![<=] | T![!=]
+                if element.parent().and_then(ast::BinExpr::cast).is_some() =>
+            {
+                HlTag::Operator(HlOperator::Comparision).into()
+            }
+            _ if element.parent().and_then(ast::BinExpr::cast).is_some() => {
+                HlTag::Operator(HlOperator::Other).into()
             }
-            _ if element.parent().and_then(ast::BinExpr::cast).is_some() => HlTag::Operator.into(),
             _ if element.parent().and_then(ast::RangeExpr::cast).is_some() => {
-                HlTag::Operator.into()
+                HlTag::Operator(HlOperator::Other).into()
+            }
+            _ if element.parent().and_then(ast::RangePat::cast).is_some() => {
+                HlTag::Operator(HlOperator::Other).into()
+            }
+            _ if element.parent().and_then(ast::RestPat::cast).is_some() => {
+                HlTag::Operator(HlOperator::Other).into()
             }
-            _ if element.parent().and_then(ast::RangePat::cast).is_some() => HlTag::Operator.into(),
-            _ if element.parent().and_then(ast::RestPat::cast).is_some() => HlTag::Operator.into(),
             _ if element.parent().and_then(ast::Attr::cast).is_some() => HlTag::Attribute.into(),
             kind => HlTag::Punctuation(match kind {
                 T!['['] | T![']'] => HlPunct::Bracket,
@@ -275,12 +310,24 @@ fn highlight_def(db: &RootDatabase, def: Definition) -> Highlight {
             hir::ModuleDef::Module(_) => HlTag::Symbol(SymbolKind::Module),
             hir::ModuleDef::Function(func) => {
                 let mut h = Highlight::new(HlTag::Symbol(SymbolKind::Function));
-                if func.as_assoc_item(db).is_some() {
+                if let Some(item) = func.as_assoc_item(db) {
                     h |= HlMod::Associated;
                     if func.self_param(db).is_none() {
                         h |= HlMod::Static
                     }
+
+                    match item.container(db) {
+                        AssocItemContainer::Impl(i) => {
+                            if i.trait_(db).is_some() {
+                                h |= HlMod::Trait;
+                            }
+                        }
+                        AssocItemContainer::Trait(_t) => {
+                            h |= HlMod::Trait;
+                        }
+                    }
                 }
+
                 if func.is_unsafe(db) {
                     h |= HlMod::Unsafe;
                 }
@@ -292,16 +339,37 @@ fn highlight_def(db: &RootDatabase, def: Definition) -> Highlight {
             hir::ModuleDef::Variant(_) => HlTag::Symbol(SymbolKind::Variant),
             hir::ModuleDef::Const(konst) => {
                 let mut h = Highlight::new(HlTag::Symbol(SymbolKind::Const));
-                if konst.as_assoc_item(db).is_some() {
-                    h |= HlMod::Associated
+                if let Some(item) = konst.as_assoc_item(db) {
+                    h |= HlMod::Associated;
+                    match item.container(db) {
+                        AssocItemContainer::Impl(i) => {
+                            if i.trait_(db).is_some() {
+                                h |= HlMod::Trait;
+                            }
+                        }
+                        AssocItemContainer::Trait(_t) => {
+                            h |= HlMod::Trait;
+                        }
+                    }
                 }
+
                 return h;
             }
             hir::ModuleDef::Trait(_) => HlTag::Symbol(SymbolKind::Trait),
             hir::ModuleDef::TypeAlias(type_) => {
                 let mut h = Highlight::new(HlTag::Symbol(SymbolKind::TypeAlias));
-                if type_.as_assoc_item(db).is_some() {
-                    h |= HlMod::Associated
+                if let Some(item) = type_.as_assoc_item(db) {
+                    h |= HlMod::Associated;
+                    match item.container(db) {
+                        AssocItemContainer::Impl(i) => {
+                            if i.trait_(db).is_some() {
+                                h |= HlMod::Trait;
+                            }
+                        }
+                        AssocItemContainer::Trait(_t) => {
+                            h |= HlMod::Trait;
+                        }
+                    }
                 }
                 return h;
             }
@@ -362,6 +430,10 @@ fn highlight_method_call(
     if func.is_unsafe(sema.db) || sema.is_unsafe_method_call(&method_call) {
         h |= HlMod::Unsafe;
     }
+    if func.as_assoc_item(sema.db).and_then(|it| it.containing_trait(sema.db)).is_some() {
+        h |= HlMod::Trait
+    }
+
     if let Some(self_param) = func.self_param(sema.db) {
         match self_param.access(sema.db) {
             hir::Access::Shared => (),
diff --git a/crates/ide/src/syntax_highlighting/inject.rs b/crates/ide/src/syntax_highlighting/inject.rs
index 963c3fb59..04fafd244 100644
--- a/crates/ide/src/syntax_highlighting/inject.rs
+++ b/crates/ide/src/syntax_highlighting/inject.rs
@@ -1,17 +1,18 @@
 //! "Recursive" Syntax highlighting for code in doctests and fixtures.
 
-use std::{mem, ops::Range};
+use std::mem;
 
 use either::Either;
-use hir::{HasAttrs, InFile, Semantics};
-use ide_db::{call_info::ActiveParameter, defs::Definition, SymbolKind};
+use hir::{InFile, Semantics};
+use ide_db::{call_info::ActiveParameter, SymbolKind};
 use syntax::{
     ast::{self, AstNode},
-    match_ast, AstToken, NodeOrToken, SyntaxNode, SyntaxToken, TextRange, TextSize,
+    AstToken, NodeOrToken, SyntaxNode, SyntaxToken, TextRange, TextSize,
 };
 
 use crate::{
-    doc_links::extract_definitions_from_markdown, Analysis, HlMod, HlRange, HlTag, RootDatabase,
+    doc_links::{doc_attributes, extract_definitions_from_markdown, resolve_doc_path_for_def},
+    Analysis, HlMod, HlRange, HlTag, RootDatabase,
 };
 
 use super::{highlights::Highlights, injector::Injector};
@@ -89,33 +90,6 @@ const RUSTDOC_FENCE_TOKENS: &[&'static str] = &[
     "edition2021",
 ];
 
-fn doc_attributes<'node>(
-    sema: &Semantics<RootDatabase>,
-    node: &'node SyntaxNode,
-) -> Option<(hir::AttrsWithOwner, Definition)> {
-    match_ast! {
-        match node {
-            ast::SourceFile(it)  => sema.to_def(&it).map(|def| (def.attrs(sema.db), Definition::ModuleDef(hir::ModuleDef::Module(def)))),
-            ast::Module(it)      => sema.to_def(&it).map(|def| (def.attrs(sema.db), Definition::ModuleDef(hir::ModuleDef::Module(def)))),
-            ast::Fn(it)          => sema.to_def(&it).map(|def| (def.attrs(sema.db), Definition::ModuleDef(hir::ModuleDef::Function(def)))),
-            ast::Struct(it)      => sema.to_def(&it).map(|def| (def.attrs(sema.db), Definition::ModuleDef(hir::ModuleDef::Adt(hir::Adt::Struct(def))))),
-            ast::Union(it)       => sema.to_def(&it).map(|def| (def.attrs(sema.db), Definition::ModuleDef(hir::ModuleDef::Adt(hir::Adt::Union(def))))),
-            ast::Enum(it)        => sema.to_def(&it).map(|def| (def.attrs(sema.db), Definition::ModuleDef(hir::ModuleDef::Adt(hir::Adt::Enum(def))))),
-            ast::Variant(it)     => sema.to_def(&it).map(|def| (def.attrs(sema.db), Definition::ModuleDef(hir::ModuleDef::Variant(def)))),
-            ast::Trait(it)       => sema.to_def(&it).map(|def| (def.attrs(sema.db), Definition::ModuleDef(hir::ModuleDef::Trait(def)))),
-            ast::Static(it)      => sema.to_def(&it).map(|def| (def.attrs(sema.db), Definition::ModuleDef(hir::ModuleDef::Static(def)))),
-            ast::Const(it)       => sema.to_def(&it).map(|def| (def.attrs(sema.db), Definition::ModuleDef(hir::ModuleDef::Const(def)))),
-            ast::TypeAlias(it)   => sema.to_def(&it).map(|def| (def.attrs(sema.db), Definition::ModuleDef(hir::ModuleDef::TypeAlias(def)))),
-            ast::Impl(it)        => sema.to_def(&it).map(|def| (def.attrs(sema.db), Definition::SelfType(def))),
-            ast::RecordField(it) => sema.to_def(&it).map(|def| (def.attrs(sema.db), Definition::Field(def))),
-            ast::TupleField(it)  => sema.to_def(&it).map(|def| (def.attrs(sema.db), Definition::Field(def))),
-            ast::Macro(it)       => sema.to_def(&it).map(|def| (def.attrs(sema.db), Definition::Macro(def))),
-            // ast::Use(it) => sema.to_def(&it).map(|def| (Box::new(it) as _, def.attrs(sema.db))),
-            _ => return None
-        }
-    }
-}
-
 /// Injection of syntax highlighting of doctests.
 pub(super) fn doc_comment(
     hl: &mut Highlights,
@@ -138,8 +112,28 @@ pub(super) fn doc_comment(
     // Replace the original, line-spanning comment ranges by new, only comment-prefix
     // spanning comment ranges.
     let mut new_comments = Vec::new();
-    let mut intra_doc_links = Vec::new();
     let mut string;
+
+    if let Some((docs, doc_mapping)) = attributes.docs_with_rangemap(sema.db) {
+        extract_definitions_from_markdown(docs.as_str())
+            .into_iter()
+            .filter_map(|(range, link, ns)| {
+                let def = resolve_doc_path_for_def(sema.db, def, &link, ns)?;
+                let InFile { file_id, value: range } = doc_mapping.map(range)?;
+                (file_id == node.file_id).then(|| (range, def))
+            })
+            .for_each(|(range, def)| {
+                hl.add(HlRange {
+                    range,
+                    highlight: module_def_to_hl_tag(def)
+                        | HlMod::Documentation
+                        | HlMod::Injected
+                        | HlMod::IntraDocLink,
+                    binding_hash: None,
+                })
+            });
+    }
+
     for attr in attributes.by_key("doc").attrs() {
         let InFile { file_id, value: src } = attrs_source_map.source_of(&attr);
         if file_id != node.file_id {
@@ -185,25 +179,7 @@ pub(super) fn doc_comment(
                     is_doctest = is_codeblock && is_rust;
                     continue;
                 }
-                None if !is_doctest => {
-                    intra_doc_links.extend(
-                        extract_definitions_from_markdown(line)
-                            .into_iter()
-                            .filter_map(|(range, link, ns)| {
-                                Some(range).zip(validate_intra_doc_link(sema.db, &def, &link, ns))
-                            })
-                            .map(|(Range { start, end }, def)| {
-                                (
-                                    def,
-                                    TextRange::at(
-                                        prev_range_start + TextSize::from(start as u32),
-                                        TextSize::from((end - start) as u32),
-                                    ),
-                                )
-                            }),
-                    );
-                    continue;
-                }
+                None if !is_doctest => continue,
                 None => (),
             }
 
@@ -222,17 +198,6 @@ pub(super) fn doc_comment(
         }
     }
 
-    for (def, range) in intra_doc_links {
-        hl.add(HlRange {
-            range,
-            highlight: module_def_to_hl_tag(def)
-                | HlMod::Documentation
-                | HlMod::Injected
-                | HlMod::IntraDocLink,
-            binding_hash: None,
-        });
-    }
-
     if new_comments.is_empty() {
         return; // no need to run an analysis on an empty file
     }
@@ -283,33 +248,6 @@ fn find_doc_string_in_attr(attr: &hir::Attr, it: &ast::Attr) -> Option<ast::Stri
     }
 }
 
-fn validate_intra_doc_link(
-    db: &RootDatabase,
-    def: &Definition,
-    link: &str,
-    ns: Option<hir::Namespace>,
-) -> Option<hir::ModuleDef> {
-    match def {
-        Definition::ModuleDef(def) => match def {
-            hir::ModuleDef::Module(it) => it.resolve_doc_path(db, &link, ns),
-            hir::ModuleDef::Function(it) => it.resolve_doc_path(db, &link, ns),
-            hir::ModuleDef::Adt(it) => it.resolve_doc_path(db, &link, ns),
-            hir::ModuleDef::Variant(it) => it.resolve_doc_path(db, &link, ns),
-            hir::ModuleDef::Const(it) => it.resolve_doc_path(db, &link, ns),
-            hir::ModuleDef::Static(it) => it.resolve_doc_path(db, &link, ns),
-            hir::ModuleDef::Trait(it) => it.resolve_doc_path(db, &link, ns),
-            hir::ModuleDef::TypeAlias(it) => it.resolve_doc_path(db, &link, ns),
-            hir::ModuleDef::BuiltinType(_) => None,
-        },
-        Definition::Macro(it) => it.resolve_doc_path(db, &link, ns),
-        Definition::Field(it) => it.resolve_doc_path(db, &link, ns),
-        Definition::SelfType(_)
-        | Definition::Local(_)
-        | Definition::GenericParam(_)
-        | Definition::Label(_) => None,
-    }
-}
-
 fn module_def_to_hl_tag(def: hir::ModuleDef) -> HlTag {
     let symbol = match def {
         hir::ModuleDef::Module(_) => SymbolKind::Module,
diff --git a/crates/ide/src/syntax_highlighting/tags.rs b/crates/ide/src/syntax_highlighting/tags.rs
index 93db79b89..8128d231d 100644
--- a/crates/ide/src/syntax_highlighting/tags.rs
+++ b/crates/ide/src/syntax_highlighting/tags.rs
@@ -28,7 +28,7 @@ pub enum HlTag {
     FormatSpecifier,
     Keyword,
     NumericLiteral,
-    Operator,
+    Operator(HlOperator),
     Punctuation(HlPunct),
     StringLiteral,
     UnresolvedReference,
@@ -58,6 +58,8 @@ pub enum HlMod {
     Associated,
     /// Used for intra doc links in doc injection.
     IntraDocLink,
+    /// Used for items in traits and trait impls.
+    Trait,
 
     /// Keep this last!
     Unsafe,
@@ -85,6 +87,20 @@ pub enum HlPunct {
     Other,
 }
 
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
+pub enum HlOperator {
+    /// |, &, !, ^, |=, &=, ^=
+    Bitwise,
+    /// +, -, *, /, +=, -=, *=, /=
+    Arithmetic,
+    /// &&, ||, !
+    Logical,
+    /// >, <, ==, >=, <=, !=
+    Comparision,
+    ///
+    Other,
+}
+
 impl HlTag {
     fn as_str(self) -> &'static str {
         match self {
@@ -131,7 +147,13 @@ impl HlTag {
                 HlPunct::Other => "punctuation",
             },
             HlTag::NumericLiteral => "numeric_literal",
-            HlTag::Operator => "operator",
+            HlTag::Operator(op) => match op {
+                HlOperator::Bitwise => "bitwise",
+                HlOperator::Arithmetic => "arithmetic",
+                HlOperator::Logical => "logical",
+                HlOperator::Comparision => "comparision",
+                HlOperator::Other => "operator",
+            },
             HlTag::StringLiteral => "string_literal",
             HlTag::UnresolvedReference => "unresolved_reference",
             HlTag::None => "none",
@@ -158,6 +180,7 @@ impl HlMod {
         HlMod::Callable,
         HlMod::Static,
         HlMod::Associated,
+        HlMod::Trait,
         HlMod::Unsafe,
     ];
 
@@ -174,6 +197,7 @@ impl HlMod {
             HlMod::IntraDocLink => "intra_doc_link",
             HlMod::Mutable => "mutable",
             HlMod::Static => "static",
+            HlMod::Trait => "trait",
             HlMod::Unsafe => "unsafe",
         }
     }
diff --git a/crates/ide/src/syntax_highlighting/test_data/highlight_assoc_functions.html b/crates/ide/src/syntax_highlighting/test_data/highlight_assoc_functions.html
index 4635ea927..8cde3906c 100644
--- a/crates/ide/src/syntax_highlighting/test_data/highlight_assoc_functions.html
+++ b/crates/ide/src/syntax_highlighting/test_data/highlight_assoc_functions.html
@@ -47,12 +47,12 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
 <span class="brace">}</span>
 
 <span class="keyword">trait</span> <span class="trait declaration">t</span> <span class="brace">{</span>
-    <span class="keyword">fn</span> <span class="function declaration static associated">t_is_static</span><span class="parenthesis">(</span><span class="parenthesis">)</span> <span class="brace">{</span><span class="brace">}</span>
-    <span class="keyword">fn</span> <span class="function declaration associated">t_is_not_static</span><span class="parenthesis">(</span><span class="operator">&</span><span class="self_keyword declaration">self</span><span class="parenthesis">)</span> <span class="brace">{</span><span class="brace">}</span>
+    <span class="keyword">fn</span> <span class="function declaration static associated trait">t_is_static</span><span class="parenthesis">(</span><span class="parenthesis">)</span> <span class="brace">{</span><span class="brace">}</span>
+    <span class="keyword">fn</span> <span class="function declaration associated trait">t_is_not_static</span><span class="parenthesis">(</span><span class="operator">&</span><span class="self_keyword declaration">self</span><span class="parenthesis">)</span> <span class="brace">{</span><span class="brace">}</span>
 <span class="brace">}</span>
 
 <span class="keyword">impl</span> <span class="trait">t</span> <span class="keyword">for</span> <span class="struct">foo</span> <span class="brace">{</span>
-    <span class="keyword">pub</span> <span class="keyword">fn</span> <span class="function declaration static associated">is_static</span><span class="parenthesis">(</span><span class="parenthesis">)</span> <span class="brace">{</span><span class="brace">}</span>
-    <span class="keyword">pub</span> <span class="keyword">fn</span> <span class="function declaration associated">is_not_static</span><span class="parenthesis">(</span><span class="operator">&</span><span class="self_keyword declaration">self</span><span class="parenthesis">)</span> <span class="brace">{</span><span class="brace">}</span>
+    <span class="keyword">pub</span> <span class="keyword">fn</span> <span class="function declaration static associated trait">is_static</span><span class="parenthesis">(</span><span class="parenthesis">)</span> <span class="brace">{</span><span class="brace">}</span>
+    <span class="keyword">pub</span> <span class="keyword">fn</span> <span class="function declaration associated trait">is_not_static</span><span class="parenthesis">(</span><span class="operator">&</span><span class="self_keyword declaration">self</span><span class="parenthesis">)</span> <span class="brace">{</span><span class="brace">}</span>
 <span class="brace">}</span>
         </code></pre>
\ No newline at end of file
diff --git a/crates/ide/src/syntax_highlighting/test_data/highlight_doctest.html b/crates/ide/src/syntax_highlighting/test_data/highlight_doctest.html
index 045162eb8..6ee6d85fb 100644
--- a/crates/ide/src/syntax_highlighting/test_data/highlight_doctest.html
+++ b/crates/ide/src/syntax_highlighting/test_data/highlight_doctest.html
@@ -76,7 +76,7 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
     <span class="comment documentation">/// </span><span class="comment injected">// calls bar on foo</span>
     <span class="comment documentation">/// </span><span class="macro injected">assert!</span><span class="parenthesis injected">(</span><span class="none injected">foo</span><span class="operator injected">.</span><span class="none injected">bar</span><span class="parenthesis injected">(</span><span class="parenthesis injected">)</span><span class="parenthesis injected">)</span><span class="semicolon injected">;</span>
     <span class="comment documentation">///</span>
-    <span class="comment documentation">/// </span><span class="keyword injected">let</span><span class="none injected"> </span><span class="variable declaration injected">bar</span><span class="none injected"> </span><span class="operator injected">=</span><span class="none injected"> </span><span class="variable injected">foo</span><span class="operator injected">.</span><span class="field injected">bar</span><span class="none injected"> </span><span class="operator injected">||</span><span class="none injected"> </span><span class="struct injected">Foo</span><span class="operator injected">::</span><span class="constant injected">bar</span><span class="semicolon injected">;</span>
+    <span class="comment documentation">/// </span><span class="keyword injected">let</span><span class="none injected"> </span><span class="variable declaration injected">bar</span><span class="none injected"> </span><span class="operator injected">=</span><span class="none injected"> </span><span class="variable injected">foo</span><span class="operator injected">.</span><span class="field injected">bar</span><span class="none injected"> </span><span class="logical injected">||</span><span class="none injected"> </span><span class="struct injected">Foo</span><span class="operator injected">::</span><span class="constant injected">bar</span><span class="semicolon injected">;</span>
     <span class="comment documentation">///</span>
     <span class="comment documentation">/// </span><span class="comment injected">/* multi-line</span>
     <span class="comment documentation">/// </span><span class="comment injected">       comment */</span>
@@ -100,10 +100,18 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
 <span class="brace">}</span>
 
 <span class="comment documentation">/// </span><span class="struct documentation intra_doc_link injected">[`Foo`](Foo)</span><span class="comment documentation"> is a struct</span>
-<span class="comment documentation">/// </span><span class="function documentation intra_doc_link injected">[`all_the_links`](all_the_links)</span><span class="comment documentation"> is this function</span>
+<span class="comment documentation">/// This function is &gt; </span><span class="function documentation intra_doc_link injected">[`all_the_links`](all_the_links)</span><span class="comment documentation"> &lt;</span>
 <span class="comment documentation">/// [`noop`](noop) is a macro below</span>
+<span class="comment documentation">/// </span><span class="struct documentation intra_doc_link injected">[`Item`]</span><span class="comment documentation"> is a struct in the module </span><span class="module documentation intra_doc_link injected">[`module`]</span>
+<span class="comment documentation">///</span>
+<span class="comment documentation">/// [`Item`]: module::Item</span>
+<span class="comment documentation">/// [mix_and_match]: ThisShouldntResolve</span>
 <span class="keyword">pub</span> <span class="keyword">fn</span> <span class="function declaration">all_the_links</span><span class="parenthesis">(</span><span class="parenthesis">)</span> <span class="brace">{</span><span class="brace">}</span>
 
+<span class="keyword">pub</span> <span class="keyword">mod</span> <span class="module declaration">module</span> <span class="brace">{</span>
+    <span class="keyword">pub</span> <span class="keyword">struct</span> <span class="struct declaration">Item</span><span class="semicolon">;</span>
+<span class="brace">}</span>
+
 <span class="comment documentation">/// ```</span>
 <span class="comment documentation">/// </span><span class="macro injected">noop!</span><span class="parenthesis injected">(</span><span class="numeric_literal injected">1</span><span class="parenthesis injected">)</span><span class="semicolon injected">;</span>
 <span class="comment documentation">/// ```</span>
diff --git a/crates/ide/src/syntax_highlighting/test_data/highlight_injection.html b/crates/ide/src/syntax_highlighting/test_data/highlight_injection.html
index 9215ddd9e..7c6694a27 100644
--- a/crates/ide/src/syntax_highlighting/test_data/highlight_injection.html
+++ b/crates/ide/src/syntax_highlighting/test_data/highlight_injection.html
@@ -42,7 +42,7 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
 <span class="keyword">fn</span> <span class="function declaration">main</span><span class="parenthesis">(</span><span class="parenthesis">)</span> <span class="brace">{</span>
     <span class="function">fixture</span><span class="parenthesis">(</span><span class="string_literal">r#"</span>
         <span class="keyword">trait</span> <span class="trait declaration">Foo</span> <span class="brace">{</span>
-            <span class="keyword">fn</span> <span class="function declaration static associated">foo</span><span class="parenthesis">(</span><span class="parenthesis">)</span> <span class="brace">{</span>
+            <span class="keyword">fn</span> <span class="function declaration static associated trait">foo</span><span class="parenthesis">(</span><span class="parenthesis">)</span> <span class="brace">{</span>
                 <span class="macro">println!</span><span class="parenthesis">(</span><span class="string_literal">"2 + 2 = {}"</span><span class="comma">,</span> <span class="numeric_literal">4</span><span class="parenthesis">)</span><span class="semicolon">;</span>
             <span class="brace">}</span>
         <span class="brace">}</span><span class="string_literal">"#</span>
diff --git a/crates/ide/src/syntax_highlighting/test_data/highlight_unsafe.html b/crates/ide/src/syntax_highlighting/test_data/highlight_unsafe.html
index 6a6555208..72910421d 100644
--- a/crates/ide/src/syntax_highlighting/test_data/highlight_unsafe.html
+++ b/crates/ide/src/syntax_highlighting/test_data/highlight_unsafe.html
@@ -62,11 +62,11 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
 <span class="brace">}</span>
 
 <span class="keyword">trait</span> <span class="trait declaration">DoTheAutoref</span> <span class="brace">{</span>
-    <span class="keyword">fn</span> <span class="function declaration associated">calls_autoref</span><span class="parenthesis">(</span><span class="operator">&</span><span class="self_keyword declaration">self</span><span class="parenthesis">)</span><span class="semicolon">;</span>
+    <span class="keyword">fn</span> <span class="function declaration associated trait">calls_autoref</span><span class="parenthesis">(</span><span class="operator">&</span><span class="self_keyword declaration">self</span><span class="parenthesis">)</span><span class="semicolon">;</span>
 <span class="brace">}</span>
 
 <span class="keyword">impl</span> <span class="trait">DoTheAutoref</span> <span class="keyword">for</span> <span class="builtin_type">u16</span> <span class="brace">{</span>
-    <span class="keyword">fn</span> <span class="function declaration associated">calls_autoref</span><span class="parenthesis">(</span><span class="operator">&</span><span class="self_keyword declaration">self</span><span class="parenthesis">)</span> <span class="brace">{</span><span class="brace">}</span>
+    <span class="keyword">fn</span> <span class="function declaration associated trait">calls_autoref</span><span class="parenthesis">(</span><span class="operator">&</span><span class="self_keyword declaration">self</span><span class="parenthesis">)</span> <span class="brace">{</span><span class="brace">}</span>
 <span class="brace">}</span>
 
 <span class="keyword">fn</span> <span class="function declaration">main</span><span class="parenthesis">(</span><span class="parenthesis">)</span> <span class="brace">{</span>
@@ -96,6 +96,6 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
         <span class="keyword">let</span> <span class="struct">Packed</span> <span class="brace">{</span> <span class="field">a</span><span class="colon">:</span> <span class="keyword unsafe">ref</span> <span class="variable declaration">_a</span> <span class="brace">}</span> <span class="operator">=</span> <span class="variable">packed</span><span class="semicolon">;</span>
 
         <span class="comment">// unsafe auto ref of packed field</span>
-        <span class="variable">packed</span><span class="operator">.</span><span class="field">a</span><span class="operator">.</span><span class="function associated unsafe">calls_autoref</span><span class="parenthesis">(</span><span class="parenthesis">)</span><span class="semicolon">;</span>
+        <span class="variable">packed</span><span class="operator">.</span><span class="field">a</span><span class="operator">.</span><span class="function associated trait unsafe">calls_autoref</span><span class="parenthesis">(</span><span class="parenthesis">)</span><span class="semicolon">;</span>
     <span class="brace">}</span>
 <span class="brace">}</span></code></pre>
\ No newline at end of file
diff --git a/crates/ide/src/syntax_highlighting/test_data/highlighting.html b/crates/ide/src/syntax_highlighting/test_data/highlighting.html
index 1eaa7b75b..c43bcb691 100644
--- a/crates/ide/src/syntax_highlighting/test_data/highlighting.html
+++ b/crates/ide/src/syntax_highlighting/test_data/highlighting.html
@@ -67,11 +67,11 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
 <span class="brace">}</span>
 
 <span class="keyword">trait</span> <span class="trait declaration">Bar</span> <span class="brace">{</span>
-    <span class="keyword">fn</span> <span class="function declaration associated">bar</span><span class="parenthesis">(</span><span class="operator">&</span><span class="self_keyword declaration">self</span><span class="parenthesis">)</span> <span class="operator">-&gt;</span> <span class="builtin_type">i32</span><span class="semicolon">;</span>
+    <span class="keyword">fn</span> <span class="function declaration associated trait">bar</span><span class="parenthesis">(</span><span class="operator">&</span><span class="self_keyword declaration">self</span><span class="parenthesis">)</span> <span class="operator">-&gt;</span> <span class="builtin_type">i32</span><span class="semicolon">;</span>
 <span class="brace">}</span>
 
 <span class="keyword">impl</span> <span class="trait">Bar</span> <span class="keyword">for</span> <span class="struct">Foo</span> <span class="brace">{</span>
-    <span class="keyword">fn</span> <span class="function declaration associated">bar</span><span class="parenthesis">(</span><span class="operator">&</span><span class="self_keyword declaration">self</span><span class="parenthesis">)</span> <span class="operator">-&gt;</span> <span class="builtin_type">i32</span> <span class="brace">{</span>
+    <span class="keyword">fn</span> <span class="function declaration associated trait">bar</span><span class="parenthesis">(</span><span class="operator">&</span><span class="self_keyword declaration">self</span><span class="parenthesis">)</span> <span class="operator">-&gt;</span> <span class="builtin_type">i32</span> <span class="brace">{</span>
         <span class="self_keyword">self</span><span class="operator">.</span><span class="field">x</span>
     <span class="brace">}</span>
 <span class="brace">}</span>
@@ -213,7 +213,7 @@ pre                 { color: #DCDCCC; background: #3F3F3F; font-size: 22px; padd
     <span class="keyword">let</span> <span class="variable declaration">baz</span> <span class="operator">=</span> <span class="numeric_literal">-</span><span class="numeric_literal">42</span><span class="semicolon">;</span>
     <span class="keyword">let</span> <span class="variable declaration">baz</span> <span class="operator">=</span> <span class="operator">-</span><span class="variable">baz</span><span class="semicolon">;</span>
 
-    <span class="keyword">let</span> <span class="punctuation">_</span> <span class="operator">=</span> <span class="operator">!</span><span class="bool_literal">true</span><span class="semicolon">;</span>
+    <span class="keyword">let</span> <span class="punctuation">_</span> <span class="operator">=</span> <span class="logical">!</span><span class="bool_literal">true</span><span class="semicolon">;</span>
 
     <span class="label declaration">'foo</span><span class="colon">:</span> <span class="keyword control">loop</span> <span class="brace">{</span>
         <span class="keyword control">break</span> <span class="label">'foo</span><span class="semicolon">;</span>
diff --git a/crates/ide/src/syntax_highlighting/tests.rs b/crates/ide/src/syntax_highlighting/tests.rs
index 369ae0972..933cfa6f3 100644
--- a/crates/ide/src/syntax_highlighting/tests.rs
+++ b/crates/ide/src/syntax_highlighting/tests.rs
@@ -1,6 +1,8 @@
+use std::time::Instant;
+
 use expect_test::{expect_file, ExpectFile};
 use ide_db::SymbolKind;
-use test_utils::{bench, bench_fixture, skip_slow_tests};
+use test_utils::{bench, bench_fixture, skip_slow_tests, AssertLinear};
 
 use crate::{fixture, FileRange, HlTag, TextRange};
 
@@ -258,6 +260,36 @@ fn benchmark_syntax_highlighting_long_struct() {
 }
 
 #[test]
+fn syntax_highlighting_not_quadratic() {
+    if skip_slow_tests() {
+        return;
+    }
+
+    let mut al = AssertLinear::default();
+    while al.next_round() {
+        for i in 6..=10 {
+            let n = 1 << i;
+
+            let fixture = bench_fixture::big_struct_n(n);
+            let (analysis, file_id) = fixture::file(&fixture);
+
+            let time = Instant::now();
+
+            let hash = analysis
+                .highlight(file_id)
+                .unwrap()
+                .iter()
+                .filter(|it| it.highlight.tag == HlTag::Symbol(SymbolKind::Struct))
+                .count();
+            assert!(hash > n as usize);
+
+            let elapsed = time.elapsed();
+            al.sample(n as f64, elapsed.as_millis() as f64);
+        }
+    }
+}
+
+#[test]
 fn benchmark_syntax_highlighting_parser() {
     if skip_slow_tests() {
         return;
@@ -544,10 +576,18 @@ impl Foo {
 }
 
 /// [`Foo`](Foo) is a struct
-/// [`all_the_links`](all_the_links) is this function
+/// This function is > [`all_the_links`](all_the_links) <
 /// [`noop`](noop) is a macro below
+/// [`Item`] is a struct in the module [`module`]
+///
+/// [`Item`]: module::Item
+/// [mix_and_match]: ThisShouldntResolve
 pub fn all_the_links() {}
 
+pub mod module {
+    pub struct Item;
+}
+
 /// ```
 /// noop!(1);
 /// ```
diff --git a/crates/ide/src/syntax_tree.rs b/crates/ide/src/syntax_tree.rs
index 8979de528..633878d1c 100644
--- a/crates/ide/src/syntax_tree.rs
+++ b/crates/ide/src/syntax_tree.rs
@@ -14,6 +14,7 @@ use syntax::{
 //
 // | VS Code | **Rust Analyzer: Show Syntax Tree**
 // |===
+// image::https://user-images.githubusercontent.com/48062697/113065586-068bdb80-91b1-11eb-9507-fee67f9f45a0.gif[]
 pub(crate) fn syntax_tree(
     db: &RootDatabase,
     file_id: FileId,
diff --git a/crates/ide/src/typing.rs b/crates/ide/src/typing.rs
index e10b7d98e..82c732390 100644
--- a/crates/ide/src/typing.rs
+++ b/crates/ide/src/typing.rs
@@ -22,18 +22,19 @@ use ide_db::{
 use syntax::{
     algo::find_node_at_offset,
     ast::{self, edit::IndentLevel, AstToken},
-    AstNode, SourceFile,
+    AstNode, Parse, SourceFile,
     SyntaxKind::{FIELD_EXPR, METHOD_CALL_EXPR},
     TextRange, TextSize,
 };
 
-use text_edit::TextEdit;
+use text_edit::{Indel, TextEdit};
 
 use crate::SourceChange;
 
 pub(crate) use on_enter::on_enter;
 
-pub(crate) const TRIGGER_CHARS: &str = ".=>";
+// Don't forget to add new trigger characters to `server_capabilities` in `caps.rs`.
+pub(crate) const TRIGGER_CHARS: &str = ".=>{";
 
 // Feature: On Typing Assists
 //
@@ -41,6 +42,7 @@ pub(crate) const TRIGGER_CHARS: &str = ".=>";
 //
 // - typing `let =` tries to smartly add `;` if `=` is followed by an existing expression
 // - typing `.` in a chain method call auto-indents
+// - typing `{` in front of an expression inserts a closing `}` after the expression
 //
 // VS Code::
 //
@@ -49,33 +51,87 @@ pub(crate) const TRIGGER_CHARS: &str = ".=>";
 // ----
 // "editor.formatOnType": true,
 // ----
+//
+// image::https://user-images.githubusercontent.com/48062697/113166163-69758500-923a-11eb-81ee-eb33ec380399.gif[]
+// image::https://user-images.githubusercontent.com/48062697/113171066-105c2000-923f-11eb-87ab-f4a263346567.gif[]
 pub(crate) fn on_char_typed(
     db: &RootDatabase,
     position: FilePosition,
     char_typed: char,
 ) -> Option<SourceChange> {
-    assert!(TRIGGER_CHARS.contains(char_typed));
-    let file = &db.parse(position.file_id).tree();
-    assert_eq!(file.syntax().text().char_at(position.offset), Some(char_typed));
+    if !stdx::always!(TRIGGER_CHARS.contains(char_typed)) {
+        return None;
+    }
+    let file = &db.parse(position.file_id);
+    if !stdx::always!(file.tree().syntax().text().char_at(position.offset) == Some(char_typed)) {
+        return None;
+    }
     let edit = on_char_typed_inner(file, position.offset, char_typed)?;
     Some(SourceChange::from_text_edit(position.file_id, edit))
 }
 
-fn on_char_typed_inner(file: &SourceFile, offset: TextSize, char_typed: char) -> Option<TextEdit> {
-    assert!(TRIGGER_CHARS.contains(char_typed));
+fn on_char_typed_inner(
+    file: &Parse<SourceFile>,
+    offset: TextSize,
+    char_typed: char,
+) -> Option<TextEdit> {
+    if !stdx::always!(TRIGGER_CHARS.contains(char_typed)) {
+        return None;
+    }
     match char_typed {
-        '.' => on_dot_typed(file, offset),
-        '=' => on_eq_typed(file, offset),
-        '>' => on_arrow_typed(file, offset),
+        '.' => on_dot_typed(&file.tree(), offset),
+        '=' => on_eq_typed(&file.tree(), offset),
+        '>' => on_arrow_typed(&file.tree(), offset),
+        '{' => on_opening_brace_typed(file, offset),
         _ => unreachable!(),
     }
 }
 
+/// Inserts a closing `}` when the user types an opening `{`, wrapping an existing expression in a
+/// block.
+fn on_opening_brace_typed(file: &Parse<SourceFile>, offset: TextSize) -> Option<TextEdit> {
+    if !stdx::always!(file.tree().syntax().text().char_at(offset) == Some('{')) {
+        return None;
+    }
+
+    let brace_token = file.tree().syntax().token_at_offset(offset).right_biased()?;
+
+    // Remove the `{` to get a better parse tree, and reparse
+    let file = file.reparse(&Indel::delete(brace_token.text_range()));
+
+    let mut expr: ast::Expr = find_node_at_offset(file.tree().syntax(), offset)?;
+    if expr.syntax().text_range().start() != offset {
+        return None;
+    }
+
+    // Enclose the outermost expression starting at `offset`
+    while let Some(parent) = expr.syntax().parent() {
+        if parent.text_range().start() != expr.syntax().text_range().start() {
+            break;
+        }
+
+        match ast::Expr::cast(parent) {
+            Some(parent) => expr = parent,
+            None => break,
+        }
+    }
+
+    // If it's a statement in a block, we don't know how many statements should be included
+    if ast::ExprStmt::can_cast(expr.syntax().parent()?.kind()) {
+        return None;
+    }
+
+    // Insert `}` right after the expression.
+    Some(TextEdit::insert(expr.syntax().text_range().end() + TextSize::of("{"), "}".to_string()))
+}
+
 /// Returns an edit which should be applied after `=` was typed. Primarily,
 /// this works when adding `let =`.
 // FIXME: use a snippet completion instead of this hack here.
 fn on_eq_typed(file: &SourceFile, offset: TextSize) -> Option<TextEdit> {
-    assert_eq!(file.syntax().text().char_at(offset), Some('='));
+    if !stdx::always!(file.syntax().text().char_at(offset) == Some('=')) {
+        return None;
+    }
     let let_stmt: ast::LetStmt = find_node_at_offset(file.syntax(), offset)?;
     if let_stmt.semicolon_token().is_some() {
         return None;
@@ -97,7 +153,9 @@ fn on_eq_typed(file: &SourceFile, offset: TextSize) -> Option<TextEdit> {
 
 /// Returns an edit which should be applied when a dot ('.') is typed on a blank line, indenting the line appropriately.
 fn on_dot_typed(file: &SourceFile, offset: TextSize) -> Option<TextEdit> {
-    assert_eq!(file.syntax().text().char_at(offset), Some('.'));
+    if !stdx::always!(file.syntax().text().char_at(offset) == Some('.')) {
+        return None;
+    }
     let whitespace =
         file.syntax().token_at_offset(offset).left_biased().and_then(ast::Whitespace::cast)?;
 
@@ -126,7 +184,9 @@ fn on_dot_typed(file: &SourceFile, offset: TextSize) -> Option<TextEdit> {
 /// Adds a space after an arrow when `fn foo() { ... }` is turned into `fn foo() -> { ... }`
 fn on_arrow_typed(file: &SourceFile, offset: TextSize) -> Option<TextEdit> {
     let file_text = file.syntax().text();
-    assert_eq!(file_text.char_at(offset), Some('>'));
+    if !stdx::always!(file_text.char_at(offset) == Some('>')) {
+        return None;
+    }
     let after_arrow = offset + TextSize::of('>');
     if file_text.char_at(after_arrow) != Some('{') {
         return None;
@@ -149,7 +209,7 @@ mod tests {
         let edit = TextEdit::insert(offset, char_typed.to_string());
         edit.apply(&mut before);
         let parse = SourceFile::parse(&before);
-        on_char_typed_inner(&parse.tree(), offset, char_typed).map(|it| {
+        on_char_typed_inner(&parse, offset, char_typed).map(|it| {
             it.apply(&mut before);
             before.to_string()
         })
@@ -162,8 +222,8 @@ mod tests {
         assert_eq_text!(ra_fixture_after, &actual);
     }
 
-    fn type_char_noop(char_typed: char, before: &str) {
-        let file_change = do_type_char(char_typed, before);
+    fn type_char_noop(char_typed: char, ra_fixture_before: &str) {
+        let file_change = do_type_char(char_typed, ra_fixture_before);
         assert!(file_change.is_none())
     }
 
@@ -180,16 +240,16 @@ mod tests {
         // ");
         type_char(
             '=',
-            r"
+            r#"
 fn foo() {
     let foo $0 1 + 1
 }
-",
-            r"
+"#,
+            r#"
 fn foo() {
     let foo = 1 + 1;
 }
-",
+"#,
         );
         //     do_check(r"
         // fn foo() {
@@ -208,27 +268,27 @@ fn foo() {
     fn indents_new_chain_call() {
         type_char(
             '.',
-            r"
-            fn main() {
-                xs.foo()
-                $0
-            }
-            ",
-            r"
-            fn main() {
-                xs.foo()
-                    .
-            }
-            ",
+            r#"
+fn main() {
+    xs.foo()
+    $0
+}
+            "#,
+            r#"
+fn main() {
+    xs.foo()
+        .
+}
+            "#,
         );
         type_char_noop(
             '.',
-            r"
-            fn main() {
-                xs.foo()
-                    $0
-            }
-            ",
+            r#"
+fn main() {
+    xs.foo()
+        $0
+}
+            "#,
         )
     }
 
@@ -237,26 +297,26 @@ fn foo() {
         type_char(
             '.',
             r"
-            fn main() {
-                xs.foo()
-                $0;
-            }
-            ",
-            r"
-            fn main() {
-                xs.foo()
-                    .;
-            }
+fn main() {
+    xs.foo()
+    $0;
+}
             ",
+            r#"
+fn main() {
+    xs.foo()
+        .;
+}
+            "#,
         );
         type_char_noop(
             '.',
-            r"
-            fn main() {
-                xs.foo()
-                    $0;
-            }
-            ",
+            r#"
+fn main() {
+    xs.foo()
+        $0;
+}
+            "#,
         )
     }
 
@@ -285,30 +345,30 @@ fn main() {
     fn indents_continued_chain_call() {
         type_char(
             '.',
-            r"
-            fn main() {
-                xs.foo()
-                    .first()
-                $0
-            }
-            ",
-            r"
-            fn main() {
-                xs.foo()
-                    .first()
-                    .
-            }
-            ",
+            r#"
+fn main() {
+    xs.foo()
+        .first()
+    $0
+}
+            "#,
+            r#"
+fn main() {
+    xs.foo()
+        .first()
+        .
+}
+            "#,
         );
         type_char_noop(
             '.',
-            r"
-            fn main() {
-                xs.foo()
-                    .first()
-                    $0
-            }
-            ",
+            r#"
+fn main() {
+    xs.foo()
+        .first()
+        $0
+}
+            "#,
         );
     }
 
@@ -316,33 +376,33 @@ fn main() {
     fn indents_middle_of_chain_call() {
         type_char(
             '.',
-            r"
-            fn source_impl() {
-                let var = enum_defvariant_list().unwrap()
-                $0
-                    .nth(92)
-                    .unwrap();
-            }
-            ",
-            r"
-            fn source_impl() {
-                let var = enum_defvariant_list().unwrap()
-                    .
-                    .nth(92)
-                    .unwrap();
-            }
-            ",
+            r#"
+fn source_impl() {
+    let var = enum_defvariant_list().unwrap()
+    $0
+        .nth(92)
+        .unwrap();
+}
+            "#,
+            r#"
+fn source_impl() {
+    let var = enum_defvariant_list().unwrap()
+        .
+        .nth(92)
+        .unwrap();
+}
+            "#,
         );
         type_char_noop(
             '.',
-            r"
-            fn source_impl() {
-                let var = enum_defvariant_list().unwrap()
-                    $0
-                    .nth(92)
-                    .unwrap();
-            }
-            ",
+            r#"
+fn source_impl() {
+    let var = enum_defvariant_list().unwrap()
+        $0
+        .nth(92)
+        .unwrap();
+}
+            "#,
         );
     }
 
@@ -350,24 +410,113 @@ fn main() {
     fn dont_indent_freestanding_dot() {
         type_char_noop(
             '.',
-            r"
-            fn main() {
-                $0
-            }
-            ",
+            r#"
+fn main() {
+    $0
+}
+            "#,
         );
         type_char_noop(
             '.',
-            r"
-            fn main() {
-            $0
-            }
-            ",
+            r#"
+fn main() {
+$0
+}
+            "#,
         );
     }
 
     #[test]
     fn adds_space_after_return_type() {
-        type_char('>', "fn foo() -$0{ 92 }", "fn foo() -> { 92 }")
+        type_char(
+            '>',
+            r#"
+fn foo() -$0{ 92 }
+"#,
+            r#"
+fn foo() -> { 92 }
+"#,
+        );
+    }
+
+    #[test]
+    fn adds_closing_brace() {
+        type_char(
+            '{',
+            r#"
+fn f() { match () { _ => $0() } }
+            "#,
+            r#"
+fn f() { match () { _ => {()} } }
+            "#,
+        );
+        type_char(
+            '{',
+            r#"
+fn f() { $0() }
+            "#,
+            r#"
+fn f() { {()} }
+            "#,
+        );
+        type_char(
+            '{',
+            r#"
+fn f() { let x = $0(); }
+            "#,
+            r#"
+fn f() { let x = {()}; }
+            "#,
+        );
+        type_char(
+            '{',
+            r#"
+fn f() { let x = $0a.b(); }
+            "#,
+            r#"
+fn f() { let x = {a.b()}; }
+            "#,
+        );
+        type_char(
+            '{',
+            r#"
+const S: () = $0();
+fn f() {}
+            "#,
+            r#"
+const S: () = {()};
+fn f() {}
+            "#,
+        );
+        type_char(
+            '{',
+            r#"
+const S: () = $0a.b();
+fn f() {}
+            "#,
+            r#"
+const S: () = {a.b()};
+fn f() {}
+            "#,
+        );
+        type_char(
+            '{',
+            r#"
+fn f() {
+    match x {
+        0 => $0(),
+        1 => (),
+    }
+}
+            "#,
+            r#"
+fn f() {
+    match x {
+        0 => {()},
+        1 => (),
+    }
+}
+            "#,
+        );
     }
 }
diff --git a/crates/ide/src/typing/on_enter.rs b/crates/ide/src/typing/on_enter.rs
index 978c479de..7d2db201a 100644
--- a/crates/ide/src/typing/on_enter.rs
+++ b/crates/ide/src/typing/on_enter.rs
@@ -4,10 +4,11 @@
 use ide_db::base_db::{FilePosition, SourceDatabase};
 use ide_db::RootDatabase;
 use syntax::{
-    ast::{self, AstToken},
+    algo::find_node_at_offset,
+    ast::{self, edit::IndentLevel, AstToken},
     AstNode, SmolStr, SourceFile,
     SyntaxKind::*,
-    SyntaxToken, TextRange, TextSize, TokenAtOffset,
+    SyntaxNode, SyntaxToken, TextRange, TextSize, TokenAtOffset,
 };
 
 use text_edit::TextEdit;
@@ -18,6 +19,8 @@ use text_edit::TextEdit;
 //
 // - kbd:[Enter] inside triple-slash comments automatically inserts `///`
 // - kbd:[Enter] in the middle or after a trailing space in `//` inserts `//`
+// - kbd:[Enter] inside `//!` doc comments automatically inserts `//!`
+// - kbd:[Enter] after `{` indents contents and closing `}` of single-line block
 //
 // This action needs to be assigned to shortcut explicitly.
 //
@@ -32,28 +35,48 @@ use text_edit::TextEdit;
 //   "when": "editorTextFocus && !suggestWidgetVisible && editorLangId == rust"
 // }
 // ----
+//
+// image::https://user-images.githubusercontent.com/48062697/113065578-04c21800-91b1-11eb-82b8-22b8c481e645.gif[]
 pub(crate) fn on_enter(db: &RootDatabase, position: FilePosition) -> Option<TextEdit> {
     let parse = db.parse(position.file_id);
     let file = parse.tree();
-    let comment = file
-        .syntax()
-        .token_at_offset(position.offset)
-        .left_biased()
-        .and_then(ast::Comment::cast)?;
+    let token = file.syntax().token_at_offset(position.offset).left_biased()?;
+
+    if let Some(comment) = ast::Comment::cast(token.clone()) {
+        return on_enter_in_comment(&comment, &file, position.offset);
+    }
+
+    if token.kind() == L_CURLY {
+        // Typing enter after the `{` of a block expression, where the `}` is on the same line
+        if let Some(edit) = find_node_at_offset(file.syntax(), position.offset - TextSize::of('{'))
+            .and_then(|block| on_enter_in_block(block, position))
+        {
+            cov_mark::hit!(indent_block_contents);
+            return Some(edit);
+        }
+    }
+
+    None
+}
 
+fn on_enter_in_comment(
+    comment: &ast::Comment,
+    file: &ast::SourceFile,
+    offset: TextSize,
+) -> Option<TextEdit> {
     if comment.kind().shape.is_block() {
         return None;
     }
 
     let prefix = comment.prefix();
     let comment_range = comment.syntax().text_range();
-    if position.offset < comment_range.start() + TextSize::of(prefix) {
+    if offset < comment_range.start() + TextSize::of(prefix) {
         return None;
     }
 
     let mut remove_trailing_whitespace = false;
     // Continuing single-line non-doc comments (like this one :) ) is annoying
-    if prefix == "//" && comment_range.end() == position.offset {
+    if prefix == "//" && comment_range.end() == offset {
         if comment.text().ends_with(' ') {
             cov_mark::hit!(continues_end_of_line_comment_with_space);
             remove_trailing_whitespace = true;
@@ -67,14 +90,42 @@ pub(crate) fn on_enter(db: &RootDatabase, position: FilePosition) -> Option<Text
     let delete = if remove_trailing_whitespace {
         let trimmed_len = comment.text().trim_end().len() as u32;
         let trailing_whitespace_len = comment.text().len() as u32 - trimmed_len;
-        TextRange::new(position.offset - TextSize::from(trailing_whitespace_len), position.offset)
+        TextRange::new(offset - TextSize::from(trailing_whitespace_len), offset)
     } else {
-        TextRange::empty(position.offset)
+        TextRange::empty(offset)
     };
     let edit = TextEdit::replace(delete, inserted);
     Some(edit)
 }
 
+fn on_enter_in_block(block: ast::BlockExpr, position: FilePosition) -> Option<TextEdit> {
+    let contents = block_contents(&block)?;
+
+    if block.syntax().text().contains_char('\n') {
+        return None;
+    }
+
+    let indent = IndentLevel::from_node(block.syntax());
+    let mut edit = TextEdit::insert(position.offset, format!("\n{}$0", indent + 1));
+    edit.union(TextEdit::insert(contents.text_range().end(), format!("\n{}", indent))).ok()?;
+    Some(edit)
+}
+
+fn block_contents(block: &ast::BlockExpr) -> Option<SyntaxNode> {
+    let mut node = block.tail_expr().map(|e| e.syntax().clone());
+
+    for stmt in block.statements() {
+        if node.is_some() {
+            // More than 1 node in the block
+            return None;
+        }
+
+        node = Some(stmt.syntax().clone());
+    }
+
+    node
+}
+
 fn followed_by_comment(comment: &ast::Comment) -> bool {
     let ws = match comment.syntax().next_token().and_then(ast::Whitespace::cast) {
         Some(it) => it,
@@ -185,6 +236,25 @@ fn foo() {
     }
 
     #[test]
+    fn continues_another_doc_comment() {
+        do_check(
+            r#"
+fn main() {
+    //! Documentation for$0 on enter
+    let x = 1 + 1;
+}
+"#,
+            r#"
+fn main() {
+    //! Documentation for
+    //! $0 on enter
+    let x = 1 + 1;
+}
+"#,
+        );
+    }
+
+    #[test]
     fn continues_code_comment_in_the_middle_of_line() {
         do_check(
             r"
@@ -274,4 +344,144 @@ fn main() {
 ",
         );
     }
+
+    #[test]
+    fn indents_fn_body_block() {
+        cov_mark::check!(indent_block_contents);
+        do_check(
+            r#"
+fn f() {$0()}
+        "#,
+            r#"
+fn f() {
+    $0()
+}
+        "#,
+        );
+    }
+
+    #[test]
+    fn indents_block_expr() {
+        do_check(
+            r#"
+fn f() {
+    let x = {$0()};
+}
+        "#,
+            r#"
+fn f() {
+    let x = {
+        $0()
+    };
+}
+        "#,
+        );
+    }
+
+    #[test]
+    fn indents_match_arm() {
+        do_check(
+            r#"
+fn f() {
+    match 6 {
+        1 => {$0f()},
+        _ => (),
+    }
+}
+        "#,
+            r#"
+fn f() {
+    match 6 {
+        1 => {
+            $0f()
+        },
+        _ => (),
+    }
+}
+        "#,
+        );
+    }
+
+    #[test]
+    fn indents_block_with_statement() {
+        do_check(
+            r#"
+fn f() {$0a = b}
+        "#,
+            r#"
+fn f() {
+    $0a = b
+}
+        "#,
+        );
+        do_check(
+            r#"
+fn f() {$0fn f() {}}
+        "#,
+            r#"
+fn f() {
+    $0fn f() {}
+}
+        "#,
+        );
+    }
+
+    #[test]
+    fn indents_nested_blocks() {
+        do_check(
+            r#"
+fn f() {$0{}}
+        "#,
+            r#"
+fn f() {
+    $0{}
+}
+        "#,
+        );
+    }
+
+    #[test]
+    fn does_not_indent_empty_block() {
+        do_check_noop(
+            r#"
+fn f() {$0}
+        "#,
+        );
+        do_check_noop(
+            r#"
+fn f() {{$0}}
+        "#,
+        );
+    }
+
+    #[test]
+    fn does_not_indent_block_with_too_much_content() {
+        do_check_noop(
+            r#"
+fn f() {$0 a = b; ()}
+        "#,
+        );
+        do_check_noop(
+            r#"
+fn f() {$0 a = b; a = b; }
+        "#,
+        );
+    }
+
+    #[test]
+    fn does_not_indent_multiline_block() {
+        do_check_noop(
+            r#"
+fn f() {$0
+}
+        "#,
+        );
+        do_check_noop(
+            r#"
+fn f() {$0
+
+}
+        "#,
+        );
+    }
 }
diff --git a/crates/ide/src/view_hir.rs b/crates/ide/src/view_hir.rs
index f8f3fae3d..7312afe53 100644
--- a/crates/ide/src/view_hir.rs
+++ b/crates/ide/src/view_hir.rs
@@ -10,6 +10,7 @@ use syntax::{algo::find_node_at_offset, ast, AstNode};
 //
 // | VS Code | **Rust Analyzer: View Hir**
 // |===
+// image::https://user-images.githubusercontent.com/48062697/113065588-068bdb80-91b1-11eb-9a78-0b4ef1e972fb.gif[]
 pub(crate) fn view_hir(db: &RootDatabase, position: FilePosition) -> String {
     body_hir(db, position).unwrap_or_else(|| "Not inside a function body".to_string())
 }
diff --git a/crates/ide_assists/src/assist_context.rs b/crates/ide_assists/src/assist_context.rs
index 1482d37f8..8714e4978 100644
--- a/crates/ide_assists/src/assist_context.rs
+++ b/crates/ide_assists/src/assist_context.rs
@@ -13,7 +13,7 @@ use ide_db::{
     RootDatabase,
 };
 use syntax::{
-    algo::{self, find_node_at_offset, SyntaxRewriter},
+    algo::{self, find_node_at_offset, find_node_at_range, SyntaxRewriter},
     AstNode, AstToken, SourceFile, SyntaxElement, SyntaxKind, SyntaxNode, SyntaxNodePtr,
     SyntaxToken, TextRange, TextSize, TokenAtOffset,
 };
@@ -89,6 +89,9 @@ impl<'a> AssistContext<'a> {
     pub(crate) fn find_node_at_offset<N: AstNode>(&self) -> Option<N> {
         find_node_at_offset(self.source_file.syntax(), self.offset())
     }
+    pub(crate) fn find_node_at_range<N: AstNode>(&self) -> Option<N> {
+        find_node_at_range(self.source_file.syntax(), self.frange.range)
+    }
     pub(crate) fn find_node_at_offset_with_descend<N: AstNode>(&self) -> Option<N> {
         self.sema.find_node_at_offset_with_descend(self.source_file.syntax(), self.offset())
     }
diff --git a/crates/ide_assists/src/handlers/auto_import.rs b/crates/ide_assists/src/handlers/auto_import.rs
index 7019039b9..5ccd7f7a2 100644
--- a/crates/ide_assists/src/handlers/auto_import.rs
+++ b/crates/ide_assists/src/handlers/auto_import.rs
@@ -61,6 +61,8 @@ use crate::{AssistContext, AssistId, AssistKind, Assists, GroupLabel};
 // - `plain`: This setting does not impose any restrictions in imports.
 //
 // In `VS Code` the configuration for this is `rust-analyzer.assist.importPrefix`.
+//
+// image::https://user-images.githubusercontent.com/48062697/113020673-b85be580-917a-11eb-9022-59585f35d4f8.gif[]
 
 // Assist: auto_import
 //
diff --git a/crates/ide_assists/src/handlers/convert_into_to_from.rs b/crates/ide_assists/src/handlers/convert_into_to_from.rs
new file mode 100644
index 000000000..199e1ad5c
--- /dev/null
+++ b/crates/ide_assists/src/handlers/convert_into_to_from.rs
@@ -0,0 +1,355 @@
+use ide_db::{
+    helpers::{mod_path_to_ast, FamousDefs},
+    traits::resolve_target_trait,
+};
+use syntax::ast::{self, AstNode, NameOwner};
+
+use crate::{AssistContext, AssistId, AssistKind, Assists};
+
+// Assist: convert_into_to_from
+//
+// Converts an Into impl to an equivalent From impl.
+//
+// ```
+// # //- /lib.rs crate:core
+// # pub mod convert { pub trait Into<T> { pub fn into(self) -> T; } }
+// # //- /lib.rs crate:main deps:core
+// # use core::convert::Into;
+// impl $0Into<Thing> for usize {
+//     fn into(self) -> Thing {
+//         Thing {
+//             b: self.to_string(),
+//             a: self
+//         }
+//     }
+// }
+// ```
+// ->
+// ```
+// # use core::convert::Into;
+// impl From<usize> for Thing {
+//     fn from(val: usize) -> Self {
+//         Thing {
+//             b: val.to_string(),
+//             a: val
+//         }
+//     }
+// }
+// ```
+pub(crate) fn convert_into_to_from(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
+    let impl_ = ctx.find_node_at_offset::<ast::Impl>()?;
+    let src_type = impl_.self_ty()?;
+    let ast_trait = impl_.trait_()?;
+
+    let module = ctx.sema.scope(impl_.syntax()).module()?;
+
+    let trait_ = resolve_target_trait(&ctx.sema, &impl_)?;
+    if trait_ != FamousDefs(&ctx.sema, Some(module.krate())).core_convert_Into()? {
+        return None;
+    }
+
+    let src_type_path = {
+        let src_type_path = src_type.syntax().descendants().find_map(ast::Path::cast)?;
+        let src_type_def = match ctx.sema.resolve_path(&src_type_path) {
+            Some(hir::PathResolution::Def(module_def)) => module_def,
+            _ => return None,
+        };
+
+        mod_path_to_ast(&module.find_use_path(ctx.db(), src_type_def)?)
+    };
+
+    let dest_type = match &ast_trait {
+        ast::Type::PathType(path) => {
+            path.path()?.segment()?.generic_arg_list()?.generic_args().next()?
+        }
+        _ => return None,
+    };
+
+    let into_fn = impl_.assoc_item_list()?.assoc_items().find_map(|item| {
+        if let ast::AssocItem::Fn(f) = item {
+            if f.name()?.text() == "into" {
+                return Some(f);
+            }
+        };
+        None
+    })?;
+
+    let into_fn_name = into_fn.name()?;
+    let into_fn_params = into_fn.param_list()?;
+    let into_fn_return = into_fn.ret_type()?;
+
+    let selfs = into_fn
+        .body()?
+        .syntax()
+        .descendants()
+        .filter_map(ast::NameRef::cast)
+        .filter(|name| name.text() == "self" || name.text() == "Self");
+
+    acc.add(
+        AssistId("convert_into_to_from", AssistKind::RefactorRewrite),
+        "Convert Into to From",
+        impl_.syntax().text_range(),
+        |builder| {
+            builder.replace(src_type.syntax().text_range(), dest_type.to_string());
+            builder.replace(ast_trait.syntax().text_range(), format!("From<{}>", src_type));
+            builder.replace(into_fn_return.syntax().text_range(), "-> Self");
+            builder.replace(
+                into_fn_params.syntax().text_range(),
+                format!("(val: {})", src_type.to_string()),
+            );
+            builder.replace(into_fn_name.syntax().text_range(), "from");
+
+            for s in selfs {
+                match s.text().as_ref() {
+                    "self" => builder.replace(s.syntax().text_range(), "val"),
+                    "Self" => builder.replace(s.syntax().text_range(), src_type_path.to_string()),
+                    _ => {}
+                }
+            }
+        },
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    use crate::tests::check_assist;
+
+    #[test]
+    fn convert_into_to_from_converts_a_struct() {
+        check_convert_into_to_from(
+            r#"
+struct Thing {
+    a: String,
+    b: usize
+}
+
+impl $0core::convert::Into<Thing> for usize {
+    fn into(self) -> Thing {
+        Thing {
+            b: self.to_string(),
+            a: self
+        }
+    }
+}
+"#,
+            r#"
+struct Thing {
+    a: String,
+    b: usize
+}
+
+impl From<usize> for Thing {
+    fn from(val: usize) -> Self {
+        Thing {
+            b: val.to_string(),
+            a: val
+        }
+    }
+}
+"#,
+        )
+    }
+
+    #[test]
+    fn convert_into_to_from_converts_enums() {
+        check_convert_into_to_from(
+            r#"
+enum Thing {
+    Foo(String),
+    Bar(String)
+}
+
+impl $0core::convert::Into<String> for Thing {
+    fn into(self) -> String {
+        match self {
+            Self::Foo(s) => s,
+            Self::Bar(s) => s
+        }
+    }
+}
+"#,
+            r#"
+enum Thing {
+    Foo(String),
+    Bar(String)
+}
+
+impl From<Thing> for String {
+    fn from(val: Thing) -> Self {
+        match val {
+            Thing::Foo(s) => s,
+            Thing::Bar(s) => s
+        }
+    }
+}
+"#,
+        )
+    }
+
+    #[test]
+    fn convert_into_to_from_on_enum_with_lifetimes() {
+        check_convert_into_to_from(
+            r#"
+enum Thing<'a> {
+    Foo(&'a str),
+    Bar(&'a str)
+}
+
+impl<'a> $0core::convert::Into<&'a str> for Thing<'a> {
+    fn into(self) -> &'a str {
+        match self {
+            Self::Foo(s) => s,
+            Self::Bar(s) => s
+        }
+    }
+}
+"#,
+            r#"
+enum Thing<'a> {
+    Foo(&'a str),
+    Bar(&'a str)
+}
+
+impl<'a> From<Thing<'a>> for &'a str {
+    fn from(val: Thing<'a>) -> Self {
+        match val {
+            Thing::Foo(s) => s,
+            Thing::Bar(s) => s
+        }
+    }
+}
+"#,
+        )
+    }
+
+    #[test]
+    fn convert_into_to_from_works_on_references() {
+        check_convert_into_to_from(
+            r#"
+struct Thing(String);
+
+impl $0core::convert::Into<String> for &Thing {
+    fn into(self) -> Thing {
+        self.0.clone()
+    }
+}
+"#,
+            r#"
+struct Thing(String);
+
+impl From<&Thing> for String {
+    fn from(val: &Thing) -> Self {
+        val.0.clone()
+    }
+}
+"#,
+        )
+    }
+
+    #[test]
+    fn convert_into_to_from_works_on_qualified_structs() {
+        check_convert_into_to_from(
+            r#"
+mod things {
+    pub struct Thing(String);
+    pub struct BetterThing(String);
+}
+
+impl $0core::convert::Into<things::BetterThing> for &things::Thing {
+    fn into(self) -> Thing {
+        things::BetterThing(self.0.clone())
+    }
+}
+"#,
+            r#"
+mod things {
+    pub struct Thing(String);
+    pub struct BetterThing(String);
+}
+
+impl From<&things::Thing> for things::BetterThing {
+    fn from(val: &things::Thing) -> Self {
+        things::BetterThing(val.0.clone())
+    }
+}
+"#,
+        )
+    }
+
+    #[test]
+    fn convert_into_to_from_works_on_qualified_enums() {
+        check_convert_into_to_from(
+            r#"
+mod things {
+    pub enum Thing {
+        A(String)
+    }
+    pub struct BetterThing {
+        B(String)
+    }
+}
+
+impl $0core::convert::Into<things::BetterThing> for &things::Thing {
+    fn into(self) -> Thing {
+        match self {
+            Self::A(s) => things::BetterThing::B(s)
+        }
+    }
+}
+"#,
+            r#"
+mod things {
+    pub enum Thing {
+        A(String)
+    }
+    pub struct BetterThing {
+        B(String)
+    }
+}
+
+impl From<&things::Thing> for things::BetterThing {
+    fn from(val: &things::Thing) -> Self {
+        match val {
+            things::Thing::A(s) => things::BetterThing::B(s)
+        }
+    }
+}
+"#,
+        )
+    }
+
+    #[test]
+    fn convert_into_to_from_not_applicable_on_any_trait_named_into() {
+        check_assist_not_applicable(
+            r#"
+pub trait Into<T> {{
+    pub fn into(self) -> T;
+}}
+
+struct Thing {
+    a: String,
+}
+
+impl $0Into<Thing> for String {
+    fn into(self) -> Thing {
+        Thing {
+            a: self
+        }
+    }
+}
+"#,
+        );
+    }
+
+    fn check_convert_into_to_from(before: &str, after: &str) {
+        let before = &format!("//- /main.rs crate:main deps:core{}{}", before, FamousDefs::FIXTURE);
+        check_assist(convert_into_to_from, before, after);
+    }
+
+    fn check_assist_not_applicable(before: &str) {
+        let before = &format!("//- /main.rs crate:main deps:core{}{}", before, FamousDefs::FIXTURE);
+        crate::tests::check_assist_not_applicable(convert_into_to_from, before);
+    }
+}
diff --git a/crates/ide_assists/src/handlers/extract_function.rs b/crates/ide_assists/src/handlers/extract_function.rs
index 5fdc8bf38..059414274 100644
--- a/crates/ide_assists/src/handlers/extract_function.rs
+++ b/crates/ide_assists/src/handlers/extract_function.rs
@@ -75,7 +75,8 @@ pub(crate) fn extract_function(acc: &mut Assists, ctx: &AssistContext) -> Option
     let insert_after = scope_for_fn_insertion(&body, anchor)?;
     let module = ctx.sema.scope(&insert_after).module()?;
 
-    let vars_defined_in_body_and_outlive = vars_defined_in_body_and_outlive(ctx, &body);
+    let vars_defined_in_body_and_outlive =
+        vars_defined_in_body_and_outlive(ctx, &body, &node.parent().as_ref().unwrap_or(&node));
     let ret_ty = body_return_ty(ctx, &body)?;
 
     // FIXME: we compute variables that outlive here just to check `never!` condition
@@ -257,7 +258,7 @@ struct Function {
     control_flow: ControlFlow,
     ret_ty: RetType,
     body: FunctionBody,
-    vars_defined_in_body_and_outlive: Vec<Local>,
+    vars_defined_in_body_and_outlive: Vec<OutlivedLocal>,
 }
 
 #[derive(Debug)]
@@ -296,9 +297,9 @@ impl Function {
             RetType::Expr(ty) => FunType::Single(ty.clone()),
             RetType::Stmt => match self.vars_defined_in_body_and_outlive.as_slice() {
                 [] => FunType::Unit,
-                [var] => FunType::Single(var.ty(ctx.db())),
+                [var] => FunType::Single(var.local.ty(ctx.db())),
                 vars => {
-                    let types = vars.iter().map(|v| v.ty(ctx.db())).collect();
+                    let types = vars.iter().map(|v| v.local.ty(ctx.db())).collect();
                     FunType::Tuple(types)
                 }
             },
@@ -562,6 +563,12 @@ impl HasTokenAtOffset for FunctionBody {
     }
 }
 
+#[derive(Debug)]
+struct OutlivedLocal {
+    local: Local,
+    mut_usage_outside_body: bool,
+}
+
 /// Try to guess what user wants to extract
 ///
 /// We have basically have two cases:
@@ -707,10 +714,10 @@ fn has_exclusive_usages(ctx: &AssistContext, usages: &LocalUsages, body: &Functi
         .any(|reference| reference_is_exclusive(reference, body, ctx))
 }
 
-/// checks if this reference requires `&mut` access inside body
+/// checks if this reference requires `&mut` access inside node
 fn reference_is_exclusive(
     reference: &FileReference,
-    body: &FunctionBody,
+    node: &dyn HasTokenAtOffset,
     ctx: &AssistContext,
 ) -> bool {
     // we directly modify variable with set: `n = 0`, `n += 1`
@@ -719,7 +726,7 @@ fn reference_is_exclusive(
     }
 
     // we take `&mut` reference to variable: `&mut v`
-    let path = match path_element_of_reference(body, reference) {
+    let path = match path_element_of_reference(node, reference) {
         Some(path) => path,
         None => return false,
     };
@@ -729,6 +736,14 @@ fn reference_is_exclusive(
 
 /// checks if this expr requires `&mut` access, recurses on field access
 fn expr_require_exclusive_access(ctx: &AssistContext, expr: &ast::Expr) -> Option<bool> {
+    match expr {
+        ast::Expr::MacroCall(_) => {
+            // FIXME: expand macro and check output for mutable usages of the variable?
+            return None;
+        }
+        _ => (),
+    }
+
     let parent = expr.syntax().parent()?;
 
     if let Some(bin_expr) = ast::BinExpr::cast(parent.clone()) {
@@ -787,7 +802,7 @@ impl HasTokenAtOffset for SyntaxNode {
     }
 }
 
-/// find relevant `ast::PathExpr` for reference
+/// find relevant `ast::Expr` for reference
 ///
 /// # Preconditions
 ///
@@ -804,7 +819,11 @@ fn path_element_of_reference(
         stdx::never!(false, "cannot find path parent of variable usage: {:?}", token);
         None
     })?;
-    stdx::always!(matches!(path, ast::Expr::PathExpr(_)));
+    stdx::always!(
+        matches!(path, ast::Expr::PathExpr(_) | ast::Expr::MacroCall(_)),
+        "unexpected expression type for variable usage: {:?}",
+        path
+    );
     Some(path)
 }
 
@@ -820,10 +839,16 @@ fn vars_defined_in_body(body: &FunctionBody, ctx: &AssistContext) -> Vec<Local>
 }
 
 /// list local variables defined inside `body` that should be returned from extracted function
-fn vars_defined_in_body_and_outlive(ctx: &AssistContext, body: &FunctionBody) -> Vec<Local> {
-    let mut vars_defined_in_body = vars_defined_in_body(&body, ctx);
-    vars_defined_in_body.retain(|var| var_outlives_body(ctx, body, var));
+fn vars_defined_in_body_and_outlive(
+    ctx: &AssistContext,
+    body: &FunctionBody,
+    parent: &SyntaxNode,
+) -> Vec<OutlivedLocal> {
+    let vars_defined_in_body = vars_defined_in_body(&body, ctx);
     vars_defined_in_body
+        .into_iter()
+        .filter_map(|var| var_outlives_body(ctx, body, var, parent))
+        .collect()
 }
 
 /// checks if the relevant local was defined before(outside of) body
@@ -843,11 +868,23 @@ fn either_syntax(value: &Either<ast::IdentPat, ast::SelfParam>) -> &SyntaxNode {
     }
 }
 
-/// checks if local variable is used after(outside of) body
-fn var_outlives_body(ctx: &AssistContext, body: &FunctionBody, var: &Local) -> bool {
-    let usages = LocalUsages::find(ctx, *var);
+/// returns usage details if local variable is used after(outside of) body
+fn var_outlives_body(
+    ctx: &AssistContext,
+    body: &FunctionBody,
+    var: Local,
+    parent: &SyntaxNode,
+) -> Option<OutlivedLocal> {
+    let usages = LocalUsages::find(ctx, var);
     let has_usages = usages.iter().any(|reference| body.preceedes_range(reference.range));
-    has_usages
+    if !has_usages {
+        return None;
+    }
+    let has_mut_usages = usages
+        .iter()
+        .filter(|reference| body.preceedes_range(reference.range))
+        .any(|reference| reference_is_exclusive(reference, parent, ctx));
+    Some(OutlivedLocal { local: var, mut_usage_outside_body: has_mut_usages })
 }
 
 fn body_return_ty(ctx: &AssistContext, body: &FunctionBody) -> Option<RetType> {
@@ -927,16 +964,25 @@ fn format_replacement(ctx: &AssistContext, fun: &Function, indent: IndentLevel)
     let mut buf = String::new();
     match fun.vars_defined_in_body_and_outlive.as_slice() {
         [] => {}
-        [var] => format_to!(buf, "let {} = ", var.name(ctx.db()).unwrap()),
+        [var] => {
+            format_to!(buf, "let {}{} = ", mut_modifier(var), var.local.name(ctx.db()).unwrap())
+        }
         [v0, vs @ ..] => {
             buf.push_str("let (");
-            format_to!(buf, "{}", v0.name(ctx.db()).unwrap());
+            format_to!(buf, "{}{}", mut_modifier(v0), v0.local.name(ctx.db()).unwrap());
             for var in vs {
-                format_to!(buf, ", {}", var.name(ctx.db()).unwrap());
+                format_to!(buf, ", {}{}", mut_modifier(var), var.local.name(ctx.db()).unwrap());
             }
             buf.push_str(") = ");
         }
     }
+    fn mut_modifier(var: &OutlivedLocal) -> &'static str {
+        if var.mut_usage_outside_body {
+            "mut "
+        } else {
+            ""
+        }
+    }
     format_to!(buf, "{}", expr);
     if fun.ret_ty.is_unit()
         && (!fun.vars_defined_in_body_and_outlive.is_empty() || !expr.is_block_like())
@@ -1199,10 +1245,10 @@ fn make_body(
                 match fun.vars_defined_in_body_and_outlive.as_slice() {
                     [] => {}
                     [var] => {
-                        tail_expr = Some(path_expr_from_local(ctx, *var));
+                        tail_expr = Some(path_expr_from_local(ctx, var.local));
                     }
                     vars => {
-                        let exprs = vars.iter().map(|var| path_expr_from_local(ctx, *var));
+                        let exprs = vars.iter().map(|var| path_expr_from_local(ctx, var.local));
                         let expr = make::expr_tuple(exprs);
                         tail_expr = Some(expr);
                     }
@@ -2111,6 +2157,30 @@ fn $0fun_name(n: i32) -> i32 {
     }
 
     #[test]
+    fn variable_defined_inside_and_used_after_mutably_no_ret() {
+        check_assist(
+            extract_function,
+            r"
+fn foo() {
+    let n = 1;
+    $0let mut k = n * n;$0
+    k += 1;
+}",
+            r"
+fn foo() {
+    let n = 1;
+    let mut k = fun_name(n);
+    k += 1;
+}
+
+fn $0fun_name(n: i32) -> i32 {
+    let mut k = n * n;
+    k
+}",
+        );
+    }
+
+    #[test]
     fn two_variables_defined_inside_and_used_after_no_ret() {
         check_assist(
             extract_function,
@@ -2137,6 +2207,38 @@ fn $0fun_name(n: i32) -> (i32, i32) {
     }
 
     #[test]
+    fn multi_variables_defined_inside_and_used_after_mutably_no_ret() {
+        check_assist(
+            extract_function,
+            r"
+fn foo() {
+    let n = 1;
+    $0let mut k = n * n;
+    let mut m = k + 2;
+    let mut o = m + 3;
+    o += 1;$0
+    k += o;
+    m = 1;
+}",
+            r"
+fn foo() {
+    let n = 1;
+    let (mut k, mut m, o) = fun_name(n);
+    k += o;
+    m = 1;
+}
+
+fn $0fun_name(n: i32) -> (i32, i32, i32) {
+    let mut k = n * n;
+    let mut m = k + 2;
+    let mut o = m + 3;
+    o += 1;
+    (k, m, o)
+}",
+        );
+    }
+
+    #[test]
     fn nontrivial_patterns_define_variables() {
         check_assist(
             extract_function,
@@ -3372,4 +3474,36 @@ fn foo() -> Result<(), i64> {
 }"##,
         );
     }
+
+    #[test]
+    fn param_usage_in_macro() {
+        check_assist(
+            extract_function,
+            r"
+macro_rules! m {
+    ($val:expr) => { $val };
+}
+
+fn foo() {
+    let n = 1;
+    $0let k = n * m!(n);$0
+    let m = k + 1;
+}",
+            r"
+macro_rules! m {
+    ($val:expr) => { $val };
+}
+
+fn foo() {
+    let n = 1;
+    let k = fun_name(n);
+    let m = k + 1;
+}
+
+fn $0fun_name(n: i32) -> i32 {
+    let k = n * m!(n);
+    k
+}",
+        );
+    }
 }
diff --git a/crates/ide_assists/src/handlers/extract_type_alias.rs b/crates/ide_assists/src/handlers/extract_type_alias.rs
new file mode 100644
index 000000000..442a209b9
--- /dev/null
+++ b/crates/ide_assists/src/handlers/extract_type_alias.rs
@@ -0,0 +1,149 @@
+use syntax::ast::{self, AstNode};
+
+use crate::{AssistContext, AssistId, AssistKind, Assists};
+
+// Assist: extract_type_alias
+//
+// Extracts the selected type as a type alias.
+//
+// ```
+// struct S {
+//     field: $0(u8, u8, u8)$0,
+// }
+// ```
+// ->
+// ```
+// type $0Type = (u8, u8, u8);
+//
+// struct S {
+//     field: Type,
+// }
+// ```
+pub(crate) fn extract_type_alias(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
+    if ctx.frange.range.is_empty() {
+        return None;
+    }
+
+    let node = ctx.find_node_at_range::<ast::Type>()?;
+    let insert = ctx.find_node_at_offset::<ast::Item>()?.syntax().text_range().start();
+    let target = node.syntax().text_range();
+
+    acc.add(
+        AssistId("extract_type_alias", AssistKind::RefactorExtract),
+        "Extract type as type alias",
+        target,
+        |builder| {
+            builder.edit_file(ctx.frange.file_id);
+            builder.replace(target, "Type");
+            match ctx.config.snippet_cap {
+                Some(cap) => {
+                    builder.insert_snippet(cap, insert, format!("type $0Type = {};\n\n", node));
+                }
+                None => {
+                    builder.insert(insert, format!("type Type = {};\n\n", node));
+                }
+            }
+        },
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::tests::{check_assist, check_assist_not_applicable};
+
+    use super::*;
+
+    #[test]
+    fn test_not_applicable_without_selection() {
+        check_assist_not_applicable(
+            extract_type_alias,
+            r"
+struct S {
+    field: $0(u8, u8, u8),
+}
+            ",
+        );
+    }
+
+    #[test]
+    fn test_simple_types() {
+        check_assist(
+            extract_type_alias,
+            r"
+struct S {
+    field: $0u8$0,
+}
+            ",
+            r#"
+type $0Type = u8;
+
+struct S {
+    field: Type,
+}
+            "#,
+        );
+    }
+
+    #[test]
+    fn test_generic_type_arg() {
+        check_assist(
+            extract_type_alias,
+            r"
+fn generic<T>() {}
+
+fn f() {
+    generic::<$0()$0>();
+}
+            ",
+            r#"
+fn generic<T>() {}
+
+type $0Type = ();
+
+fn f() {
+    generic::<Type>();
+}
+            "#,
+        );
+    }
+
+    #[test]
+    fn test_inner_type_arg() {
+        check_assist(
+            extract_type_alias,
+            r"
+struct Vec<T> {}
+struct S {
+    v: Vec<Vec<$0Vec<u8>$0>>,
+}
+            ",
+            r#"
+struct Vec<T> {}
+type $0Type = Vec<u8>;
+
+struct S {
+    v: Vec<Vec<Type>>,
+}
+            "#,
+        );
+    }
+
+    #[test]
+    fn test_extract_inner_type() {
+        check_assist(
+            extract_type_alias,
+            r"
+struct S {
+    field: ($0u8$0,),
+}
+            ",
+            r#"
+type $0Type = u8;
+
+struct S {
+    field: (Type,),
+}
+            "#,
+        );
+    }
+}
diff --git a/crates/ide_assists/src/handlers/extract_variable.rs b/crates/ide_assists/src/handlers/extract_variable.rs
index 7a32483dc..136b9a55b 100644
--- a/crates/ide_assists/src/handlers/extract_variable.rs
+++ b/crates/ide_assists/src/handlers/extract_variable.rs
@@ -2,7 +2,8 @@ use stdx::format_to;
 use syntax::{
     ast::{self, AstNode},
     SyntaxKind::{
-        BLOCK_EXPR, BREAK_EXPR, CLOSURE_EXPR, COMMENT, LOOP_EXPR, MATCH_ARM, PATH_EXPR, RETURN_EXPR,
+        BLOCK_EXPR, BREAK_EXPR, CLOSURE_EXPR, COMMENT, LOOP_EXPR, MATCH_ARM, MATCH_GUARD,
+        PATH_EXPR, RETURN_EXPR,
     },
     SyntaxNode,
 };
@@ -147,9 +148,18 @@ impl Anchor {
             }
 
             if let Some(parent) = node.parent() {
-                if parent.kind() == MATCH_ARM || parent.kind() == CLOSURE_EXPR {
+                if parent.kind() == CLOSURE_EXPR {
+                    cov_mark::hit!(test_extract_var_in_closure_no_block);
                     return Some(Anchor::WrapInBlock(node));
                 }
+                if parent.kind() == MATCH_ARM {
+                    if node.kind() == MATCH_GUARD {
+                        cov_mark::hit!(test_extract_var_in_match_guard);
+                    } else {
+                        cov_mark::hit!(test_extract_var_in_match_arm_no_block);
+                        return Some(Anchor::WrapInBlock(node));
+                    }
+                }
             }
 
             if let Some(stmt) = ast::Stmt::cast(node.clone()) {
@@ -280,9 +290,10 @@ fn foo() {
 
     #[test]
     fn test_extract_var_in_match_arm_no_block() {
+        cov_mark::check!(test_extract_var_in_match_arm_no_block);
         check_assist(
             extract_variable,
-            "
+            r#"
 fn main() {
     let x = true;
     let tuple = match x {
@@ -290,8 +301,8 @@ fn main() {
         _ => (0, false)
     };
 }
-",
-            "
+"#,
+            r#"
 fn main() {
     let x = true;
     let tuple = match x {
@@ -299,7 +310,7 @@ fn main() {
         _ => (0, false)
     };
 }
-",
+"#,
         );
     }
 
@@ -307,7 +318,7 @@ fn main() {
     fn test_extract_var_in_match_arm_with_block() {
         check_assist(
             extract_variable,
-            "
+            r#"
 fn main() {
     let x = true;
     let tuple = match x {
@@ -318,8 +329,8 @@ fn main() {
         _ => (0, false)
     };
 }
-",
-            "
+"#,
+            r#"
 fn main() {
     let x = true;
     let tuple = match x {
@@ -331,24 +342,50 @@ fn main() {
         _ => (0, false)
     };
 }
-",
+"#,
+        );
+    }
+
+    #[test]
+    fn test_extract_var_in_match_guard() {
+        cov_mark::check!(test_extract_var_in_match_guard);
+        check_assist(
+            extract_variable,
+            r#"
+fn main() {
+    match () {
+        () if $010 > 0$0 => 1
+        _ => 2
+    };
+}
+"#,
+            r#"
+fn main() {
+    let $0var_name = 10 > 0;
+    match () {
+        () if var_name => 1
+        _ => 2
+    };
+}
+"#,
         );
     }
 
     #[test]
     fn test_extract_var_in_closure_no_block() {
+        cov_mark::check!(test_extract_var_in_closure_no_block);
         check_assist(
             extract_variable,
-            "
+            r#"
 fn main() {
     let lambda = |x: u32| $0x * 2$0;
 }
-",
-            "
+"#,
+            r#"
 fn main() {
     let lambda = |x: u32| { let $0var_name = x * 2; var_name };
 }
-",
+"#,
         );
     }
 
@@ -356,16 +393,16 @@ fn main() {
     fn test_extract_var_in_closure_with_block() {
         check_assist(
             extract_variable,
-            "
+            r#"
 fn main() {
     let lambda = |x: u32| { $0x * 2$0 };
 }
-",
-            "
+"#,
+            r#"
 fn main() {
     let lambda = |x: u32| { let $0var_name = x * 2; var_name };
 }
-",
+"#,
         );
     }
 
diff --git a/crates/ide_assists/src/handlers/fill_match_arms.rs b/crates/ide_assists/src/handlers/fill_match_arms.rs
index 878b3a3fa..80bd1b7e8 100644
--- a/crates/ide_assists/src/handlers/fill_match_arms.rs
+++ b/crates/ide_assists/src/handlers/fill_match_arms.rs
@@ -71,12 +71,6 @@ pub(crate) fn fill_match_arms(acc: &mut Assists, ctx: &AssistContext) -> Option<
             return None;
         }
 
-        // We do not currently support filling match arms for a tuple
-        // containing a single enum.
-        if enum_defs.len() < 2 {
-            return None;
-        }
-
         // When calculating the match arms for a tuple of enums, we want
         // to create a match arm for each possible combination of enum
         // values. The `multi_cartesian_product` method transforms
@@ -514,10 +508,7 @@ fn main() {
 
     #[test]
     fn fill_match_arms_single_element_tuple_of_enum() {
-        // For now we don't hande the case of a single element tuple, but
-        // we could handle this in the future if `make::tuple_pat` allowed
-        // creating a tuple with a single pattern.
-        check_assist_not_applicable(
+        check_assist(
             fill_match_arms,
             r#"
             enum A { One, Two }
@@ -528,6 +519,17 @@ fn main() {
                 }
             }
             "#,
+            r#"
+            enum A { One, Two }
+
+            fn main() {
+                let a = A::One;
+                match (a, ) {
+                    $0(A::One,) => {}
+                    (A::Two,) => {}
+                }
+            }
+            "#,
         );
     }
 
diff --git a/crates/ide_assists/src/handlers/flip_comma.rs b/crates/ide_assists/src/handlers/flip_comma.rs
index 7f5e75d34..99be5e090 100644
--- a/crates/ide_assists/src/handlers/flip_comma.rs
+++ b/crates/ide_assists/src/handlers/flip_comma.rs
@@ -66,26 +66,12 @@ mod tests {
     }
 
     #[test]
-    #[should_panic]
     fn flip_comma_before_punct() {
         // See https://github.com/rust-analyzer/rust-analyzer/issues/1619
         // "Flip comma" assist shouldn't be applicable to the last comma in enum or struct
         // declaration body.
-        check_assist_target(
-            flip_comma,
-            "pub enum Test { \
-             A,$0 \
-             }",
-            ",",
-        );
-
-        check_assist_target(
-            flip_comma,
-            "pub struct Test { \
-             foo: usize,$0 \
-             }",
-            ",",
-        );
+        check_assist_not_applicable(flip_comma, "pub enum Test { A,$0 }");
+        check_assist_not_applicable(flip_comma, "pub struct Test { foo: usize,$0 }");
     }
 
     #[test]
diff --git a/crates/ide_assists/src/handlers/generate_default_from_new.rs b/crates/ide_assists/src/handlers/generate_default_from_new.rs
index 81c54ba3e..dc14552d6 100644
--- a/crates/ide_assists/src/handlers/generate_default_from_new.rs
+++ b/crates/ide_assists/src/handlers/generate_default_from_new.rs
@@ -92,7 +92,7 @@ fn is_default_implemented(ctx: &AssistContext, impl_: &Impl) -> bool {
         None => return false,
     };
 
-    let ty = impl_def.target_ty(db);
+    let ty = impl_def.self_ty(db);
     let krate = impl_def.module(db).krate();
     let default = FamousDefs(&ctx.sema, Some(krate)).core_default_Default();
     let default_trait = match default {
diff --git a/crates/ide_assists/src/handlers/generate_is_empty_from_len.rs b/crates/ide_assists/src/handlers/generate_is_empty_from_len.rs
index b8834d283..910010a04 100644
--- a/crates/ide_assists/src/handlers/generate_is_empty_from_len.rs
+++ b/crates/ide_assists/src/handlers/generate_is_empty_from_len.rs
@@ -91,7 +91,7 @@ fn get_impl_method(
 
     let scope = ctx.sema.scope(impl_.syntax());
     let krate = impl_def.module(db).krate();
-    let ty = impl_def.target_ty(db);
+    let ty = impl_def.self_ty(db);
     let traits_in_scope = scope.traits_in_scope();
     ty.iterate_method_candidates(db, krate, &traits_in_scope, Some(fn_name), |_, func| Some(func))
 }
diff --git a/crates/ide_assists/src/handlers/remove_dbg.rs b/crates/ide_assists/src/handlers/remove_dbg.rs
index 6114091f2..c8226550f 100644
--- a/crates/ide_assists/src/handlers/remove_dbg.rs
+++ b/crates/ide_assists/src/handlers/remove_dbg.rs
@@ -1,5 +1,5 @@
 use syntax::{
-    ast::{self, AstNode},
+    ast::{self, AstNode, AstToken},
     match_ast, SyntaxElement, TextRange, TextSize, T,
 };
 
@@ -24,7 +24,39 @@ pub(crate) fn remove_dbg(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
     let macro_call = ctx.find_node_at_offset::<ast::MacroCall>()?;
     let new_contents = adjusted_macro_contents(&macro_call)?;
 
-    let macro_text_range = macro_call.syntax().text_range();
+    let parent = macro_call.syntax().parent();
+
+    let macro_text_range = if let Some(it) = parent.as_ref() {
+        if new_contents.is_empty() {
+            match_ast! {
+                match it {
+                    ast::BlockExpr(_it) => {
+                        macro_call.syntax()
+                            .prev_sibling_or_token()
+                            .and_then(whitespace_start)
+                            .map(|start| TextRange::new(start, macro_call.syntax().text_range().end()))
+                            .unwrap_or(macro_call.syntax().text_range())
+                    },
+                    ast::ExprStmt(it) => {
+                        let start = it
+                            .syntax()
+                            .prev_sibling_or_token()
+                            .and_then(whitespace_start)
+                            .unwrap_or(it.syntax().text_range().start());
+                        let end = it.syntax().text_range().end();
+
+                        TextRange::new(start, end)
+                    },
+                    _ => macro_call.syntax().text_range()
+                }
+            }
+        } else {
+            macro_call.syntax().text_range()
+        }
+    } else {
+        macro_call.syntax().text_range()
+    };
+
     let macro_end = if macro_call.semicolon_token().is_some() {
         macro_text_range.end() - TextSize::of(';')
     } else {
@@ -36,11 +68,22 @@ pub(crate) fn remove_dbg(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
         "Remove dbg!()",
         macro_text_range,
         |builder| {
-            builder.replace(TextRange::new(macro_text_range.start(), macro_end), new_contents);
+            builder.replace(
+                TextRange::new(macro_text_range.start(), macro_end),
+                if new_contents.is_empty() && parent.and_then(ast::LetStmt::cast).is_some() {
+                    ast::make::expr_unit().to_string()
+                } else {
+                    new_contents
+                },
+            );
         },
     )
 }
 
+fn whitespace_start(it: SyntaxElement) -> Option<TextSize> {
+    Some(it.into_token().and_then(ast::Whitespace::cast)?.syntax().text_range().start())
+}
+
 fn adjusted_macro_contents(macro_call: &ast::MacroCall) -> Option<String> {
     let contents = get_valid_macrocall_contents(&macro_call, "dbg")?;
     let macro_text_with_brackets = macro_call.token_tree()?.syntax().text();
@@ -94,15 +137,11 @@ fn get_valid_macrocall_contents(
     let mut contents_between_brackets = children_with_tokens.collect::<Vec<_>>();
     let last_child = contents_between_brackets.pop()?;
 
-    if contents_between_brackets.is_empty() {
-        None
-    } else {
-        match (first_child.kind(), last_child.kind()) {
-            (T!['('], T![')']) | (T!['['], T![']']) | (T!['{'], T!['}']) => {
-                Some(contents_between_brackets)
-            }
-            _ => None,
+    match (first_child.kind(), last_child.kind()) {
+        (T!['('], T![')']) | (T!['['], T![']']) | (T!['{'], T!['}']) => {
+            Some(contents_between_brackets)
         }
+        _ => None,
     }
 }
 
@@ -418,4 +457,48 @@ fn main() {
 }"#,
         );
     }
+
+    #[test]
+    fn test_remove_empty_dbg() {
+        check_assist(remove_dbg, r#"fn foo() { $0dbg!(); }"#, r#"fn foo() { }"#);
+        check_assist(
+            remove_dbg,
+            r#"
+fn foo() {
+    $0dbg!();
+}
+"#,
+            r#"
+fn foo() {
+}
+"#,
+        );
+        check_assist(
+            remove_dbg,
+            r#"
+fn foo() {
+    let test = $0dbg!();
+}"#,
+            r#"
+fn foo() {
+    let test = ();
+}"#,
+        );
+        check_assist(
+            remove_dbg,
+            r#"
+fn foo() {
+    let t = {
+        println!("Hello, world");
+        $0dbg!()
+    };
+}"#,
+            r#"
+fn foo() {
+    let t = {
+        println!("Hello, world");
+    };
+}"#,
+        );
+    }
 }
diff --git a/crates/ide_assists/src/handlers/reorder_fields.rs b/crates/ide_assists/src/handlers/reorder_fields.rs
index 383ca6c47..1a95135ca 100644
--- a/crates/ide_assists/src/handlers/reorder_fields.rs
+++ b/crates/ide_assists/src/handlers/reorder_fields.rs
@@ -1,6 +1,8 @@
+use either::Either;
+use itertools::Itertools;
 use rustc_hash::FxHashMap;
 
-use syntax::{algo, ast, match_ast, AstNode, SyntaxKind::*, SyntaxNode};
+use syntax::{ast, ted, AstNode};
 
 use crate::{AssistContext, AssistId, AssistKind, Assists};
 
@@ -22,60 +24,70 @@ use crate::{AssistContext, AssistId, AssistKind, Assists};
 pub(crate) fn reorder_fields(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
     let record = ctx
         .find_node_at_offset::<ast::RecordExpr>()
-        .map(|it| it.syntax().clone())
-        .or_else(|| ctx.find_node_at_offset::<ast::RecordPat>().map(|it| it.syntax().clone()))?;
-
-    let path = record.children().find_map(ast::Path::cast)?;
+        .map(Either::Left)
+        .or_else(|| ctx.find_node_at_offset::<ast::RecordPat>().map(Either::Right))?;
 
+    let path = record.as_ref().either(|it| it.path(), |it| it.path())?;
     let ranks = compute_fields_ranks(&path, &ctx)?;
+    let get_rank_of_field =
+        |of: Option<_>| *ranks.get(&of.unwrap_or_default()).unwrap_or(&usize::MAX);
 
-    let fields: Vec<SyntaxNode> = {
-        let field_kind = match record.kind() {
-            RECORD_EXPR => RECORD_EXPR_FIELD,
-            RECORD_PAT => RECORD_PAT_FIELD,
-            _ => {
-                stdx::never!();
-                return None;
-            }
-        };
-        record.children().flat_map(|n| n.children()).filter(|n| n.kind() == field_kind).collect()
+    let field_list = match &record {
+        Either::Left(it) => Either::Left(it.record_expr_field_list()?),
+        Either::Right(it) => Either::Right(it.record_pat_field_list()?),
     };
-
-    let sorted_fields = {
-        let mut fields = fields.clone();
-        fields.sort_by_key(|node| *ranks.get(&get_field_name(node)).unwrap_or(&usize::max_value()));
-        fields
+    let fields = match field_list {
+        Either::Left(it) => Either::Left((
+            it.fields()
+                .sorted_unstable_by_key(|field| {
+                    get_rank_of_field(field.field_name().map(|it| it.to_string()))
+                })
+                .collect::<Vec<_>>(),
+            it,
+        )),
+        Either::Right(it) => Either::Right((
+            it.fields()
+                .sorted_unstable_by_key(|field| {
+                    get_rank_of_field(field.field_name().map(|it| it.to_string()))
+                })
+                .collect::<Vec<_>>(),
+            it,
+        )),
     };
 
-    if sorted_fields == fields {
+    let is_sorted = fields.as_ref().either(
+        |(sorted, field_list)| field_list.fields().zip(sorted).all(|(a, b)| a == *b),
+        |(sorted, field_list)| field_list.fields().zip(sorted).all(|(a, b)| a == *b),
+    );
+    if is_sorted {
         cov_mark::hit!(reorder_sorted_fields);
         return None;
     }
-
-    let target = record.text_range();
+    let target = record.as_ref().either(AstNode::syntax, AstNode::syntax).text_range();
     acc.add(
         AssistId("reorder_fields", AssistKind::RefactorRewrite),
         "Reorder record fields",
         target,
-        |edit| {
-            let mut rewriter = algo::SyntaxRewriter::default();
-            for (old, new) in fields.iter().zip(&sorted_fields) {
-                rewriter.replace(old, new);
+        |builder| match fields {
+            Either::Left((sorted, field_list)) => {
+                replace(builder.make_ast_mut(field_list).fields(), sorted)
+            }
+            Either::Right((sorted, field_list)) => {
+                replace(builder.make_ast_mut(field_list).fields(), sorted)
             }
-            edit.rewrite(rewriter);
         },
     )
 }
 
-fn get_field_name(node: &SyntaxNode) -> String {
-    let res = match_ast! {
-        match node {
-            ast::RecordExprField(field) => field.field_name().map(|it| it.to_string()),
-            ast::RecordPatField(field) => field.field_name().map(|it| it.to_string()),
-            _ => None,
-        }
-    };
-    res.unwrap_or_default()
+fn replace<T: AstNode + PartialEq>(
+    fields: impl Iterator<Item = T>,
+    sorted_fields: impl IntoIterator<Item = T>,
+) {
+    fields.zip(sorted_fields).filter(|(field, sorted)| field != sorted).for_each(
+        |(field, sorted_field)| {
+            ted::replace(field.syntax(), sorted_field.syntax().clone_for_update());
+        },
+    );
 }
 
 fn compute_fields_ranks(path: &ast::Path, ctx: &AssistContext) -> Option<FxHashMap<String, usize>> {
@@ -86,7 +98,7 @@ fn compute_fields_ranks(path: &ast::Path, ctx: &AssistContext) -> Option<FxHashM
 
     let res = strukt
         .fields(ctx.db())
-        .iter()
+        .into_iter()
         .enumerate()
         .map(|(idx, field)| (field.name(ctx.db()).to_string(), idx))
         .collect();
@@ -137,7 +149,6 @@ const test: Foo = Foo { foo: 1, bar: 0 };
 "#,
         )
     }
-
     #[test]
     fn reorder_struct_pattern() {
         check_assist(
diff --git a/crates/ide_assists/src/lib.rs b/crates/ide_assists/src/lib.rs
index 8c068a6c0..3694f468f 100644
--- a/crates/ide_assists/src/lib.rs
+++ b/crates/ide_assists/src/lib.rs
@@ -28,7 +28,9 @@ pub use assist_config::AssistConfig;
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum AssistKind {
+    // FIXME: does the None variant make sense? Probably not.
     None,
+
     QuickFix,
     Generate,
     Refactor,
@@ -117,10 +119,12 @@ mod handlers {
     mod convert_integer_literal;
     mod convert_comment_block;
     mod convert_iter_for_each_to_for;
+    mod convert_into_to_from;
     mod early_return;
     mod expand_glob_import;
     mod extract_function;
     mod extract_struct_from_enum_variant;
+    mod extract_type_alias;
     mod extract_variable;
     mod fill_match_arms;
     mod fix_visibility;
@@ -184,9 +188,11 @@ mod handlers {
             convert_integer_literal::convert_integer_literal,
             convert_comment_block::convert_comment_block,
             convert_iter_for_each_to_for::convert_iter_for_each_to_for,
+            convert_into_to_from::convert_into_to_from,
             early_return::convert_to_guarded_return,
             expand_glob_import::expand_glob_import,
             extract_struct_from_enum_variant::extract_struct_from_enum_variant,
+            extract_type_alias::extract_type_alias,
             fill_match_arms::fill_match_arms,
             fix_visibility::fix_visibility,
             flip_binexpr::flip_binexpr,
diff --git a/crates/ide_assists/src/tests.rs b/crates/ide_assists/src/tests.rs
index a7a923beb..60e3a1474 100644
--- a/crates/ide_assists/src/tests.rs
+++ b/crates/ide_assists/src/tests.rs
@@ -84,7 +84,8 @@ fn check_doc_test(assist_id: &str, before: &str, after: &str) {
         });
 
     let actual = {
-        let source_change = assist.source_change.unwrap();
+        let source_change =
+            assist.source_change.expect("Assist did not contain any source changes");
         let mut actual = before;
         if let Some(source_file_edit) = source_change.get_source_edit(file_id) {
             source_file_edit.apply(&mut actual);
@@ -121,7 +122,8 @@ fn check(handler: Handler, before: &str, expected: ExpectedResult, assist_label:
 
     match (assist, expected) {
         (Some(assist), ExpectedResult::After(after)) => {
-            let source_change = assist.source_change.unwrap();
+            let source_change =
+                assist.source_change.expect("Assist did not contain any source changes");
             assert!(!source_change.source_file_edits.is_empty());
             let skip_header = source_change.source_file_edits.len() == 1
                 && source_change.file_system_edits.len() == 0;
diff --git a/crates/ide_assists/src/tests/generated.rs b/crates/ide_assists/src/tests/generated.rs
index 736027ff0..27a22ca10 100644
--- a/crates/ide_assists/src/tests/generated.rs
+++ b/crates/ide_assists/src/tests/generated.rs
@@ -206,6 +206,38 @@ const _: i32 = 0b1010;
 }
 
 #[test]
+fn doctest_convert_into_to_from() {
+    check_doc_test(
+        "convert_into_to_from",
+        r#####"
+//- /lib.rs crate:core
+pub mod convert { pub trait Into<T> { pub fn into(self) -> T; } }
+//- /lib.rs crate:main deps:core
+use core::convert::Into;
+impl $0Into<Thing> for usize {
+    fn into(self) -> Thing {
+        Thing {
+            b: self.to_string(),
+            a: self
+        }
+    }
+}
+"#####,
+        r#####"
+use core::convert::Into;
+impl From<usize> for Thing {
+    fn from(val: usize) -> Self {
+        Thing {
+            b: val.to_string(),
+            a: val
+        }
+    }
+}
+"#####,
+    )
+}
+
+#[test]
 fn doctest_convert_iter_for_each_to_for() {
     check_doc_test(
         "convert_iter_for_each_to_for",
@@ -329,6 +361,25 @@ enum A { One(One) }
 }
 
 #[test]
+fn doctest_extract_type_alias() {
+    check_doc_test(
+        "extract_type_alias",
+        r#####"
+struct S {
+    field: $0(u8, u8, u8)$0,
+}
+"#####,
+        r#####"
+type $0Type = (u8, u8, u8);
+
+struct S {
+    field: Type,
+}
+"#####,
+    )
+}
+
+#[test]
 fn doctest_extract_variable() {
     check_doc_test(
         "extract_variable",
diff --git a/crates/ide_assists/src/utils.rs b/crates/ide_assists/src/utils.rs
index 5f630ec75..d67524937 100644
--- a/crates/ide_assists/src/utils.rs
+++ b/crates/ide_assists/src/utils.rs
@@ -338,11 +338,11 @@ pub(crate) fn find_struct_impl(
         // (we currently use the wrong type parameter)
         // also we wouldn't want to use e.g. `impl S<u32>`
 
-        let same_ty = match blk.target_ty(db).as_adt() {
+        let same_ty = match blk.self_ty(db).as_adt() {
             Some(def) => def == struct_def,
             None => false,
         };
-        let not_trait_impl = blk.target_trait(db).is_none();
+        let not_trait_impl = blk.trait_(db).is_none();
 
         if !(same_ty && not_trait_impl) {
             None
diff --git a/crates/ide_completion/src/completions.rs b/crates/ide_completion/src/completions.rs
index 6d572a836..e2994eed4 100644
--- a/crates/ide_completion/src/completions.rs
+++ b/crates/ide_completion/src/completions.rs
@@ -220,7 +220,7 @@ fn complete_enum_variants(
         };
 
         if let Some(impl_) = ctx.impl_def.as_ref().and_then(|impl_| ctx.sema.to_def(impl_)) {
-            if impl_.target_ty(ctx.db) == *ty {
+            if impl_.self_ty(ctx.db) == *ty {
                 for &variant in &variants {
                     let self_path = hir::ModPath::from_segments(
                         hir::PathKind::Plain,
diff --git a/crates/ide_completion/src/completions/flyimport.rs b/crates/ide_completion/src/completions/flyimport.rs
index 1ad017198..8e211ae1e 100644
--- a/crates/ide_completion/src/completions/flyimport.rs
+++ b/crates/ide_completion/src/completions/flyimport.rs
@@ -113,6 +113,9 @@ pub(crate) fn import_on_the_fly(acc: &mut Completions, ctx: &CompletionContext)
     if ctx.use_item_syntax.is_some()
         || ctx.attribute_under_caret.is_some()
         || ctx.mod_declaration_under_caret.is_some()
+        || ctx.record_lit_syntax.is_some()
+        || ctx.has_trait_parent
+        || ctx.has_impl_parent
     {
         return None;
     }
@@ -1034,4 +1037,117 @@ fn main() {
             expect![[]],
         );
     }
+
+    #[test]
+    fn no_fuzzy_during_fields_of_record_lit_syntax() {
+        check(
+            r#"
+mod m {
+    pub fn some_fn() -> i32 {
+        42
+    }
+}
+struct Foo {
+    some_field: i32,
+}
+fn main() {
+    let _ = Foo { so$0 };
+}
+"#,
+            expect![[]],
+        );
+    }
+
+    #[test]
+    fn fuzzy_after_fields_of_record_lit_syntax() {
+        check(
+            r#"
+mod m {
+    pub fn some_fn() -> i32 {
+        42
+    }
+}
+struct Foo {
+    some_field: i32,
+}
+fn main() {
+    let _ = Foo { some_field: so$0 };
+}
+"#,
+            expect![[r#"
+                fn some_fn() (m::some_fn) fn() -> i32
+            "#]],
+        );
+    }
+
+    #[test]
+    fn no_flyimports_in_traits_and_impl_declarations() {
+        check(
+            r#"
+mod m {
+    pub fn some_fn() -> i32 {
+        42
+    }
+}
+trait Foo {
+    som$0
+}
+"#,
+            expect![[r#""#]],
+        );
+
+        check(
+            r#"
+mod m {
+    pub fn some_fn() -> i32 {
+        42
+    }
+}
+struct Foo;
+impl Foo {
+    som$0
+}
+"#,
+            expect![[r#""#]],
+        );
+
+        check(
+            r#"
+mod m {
+    pub fn some_fn() -> i32 {
+        42
+    }
+}
+struct Foo;
+trait Bar {}
+impl Bar for Foo {
+    som$0
+}
+"#,
+            expect![[r#""#]],
+        );
+    }
+
+    #[test]
+    fn no_inherent_candidates_proposed() {
+        check(
+            r#"
+mod baz {
+    pub trait DefDatabase {
+        fn method1(&self);
+    }
+    pub trait HirDatabase: DefDatabase {
+        fn method2(&self);
+    }
+}
+
+mod bar {
+    fn test(db: &dyn crate::baz::HirDatabase) {
+        db.metho$0
+    }
+}
+            "#,
+            expect![[r#""#]],
+        );
+    }
 }
diff --git a/crates/ide_completion/src/completions/pattern.rs b/crates/ide_completion/src/completions/pattern.rs
index b06498e6d..808d7ff7e 100644
--- a/crates/ide_completion/src/completions/pattern.rs
+++ b/crates/ide_completion/src/completions/pattern.rs
@@ -40,7 +40,7 @@ pub(crate) fn complete_pattern(acc: &mut Completions, ctx: &CompletionContext) {
                 _ => false,
             },
             hir::ScopeDef::MacroDef(_) => true,
-            hir::ScopeDef::ImplSelfType(impl_) => match impl_.target_ty(ctx.db).as_adt() {
+            hir::ScopeDef::ImplSelfType(impl_) => match impl_.self_ty(ctx.db).as_adt() {
                 Some(hir::Adt::Struct(strukt)) => {
                     acc.add_struct_pat(ctx, strukt, Some(name.clone()));
                     true
diff --git a/crates/ide_completion/src/completions/postfix/format_like.rs b/crates/ide_completion/src/completions/postfix/format_like.rs
index 3f1c6730b..e86ffa8f8 100644
--- a/crates/ide_completion/src/completions/postfix/format_like.rs
+++ b/crates/ide_completion/src/completions/postfix/format_like.rs
@@ -13,6 +13,8 @@
 //   + `logi` -> `log::info!(...)`
 //   + `logw` -> `log::warn!(...)`
 //   + `loge` -> `log::error!(...)`
+//
+// image::https://user-images.githubusercontent.com/48062697/113020656-b560f500-917a-11eb-87de-02991f61beb8.gif[]
 
 use ide_db::helpers::SnippetCap;
 use syntax::ast::{self, AstToken};
diff --git a/crates/ide_completion/src/completions/qualified_path.rs b/crates/ide_completion/src/completions/qualified_path.rs
index 105ff6013..969249df6 100644
--- a/crates/ide_completion/src/completions/qualified_path.rs
+++ b/crates/ide_completion/src/completions/qualified_path.rs
@@ -24,7 +24,7 @@ pub(crate) fn complete_qualified_path(acc: &mut Completions, ctx: &CompletionCon
     };
 
     // Add associated types on type parameters and `Self`.
-    resolution.assoc_type_shorthand_candidates(ctx.db, |alias| {
+    resolution.assoc_type_shorthand_candidates(ctx.db, |_, alias| {
         acc.add_type_alias(ctx, alias);
         None::<()>
     });
@@ -117,7 +117,7 @@ pub(crate) fn complete_qualified_path(acc: &mut Completions, ctx: &CompletionCon
             if let Some(krate) = ctx.krate {
                 let ty = match resolution {
                     PathResolution::TypeParam(param) => param.ty(ctx.db),
-                    PathResolution::SelfType(impl_def) => impl_def.target_ty(ctx.db),
+                    PathResolution::SelfType(impl_def) => impl_def.self_ty(ctx.db),
                     _ => return,
                 };
 
diff --git a/crates/ide_completion/src/item.rs b/crates/ide_completion/src/item.rs
index cc4ac9ea2..16991b688 100644
--- a/crates/ide_completion/src/item.rs
+++ b/crates/ide_completion/src/item.rs
@@ -29,7 +29,7 @@ pub struct CompletionItem {
     /// Range of identifier that is being completed.
     ///
     /// It should be used primarily for UI, but we also use this to convert
-    /// genetic TextEdit into LSP's completion edit (see conv.rs).
+    /// generic TextEdit into LSP's completion edit (see conv.rs).
     ///
     /// `source_range` must contain the completion offset. `insert_text` should
     /// start with what `source_range` points to, or VSCode will filter out the
diff --git a/crates/ide_completion/src/lib.rs b/crates/ide_completion/src/lib.rs
index 5ac1cb48d..6f3d5c5c5 100644
--- a/crates/ide_completion/src/lib.rs
+++ b/crates/ide_completion/src/lib.rs
@@ -81,6 +81,8 @@ pub use crate::{
 // And the auto import completions, enabled with the `rust-analyzer.completion.autoimport.enable` setting and the corresponding LSP client capabilities.
 // Those are the additional completion options with automatic `use` import and options from all project importable items,
 // fuzzy matched agains the completion imput.
+//
+// image::https://user-images.githubusercontent.com/48062697/113020667-b72ab880-917a-11eb-8778-716cf26a0eb3.gif[]
 
 /// Main entry point for completion. We run completion as a two-phase process.
 ///
@@ -104,6 +106,34 @@ pub use crate::{
 /// `foo` *should* be present among the completion variants. Filtering by
 /// identifier prefix/fuzzy match should be done higher in the stack, together
 /// with ordering of completions (currently this is done by the client).
+///
+/// # Hypothetical Completion Problem
+///
+/// There's a curious unsolved problem in the current implementation. Often, you
+/// want to compute completions on a *slightly different* text document.
+///
+/// In the simplest case, when the code looks like `let x = `, you want to
+/// insert a fake identifier to get a better syntax tree: `let x = complete_me`.
+///
+/// We do this in `CompletionContext`, and it works OK-enough for *syntax*
+/// analysis. However, we might want to, eg, ask for the type of `complete_me`
+/// variable, and that's where our current infrastructure breaks down. salsa
+/// doesn't allow such "phantom" inputs.
+///
+/// Another case where this would be instrumental is macro expansion. We want to
+/// insert a fake ident and re-expand code. There's `expand_hypothetical` as a
+/// work-around for this.
+///
+/// A different use-case is completion of injection (examples and links in doc
+/// comments). When computing completion for a path in a doc-comment, you want
+/// to inject a fake path expression into the item being documented and complete
+/// that.
+///
+/// IntelliJ has CodeFragment/Context infrastructure for that. You can create a
+/// temporary PSI node, and say that the context ("parent") of this node is some
+/// existing node. Asking for, eg, type of this `CodeFragment` node works
+/// correctly, as the underlying infrastructure makes use of contexts to do
+/// analysis.
 pub fn completions(
     db: &RootDatabase,
     config: &CompletionConfig,
diff --git a/crates/ide_db/src/apply_change.rs b/crates/ide_db/src/apply_change.rs
index 047a9b6bc..eac5ef6b9 100644
--- a/crates/ide_db/src/apply_change.rs
+++ b/crates/ide_db/src/apply_change.rs
@@ -101,6 +101,7 @@ impl RootDatabase {
     //
     // | VS Code | **Rust Analyzer: Memory Usage (Clears Database)**
     // |===
+    // image::https://user-images.githubusercontent.com/48062697/113065592-08559f00-91b1-11eb-8c96-64b88068ec02.gif[]
     pub fn per_query_memory_usage(&mut self) -> Vec<(String, Bytes)> {
         let mut acc: Vec<(String, Bytes)> = vec![];
         let sweep = SweepStrategy::default().discard_values().sweep_all_revisions();
@@ -151,6 +152,10 @@ impl RootDatabase {
             hir::db::FileItemTreeQuery
             hir::db::BlockDefMapQuery
             hir::db::CrateDefMapQueryQuery
+            hir::db::FieldsAttrsQuery
+            hir::db::VariantsAttrsQuery
+            hir::db::FieldsAttrsSourceMapQuery
+            hir::db::VariantsAttrsSourceMapQuery
             hir::db::StructDataQuery
             hir::db::UnionDataQuery
             hir::db::EnumDataQuery
@@ -196,7 +201,7 @@ impl RootDatabase {
             hir::db::InternImplTraitIdQuery
             hir::db::InternClosureQuery
             hir::db::AssociatedTyValueQuery
-            hir::db::TraitSolveQuery
+            hir::db::TraitSolveQueryQuery
 
             // SymbolsDatabase
             crate::symbol_index::FileSymbolsQuery
diff --git a/crates/ide_db/src/call_info.rs b/crates/ide_db/src/call_info.rs
index e583a52f4..bad277a95 100644
--- a/crates/ide_db/src/call_info.rs
+++ b/crates/ide_db/src/call_info.rs
@@ -4,8 +4,9 @@ use either::Either;
 use hir::{HasAttrs, HirDisplay, Semantics, Type};
 use stdx::format_to;
 use syntax::{
+    algo,
     ast::{self, ArgListOwner, NameOwner},
-    match_ast, AstNode, SyntaxNode, SyntaxToken, TextRange, TextSize,
+    match_ast, AstNode, Direction, SyntaxNode, SyntaxToken, TextRange, TextSize,
 };
 
 use crate::RootDatabase;
@@ -43,7 +44,12 @@ pub fn call_info(db: &RootDatabase, position: FilePosition) -> Option<CallInfo>
     let sema = Semantics::new(db);
     let file = sema.parse(position.file_id);
     let file = file.syntax();
-    let token = file.token_at_offset(position.offset).next()?;
+    let token = file
+        .token_at_offset(position.offset)
+        .left_biased()
+        // if the cursor is sandwiched between two space tokens and the call is unclosed
+        // this prevents us from leaving the CallExpression
+        .and_then(|tok| algo::skip_trivia_token(tok, Direction::Prev))?;
     let token = sema.descend_into_macros(token);
 
     let (callable, active_parameter) = call_info_impl(&sema, token)?;
diff --git a/crates/ide_db/src/call_info/tests.rs b/crates/ide_db/src/call_info/tests.rs
index 281a081a3..be1cc12de 100644
--- a/crates/ide_db/src/call_info/tests.rs
+++ b/crates/ide_db/src/call_info/tests.rs
@@ -522,3 +522,30 @@ fn main(f: fn(i32, f64) -> char) {
             "#]],
     )
 }
+
+#[test]
+fn call_info_for_unclosed_call() {
+    check(
+        r#"
+fn foo(foo: u32, bar: u32) {}
+fn main() {
+    foo($0
+}"#,
+        expect![[r#"
+            fn foo(foo: u32, bar: u32)
+            (<foo: u32>, bar: u32)
+        "#]],
+    );
+    // check with surrounding space
+    check(
+        r#"
+fn foo(foo: u32, bar: u32) {}
+fn main() {
+    foo( $0
+}"#,
+        expect![[r#"
+            fn foo(foo: u32, bar: u32)
+            (<foo: u32>, bar: u32)
+        "#]],
+    )
+}
diff --git a/crates/ide_db/src/defs.rs b/crates/ide_db/src/defs.rs
index 0d9808d24..de0dc2a40 100644
--- a/crates/ide_db/src/defs.rs
+++ b/crates/ide_db/src/defs.rs
@@ -330,25 +330,30 @@ impl NameRefClass {
             }
         }
 
-        if ast::AssocTypeArg::cast(parent.clone()).is_some() {
-            // `Trait<Assoc = Ty>`
-            //        ^^^^^
-            let path = name_ref.syntax().ancestors().find_map(ast::Path::cast)?;
-            let resolved = sema.resolve_path(&path)?;
-            if let PathResolution::Def(ModuleDef::Trait(tr)) = resolved {
-                if let Some(ty) = tr
-                    .items(sema.db)
-                    .iter()
-                    .filter_map(|assoc| match assoc {
-                        hir::AssocItem::TypeAlias(it) => Some(*it),
-                        _ => None,
-                    })
-                    .find(|alias| &alias.name(sema.db).to_string() == &name_ref.text())
-                {
-                    return Some(NameRefClass::Definition(Definition::ModuleDef(
-                        ModuleDef::TypeAlias(ty),
-                    )));
+        if let Some(assoc_type_arg) = ast::AssocTypeArg::cast(parent.clone()) {
+            if assoc_type_arg.name_ref().as_ref() == Some(name_ref) {
+                // `Trait<Assoc = Ty>`
+                //        ^^^^^
+                let path = name_ref.syntax().ancestors().find_map(ast::Path::cast)?;
+                let resolved = sema.resolve_path(&path)?;
+                if let PathResolution::Def(ModuleDef::Trait(tr)) = resolved {
+                    // FIXME: resolve in supertraits
+                    if let Some(ty) = tr
+                        .items(sema.db)
+                        .iter()
+                        .filter_map(|assoc| match assoc {
+                            hir::AssocItem::TypeAlias(it) => Some(*it),
+                            _ => None,
+                        })
+                        .find(|alias| &alias.name(sema.db).to_string() == &name_ref.text())
+                    {
+                        return Some(NameRefClass::Definition(Definition::ModuleDef(
+                            ModuleDef::TypeAlias(ty),
+                        )));
+                    }
                 }
+
+                return None;
             }
         }
 
diff --git a/crates/ide_db/src/helpers.rs b/crates/ide_db/src/helpers.rs
index 9992a92bd..66798ea3a 100644
--- a/crates/ide_db/src/helpers.rs
+++ b/crates/ide_db/src/helpers.rs
@@ -93,6 +93,10 @@ impl FamousDefs<'_, '_> {
         self.find_trait("core:convert:From")
     }
 
+    pub fn core_convert_Into(&self) -> Option<Trait> {
+        self.find_trait("core:convert:Into")
+    }
+
     pub fn core_option_Option(&self) -> Option<Enum> {
         self.find_enum("core:option:Option")
     }
diff --git a/crates/ide_db/src/helpers/famous_defs_fixture.rs b/crates/ide_db/src/helpers/famous_defs_fixture.rs
index d3464ae17..4d79e064e 100644
--- a/crates/ide_db/src/helpers/famous_defs_fixture.rs
+++ b/crates/ide_db/src/helpers/famous_defs_fixture.rs
@@ -14,6 +14,10 @@ pub mod convert {
     pub trait From<T> {
         fn from(t: T) -> Self;
     }
+
+    pub trait Into<T> {
+        pub fn into(self) -> T;
+    }
 }
 
 pub mod default {
@@ -120,7 +124,7 @@ pub mod option {
 pub mod prelude {
     pub use crate::{
         cmp::Ord,
-        convert::From,
+        convert::{From, Into},
         default::Default,
         iter::{IntoIterator, Iterator},
         ops::{Fn, FnMut, FnOnce},
diff --git a/crates/ide_db/src/helpers/import_assets.rs b/crates/ide_db/src/helpers/import_assets.rs
index 3deb0d159..91d6a4665 100644
--- a/crates/ide_db/src/helpers/import_assets.rs
+++ b/crates/ide_db/src/helpers/import_assets.rs
@@ -361,7 +361,7 @@ fn item_for_path_search(db: &RootDatabase, item: ItemInNs) -> Option<ItemInNs> {
             Some(assoc_item) => match assoc_item.container(db) {
                 AssocItemContainer::Trait(trait_) => ItemInNs::from(ModuleDef::from(trait_)),
                 AssocItemContainer::Impl(impl_) => {
-                    ItemInNs::from(ModuleDef::from(impl_.target_ty(db).as_adt()?))
+                    ItemInNs::from(ModuleDef::from(impl_.self_ty(db).as_adt()?))
                 }
             },
             None => item,
@@ -436,6 +436,8 @@ fn trait_applicable_items(
     })
     .collect();
 
+    let related_dyn_traits =
+        trait_candidate.receiver_ty.applicable_inherent_traits(db).collect::<FxHashSet<_>>();
     let mut located_imports = FxHashSet::default();
 
     if trait_assoc_item {
@@ -451,12 +453,16 @@ fn trait_applicable_items(
                             return None;
                         }
                     }
+                    let located_trait = assoc.containing_trait(db)?;
+                    if related_dyn_traits.contains(&located_trait) {
+                        return None;
+                    }
 
-                    let item = ItemInNs::from(ModuleDef::from(assoc.containing_trait(db)?));
+                    let trait_item = ItemInNs::from(ModuleDef::from(located_trait));
                     let original_item = assoc_to_item(assoc);
                     located_imports.insert(LocatedImport::new(
-                        mod_path(item)?,
-                        item,
+                        mod_path(trait_item)?,
+                        trait_item,
                         original_item,
                         mod_path(original_item),
                     ));
@@ -473,11 +479,15 @@ fn trait_applicable_items(
             |_, function| {
                 let assoc = function.as_assoc_item(db)?;
                 if required_assoc_items.contains(&assoc) {
-                    let item = ItemInNs::from(ModuleDef::from(assoc.containing_trait(db)?));
+                    let located_trait = assoc.containing_trait(db)?;
+                    if related_dyn_traits.contains(&located_trait) {
+                        return None;
+                    }
+                    let trait_item = ItemInNs::from(ModuleDef::from(located_trait));
                     let original_item = assoc_to_item(assoc);
                     located_imports.insert(LocatedImport::new(
-                        mod_path(item)?,
-                        item,
+                        mod_path(trait_item)?,
+                        trait_item,
                         original_item,
                         mod_path(original_item),
                     ));
diff --git a/crates/mbe/src/benchmark.rs b/crates/mbe/src/benchmark.rs
index ba814a2e1..38707ffa5 100644
--- a/crates/mbe/src/benchmark.rs
+++ b/crates/mbe/src/benchmark.rs
@@ -65,7 +65,7 @@ fn macro_rules_fixtures_tt() -> FxHashMap<String, tt::Subtree> {
         .filter_map(ast::MacroRules::cast)
         .map(|rule| {
             let id = rule.name().unwrap().to_string();
-            let (def_tt, _) = ast_to_token_tree(&rule.token_tree().unwrap()).unwrap();
+            let (def_tt, _) = ast_to_token_tree(&rule.token_tree().unwrap());
             (id, def_tt)
         })
         .collect()
diff --git a/crates/mbe/src/expander.rs b/crates/mbe/src/expander.rs
index 3197c834c..bfef7f73d 100644
--- a/crates/mbe/src/expander.rs
+++ b/crates/mbe/src/expander.rs
@@ -159,8 +159,7 @@ mod tests {
         let macro_definition =
             source_file.syntax().descendants().find_map(ast::MacroRules::cast).unwrap();
 
-        let (definition_tt, _) =
-            ast_to_token_tree(&macro_definition.token_tree().unwrap()).unwrap();
+        let (definition_tt, _) = ast_to_token_tree(&macro_definition.token_tree().unwrap());
         crate::MacroRules::parse(&definition_tt).unwrap()
     }
 
@@ -169,8 +168,7 @@ mod tests {
         let macro_invocation =
             source_file.syntax().descendants().find_map(ast::MacroCall::cast).unwrap();
 
-        let (invocation_tt, _) =
-            ast_to_token_tree(&macro_invocation.token_tree().unwrap()).unwrap();
+        let (invocation_tt, _) = ast_to_token_tree(&macro_invocation.token_tree().unwrap());
 
         expand_rules(&rules.rules, &invocation_tt)
     }
diff --git a/crates/mbe/src/lib.rs b/crates/mbe/src/lib.rs
index e74f8cf3f..3af5bc18b 100644
--- a/crates/mbe/src/lib.rs
+++ b/crates/mbe/src/lib.rs
@@ -220,9 +220,11 @@ impl MacroDef {
             while src.len() > 0 {
                 let rule = Rule::parse(&mut src, true)?;
                 rules.push(rule);
-                if let Err(()) = src.expect_char(';') {
+                if let Err(()) = src.expect_any_char(&[';', ',']) {
                     if src.len() > 0 {
-                        return Err(ParseError::Expected("expected `;`".to_string()));
+                        return Err(ParseError::Expected(
+                            "expected `;` or `,` to delimit rules".to_string(),
+                        ));
                     }
                     break;
                 }
diff --git a/crates/mbe/src/syntax_bridge.rs b/crates/mbe/src/syntax_bridge.rs
index cfab99da8..a7c8c13c6 100644
--- a/crates/mbe/src/syntax_bridge.rs
+++ b/crates/mbe/src/syntax_bridge.rs
@@ -43,18 +43,18 @@ pub struct TokenMap {
 
 /// Convert the syntax tree (what user has written) to a `TokenTree` (what macro
 /// will consume).
-pub fn ast_to_token_tree(ast: &impl ast::AstNode) -> Option<(tt::Subtree, TokenMap)> {
+pub fn ast_to_token_tree(ast: &impl ast::AstNode) -> (tt::Subtree, TokenMap) {
     syntax_node_to_token_tree(ast.syntax())
 }
 
 /// Convert the syntax node to a `TokenTree` (what macro
 /// will consume).
-pub fn syntax_node_to_token_tree(node: &SyntaxNode) -> Option<(tt::Subtree, TokenMap)> {
+pub fn syntax_node_to_token_tree(node: &SyntaxNode) -> (tt::Subtree, TokenMap) {
     let global_offset = node.text_range().start();
     let mut c = Convertor::new(node, global_offset);
-    let subtree = c.go()?;
+    let subtree = c.go();
     c.id_alloc.map.entries.shrink_to_fit();
-    Some((subtree, c.id_alloc.map))
+    (subtree, c.id_alloc.map)
 }
 
 // The following items are what `rustc` macro can be parsed into :
@@ -108,7 +108,7 @@ pub fn parse_to_token_tree(text: &str) -> Option<(tt::Subtree, TokenMap)> {
         },
     };
 
-    let subtree = conv.go()?;
+    let subtree = conv.go();
     Some((subtree, conv.id_alloc.map))
 }
 
@@ -319,21 +319,18 @@ trait SrcToken: std::fmt::Debug {
 trait TokenConvertor {
     type Token: SrcToken;
 
-    fn go(&mut self) -> Option<tt::Subtree> {
+    fn go(&mut self) -> tt::Subtree {
         let mut subtree = tt::Subtree::default();
         subtree.delimiter = None;
         while self.peek().is_some() {
             self.collect_leaf(&mut subtree.token_trees);
         }
-        if subtree.token_trees.is_empty() {
-            return None;
-        }
         if subtree.token_trees.len() == 1 {
             if let tt::TokenTree::Subtree(first) = &subtree.token_trees[0] {
-                return Some(first.clone());
+                return first.clone();
             }
         }
-        Some(subtree)
+        subtree
     }
 
     fn collect_leaf(&mut self, result: &mut Vec<tt::TokenTree>) {
@@ -861,7 +858,7 @@ mod tests {
         // - T!['}']
         // - WHITE_SPACE
         let token_tree = ast::TokenTree::cast(token_tree).unwrap();
-        let tt = ast_to_token_tree(&token_tree).unwrap().0;
+        let tt = ast_to_token_tree(&token_tree).0;
 
         assert_eq!(tt.delimiter_kind(), Some(tt::DelimiterKind::Brace));
     }
@@ -870,7 +867,7 @@ mod tests {
     fn test_token_tree_multi_char_punct() {
         let source_file = ast::SourceFile::parse("struct Foo { a: x::Y }").ok().unwrap();
         let struct_def = source_file.syntax().descendants().find_map(ast::Struct::cast).unwrap();
-        let tt = ast_to_token_tree(&struct_def).unwrap().0;
+        let tt = ast_to_token_tree(&struct_def).0;
         token_tree_to_syntax_node(&tt, FragmentKind::Item).unwrap();
     }
 }
diff --git a/crates/mbe/src/tests.rs b/crates/mbe/src/tests.rs
index 6da18ecf4..3698ff3f0 100644
--- a/crates/mbe/src/tests.rs
+++ b/crates/mbe/src/tests.rs
@@ -29,8 +29,7 @@ macro_rules! impl_fixture {
                 let macro_invocation =
                     source_file.syntax().descendants().find_map(ast::MacroCall::cast).unwrap();
 
-                let (invocation_tt, _) = ast_to_token_tree(&macro_invocation.token_tree().unwrap())
-                    .ok_or_else(|| ExpandError::ConversionError)?;
+                let (invocation_tt, _) = ast_to_token_tree(&macro_invocation.token_tree().unwrap());
 
                 self.rules.expand(&invocation_tt).result()
             }
@@ -101,7 +100,7 @@ macro_rules! impl_fixture {
                         .descendants()
                         .find_map(ast::TokenTree::cast)
                         .unwrap();
-                    let mut wrapped = ast_to_token_tree(&wrapped).unwrap().0;
+                    let mut wrapped = ast_to_token_tree(&wrapped).0;
                     wrapped.delimiter = None;
                     wrapped
                 };
@@ -151,7 +150,7 @@ pub(crate) fn parse_macro_error(ra_fixture: &str) -> ParseError {
 
 pub(crate) fn parse_to_token_tree_by_syntax(ra_fixture: &str) -> tt::Subtree {
     let source_file = ast::SourceFile::parse(ra_fixture).ok().unwrap();
-    let tt = syntax_node_to_token_tree(source_file.syntax()).unwrap().0;
+    let tt = syntax_node_to_token_tree(source_file.syntax()).0;
 
     let parsed = parse_to_token_tree(ra_fixture).unwrap().0;
     assert_eq!(tt, parsed);
@@ -164,7 +163,7 @@ fn parse_macro_rules_to_tt(ra_fixture: &str) -> tt::Subtree {
     let macro_definition =
         source_file.syntax().descendants().find_map(ast::MacroRules::cast).unwrap();
 
-    let (definition_tt, _) = ast_to_token_tree(&macro_definition.token_tree().unwrap()).unwrap();
+    let (definition_tt, _) = ast_to_token_tree(&macro_definition.token_tree().unwrap());
 
     let parsed = parse_to_token_tree(
         &ra_fixture[macro_definition.token_tree().unwrap().syntax().text_range()],
@@ -181,7 +180,7 @@ fn parse_macro_def_to_tt(ra_fixture: &str) -> tt::Subtree {
     let macro_definition =
         source_file.syntax().descendants().find_map(ast::MacroDef::cast).unwrap();
 
-    let (definition_tt, _) = ast_to_token_tree(&macro_definition.body().unwrap()).unwrap();
+    let (definition_tt, _) = ast_to_token_tree(&macro_definition.body().unwrap());
 
     let parsed =
         parse_to_token_tree(&ra_fixture[macro_definition.body().unwrap().syntax().text_range()])
diff --git a/crates/mbe/src/tests/expand.rs b/crates/mbe/src/tests/expand.rs
index 84f19d3e2..3a1d840ea 100644
--- a/crates/mbe/src/tests/expand.rs
+++ b/crates/mbe/src/tests/expand.rs
@@ -663,6 +663,21 @@ macro foo {
 }
 
 #[test]
+fn test_macro_2_0_panic_2015() {
+    parse_macro2(
+        r#"
+macro panic_2015 {
+    () => (
+    ),
+    (bar) => (
+    ),
+}
+"#,
+    )
+    .assert_expand_items("panic_2015!(bar);", "");
+}
+
+#[test]
 fn test_path() {
     parse_macro(
         r#"
@@ -926,6 +941,24 @@ fn test_meta_doc_comments() {
 }
 
 #[test]
+fn test_meta_extended_key_value_attributes() {
+    parse_macro(
+        r#"
+macro_rules! foo {
+    (#[$i:meta]) => (
+        #[$ i]
+        fn bar() {}
+    )
+}
+"#,
+    )
+    .assert_expand_items(
+        r#"foo! { #[doc = concat!("The `", "bla", "` lang item.")] }"#,
+        r#"# [doc = concat ! ("The `" , "bla" , "` lang item.")] fn bar () {}"#,
+    );
+}
+
+#[test]
 fn test_meta_doc_comments_non_latin() {
     parse_macro(
         r#"
diff --git a/crates/mbe/src/tests/rule.rs b/crates/mbe/src/tests/rule.rs
index bf48112b3..5c61a98fd 100644
--- a/crates/mbe/src/tests/rule.rs
+++ b/crates/mbe/src/tests/rule.rs
@@ -44,6 +44,6 @@ fn parse_macro_arm(arm_definition: &str) -> Result<crate::MacroRules, ParseError
     let macro_definition =
         source_file.syntax().descendants().find_map(ast::MacroRules::cast).unwrap();
 
-    let (definition_tt, _) = ast_to_token_tree(&macro_definition.token_tree().unwrap()).unwrap();
+    let (definition_tt, _) = ast_to_token_tree(&macro_definition.token_tree().unwrap());
     crate::MacroRules::parse(&definition_tt)
 }
diff --git a/crates/mbe/src/tt_iter.rs b/crates/mbe/src/tt_iter.rs
index 319a40f2a..195b8cf30 100644
--- a/crates/mbe/src/tt_iter.rs
+++ b/crates/mbe/src/tt_iter.rs
@@ -34,6 +34,17 @@ impl<'a> TtIter<'a> {
         }
     }
 
+    pub(crate) fn expect_any_char(&mut self, chars: &[char]) -> Result<(), ()> {
+        match self.next() {
+            Some(tt::TokenTree::Leaf(tt::Leaf::Punct(tt::Punct { char: c, .. })))
+                if chars.contains(c) =>
+            {
+                Ok(())
+            }
+            _ => Err(()),
+        }
+    }
+
     pub(crate) fn expect_subtree(&mut self) -> Result<&'a tt::Subtree, ()> {
         match self.next() {
             Some(tt::TokenTree::Subtree(it)) => Ok(it),
diff --git a/crates/parser/src/grammar.rs b/crates/parser/src/grammar.rs
index cebb8f400..9bdf0b5fa 100644
--- a/crates/parser/src/grammar.rs
+++ b/crates/parser/src/grammar.rs
@@ -76,42 +76,7 @@ pub(crate) mod fragments {
 
     // Parse a meta item , which excluded [], e.g : #[ MetaItem ]
     pub(crate) fn meta_item(p: &mut Parser) {
-        fn is_delimiter(p: &mut Parser) -> bool {
-            matches!(p.current(), T!['{'] | T!['('] | T!['['])
-        }
-
-        if is_delimiter(p) {
-            items::token_tree(p);
-            return;
-        }
-
-        let m = p.start();
-        while !p.at(EOF) {
-            if is_delimiter(p) {
-                items::token_tree(p);
-                break;
-            } else {
-                // https://doc.rust-lang.org/reference/attributes.html
-                // https://doc.rust-lang.org/reference/paths.html#simple-paths
-                // The start of an meta must be a simple path
-                match p.current() {
-                    IDENT | T![super] | T![self] | T![crate] => p.bump_any(),
-                    T![=] => {
-                        p.bump_any();
-                        match p.current() {
-                            c if c.is_literal() => p.bump_any(),
-                            T![true] | T![false] => p.bump_any(),
-                            _ => {}
-                        }
-                        break;
-                    }
-                    _ if p.at(T![::]) => p.bump(T![::]),
-                    _ => break,
-                }
-            }
-        }
-
-        m.complete(p, TOKEN_TREE);
+        attributes::meta(p);
     }
 
     pub(crate) fn item(p: &mut Parser) {
diff --git a/crates/parser/src/grammar/attributes.rs b/crates/parser/src/grammar/attributes.rs
index 96791ffc2..124a10eb2 100644
--- a/crates/parser/src/grammar/attributes.rs
+++ b/crates/parser/src/grammar/attributes.rs
@@ -14,6 +14,21 @@ pub(super) fn outer_attrs(p: &mut Parser) {
     }
 }
 
+pub(super) fn meta(p: &mut Parser) {
+    paths::use_path(p);
+
+    match p.current() {
+        T![=] => {
+            p.bump(T![=]);
+            if expressions::expr(p).0.is_none() {
+                p.error("expected expression");
+            }
+        }
+        T!['('] | T!['['] | T!['{'] => items::token_tree(p),
+        _ => {}
+    }
+}
+
 fn attr(p: &mut Parser, inner: bool) {
     let attr = p.start();
     assert!(p.at(T![#]));
@@ -25,18 +40,7 @@ fn attr(p: &mut Parser, inner: bool) {
     }
 
     if p.eat(T!['[']) {
-        paths::use_path(p);
-
-        match p.current() {
-            T![=] => {
-                p.bump(T![=]);
-                if expressions::expr(p).0.is_none() {
-                    p.error("expected expression");
-                }
-            }
-            T!['('] | T!['['] | T!['{'] => items::token_tree(p),
-            _ => {}
-        }
+        meta(p);
 
         if !p.eat(T![']']) {
             p.error("expected `]`");
diff --git a/crates/paths/src/lib.rs b/crates/paths/src/lib.rs
index 22011cb33..f09ad37e3 100644
--- a/crates/paths/src/lib.rs
+++ b/crates/paths/src/lib.rs
@@ -1,6 +1,7 @@
 //! Thin wrappers around `std::path`, distinguishing between absolute and
 //! relative paths.
 use std::{
+    borrow::Borrow,
     convert::{TryFrom, TryInto},
     ops,
     path::{Component, Path, PathBuf},
@@ -35,6 +36,12 @@ impl AsRef<AbsPath> for AbsPathBuf {
     }
 }
 
+impl Borrow<AbsPath> for AbsPathBuf {
+    fn borrow(&self) -> &AbsPath {
+        self.as_path()
+    }
+}
+
 impl TryFrom<PathBuf> for AbsPathBuf {
     type Error = PathBuf;
     fn try_from(path_buf: PathBuf) -> Result<AbsPathBuf, PathBuf> {
diff --git a/crates/proc_macro_srv/src/rustc_server.rs b/crates/proc_macro_srv/src/rustc_server.rs
index c147484c0..5d765f6e2 100644
--- a/crates/proc_macro_srv/src/rustc_server.rs
+++ b/crates/proc_macro_srv/src/rustc_server.rs
@@ -534,8 +534,12 @@ impl server::Literal for Rustc {
     }
 
     fn integer(&mut self, n: &str) -> Self::Literal {
-        let n: i128 = n.parse().unwrap();
-        Literal { text: n.to_string().into(), id: tt::TokenId::unspecified() }
+        let n = if let Ok(n) = n.parse::<i128>() {
+            n.to_string()
+        } else {
+            n.parse::<u128>().unwrap().to_string()
+        };
+        return Literal { text: n.into(), id: tt::TokenId::unspecified() };
     }
 
     fn typed_integer(&mut self, n: &str, kind: &str) -> Self::Literal {
@@ -757,6 +761,17 @@ mod tests {
         assert_eq!(srv.string("hello_world").text, "\"hello_world\"");
         assert_eq!(srv.character('c').text, "'c'");
         assert_eq!(srv.byte_string(b"1234586\x88").text, "b\"1234586\\x88\"");
+
+        // u128::max
+        assert_eq!(
+            srv.integer("340282366920938463463374607431768211455").text,
+            "340282366920938463463374607431768211455"
+        );
+        // i128::min
+        assert_eq!(
+            srv.integer("-170141183460469231731687303715884105728").text,
+            "-170141183460469231731687303715884105728"
+        );
     }
 
     #[test]
diff --git a/crates/profile/src/google_cpu_profiler.rs b/crates/profile/src/google_cpu_profiler.rs
index db865c65b..cae6caeaa 100644
--- a/crates/profile/src/google_cpu_profiler.rs
+++ b/crates/profile/src/google_cpu_profiler.rs
@@ -14,26 +14,31 @@ extern "C" {
     fn ProfilerStop();
 }
 
-static PROFILER_STATE: AtomicUsize = AtomicUsize::new(OFF);
 const OFF: usize = 0;
 const ON: usize = 1;
 const PENDING: usize = 2;
 
-pub fn start(path: &Path) {
-    if PROFILER_STATE.compare_and_swap(OFF, PENDING, Ordering::SeqCst) != OFF {
+fn transition(current: usize, new: usize) -> bool {
+    static STATE: AtomicUsize = AtomicUsize::new(OFF);
+
+    STATE.compare_exchange(current, new, Ordering::SeqCst, Ordering::SeqCst).is_ok()
+}
+
+pub(crate) fn start(path: &Path) {
+    if !transition(OFF, PENDING) {
         panic!("profiler already started");
     }
     let path = CString::new(path.display().to_string()).unwrap();
     if unsafe { ProfilerStart(path.as_ptr()) } == 0 {
         panic!("profiler failed to start")
     }
-    assert!(PROFILER_STATE.compare_and_swap(PENDING, ON, Ordering::SeqCst) == PENDING);
+    assert!(transition(PENDING, ON));
 }
 
-pub fn stop() {
-    if PROFILER_STATE.compare_and_swap(ON, PENDING, Ordering::SeqCst) != ON {
+pub(crate) fn stop() {
+    if !transition(ON, PENDING) {
         panic!("profiler is not started")
     }
     unsafe { ProfilerStop() };
-    assert!(PROFILER_STATE.compare_and_swap(PENDING, OFF, Ordering::SeqCst) == PENDING);
+    assert!(transition(PENDING, OFF));
 }
diff --git a/crates/profile/src/hprof.rs b/crates/profile/src/hprof.rs
index 29d2ed518..5fdb37206 100644
--- a/crates/profile/src/hprof.rs
+++ b/crates/profile/src/hprof.rs
@@ -1,5 +1,4 @@
 //! Simple hierarchical profiler
-use once_cell::sync::Lazy;
 use std::{
     cell::RefCell,
     collections::{BTreeMap, HashSet},
@@ -12,6 +11,8 @@ use std::{
     time::{Duration, Instant},
 };
 
+use once_cell::sync::Lazy;
+
 use crate::tree::{Idx, Tree};
 
 /// Filtering syntax
@@ -56,18 +57,32 @@ type Label = &'static str;
 ///  0ms - profile
 ///      0ms - profile2
 /// ```
+#[inline]
 pub fn span(label: Label) -> ProfileSpan {
-    assert!(!label.is_empty());
+    debug_assert!(!label.is_empty());
 
-    if PROFILING_ENABLED.load(Ordering::Relaxed)
-        && PROFILE_STACK.with(|stack| stack.borrow_mut().push(label))
-    {
+    let enabled = PROFILING_ENABLED.load(Ordering::Relaxed);
+    if enabled && with_profile_stack(|stack| stack.push(label)) {
         ProfileSpan(Some(ProfilerImpl { label, detail: None }))
     } else {
         ProfileSpan(None)
     }
 }
 
+#[inline]
+pub fn heartbeat_span() -> HeartbeatSpan {
+    let enabled = PROFILING_ENABLED.load(Ordering::Relaxed);
+    HeartbeatSpan::new(enabled)
+}
+
+#[inline]
+pub fn heartbeat() {
+    let enabled = PROFILING_ENABLED.load(Ordering::Relaxed);
+    if enabled {
+        with_profile_stack(|it| it.heartbeat(1));
+    }
+}
+
 pub struct ProfileSpan(Option<ProfilerImpl>);
 
 struct ProfilerImpl {
@@ -85,20 +100,48 @@ impl ProfileSpan {
 }
 
 impl Drop for ProfilerImpl {
+    #[inline]
+    fn drop(&mut self) {
+        with_profile_stack(|it| it.pop(self.label, self.detail.take()));
+    }
+}
+
+pub struct HeartbeatSpan {
+    enabled: bool,
+}
+
+impl HeartbeatSpan {
+    #[inline]
+    pub fn new(enabled: bool) -> Self {
+        if enabled {
+            with_profile_stack(|it| it.heartbeats(true))
+        }
+        Self { enabled }
+    }
+}
+
+impl Drop for HeartbeatSpan {
     fn drop(&mut self) {
-        PROFILE_STACK.with(|it| it.borrow_mut().pop(self.label, self.detail.take()));
+        if self.enabled {
+            with_profile_stack(|it| it.heartbeats(false))
+        }
     }
 }
 
 static PROFILING_ENABLED: AtomicBool = AtomicBool::new(false);
 static FILTER: Lazy<RwLock<Filter>> = Lazy::new(Default::default);
-thread_local!(static PROFILE_STACK: RefCell<ProfileStack> = RefCell::new(ProfileStack::new()));
+
+fn with_profile_stack<T>(f: impl FnOnce(&mut ProfileStack) -> T) -> T {
+    thread_local!(static STACK: RefCell<ProfileStack> = RefCell::new(ProfileStack::new()));
+    STACK.with(|it| f(&mut *it.borrow_mut()))
+}
 
 #[derive(Default, Clone, Debug)]
 struct Filter {
     depth: usize,
     allowed: HashSet<String>,
     longer_than: Duration,
+    heartbeat_longer_than: Duration,
     version: usize,
 }
 
@@ -115,6 +158,7 @@ impl Filter {
         } else {
             Duration::new(0, 0)
         };
+        let heartbeat_longer_than = longer_than;
 
         let depth = if let Some(idx) = spec.rfind('@') {
             let depth: usize = spec[idx + 1..].parse().expect("invalid profile depth");
@@ -125,7 +169,7 @@ impl Filter {
         };
         let allowed =
             if spec == "*" { HashSet::new() } else { spec.split('|').map(String::from).collect() };
-        Filter { depth, allowed, longer_than, version: 0 }
+        Filter { depth, allowed, longer_than, heartbeat_longer_than, version: 0 }
     }
 
     fn install(mut self) {
@@ -137,9 +181,15 @@ impl Filter {
 }
 
 struct ProfileStack {
-    starts: Vec<Instant>,
+    frames: Vec<Frame>,
     filter: Filter,
     messages: Tree<Message>,
+    heartbeats: bool,
+}
+
+struct Frame {
+    t: Instant,
+    heartbeats: u32,
 }
 
 #[derive(Default)]
@@ -151,35 +201,49 @@ struct Message {
 
 impl ProfileStack {
     fn new() -> ProfileStack {
-        ProfileStack { starts: Vec::new(), messages: Tree::default(), filter: Default::default() }
+        ProfileStack {
+            frames: Vec::new(),
+            messages: Tree::default(),
+            filter: Default::default(),
+            heartbeats: false,
+        }
     }
 
     fn push(&mut self, label: Label) -> bool {
-        if self.starts.is_empty() {
+        if self.frames.is_empty() {
             if let Ok(f) = FILTER.try_read() {
                 if f.version > self.filter.version {
                     self.filter = f.clone();
                 }
             };
         }
-        if self.starts.len() > self.filter.depth {
+        if self.frames.len() > self.filter.depth {
             return false;
         }
         let allowed = &self.filter.allowed;
-        if self.starts.is_empty() && !allowed.is_empty() && !allowed.contains(label) {
+        if self.frames.is_empty() && !allowed.is_empty() && !allowed.contains(label) {
             return false;
         }
 
-        self.starts.push(Instant::now());
+        self.frames.push(Frame { t: Instant::now(), heartbeats: 0 });
         self.messages.start();
         true
     }
 
     fn pop(&mut self, label: Label, detail: Option<String>) {
-        let start = self.starts.pop().unwrap();
-        let duration = start.elapsed();
+        let frame = self.frames.pop().unwrap();
+        let duration = frame.t.elapsed();
+
+        if self.heartbeats {
+            self.heartbeat(frame.heartbeats);
+            let avg_span = duration / (frame.heartbeats + 1);
+            if avg_span > self.filter.heartbeat_longer_than {
+                eprintln!("Too few heartbeats {} ({}/{:?})?", label, frame.heartbeats, duration)
+            }
+        }
+
         self.messages.finish(Message { duration, label, detail });
-        if self.starts.is_empty() {
+        if self.frames.is_empty() {
             let longer_than = self.filter.longer_than;
             // Convert to millis for comparison to avoid problems with rounding
             // (otherwise we could print `0ms` despite user's `>0` filter when
@@ -192,6 +256,15 @@ impl ProfileStack {
             self.messages.clear();
         }
     }
+
+    fn heartbeats(&mut self, yes: bool) {
+        self.heartbeats = yes;
+    }
+    fn heartbeat(&mut self, n: u32) {
+        if let Some(frame) = self.frames.last_mut() {
+            frame.heartbeats += n;
+        }
+    }
 }
 
 fn print(
diff --git a/crates/profile/src/lib.rs b/crates/profile/src/lib.rs
index 79dba47d5..a31fb8f43 100644
--- a/crates/profile/src/lib.rs
+++ b/crates/profile/src/lib.rs
@@ -10,7 +10,7 @@ mod tree;
 use std::cell::RefCell;
 
 pub use crate::{
-    hprof::{init, init_from, span},
+    hprof::{heartbeat, heartbeat_span, init, init_from, span},
     memory_usage::{Bytes, MemoryUsage},
     stop_watch::{StopWatch, StopWatchSpan},
 };
@@ -52,7 +52,7 @@ impl Drop for Scope {
 /// Usage:
 /// 1. Install gpref_tools (https://github.com/gperftools/gperftools), probably packaged with your Linux distro.
 /// 2. Build with `cpu_profiler` feature.
-/// 3. Tun the code, the *raw* output would be in the `./out.profile` file.
+/// 3. Run the code, the *raw* output would be in the `./out.profile` file.
 /// 4. Install pprof for visualization (https://github.com/google/pprof).
 /// 5. Bump sampling frequency to once per ms: `export CPUPROFILE_FREQUENCY=1000`
 /// 6. Use something like `pprof -svg target/release/rust-analyzer ./out.profile` to see the results.
@@ -60,8 +60,17 @@ impl Drop for Scope {
 /// For example, here's how I run profiling on NixOS:
 ///
 /// ```bash
-/// $ nix-shell -p gperftools --run \
-///     'cargo run --release -p rust-analyzer -- parse < ~/projects/rustbench/parser.rs > /dev/null'
+/// $ bat -p shell.nix
+/// with import <nixpkgs> {};
+/// mkShell {
+///   buildInputs = [ gperftools ];
+///   shellHook = ''
+///     export LD_LIBRARY_PATH="${gperftools}/lib:"
+///   '';
+/// }
+/// $ set -x CPUPROFILE_FREQUENCY 1000
+/// $ nix-shell --run 'cargo test --release --package rust-analyzer --lib -- benchmarks::benchmark_integrated_highlighting --exact --nocapture'
+/// $ pprof -svg target/release/deps/rust_analyzer-8739592dc93d63cb crates/rust-analyzer/out.profile > profile.svg
 /// ```
 ///
 /// See this diff for how to profile completions:
@@ -81,7 +90,9 @@ pub fn cpu_span() -> CpuSpan {
 
     #[cfg(not(feature = "cpu_profiler"))]
     {
-        eprintln!("cpu_profiler feature is disabled")
+        eprintln!(
+            r#"cpu profiling is disabled, uncomment `default = [ "cpu_profiler" ]` in Cargo.toml to enable."#
+        )
     }
 
     CpuSpan { _private: () }
@@ -91,7 +102,23 @@ impl Drop for CpuSpan {
     fn drop(&mut self) {
         #[cfg(feature = "cpu_profiler")]
         {
-            google_cpu_profiler::stop()
+            google_cpu_profiler::stop();
+            let profile_data = std::env::current_dir().unwrap().join("out.profile");
+            eprintln!("Profile data saved to:\n\n    {}\n", profile_data.display());
+            let mut cmd = std::process::Command::new("pprof");
+            cmd.arg("-svg").arg(std::env::current_exe().unwrap()).arg(&profile_data);
+            let out = cmd.output();
+
+            match out {
+                Ok(out) if out.status.success() => {
+                    let svg = profile_data.with_extension("svg");
+                    std::fs::write(&svg, &out.stdout).unwrap();
+                    eprintln!("Profile rendered to:\n\n    {}\n", svg.display());
+                }
+                _ => {
+                    eprintln!("Failed to run:\n\n   {:?}\n", cmd);
+                }
+            }
         }
     }
 }
diff --git a/crates/project_model/src/build_data.rs b/crates/project_model/src/build_data.rs
index f7050be4e..ab5cc8c49 100644
--- a/crates/project_model/src/build_data.rs
+++ b/crates/project_model/src/build_data.rs
@@ -13,12 +13,12 @@ use cargo_metadata::{BuildScript, Message};
 use itertools::Itertools;
 use paths::{AbsPath, AbsPathBuf};
 use rustc_hash::FxHashMap;
-use stdx::JodChild;
+use stdx::{format_to, JodChild};
 
 use crate::{cfg_flag::CfgFlag, CargoConfig};
 
 #[derive(Debug, Clone, Default, PartialEq, Eq)]
-pub(crate) struct BuildData {
+pub(crate) struct PackageBuildData {
     /// List of config flags defined by this package's build script
     pub(crate) cfgs: Vec<CfgFlag>,
     /// List of cargo-related environment variables with their value
@@ -32,6 +32,17 @@ pub(crate) struct BuildData {
     pub(crate) proc_macro_dylib_path: Option<AbsPathBuf>,
 }
 
+#[derive(Debug, Default, PartialEq, Eq, Clone)]
+pub(crate) struct WorkspaceBuildData {
+    per_package: FxHashMap<String, PackageBuildData>,
+    error: Option<String>,
+}
+
+#[derive(Debug, Default, PartialEq, Eq, Clone)]
+pub struct BuildDataResult {
+    per_workspace: FxHashMap<AbsPathBuf, WorkspaceBuildData>,
+}
+
 #[derive(Clone, Debug)]
 pub(crate) struct BuildDataConfig {
     cargo_toml: AbsPathBuf,
@@ -47,19 +58,17 @@ impl PartialEq for BuildDataConfig {
 
 impl Eq for BuildDataConfig {}
 
-#[derive(Debug, Default)]
+#[derive(Debug)]
 pub struct BuildDataCollector {
+    wrap_rustc: bool,
     configs: FxHashMap<AbsPathBuf, BuildDataConfig>,
 }
 
-#[derive(Debug, Default, PartialEq, Eq)]
-pub struct BuildDataResult {
-    data: FxHashMap<AbsPathBuf, BuildDataMap>,
-}
-
-pub(crate) type BuildDataMap = FxHashMap<String, BuildData>;
-
 impl BuildDataCollector {
+    pub fn new(wrap_rustc: bool) -> Self {
+        Self { wrap_rustc, configs: FxHashMap::default() }
+    }
+
     pub(crate) fn add_config(&mut self, workspace_root: &AbsPath, config: BuildDataConfig) {
         self.configs.insert(workspace_root.to_path_buf(), config);
     }
@@ -67,23 +76,41 @@ impl BuildDataCollector {
     pub fn collect(&mut self, progress: &dyn Fn(String)) -> Result<BuildDataResult> {
         let mut res = BuildDataResult::default();
         for (path, config) in self.configs.iter() {
-            res.data.insert(
-                path.clone(),
-                collect_from_workspace(
-                    &config.cargo_toml,
-                    &config.cargo_features,
-                    &config.packages,
-                    progress,
-                )?,
-            );
+            let workspace_build_data = WorkspaceBuildData::collect(
+                &config.cargo_toml,
+                &config.cargo_features,
+                &config.packages,
+                self.wrap_rustc,
+                progress,
+            )?;
+            res.per_workspace.insert(path.clone(), workspace_build_data);
         }
         Ok(res)
     }
 }
 
+impl WorkspaceBuildData {
+    pub(crate) fn get(&self, package_id: &str) -> Option<&PackageBuildData> {
+        self.per_package.get(package_id)
+    }
+}
+
 impl BuildDataResult {
-    pub(crate) fn get(&self, root: &AbsPath) -> Option<&BuildDataMap> {
-        self.data.get(&root.to_path_buf())
+    pub(crate) fn get(&self, workspace_root: &AbsPath) -> Option<&WorkspaceBuildData> {
+        self.per_workspace.get(workspace_root)
+    }
+    pub fn error(&self) -> Option<String> {
+        let mut buf = String::new();
+        for (_workspace_root, build_data) in &self.per_workspace {
+            if let Some(err) = &build_data.error {
+                format_to!(buf, "cargo check failed:\n{}", err);
+            }
+        }
+        if buf.is_empty() {
+            return None;
+        }
+
+        Some(buf)
     }
 }
 
@@ -97,108 +124,137 @@ impl BuildDataConfig {
     }
 }
 
-fn collect_from_workspace(
-    cargo_toml: &AbsPath,
-    cargo_features: &CargoConfig,
-    packages: &Vec<cargo_metadata::Package>,
-    progress: &dyn Fn(String),
-) -> Result<BuildDataMap> {
-    let mut cmd = Command::new(toolchain::cargo());
-    cmd.args(&["check", "--workspace", "--message-format=json", "--manifest-path"])
-        .arg(cargo_toml.as_ref());
-
-    // --all-targets includes tests, benches and examples in addition to the
-    // default lib and bins. This is an independent concept from the --targets
-    // flag below.
-    cmd.arg("--all-targets");
-
-    if let Some(target) = &cargo_features.target {
-        cmd.args(&["--target", target]);
-    }
+impl WorkspaceBuildData {
+    fn collect(
+        cargo_toml: &AbsPath,
+        cargo_features: &CargoConfig,
+        packages: &Vec<cargo_metadata::Package>,
+        wrap_rustc: bool,
+        progress: &dyn Fn(String),
+    ) -> Result<WorkspaceBuildData> {
+        let mut cmd = Command::new(toolchain::cargo());
+
+        if wrap_rustc {
+            // Setup RUSTC_WRAPPER to point to `rust-analyzer` binary itself. We use
+            // that to compile only proc macros and build scripts during the initial
+            // `cargo check`.
+            let myself = std::env::current_exe()?;
+            cmd.env("RUSTC_WRAPPER", myself);
+            cmd.env("RA_RUSTC_WRAPPER", "1");
+        }
+
+        cmd.args(&["check", "--workspace", "--message-format=json", "--manifest-path"])
+            .arg(cargo_toml.as_ref());
 
-    if cargo_features.all_features {
-        cmd.arg("--all-features");
-    } else {
-        if cargo_features.no_default_features {
-            // FIXME: `NoDefaultFeatures` is mutual exclusive with `SomeFeatures`
-            // https://github.com/oli-obk/cargo_metadata/issues/79
-            cmd.arg("--no-default-features");
+        // --all-targets includes tests, benches and examples in addition to the
+        // default lib and bins. This is an independent concept from the --targets
+        // flag below.
+        cmd.arg("--all-targets");
+
+        if let Some(target) = &cargo_features.target {
+            cmd.args(&["--target", target]);
         }
-        if !cargo_features.features.is_empty() {
-            cmd.arg("--features");
-            cmd.arg(cargo_features.features.join(" "));
+
+        if cargo_features.all_features {
+            cmd.arg("--all-features");
+        } else {
+            if cargo_features.no_default_features {
+                // FIXME: `NoDefaultFeatures` is mutual exclusive with `SomeFeatures`
+                // https://github.com/oli-obk/cargo_metadata/issues/79
+                cmd.arg("--no-default-features");
+            }
+            if !cargo_features.features.is_empty() {
+                cmd.arg("--features");
+                cmd.arg(cargo_features.features.join(" "));
+            }
         }
-    }
 
-    cmd.stdout(Stdio::piped()).stderr(Stdio::null()).stdin(Stdio::null());
-
-    let mut child = cmd.spawn().map(JodChild)?;
-    let child_stdout = child.stdout.take().unwrap();
-    let stdout = BufReader::new(child_stdout);
-
-    let mut res = BuildDataMap::default();
-    for message in cargo_metadata::Message::parse_stream(stdout).flatten() {
-        match message {
-            Message::BuildScriptExecuted(BuildScript {
-                package_id, out_dir, cfgs, env, ..
-            }) => {
-                let cfgs = {
-                    let mut acc = Vec::new();
-                    for cfg in cfgs {
-                        match cfg.parse::<CfgFlag>() {
-                            Ok(it) => acc.push(it),
-                            Err(err) => {
-                                anyhow::bail!("invalid cfg from cargo-metadata: {}", err)
-                            }
-                        };
+        cmd.stdout(Stdio::piped()).stderr(Stdio::piped()).stdin(Stdio::null());
+
+        let mut child = cmd.spawn().map(JodChild)?;
+        let child_stdout = child.stdout.take().unwrap();
+        let stdout = BufReader::new(child_stdout);
+
+        let mut res = WorkspaceBuildData::default();
+        for message in cargo_metadata::Message::parse_stream(stdout).flatten() {
+            match message {
+                Message::BuildScriptExecuted(BuildScript {
+                    package_id,
+                    out_dir,
+                    cfgs,
+                    env,
+                    ..
+                }) => {
+                    let cfgs = {
+                        let mut acc = Vec::new();
+                        for cfg in cfgs {
+                            match cfg.parse::<CfgFlag>() {
+                                Ok(it) => acc.push(it),
+                                Err(err) => {
+                                    anyhow::bail!("invalid cfg from cargo-metadata: {}", err)
+                                }
+                            };
+                        }
+                        acc
+                    };
+                    let package_build_data =
+                        res.per_package.entry(package_id.repr.clone()).or_default();
+                    // cargo_metadata crate returns default (empty) path for
+                    // older cargos, which is not absolute, so work around that.
+                    if !out_dir.as_str().is_empty() {
+                        let out_dir = AbsPathBuf::assert(PathBuf::from(out_dir.into_os_string()));
+                        package_build_data.out_dir = Some(out_dir);
+                        package_build_data.cfgs = cfgs;
                     }
-                    acc
-                };
-                let res = res.entry(package_id.repr.clone()).or_default();
-                // cargo_metadata crate returns default (empty) path for
-                // older cargos, which is not absolute, so work around that.
-                if !out_dir.as_str().is_empty() {
-                    let out_dir = AbsPathBuf::assert(PathBuf::from(out_dir.into_os_string()));
-                    res.out_dir = Some(out_dir);
-                    res.cfgs = cfgs;
-                }
 
-                res.envs = env;
-            }
-            Message::CompilerArtifact(message) => {
-                progress(format!("metadata {}", message.target.name));
-
-                if message.target.kind.contains(&"proc-macro".to_string()) {
-                    let package_id = message.package_id;
-                    // Skip rmeta file
-                    if let Some(filename) = message.filenames.iter().find(|name| is_dylib(name)) {
-                        let filename = AbsPathBuf::assert(PathBuf::from(&filename));
-                        let res = res.entry(package_id.repr.clone()).or_default();
-                        res.proc_macro_dylib_path = Some(filename);
+                    package_build_data.envs = env;
+                }
+                Message::CompilerArtifact(message) => {
+                    progress(format!("metadata {}", message.target.name));
+
+                    if message.target.kind.contains(&"proc-macro".to_string()) {
+                        let package_id = message.package_id;
+                        // Skip rmeta file
+                        if let Some(filename) = message.filenames.iter().find(|name| is_dylib(name))
+                        {
+                            let filename = AbsPathBuf::assert(PathBuf::from(&filename));
+                            let package_build_data =
+                                res.per_package.entry(package_id.repr.clone()).or_default();
+                            package_build_data.proc_macro_dylib_path = Some(filename);
+                        }
                     }
                 }
+                Message::CompilerMessage(message) => {
+                    progress(message.target.name.clone());
+                }
+                Message::BuildFinished(_) => {}
+                Message::TextLine(_) => {}
+                _ => {}
             }
-            Message::CompilerMessage(message) => {
-                progress(message.target.name.clone());
+        }
+
+        for package in packages {
+            let package_build_data = res.per_package.entry(package.id.repr.clone()).or_default();
+            inject_cargo_env(package, package_build_data);
+            if let Some(out_dir) = &package_build_data.out_dir {
+                // NOTE: cargo and rustc seem to hide non-UTF-8 strings from env! and option_env!()
+                if let Some(out_dir) = out_dir.to_str().map(|s| s.to_owned()) {
+                    package_build_data.envs.push(("OUT_DIR".to_string(), out_dir));
+                }
             }
-            Message::BuildFinished(_) => {}
-            Message::TextLine(_) => {}
-            _ => {}
         }
-    }
 
-    for package in packages {
-        let build_data = res.entry(package.id.repr.clone()).or_default();
-        inject_cargo_env(package, build_data);
-        if let Some(out_dir) = &build_data.out_dir {
-            // NOTE: cargo and rustc seem to hide non-UTF-8 strings from env! and option_env!()
-            if let Some(out_dir) = out_dir.to_str().map(|s| s.to_owned()) {
-                build_data.envs.push(("OUT_DIR".to_string(), out_dir));
+        let output = child.into_inner().wait_with_output()?;
+        if !output.status.success() {
+            let mut stderr = String::from_utf8(output.stderr).unwrap_or_default();
+            if stderr.is_empty() {
+                stderr = "cargo check failed".to_string();
             }
+            res.error = Some(stderr)
         }
-    }
 
-    Ok(res)
+        Ok(res)
+    }
 }
 
 // FIXME: File a better way to know if it is a dylib
@@ -212,7 +268,7 @@ fn is_dylib(path: &Utf8Path) -> bool {
 /// Recreates the compile-time environment variables that Cargo sets.
 ///
 /// Should be synced with <https://doc.rust-lang.org/cargo/reference/environment-variables.html#environment-variables-cargo-sets-for-crates>
-fn inject_cargo_env(package: &cargo_metadata::Package, build_data: &mut BuildData) {
+fn inject_cargo_env(package: &cargo_metadata::Package, build_data: &mut PackageBuildData) {
     let env = &mut build_data.envs;
 
     // FIXME: Missing variables:
diff --git a/crates/project_model/src/workspace.rs b/crates/project_model/src/workspace.rs
index 1b53fcc30..2fcd0f8fa 100644
--- a/crates/project_model/src/workspace.rs
+++ b/crates/project_model/src/workspace.rs
@@ -12,7 +12,7 @@ use proc_macro_api::ProcMacroClient;
 use rustc_hash::{FxHashMap, FxHashSet};
 
 use crate::{
-    build_data::{BuildData, BuildDataMap, BuildDataResult},
+    build_data::{BuildDataResult, PackageBuildData, WorkspaceBuildData},
     cargo_workspace,
     cfg_flag::CfgFlag,
     rustc_cfg,
@@ -354,10 +354,10 @@ fn cargo_to_crate_graph(
     proc_macro_loader: &dyn Fn(&Path) -> Vec<ProcMacro>,
     load: &mut dyn FnMut(&AbsPath) -> Option<FileId>,
     cargo: &CargoWorkspace,
-    build_data_map: Option<&BuildDataMap>,
+    build_data_map: Option<&WorkspaceBuildData>,
     sysroot: &Sysroot,
     rustc: &Option<CargoWorkspace>,
-    rustc_build_data_map: Option<&BuildDataMap>,
+    rustc_build_data_map: Option<&WorkspaceBuildData>,
 ) -> CrateGraph {
     let _p = profile::span("cargo_to_crate_graph");
     let mut crate_graph = CrateGraph::default();
@@ -464,7 +464,7 @@ fn handle_rustc_crates(
     rustc_workspace: &CargoWorkspace,
     load: &mut dyn FnMut(&AbsPath) -> Option<FileId>,
     crate_graph: &mut CrateGraph,
-    rustc_build_data_map: Option<&FxHashMap<String, BuildData>>,
+    rustc_build_data_map: Option<&WorkspaceBuildData>,
     cfg_options: &CfgOptions,
     proc_macro_loader: &dyn Fn(&Path) -> Vec<ProcMacro>,
     pkg_to_lib_crate: &mut FxHashMap<la_arena::Idx<crate::PackageData>, CrateId>,
@@ -555,7 +555,7 @@ fn handle_rustc_crates(
 fn add_target_crate_root(
     crate_graph: &mut CrateGraph,
     pkg: &cargo_workspace::PackageData,
-    build_data: Option<&BuildData>,
+    build_data: Option<&PackageBuildData>,
     cfg_options: &CfgOptions,
     proc_macro_loader: &dyn Fn(&Path) -> Vec<ProcMacro>,
     file_id: FileId,
diff --git a/crates/rust-analyzer/Cargo.toml b/crates/rust-analyzer/Cargo.toml
index 3130785cc..0571a912c 100644
--- a/crates/rust-analyzer/Cargo.toml
+++ b/crates/rust-analyzer/Cargo.toml
@@ -22,7 +22,7 @@ env_logger = { version = "0.8.1", default-features = false }
 itertools = "0.10.0"
 jod-thread = "0.1.0"
 log = "0.4.8"
-lsp-types = { version = "0.88.0", features = ["proposed"] }
+lsp-types = { version = "0.89.0", features = ["proposed"] }
 parking_lot = "0.11.0"
 xflags = "0.2.1"
 oorandom = "11.1.2"
diff --git a/crates/rust-analyzer/build.rs b/crates/rust-analyzer/build.rs
index 999dc5928..13b903891 100644
--- a/crates/rust-analyzer/build.rs
+++ b/crates/rust-analyzer/build.rs
@@ -39,7 +39,8 @@ fn set_rerun() {
 }
 
 fn rev() -> Option<String> {
-    let output = Command::new("git").args(&["describe", "--tags"]).output().ok()?;
+    let output =
+        Command::new("git").args(&["describe", "--tags", "--exclude", "nightly"]).output().ok()?;
     let stdout = String::from_utf8(output.stdout).ok()?;
     Some(stdout)
 }
diff --git a/crates/rust-analyzer/src/benchmarks.rs b/crates/rust-analyzer/src/benchmarks.rs
new file mode 100644
index 000000000..bdd94b1c4
--- /dev/null
+++ b/crates/rust-analyzer/src/benchmarks.rs
@@ -0,0 +1,74 @@
+//! Fully integrated benchmarks for rust-analyzer, which load real cargo
+//! projects.
+//!
+//! The benchmark here is used to debug specific performance regressions. If you
+//! notice that, eg, completion is slow in some specific case, you can  modify
+//! code here exercise this specific completion, and thus have a fast
+//! edit/compile/test cycle.
+//!
+//! Note that "Rust Analyzer: Run" action does not allow running a single test
+//! in release mode in VS Code. There's however "Rust Analyzer: Copy Run Command Line"
+//! which you can use to paste the command in terminal and add `--release` manually.
+
+use std::sync::Arc;
+
+use ide::Change;
+use test_utils::project_root;
+use vfs::{AbsPathBuf, VfsPath};
+
+use crate::cli::load_cargo::{load_workspace_at, LoadCargoConfig};
+
+#[test]
+fn benchmark_integrated_highlighting() {
+    // Don't run slow benchmark by default
+    if true {
+        return;
+    }
+
+    // Load rust-analyzer itself.
+    let workspace_to_load = project_root();
+    let file = "./crates/ide_db/src/apply_change.rs";
+
+    let cargo_config = Default::default();
+    let load_cargo_config = LoadCargoConfig {
+        load_out_dirs_from_check: true,
+        wrap_rustc: false,
+        with_proc_macro: false,
+    };
+
+    let (mut host, vfs, _proc_macro) = {
+        let _it = stdx::timeit("workspace loading");
+        load_workspace_at(&workspace_to_load, &cargo_config, &load_cargo_config, &|_| {}).unwrap()
+    };
+
+    let file_id = {
+        let file = workspace_to_load.join(file);
+        let path = VfsPath::from(AbsPathBuf::assert(file));
+        vfs.file_id(&path).unwrap_or_else(|| panic!("can't find virtual file for {}", path))
+    };
+
+    {
+        let _it = stdx::timeit("initial");
+        let analysis = host.analysis();
+        analysis.highlight_as_html(file_id, false).unwrap();
+    }
+
+    profile::init_from("*>100");
+    // let _s = profile::heartbeat_span();
+
+    {
+        let _it = stdx::timeit("change");
+        let mut text = host.analysis().file_text(file_id).unwrap().to_string();
+        text.push_str("\npub fn _dummy() {}\n");
+        let mut change = Change::new();
+        change.change_file(file_id, Some(Arc::new(text)));
+        host.apply_change(change);
+    }
+
+    {
+        let _it = stdx::timeit("after change");
+        let _span = profile::cpu_span();
+        let analysis = host.analysis();
+        analysis.highlight_as_html(file_id, false).unwrap();
+    }
+}
diff --git a/crates/rust-analyzer/src/bin/flags.rs b/crates/rust-analyzer/src/bin/flags.rs
index d8987633d..63953098a 100644
--- a/crates/rust-analyzer/src/bin/flags.rs
+++ b/crates/rust-analyzer/src/bin/flags.rs
@@ -1,10 +1,9 @@
 //! Grammar for the command-line arguments.
 #![allow(unreachable_pub)]
-use std::{env, path::PathBuf};
+use std::path::PathBuf;
 
 use ide_ssr::{SsrPattern, SsrRule};
-use rust_analyzer::cli::{BenchWhat, Position, Verbosity};
-use vfs::AbsPathBuf;
+use rust_analyzer::cli::Verbosity;
 
 xflags::xflags! {
     src "./src/bin/flags.rs"
@@ -72,27 +71,8 @@ xflags::xflags! {
             optional --load-output-dirs
             /// Use proc-macro-srv for proc-macro expanding.
             optional --with-proc-macro
-        }
-
-        /// Benchmark specific analysis operation
-        cmd analysis-bench
-            /// Directory with Cargo.toml.
-            required path: PathBuf
-        {
-            /// Collect memory usage statistics.
-            optional --memory-usage
-
-            /// Compute syntax highlighting for this file
-            optional --highlight path: PathBuf
-            /// Compute completions at file:line:column location.
-            optional --complete location: Position
-            /// Compute goto definition at file:line:column location.
-            optional --goto-def location: Position
-
-            /// Load OUT_DIR values by running `cargo check` before analysis.
-            optional --load-output-dirs
-            /// Use proc-macro-srv for proc-macro expanding.
-            optional --with-proc-macro
+            /// Only resolve names, don't run type inference.
+            optional --skip-inference
         }
 
         cmd diagnostics
@@ -142,7 +122,6 @@ pub enum RustAnalyzerCmd {
     Symbols(Symbols),
     Highlight(Highlight),
     AnalysisStats(AnalysisStats),
-    AnalysisBench(AnalysisBench),
     Diagnostics(Diagnostics),
     Ssr(Ssr),
     Search(Search),
@@ -181,18 +160,7 @@ pub struct AnalysisStats {
     pub no_sysroot: bool,
     pub load_output_dirs: bool,
     pub with_proc_macro: bool,
-}
-
-#[derive(Debug)]
-pub struct AnalysisBench {
-    pub path: PathBuf,
-
-    pub memory_usage: bool,
-    pub highlight: Option<PathBuf>,
-    pub complete: Option<Position>,
-    pub goto_def: Option<Position>,
-    pub load_output_dirs: bool,
-    pub with_proc_macro: bool,
+    pub skip_inference: bool,
 }
 
 #[derive(Debug)]
@@ -239,17 +207,3 @@ impl RustAnalyzer {
         }
     }
 }
-
-impl AnalysisBench {
-    pub(crate) fn what(&self) -> BenchWhat {
-        match (&self.highlight, &self.complete, &self.goto_def) {
-            (Some(path), None, None) => {
-                let path = env::current_dir().unwrap().join(path);
-                BenchWhat::Highlight { path: AbsPathBuf::assert(path) }
-            }
-            (None, Some(position), None) => BenchWhat::Complete(position.clone()),
-            (None, None, Some(position)) => BenchWhat::GotoDef(position.clone()),
-            _ => panic!("exactly one of  `--highlight`, `--complete` or `--goto-def` must be set"),
-        }
-    }
-}
diff --git a/crates/rust-analyzer/src/bin/main.rs b/crates/rust-analyzer/src/bin/main.rs
index a0b611bff..f0abb5b15 100644
--- a/crates/rust-analyzer/src/bin/main.rs
+++ b/crates/rust-analyzer/src/bin/main.rs
@@ -3,13 +3,14 @@
 //! Based on cli flags, either spawns an LSP server, or runs a batch analysis
 mod flags;
 mod logger;
+mod rustc_wrapper;
 
 use std::{convert::TryFrom, env, fs, path::Path, process};
 
 use lsp_server::Connection;
 use project_model::ProjectManifest;
 use rust_analyzer::{
-    cli::{self, AnalysisStatsCmd, BenchCmd},
+    cli::{self, AnalysisStatsCmd},
     config::Config,
     from_json,
     lsp_ext::supports_utf8,
@@ -26,6 +27,20 @@ static ALLOC: mimalloc::MiMalloc = mimalloc::MiMalloc;
 static ALLOC: jemallocator::Jemalloc = jemallocator::Jemalloc;
 
 fn main() {
+    if std::env::var("RA_RUSTC_WRAPPER").is_ok() {
+        let mut args = std::env::args_os();
+        let _me = args.next().unwrap();
+        let rustc = args.next().unwrap();
+        let code = match rustc_wrapper::run_rustc_skipping_cargo_checking(rustc, args.collect()) {
+            Ok(rustc_wrapper::ExitCode(code)) => code.unwrap_or(102),
+            Err(err) => {
+                eprintln!("{}", err);
+                101
+            }
+        };
+        process::exit(code);
+    }
+
     if let Err(err) = try_main() {
         log::error!("Unexpected error: {}", err);
         eprintln!("{}", err);
@@ -78,19 +93,9 @@ fn try_main() -> Result<()> {
             path: cmd.path,
             load_output_dirs: cmd.load_output_dirs,
             with_proc_macro: cmd.with_proc_macro,
+            skip_inference: cmd.skip_inference,
         }
         .run(verbosity)?,
-        flags::RustAnalyzerCmd::AnalysisBench(cmd) => {
-            let what = cmd.what();
-            BenchCmd {
-                memory_usage: cmd.memory_usage,
-                path: cmd.path,
-                load_output_dirs: cmd.load_output_dirs,
-                with_proc_macro: cmd.with_proc_macro,
-                what,
-            }
-            .run(verbosity)?
-        }
 
         flags::RustAnalyzerCmd::Diagnostics(cmd) => {
             cli::diagnostics(&cmd.path, cmd.load_output_dirs, cmd.with_proc_macro)?
@@ -144,7 +149,7 @@ mod tracing_setup {
 }
 
 fn run_server() -> Result<()> {
-    log::info!("server will start");
+    log::info!("server version {} will start", env!("REV"));
 
     let (connection, io_threads) = Connection::stdio();
 
diff --git a/crates/rust-analyzer/src/bin/rustc_wrapper.rs b/crates/rust-analyzer/src/bin/rustc_wrapper.rs
new file mode 100644
index 000000000..2f6d4706d
--- /dev/null
+++ b/crates/rust-analyzer/src/bin/rustc_wrapper.rs
@@ -0,0 +1,46 @@
+//! We setup RUSTC_WRAPPER to point to `rust-analyzer` binary itself during the
+//! initial `cargo check`. That way, we avoid checking the actual project, and
+//! only build proc macros and build.rs.
+//!
+//! Code taken from IntelliJ :0)
+//!     https://github.com/intellij-rust/intellij-rust/blob/master/native-helper/src/main.rs
+use std::{
+    ffi::OsString,
+    io,
+    process::{Command, Stdio},
+};
+
+/// ExitCode/ExitStatus are impossible to create :(.
+pub(crate) struct ExitCode(pub(crate) Option<i32>);
+
+pub(crate) fn run_rustc_skipping_cargo_checking(
+    rustc_executable: OsString,
+    args: Vec<OsString>,
+) -> io::Result<ExitCode> {
+    let is_cargo_check = args.iter().any(|arg| {
+        let arg = arg.to_string_lossy();
+        // `cargo check` invokes `rustc` with `--emit=metadata` argument.
+        //
+        // https://doc.rust-lang.org/rustc/command-line-arguments.html#--emit-specifies-the-types-of-output-files-to-generate
+        // link —     Generates the crates specified by --crate-type. The default
+        //            output filenames depend on the crate type and platform. This
+        //            is the default if --emit is not specified.
+        // metadata — Generates a file containing metadata about the crate.
+        //            The default output filename is CRATE_NAME.rmeta.
+        arg.starts_with("--emit=") && arg.contains("metadata") && !arg.contains("link")
+    });
+    if is_cargo_check {
+        return Ok(ExitCode(Some(0)));
+    }
+    run_rustc(rustc_executable, args)
+}
+
+fn run_rustc(rustc_executable: OsString, args: Vec<OsString>) -> io::Result<ExitCode> {
+    let mut child = Command::new(rustc_executable)
+        .args(args)
+        .stdin(Stdio::inherit())
+        .stdout(Stdio::inherit())
+        .stderr(Stdio::inherit())
+        .spawn()?;
+    Ok(ExitCode(child.wait()?.code()))
+}
diff --git a/crates/rust-analyzer/src/caps.rs b/crates/rust-analyzer/src/caps.rs
index 7a5bcb8c7..3c87782f2 100644
--- a/crates/rust-analyzer/src/caps.rs
+++ b/crates/rust-analyzer/src/caps.rs
@@ -57,7 +57,7 @@ pub fn server_capabilities(client_caps: &ClientCapabilities) -> ServerCapabiliti
         document_range_formatting_provider: None,
         document_on_type_formatting_provider: Some(DocumentOnTypeFormattingOptions {
             first_trigger_character: "=".to_string(),
-            more_trigger_character: Some(vec![".".to_string(), ">".to_string()]),
+            more_trigger_character: Some(vec![".".to_string(), ">".to_string(), "{".to_string()]),
         }),
         selection_range_provider: Some(SelectionRangeProviderCapability::Simple(true)),
         folding_range_provider: Some(FoldingRangeProviderCapability::Simple(true)),
diff --git a/crates/rust-analyzer/src/cargo_target_spec.rs b/crates/rust-analyzer/src/cargo_target_spec.rs
index 5af0802a2..909c21532 100644
--- a/crates/rust-analyzer/src/cargo_target_spec.rs
+++ b/crates/rust-analyzer/src/cargo_target_spec.rs
@@ -201,7 +201,7 @@ mod tests {
         let cfg_expr = {
             let source_file = ast::SourceFile::parse(cfg).ok().unwrap();
             let tt = source_file.syntax().descendants().find_map(ast::TokenTree::cast).unwrap();
-            let (tt, _) = ast_to_token_tree(&tt).unwrap();
+            let (tt, _) = ast_to_token_tree(&tt);
             CfgExpr::parse(&tt)
         };
 
diff --git a/crates/rust-analyzer/src/cli.rs b/crates/rust-analyzer/src/cli.rs
index ed732eb38..76b666dc2 100644
--- a/crates/rust-analyzer/src/cli.rs
+++ b/crates/rust-analyzer/src/cli.rs
@@ -1,8 +1,7 @@
 //! Various batch processing tasks, intended primarily for debugging.
 
-mod load_cargo;
+pub(crate) mod load_cargo;
 mod analysis_stats;
-mod analysis_bench;
 mod diagnostics;
 mod progress_report;
 mod ssr;
@@ -15,7 +14,6 @@ use syntax::{AstNode, SourceFile};
 use vfs::Vfs;
 
 pub use self::{
-    analysis_bench::{BenchCmd, BenchWhat, Position},
     analysis_stats::AnalysisStatsCmd,
     diagnostics::diagnostics,
     load_cargo::{load_workspace, load_workspace_at, LoadCargoConfig},
diff --git a/crates/rust-analyzer/src/cli/analysis_bench.rs b/crates/rust-analyzer/src/cli/analysis_bench.rs
deleted file mode 100644
index 49994824f..000000000
--- a/crates/rust-analyzer/src/cli/analysis_bench.rs
+++ /dev/null
@@ -1,196 +0,0 @@
-//! Benchmark operations like highlighting or goto definition.
-
-use std::{env, path::PathBuf, str::FromStr, sync::Arc, time::Instant};
-
-use anyhow::{bail, format_err, Result};
-use hir::PrefixKind;
-use ide::{
-    Analysis, AnalysisHost, Change, CompletionConfig, DiagnosticsConfig, FilePosition, LineCol,
-};
-use ide_db::{
-    base_db::{
-        salsa::{Database, Durability},
-        FileId,
-    },
-    helpers::{insert_use::InsertUseConfig, SnippetCap},
-};
-use vfs::AbsPathBuf;
-
-use crate::cli::{
-    load_cargo::{load_workspace_at, LoadCargoConfig},
-    print_memory_usage, Verbosity,
-};
-
-pub struct BenchCmd {
-    pub path: PathBuf,
-    pub what: BenchWhat,
-    pub memory_usage: bool,
-    pub load_output_dirs: bool,
-    pub with_proc_macro: bool,
-}
-
-pub enum BenchWhat {
-    Highlight { path: AbsPathBuf },
-    Complete(Position),
-    GotoDef(Position),
-}
-
-#[derive(Debug, Clone)]
-pub struct Position {
-    pub path: AbsPathBuf,
-    pub line: u32,
-    pub column: u32,
-}
-
-impl FromStr for Position {
-    type Err = anyhow::Error;
-    fn from_str(s: &str) -> Result<Self> {
-        let mut split = s.rsplitn(3, ':');
-        match (split.next(), split.next(), split.next()) {
-            (Some(column), Some(line), Some(path)) => {
-                let path = env::current_dir().unwrap().join(path);
-                let path = AbsPathBuf::assert(path);
-                Ok(Position { path, line: line.parse()?, column: column.parse()? })
-            }
-            _ => bail!("position should be in file:line:column format: {:?}", s),
-        }
-    }
-}
-
-impl BenchCmd {
-    pub fn run(self, verbosity: Verbosity) -> Result<()> {
-        profile::init();
-
-        let start = Instant::now();
-        eprint!("loading: ");
-
-        let cargo_config = Default::default();
-        let load_cargo_config = LoadCargoConfig {
-            load_out_dirs_from_check: self.load_output_dirs,
-            with_proc_macro: self.with_proc_macro,
-        };
-        let (mut host, vfs, _proc_macro) =
-            load_workspace_at(&self.path, &cargo_config, &load_cargo_config, &|_| {})?;
-        eprintln!("{:?}\n", start.elapsed());
-
-        let file_id = {
-            let path = match &self.what {
-                BenchWhat::Highlight { path } => path,
-                BenchWhat::Complete(pos) | BenchWhat::GotoDef(pos) => &pos.path,
-            };
-            let path = path.clone().into();
-            vfs.file_id(&path).ok_or_else(|| format_err!("Can't find {}", path))?
-        };
-
-        match &self.what {
-            BenchWhat::Highlight { .. } => {
-                let res = do_work(&mut host, file_id, |analysis| {
-                    analysis.diagnostics(&DiagnosticsConfig::default(), file_id).unwrap();
-                    analysis.highlight_as_html(file_id, false).unwrap()
-                });
-                if verbosity.is_verbose() {
-                    println!("\n{}", res);
-                }
-            }
-            BenchWhat::Complete(pos) | BenchWhat::GotoDef(pos) => {
-                let is_completion = matches!(self.what, BenchWhat::Complete(..));
-
-                let offset = host
-                    .analysis()
-                    .file_line_index(file_id)?
-                    .offset(LineCol { line: pos.line - 1, col: pos.column });
-                let file_position = FilePosition { file_id, offset };
-
-                if is_completion {
-                    let options = CompletionConfig {
-                        enable_postfix_completions: true,
-                        enable_imports_on_the_fly: true,
-                        add_call_parenthesis: true,
-                        add_call_argument_snippets: true,
-                        snippet_cap: SnippetCap::new(true),
-                        insert_use: InsertUseConfig {
-                            merge: None,
-                            prefix_kind: PrefixKind::Plain,
-                            group: true,
-                        },
-                    };
-                    let res = do_work(&mut host, file_id, |analysis| {
-                        analysis.completions(&options, file_position)
-                    });
-                    if verbosity.is_verbose() {
-                        println!("\n{:#?}", res);
-                    }
-                } else {
-                    let res = do_work(&mut host, file_id, |analysis| {
-                        analysis.goto_definition(file_position)
-                    });
-                    if verbosity.is_verbose() {
-                        println!("\n{:#?}", res);
-                    }
-                }
-            }
-        }
-
-        if self.memory_usage {
-            print_memory_usage(host, vfs);
-        }
-
-        Ok(())
-    }
-}
-
-fn do_work<F: Fn(&Analysis) -> T, T>(host: &mut AnalysisHost, file_id: FileId, work: F) -> T {
-    {
-        let start = Instant::now();
-        eprint!("from scratch:   ");
-        work(&host.analysis());
-        eprintln!("{:?}", start.elapsed());
-    }
-    {
-        let start = Instant::now();
-        eprint!("no change:      ");
-        work(&host.analysis());
-        eprintln!("{:?}", start.elapsed());
-    }
-    {
-        let start = Instant::now();
-        eprint!("trivial change: ");
-        host.raw_database_mut().salsa_runtime_mut().synthetic_write(Durability::LOW);
-        work(&host.analysis());
-        eprintln!("{:?}", start.elapsed());
-    }
-    {
-        let start = Instant::now();
-        eprint!("comment change: ");
-        {
-            let mut text = host.analysis().file_text(file_id).unwrap().to_string();
-            text.push_str("\n/* Hello world */\n");
-            let mut change = Change::new();
-            change.change_file(file_id, Some(Arc::new(text)));
-            host.apply_change(change);
-        }
-        work(&host.analysis());
-        eprintln!("{:?}", start.elapsed());
-    }
-    {
-        let start = Instant::now();
-        eprint!("item change:    ");
-        {
-            let mut text = host.analysis().file_text(file_id).unwrap().to_string();
-            text.push_str("\npub fn _dummy() {}\n");
-            let mut change = Change::new();
-            change.change_file(file_id, Some(Arc::new(text)));
-            host.apply_change(change);
-        }
-        work(&host.analysis());
-        eprintln!("{:?}", start.elapsed());
-    }
-    {
-        let start = Instant::now();
-        eprint!("const change:   ");
-        host.raw_database_mut().salsa_runtime_mut().synthetic_write(Durability::HIGH);
-        let res = work(&host.analysis());
-        eprintln!("{:?}", start.elapsed());
-        res
-    }
-}
diff --git a/crates/rust-analyzer/src/cli/analysis_stats.rs b/crates/rust-analyzer/src/cli/analysis_stats.rs
index 9c59e7ee4..3f3134562 100644
--- a/crates/rust-analyzer/src/cli/analysis_stats.rs
+++ b/crates/rust-analyzer/src/cli/analysis_stats.rs
@@ -9,10 +9,11 @@ use std::{
 
 use hir::{
     db::{AstDatabase, DefDatabase, HirDatabase},
-    AssocItem, Crate, HasSource, HirDisplay, ModuleDef,
+    AssocItem, Crate, Function, HasSource, HirDisplay, ModuleDef,
 };
 use hir_def::FunctionId;
-use hir_ty::TypeWalk;
+use hir_ty::{TyExt, TypeWalk};
+use ide::{AnalysisHost, RootDatabase};
 use ide_db::base_db::{
     salsa::{self, ParallelDatabase},
     SourceDatabaseExt,
@@ -24,6 +25,7 @@ use rayon::prelude::*;
 use rustc_hash::FxHashSet;
 use stdx::format_to;
 use syntax::AstNode;
+use vfs::Vfs;
 
 use crate::cli::{
     load_cargo::{load_workspace_at, LoadCargoConfig},
@@ -51,6 +53,7 @@ pub struct AnalysisStatsCmd {
     pub path: PathBuf,
     pub load_output_dirs: bool,
     pub with_proc_macro: bool,
+    pub skip_inference: bool,
 }
 
 impl AnalysisStatsCmd {
@@ -65,6 +68,7 @@ impl AnalysisStatsCmd {
         cargo_config.no_sysroot = self.no_sysroot;
         let load_cargo_config = LoadCargoConfig {
             load_out_dirs_from_check: self.load_output_dirs,
+            wrap_rustc: false,
             with_proc_macro: self.with_proc_macro,
         };
         let (host, vfs, _proc_macro) =
@@ -128,6 +132,39 @@ impl AnalysisStatsCmd {
             shuffle(&mut rng, &mut funcs);
         }
 
+        if !self.skip_inference {
+            self.run_inference(&host, db, &vfs, &funcs, verbosity);
+        }
+
+        let total_span = analysis_sw.elapsed();
+        eprintln!("{:<20} {}", "Total:", total_span);
+        report_metric("total time", total_span.time.as_millis() as u64, "ms");
+        if let Some(instructions) = total_span.instructions {
+            report_metric("total instructions", instructions, "#instr");
+        }
+        if let Some(memory) = total_span.memory {
+            report_metric("total memory", memory.allocated.megabytes() as u64, "MB");
+        }
+
+        if env::var("RA_COUNT").is_ok() {
+            eprintln!("{}", profile::countme::get_all());
+        }
+
+        if self.memory_usage && verbosity.is_verbose() {
+            print_memory_usage(host, vfs);
+        }
+
+        Ok(())
+    }
+
+    fn run_inference(
+        &self,
+        host: &AnalysisHost,
+        db: &RootDatabase,
+        vfs: &Vfs,
+        funcs: &[Function],
+        verbosity: Verbosity,
+    ) {
         let mut bar = match verbosity {
             Verbosity::Quiet | Verbosity::Spammy => ProgressReport::hidden(),
             _ if self.parallel => ProgressReport::hidden(),
@@ -154,7 +191,7 @@ impl AnalysisStatsCmd {
         let mut num_exprs_unknown = 0;
         let mut num_exprs_partially_unknown = 0;
         let mut num_type_mismatches = 0;
-        for f in funcs {
+        for f in funcs.iter().copied() {
             let name = f.name(db);
             let full_name = f
                 .module(db)
@@ -296,26 +333,6 @@ impl AnalysisStatsCmd {
         report_metric("type mismatches", num_type_mismatches, "#");
 
         eprintln!("{:<20} {}", "Inference:", inference_sw.elapsed());
-
-        let total_span = analysis_sw.elapsed();
-        eprintln!("{:<20} {}", "Total:", total_span);
-        report_metric("total time", total_span.time.as_millis() as u64, "ms");
-        if let Some(instructions) = total_span.instructions {
-            report_metric("total instructions", instructions, "#instr");
-        }
-        if let Some(memory) = total_span.memory {
-            report_metric("total memory", memory.allocated.megabytes() as u64, "MB");
-        }
-
-        if env::var("RA_COUNT").is_ok() {
-            eprintln!("{}", profile::countme::get_all());
-        }
-
-        if self.memory_usage && verbosity.is_verbose() {
-            print_memory_usage(host, vfs);
-        }
-
-        Ok(())
     }
 
     fn stop_watch(&self) -> StopWatch {
diff --git a/crates/rust-analyzer/src/cli/diagnostics.rs b/crates/rust-analyzer/src/cli/diagnostics.rs
index 8b985716b..74f784338 100644
--- a/crates/rust-analyzer/src/cli/diagnostics.rs
+++ b/crates/rust-analyzer/src/cli/diagnostics.rs
@@ -34,7 +34,8 @@ pub fn diagnostics(
     with_proc_macro: bool,
 ) -> Result<()> {
     let cargo_config = Default::default();
-    let load_cargo_config = LoadCargoConfig { load_out_dirs_from_check, with_proc_macro };
+    let load_cargo_config =
+        LoadCargoConfig { load_out_dirs_from_check, with_proc_macro, wrap_rustc: false };
     let (host, _vfs, _proc_macro) =
         load_workspace_at(path, &cargo_config, &load_cargo_config, &|_| {})?;
     let db = host.raw_database();
@@ -56,7 +57,8 @@ pub fn diagnostics(
             let crate_name =
                 module.krate().display_name(db).as_deref().unwrap_or("unknown").to_string();
             println!("processing crate: {}, module: {}", crate_name, _vfs.file_path(file_id));
-            for diagnostic in analysis.diagnostics(&DiagnosticsConfig::default(), file_id).unwrap()
+            for diagnostic in
+                analysis.diagnostics(&DiagnosticsConfig::default(), false, file_id).unwrap()
             {
                 if matches!(diagnostic.severity, Severity::Error) {
                     found_error = true;
diff --git a/crates/rust-analyzer/src/cli/load_cargo.rs b/crates/rust-analyzer/src/cli/load_cargo.rs
index 310c36904..75bad1112 100644
--- a/crates/rust-analyzer/src/cli/load_cargo.rs
+++ b/crates/rust-analyzer/src/cli/load_cargo.rs
@@ -15,6 +15,7 @@ use crate::reload::{ProjectFolders, SourceRootConfig};
 
 pub struct LoadCargoConfig {
     pub load_out_dirs_from_check: bool,
+    pub wrap_rustc: bool,
     pub with_proc_macro: bool,
 }
 
@@ -52,7 +53,7 @@ pub fn load_workspace(
     };
 
     let build_data = if config.load_out_dirs_from_check {
-        let mut collector = BuildDataCollector::default();
+        let mut collector = BuildDataCollector::new(config.wrap_rustc);
         ws.collect_build_data_configs(&mut collector);
         Some(collector.collect(progress)?)
     } else {
@@ -136,8 +137,11 @@ mod tests {
     fn test_loading_rust_analyzer() -> Result<()> {
         let path = Path::new(env!("CARGO_MANIFEST_DIR")).parent().unwrap().parent().unwrap();
         let cargo_config = Default::default();
-        let load_cargo_config =
-            LoadCargoConfig { load_out_dirs_from_check: false, with_proc_macro: false };
+        let load_cargo_config = LoadCargoConfig {
+            load_out_dirs_from_check: false,
+            wrap_rustc: false,
+            with_proc_macro: false,
+        };
         let (host, _vfs, _proc_macro) =
             load_workspace_at(path, &cargo_config, &load_cargo_config, &|_| {})?;
 
diff --git a/crates/rust-analyzer/src/cli/ssr.rs b/crates/rust-analyzer/src/cli/ssr.rs
index 79f426fff..1fd9b5a9b 100644
--- a/crates/rust-analyzer/src/cli/ssr.rs
+++ b/crates/rust-analyzer/src/cli/ssr.rs
@@ -9,8 +9,11 @@ use ide_ssr::{MatchFinder, SsrPattern, SsrRule};
 pub fn apply_ssr_rules(rules: Vec<SsrRule>) -> Result<()> {
     use ide_db::base_db::SourceDatabaseExt;
     let cargo_config = Default::default();
-    let load_cargo_config =
-        LoadCargoConfig { load_out_dirs_from_check: true, with_proc_macro: true };
+    let load_cargo_config = LoadCargoConfig {
+        load_out_dirs_from_check: true,
+        wrap_rustc: false,
+        with_proc_macro: true,
+    };
     let (host, vfs, _proc_macro) =
         load_workspace_at(&std::env::current_dir()?, &cargo_config, &load_cargo_config, &|_| {})?;
     let db = host.raw_database();
@@ -37,7 +40,7 @@ pub fn search_for_patterns(patterns: Vec<SsrPattern>, debug_snippet: Option<Stri
     use ide_db::symbol_index::SymbolsDatabase;
     let cargo_config = Default::default();
     let load_cargo_config =
-        LoadCargoConfig { load_out_dirs_from_check: true, with_proc_macro: true };
+        LoadCargoConfig { load_out_dirs_from_check: true, wrap_rustc: true, with_proc_macro: true };
     let (host, _vfs, _proc_macro) =
         load_workspace_at(&std::env::current_dir()?, &cargo_config, &load_cargo_config, &|_| {})?;
     let db = host.raw_database();
diff --git a/crates/rust-analyzer/src/config.rs b/crates/rust-analyzer/src/config.rs
index cda272fd4..1edaa394a 100644
--- a/crates/rust-analyzer/src/config.rs
+++ b/crates/rust-analyzer/src/config.rs
@@ -48,6 +48,9 @@ config_data! {
         /// Run build scripts (`build.rs`) for more precise code analysis.
         cargo_runBuildScripts |
         cargo_loadOutDirsFromCheck: bool = "true",
+        /// Use `RUSTC_WRAPPER=rust-analyzer` when running build scripts to
+        /// avoid compiling unnecessary things.
+        cargo_useRustcWrapperForBuildScripts: bool = "true",
         /// Do not activate the `default` feature.
         cargo_noDefaultFeatures: bool    = "false",
         /// Compilation target (target triple).
@@ -445,8 +448,8 @@ impl Config {
     pub fn hover_actions(&self) -> bool {
         self.experimental("hoverActions")
     }
-    pub fn status_notification(&self) -> bool {
-        self.experimental("statusNotification")
+    pub fn server_status_notification(&self) -> bool {
+        self.experimental("serverStatusNotification")
     }
 
     pub fn publish_diagnostics(&self) -> bool {
@@ -493,6 +496,9 @@ impl Config {
     pub fn run_build_scripts(&self) -> bool {
         self.data.cargo_runBuildScripts || self.data.procMacro_enable
     }
+    pub fn wrap_rustc(&self) -> bool {
+        self.data.cargo_useRustcWrapperForBuildScripts
+    }
     pub fn cargo(&self) -> CargoConfig {
         let rustc_source = self.data.rustcSource.as_ref().map(|rustc_src| {
             if rustc_src == "discover" {
@@ -656,6 +662,19 @@ impl Config {
     pub fn code_lens_refresh(&self) -> bool {
         try_or!(self.caps.workspace.as_ref()?.code_lens.as_ref()?.refresh_support?, false)
     }
+    pub fn insert_replace_support(&self) -> bool {
+        try_or!(
+            self.caps
+                .text_document
+                .as_ref()?
+                .completion
+                .as_ref()?
+                .completion_item
+                .as_ref()?
+                .insert_replace_support?,
+            false
+        )
+    }
 }
 
 #[derive(Deserialize, Debug, Clone)]
diff --git a/crates/rust-analyzer/src/diagnostics/test_data/macro_compiler_error.txt b/crates/rust-analyzer/src/diagnostics/test_data/macro_compiler_error.txt
index f999848a7..c847bbb35 100644
--- a/crates/rust-analyzer/src/diagnostics/test_data/macro_compiler_error.txt
+++ b/crates/rust-analyzer/src/diagnostics/test_data/macro_compiler_error.txt
@@ -13,16 +13,16 @@
         diagnostic: Diagnostic {
             range: Range {
                 start: Position {
-                    line: 264,
+                    line: 271,
                     character: 8,
                 },
                 end: Position {
-                    line: 264,
-                    character: 76,
+                    line: 271,
+                    character: 50,
                 },
             },
             severity: Some(
-                Error,
+                Hint,
             ),
             code: None,
             code_description: None,
@@ -40,18 +40,18 @@
                                 password: None,
                                 host: None,
                                 port: None,
-                                path: "/test/crates/hir_def/src/data.rs",
+                                path: "/test/crates/hir_def/src/path.rs",
                                 query: None,
                                 fragment: None,
                             },
                             range: Range {
                                 start: Position {
-                                    line: 79,
-                                    character: 15,
+                                    line: 264,
+                                    character: 8,
                                 },
                                 end: Position {
-                                    line: 79,
-                                    character: 41,
+                                    line: 264,
+                                    character: 76,
                                 },
                             },
                         },
@@ -87,6 +87,71 @@
                 },
             },
             severity: Some(
+                Hint,
+            ),
+            code: None,
+            code_description: None,
+            source: Some(
+                "rustc",
+            ),
+            message: "Please register your known path in the path module",
+            related_information: Some(
+                [
+                    DiagnosticRelatedInformation {
+                        location: Location {
+                            uri: Url {
+                                scheme: "file",
+                                username: "",
+                                password: None,
+                                host: None,
+                                port: None,
+                                path: "/test/crates/hir_def/src/path.rs",
+                                query: None,
+                                fragment: None,
+                            },
+                            range: Range {
+                                start: Position {
+                                    line: 264,
+                                    character: 8,
+                                },
+                                end: Position {
+                                    line: 264,
+                                    character: 76,
+                                },
+                            },
+                        },
+                        message: "Exact error occurred here",
+                    },
+                ],
+            ),
+            tags: None,
+            data: None,
+        },
+        fixes: [],
+    },
+    MappedRustDiagnostic {
+        url: Url {
+            scheme: "file",
+            username: "",
+            password: None,
+            host: None,
+            port: None,
+            path: "/test/crates/hir_def/src/path.rs",
+            query: None,
+            fragment: None,
+        },
+        diagnostic: Diagnostic {
+            range: Range {
+                start: Position {
+                    line: 264,
+                    character: 8,
+                },
+                end: Position {
+                    line: 264,
+                    character: 76,
+                },
+            },
+            severity: Some(
                 Error,
             ),
             code: None,
@@ -95,7 +160,60 @@
                 "rustc",
             ),
             message: "Please register your known path in the path module",
-            related_information: None,
+            related_information: Some(
+                [
+                    DiagnosticRelatedInformation {
+                        location: Location {
+                            uri: Url {
+                                scheme: "file",
+                                username: "",
+                                password: None,
+                                host: None,
+                                port: None,
+                                path: "/test/crates/hir_def/src/path.rs",
+                                query: None,
+                                fragment: None,
+                            },
+                            range: Range {
+                                start: Position {
+                                    line: 271,
+                                    character: 8,
+                                },
+                                end: Position {
+                                    line: 271,
+                                    character: 50,
+                                },
+                            },
+                        },
+                        message: "Error originated from macro call here",
+                    },
+                    DiagnosticRelatedInformation {
+                        location: Location {
+                            uri: Url {
+                                scheme: "file",
+                                username: "",
+                                password: None,
+                                host: None,
+                                port: None,
+                                path: "/test/crates/hir_def/src/data.rs",
+                                query: None,
+                                fragment: None,
+                            },
+                            range: Range {
+                                start: Position {
+                                    line: 79,
+                                    character: 15,
+                                },
+                                end: Position {
+                                    line: 79,
+                                    character: 41,
+                                },
+                            },
+                        },
+                        message: "Error originated from macro call here",
+                    },
+                ],
+            ),
             tags: None,
             data: None,
         },
diff --git a/crates/rust-analyzer/src/diagnostics/to_proto.rs b/crates/rust-analyzer/src/diagnostics/to_proto.rs
index 76994de71..e2f319f6b 100644
--- a/crates/rust-analyzer/src/diagnostics/to_proto.rs
+++ b/crates/rust-analyzer/src/diagnostics/to_proto.rs
@@ -34,22 +34,14 @@ fn diagnostic_severity(
     Some(res)
 }
 
-/// Check whether a file name is from macro invocation
-fn is_from_macro(file_name: &str) -> bool {
+/// Checks whether a file name is from macro invocation and does not refer to an actual file.
+fn is_dummy_macro_file(file_name: &str) -> bool {
+    // FIXME: current rustc does not seem to emit `<macro file>` files anymore?
     file_name.starts_with('<') && file_name.ends_with('>')
 }
 
-/// Converts a Rust span to a LSP location, resolving macro expansion site if neccesary
-fn location(workspace_root: &Path, span: &DiagnosticSpan) -> lsp_types::Location {
-    let mut span = span.clone();
-    while let Some(expansion) = span.expansion {
-        span = expansion.span;
-    }
-    return location_naive(workspace_root, &span);
-}
-
 /// Converts a Rust span to a LSP location
-fn location_naive(workspace_root: &Path, span: &DiagnosticSpan) -> lsp_types::Location {
+fn location(workspace_root: &Path, span: &DiagnosticSpan) -> lsp_types::Location {
     let file_name = workspace_root.join(&span.file_name);
     let uri = url_from_abs_path(&file_name);
 
@@ -62,7 +54,25 @@ fn location_naive(workspace_root: &Path, span: &DiagnosticSpan) -> lsp_types::Lo
     lsp_types::Location { uri, range }
 }
 
-/// Converts a secondary Rust span to a LSP related inflocation(ormation
+/// Extracts a suitable "primary" location from a rustc diagnostic.
+///
+/// This takes locations pointing into the standard library, or generally outside the current
+/// workspace into account and tries to avoid those, in case macros are involved.
+fn primary_location(workspace_root: &Path, span: &DiagnosticSpan) -> lsp_types::Location {
+    let span_stack = std::iter::successors(Some(span), |span| Some(&span.expansion.as_ref()?.span));
+    for span in span_stack.clone() {
+        let abs_path = workspace_root.join(&span.file_name);
+        if !is_dummy_macro_file(&span.file_name) && abs_path.starts_with(workspace_root) {
+            return location(workspace_root, span);
+        }
+    }
+
+    // Fall back to the outermost macro invocation if no suitable span comes up.
+    let last_span = span_stack.last().unwrap();
+    location(workspace_root, last_span)
+}
+
+/// Converts a secondary Rust span to a LSP related information
 ///
 /// If the span is unlabelled this will return `None`.
 fn diagnostic_related_information(
@@ -231,7 +241,7 @@ pub(crate) fn map_rust_diagnostic_to_lsp(
     primary_spans
         .iter()
         .flat_map(|primary_span| {
-            let location = location(workspace_root, &primary_span);
+            let primary_location = primary_location(workspace_root, &primary_span);
 
             let mut message = message.clone();
             if needs_primary_span_label {
@@ -243,31 +253,47 @@ pub(crate) fn map_rust_diagnostic_to_lsp(
             // Each primary diagnostic span may result in multiple LSP diagnostics.
             let mut diagnostics = Vec::new();
 
-            let mut related_macro_info = None;
+            let mut related_info_macro_calls = vec![];
 
             // If error occurs from macro expansion, add related info pointing to
             // where the error originated
             // Also, we would generate an additional diagnostic, so that exact place of macro
             // will be highlighted in the error origin place.
-            if !is_from_macro(&primary_span.file_name) && primary_span.expansion.is_some() {
-                let in_macro_location = location_naive(workspace_root, &primary_span);
+            let span_stack = std::iter::successors(Some(*primary_span), |span| {
+                Some(&span.expansion.as_ref()?.span)
+            });
+            for (i, span) in span_stack.enumerate() {
+                if is_dummy_macro_file(&span.file_name) {
+                    continue;
+                }
 
-                // Add related information for the main disagnostic.
-                related_macro_info = Some(lsp_types::DiagnosticRelatedInformation {
-                    location: in_macro_location.clone(),
-                    message: "Error originated from macro here".to_string(),
-                });
+                // First span is the original diagnostic, others are macro call locations that
+                // generated that code.
+                let is_in_macro_call = i != 0;
 
+                let secondary_location = location(workspace_root, &span);
+                if secondary_location == primary_location {
+                    continue;
+                }
+                related_info_macro_calls.push(lsp_types::DiagnosticRelatedInformation {
+                    location: secondary_location.clone(),
+                    message: if is_in_macro_call {
+                        "Error originated from macro call here".to_string()
+                    } else {
+                        "Actual error occurred here".to_string()
+                    },
+                });
                 // For the additional in-macro diagnostic we add the inverse message pointing to the error location in code.
                 let information_for_additional_diagnostic =
                     vec![lsp_types::DiagnosticRelatedInformation {
-                        location: location.clone(),
+                        location: primary_location.clone(),
                         message: "Exact error occurred here".to_string(),
                     }];
 
                 let diagnostic = lsp_types::Diagnostic {
-                    range: in_macro_location.range,
-                    severity,
+                    range: secondary_location.range,
+                    // downgrade to hint if we're pointing at the macro
+                    severity: Some(lsp_types::DiagnosticSeverity::Hint),
                     code: code.clone().map(lsp_types::NumberOrString::String),
                     code_description: code_description.clone(),
                     source: Some(source.clone()),
@@ -276,9 +302,8 @@ pub(crate) fn map_rust_diagnostic_to_lsp(
                     tags: if tags.is_empty() { None } else { Some(tags.clone()) },
                     data: None,
                 };
-
                 diagnostics.push(MappedRustDiagnostic {
-                    url: in_macro_location.uri,
+                    url: secondary_location.uri,
                     diagnostic,
                     fixes: Vec::new(),
                 });
@@ -286,23 +311,25 @@ pub(crate) fn map_rust_diagnostic_to_lsp(
 
             // Emit the primary diagnostic.
             diagnostics.push(MappedRustDiagnostic {
-                url: location.uri.clone(),
+                url: primary_location.uri.clone(),
                 diagnostic: lsp_types::Diagnostic {
-                    range: location.range,
+                    range: primary_location.range,
                     severity,
                     code: code.clone().map(lsp_types::NumberOrString::String),
                     code_description: code_description.clone(),
                     source: Some(source.clone()),
                     message,
-                    related_information: if subdiagnostics.is_empty() {
-                        None
-                    } else {
-                        let mut related = subdiagnostics
+                    related_information: {
+                        let info = related_info_macro_calls
                             .iter()
-                            .map(|sub| sub.related.clone())
+                            .cloned()
+                            .chain(subdiagnostics.iter().map(|sub| sub.related.clone()))
                             .collect::<Vec<_>>();
-                        related.extend(related_macro_info);
-                        Some(related)
+                        if info.is_empty() {
+                            None
+                        } else {
+                            Some(info)
+                        }
                     },
                     tags: if tags.is_empty() { None } else { Some(tags.clone()) },
                     data: None,
@@ -314,7 +341,7 @@ pub(crate) fn map_rust_diagnostic_to_lsp(
             // This is useful because they will show up in the user's editor, unlike
             // `related_information`, which just produces hard-to-read links, at least in VS Code.
             let back_ref = lsp_types::DiagnosticRelatedInformation {
-                location,
+                location: primary_location,
                 message: "original diagnostic".to_string(),
             };
             for sub in &subdiagnostics {
diff --git a/crates/rust-analyzer/src/from_proto.rs b/crates/rust-analyzer/src/from_proto.rs
index 5b02b2598..712d5a9c2 100644
--- a/crates/rust-analyzer/src/from_proto.rs
+++ b/crates/rust-analyzer/src/from_proto.rs
@@ -42,27 +42,27 @@ pub(crate) fn text_range(line_index: &LineIndex, range: lsp_types::Range) -> Tex
     TextRange::new(start, end)
 }
 
-pub(crate) fn file_id(world: &GlobalStateSnapshot, url: &lsp_types::Url) -> Result<FileId> {
-    world.url_to_file_id(url)
+pub(crate) fn file_id(snap: &GlobalStateSnapshot, url: &lsp_types::Url) -> Result<FileId> {
+    snap.url_to_file_id(url)
 }
 
 pub(crate) fn file_position(
-    world: &GlobalStateSnapshot,
+    snap: &GlobalStateSnapshot,
     tdpp: lsp_types::TextDocumentPositionParams,
 ) -> Result<FilePosition> {
-    let file_id = file_id(world, &tdpp.text_document.uri)?;
-    let line_index = world.file_line_index(file_id)?;
+    let file_id = file_id(snap, &tdpp.text_document.uri)?;
+    let line_index = snap.file_line_index(file_id)?;
     let offset = offset(&line_index, tdpp.position);
     Ok(FilePosition { file_id, offset })
 }
 
 pub(crate) fn file_range(
-    world: &GlobalStateSnapshot,
+    snap: &GlobalStateSnapshot,
     text_document_identifier: lsp_types::TextDocumentIdentifier,
     range: lsp_types::Range,
 ) -> Result<FileRange> {
-    let file_id = file_id(world, &text_document_identifier.uri)?;
-    let line_index = world.file_line_index(file_id)?;
+    let file_id = file_id(snap, &text_document_identifier.uri)?;
+    let line_index = snap.file_line_index(file_id)?;
     let range = text_range(&line_index, range);
     Ok(FileRange { file_id, range })
 }
@@ -82,7 +82,7 @@ pub(crate) fn assist_kind(kind: lsp_types::CodeActionKind) -> Option<AssistKind>
 }
 
 pub(crate) fn annotation(
-    world: &GlobalStateSnapshot,
+    snap: &GlobalStateSnapshot,
     code_lens: lsp_types::CodeLens,
 ) -> Result<Annotation> {
     let data = code_lens.data.unwrap();
@@ -91,25 +91,25 @@ pub(crate) fn annotation(
     match resolve {
         lsp_ext::CodeLensResolveData::Impls(params) => {
             let file_id =
-                world.url_to_file_id(&params.text_document_position_params.text_document.uri)?;
-            let line_index = world.file_line_index(file_id)?;
+                snap.url_to_file_id(&params.text_document_position_params.text_document.uri)?;
+            let line_index = snap.file_line_index(file_id)?;
 
             Ok(Annotation {
                 range: text_range(&line_index, code_lens.range),
                 kind: AnnotationKind::HasImpls {
-                    position: file_position(world, params.text_document_position_params)?,
+                    position: file_position(snap, params.text_document_position_params)?,
                     data: None,
                 },
             })
         }
         lsp_ext::CodeLensResolveData::References(params) => {
-            let file_id = world.url_to_file_id(&params.text_document.uri)?;
-            let line_index = world.file_line_index(file_id)?;
+            let file_id = snap.url_to_file_id(&params.text_document.uri)?;
+            let line_index = snap.file_line_index(file_id)?;
 
             Ok(Annotation {
                 range: text_range(&line_index, code_lens.range),
                 kind: AnnotationKind::HasReferences {
-                    position: file_position(world, params)?,
+                    position: file_position(snap, params)?,
                     data: None,
                 },
             })
diff --git a/crates/rust-analyzer/src/global_state.rs b/crates/rust-analyzer/src/global_state.rs
index 52c249713..adeb7a97e 100644
--- a/crates/rust-analyzer/src/global_state.rs
+++ b/crates/rust-analyzer/src/global_state.rs
@@ -23,6 +23,7 @@ use crate::{
     document::DocumentData,
     from_proto,
     line_index::{LineEndings, LineIndex},
+    lsp_ext,
     main_loop::Task,
     op_queue::OpQueue,
     reload::SourceRootConfig,
@@ -32,20 +33,6 @@ use crate::{
     Result,
 };
 
-#[derive(Eq, PartialEq, Copy, Clone)]
-pub(crate) enum Status {
-    Loading,
-    Ready { partial: bool },
-    Invalid,
-    NeedsReload,
-}
-
-impl Default for Status {
-    fn default() -> Self {
-        Status::Loading
-    }
-}
-
 // Enforces drop order
 pub(crate) struct Handle<H, C> {
     pub(crate) handle: H,
@@ -67,24 +54,37 @@ pub(crate) struct GlobalState {
     req_queue: ReqQueue,
     pub(crate) task_pool: Handle<TaskPool<Task>, Receiver<Task>>,
     pub(crate) loader: Handle<Box<dyn vfs::loader::Handle>, Receiver<vfs::loader::Message>>,
-    pub(crate) vfs_config_version: u32,
-    pub(crate) flycheck: Vec<FlycheckHandle>,
-    pub(crate) flycheck_sender: Sender<flycheck::Message>,
-    pub(crate) flycheck_receiver: Receiver<flycheck::Message>,
     pub(crate) config: Arc<Config>,
     pub(crate) analysis_host: AnalysisHost,
     pub(crate) diagnostics: DiagnosticCollection,
     pub(crate) mem_docs: FxHashMap<VfsPath, DocumentData>,
     pub(crate) semantic_tokens_cache: Arc<Mutex<FxHashMap<Url, SemanticTokens>>>,
-    pub(crate) vfs: Arc<RwLock<(vfs::Vfs, FxHashMap<FileId, LineEndings>)>>,
     pub(crate) shutdown_requested: bool,
-    pub(crate) status: Status,
+    pub(crate) last_reported_status: Option<lsp_ext::ServerStatusParams>,
     pub(crate) source_root_config: SourceRootConfig,
     pub(crate) proc_macro_client: Option<ProcMacroClient>,
+
+    pub(crate) flycheck: Vec<FlycheckHandle>,
+    pub(crate) flycheck_sender: Sender<flycheck::Message>,
+    pub(crate) flycheck_receiver: Receiver<flycheck::Message>,
+
+    pub(crate) vfs: Arc<RwLock<(vfs::Vfs, FxHashMap<FileId, LineEndings>)>>,
+    pub(crate) vfs_config_version: u32,
+    pub(crate) vfs_progress_config_version: u32,
+    pub(crate) vfs_progress_n_total: usize,
+    pub(crate) vfs_progress_n_done: usize,
+
+    /// For both `workspaces` and `workspace_build_data`, the field stores the
+    /// data we actually use, while the `OpQueue` stores the result of the last
+    /// fetch.
+    ///
+    /// If the fetch (partially) fails, we do not update the values.
     pub(crate) workspaces: Arc<Vec<ProjectWorkspace>>,
-    pub(crate) fetch_workspaces_queue: OpQueue<()>,
+    pub(crate) fetch_workspaces_queue: OpQueue<(), Vec<anyhow::Result<ProjectWorkspace>>>,
     pub(crate) workspace_build_data: Option<BuildDataResult>,
-    pub(crate) fetch_build_data_queue: OpQueue<BuildDataCollector>,
+    pub(crate) fetch_build_data_queue:
+        OpQueue<BuildDataCollector, Option<anyhow::Result<BuildDataResult>>>,
+
     latest_requests: Arc<RwLock<LatestRequests>>,
 }
 
@@ -121,25 +121,32 @@ impl GlobalState {
         GlobalState {
             sender,
             req_queue: ReqQueue::default(),
-            vfs_config_version: 0,
             task_pool,
             loader,
-            flycheck: Vec::new(),
-            flycheck_sender,
-            flycheck_receiver,
             config: Arc::new(config),
             analysis_host,
             diagnostics: Default::default(),
             mem_docs: FxHashMap::default(),
             semantic_tokens_cache: Arc::new(Default::default()),
-            vfs: Arc::new(RwLock::new((vfs::Vfs::default(), FxHashMap::default()))),
             shutdown_requested: false,
-            status: Status::default(),
+            last_reported_status: None,
             source_root_config: SourceRootConfig::default(),
             proc_macro_client: None,
+
+            flycheck: Vec::new(),
+            flycheck_sender,
+            flycheck_receiver,
+
+            vfs: Arc::new(RwLock::new((vfs::Vfs::default(), FxHashMap::default()))),
+            vfs_config_version: 0,
+            vfs_progress_config_version: 0,
+            vfs_progress_n_total: 0,
+            vfs_progress_n_done: 0,
+
             workspaces: Arc::new(Vec::new()),
             fetch_workspaces_queue: OpQueue::default(),
             workspace_build_data: None,
+
             fetch_build_data_queue: OpQueue::default(),
             latest_requests: Default::default(),
         }
diff --git a/crates/rust-analyzer/src/handlers.rs b/crates/rust-analyzer/src/handlers.rs
index 85e67554c..1f59402e5 100644
--- a/crates/rust-analyzer/src/handlers.rs
+++ b/crates/rust-analyzer/src/handlers.rs
@@ -17,7 +17,7 @@ use lsp_server::ErrorCode;
 use lsp_types::{
     CallHierarchyIncomingCall, CallHierarchyIncomingCallsParams, CallHierarchyItem,
     CallHierarchyOutgoingCall, CallHierarchyOutgoingCallsParams, CallHierarchyPrepareParams,
-    CodeActionKind, CodeLens, CompletionItem, Diagnostic, DiagnosticTag, DocumentFormattingParams,
+    CodeLens, CompletionItem, Diagnostic, DiagnosticTag, DocumentFormattingParams,
     DocumentHighlight, FoldingRange, FoldingRangeParams, HoverContents, Location, NumberOrString,
     Position, PrepareRenameResponse, Range, RenameParams, SemanticTokensDeltaParams,
     SemanticTokensFullDeltaResult, SemanticTokensParams, SemanticTokensRangeParams,
@@ -36,7 +36,7 @@ use crate::{
     diff::diff,
     from_proto,
     global_state::{GlobalState, GlobalStateSnapshot},
-    line_index::{LineEndings, LineIndex},
+    line_index::LineEndings,
     lsp_ext::{self, InlayHint, InlayHintsParams},
     lsp_utils::all_edits_are_disjoint,
     to_proto, LspError, Result,
@@ -84,7 +84,8 @@ pub(crate) fn handle_analyzer_status(
 
 pub(crate) fn handle_memory_usage(state: &mut GlobalState, _: ()) -> Result<String> {
     let _p = profile::span("handle_memory_usage");
-    let mem = state.analysis_host.per_query_memory_usage();
+    let mut mem = state.analysis_host.per_query_memory_usage();
+    mem.push(("Remaining".into(), profile::memory_usage().allocated));
 
     let mut out = String::new();
     for (name, bytes) in mem {
@@ -230,7 +231,6 @@ pub(crate) fn handle_on_enter(
     Ok(Some(edit))
 }
 
-// Don't forget to add new trigger characters to `ServerCapabilities` in `caps.rs`.
 pub(crate) fn handle_on_type_formatting(
     snap: GlobalStateSnapshot,
     params: lsp_types::DocumentOnTypeFormattingParams,
@@ -664,10 +664,13 @@ pub(crate) fn handle_completion(
     };
     let line_index = snap.file_line_index(position.file_id)?;
 
+    let insert_replace_support =
+        snap.config.insert_replace_support().then(|| text_document_position.position);
     let items: Vec<CompletionItem> = items
         .into_iter()
         .flat_map(|item| {
-            let mut new_completion_items = to_proto::completion_item(&line_index, item.clone());
+            let mut new_completion_items =
+                to_proto::completion_item(insert_replace_support, &line_index, item.clone());
 
             if completion_config.enable_imports_on_the_fly {
                 for new_item in &mut new_completion_items {
@@ -926,19 +929,22 @@ pub(crate) fn handle_formatting(
     let captured_stderr = String::from_utf8(output.stderr).unwrap_or_default();
 
     if !output.status.success() {
-        match output.status.code() {
-            Some(1) if !captured_stderr.contains("not installed") => {
+        let rustfmt_not_installed =
+            captured_stderr.contains("not installed") || captured_stderr.contains("not available");
+
+        return match output.status.code() {
+            Some(1) if !rustfmt_not_installed => {
                 // While `rustfmt` doesn't have a specific exit code for parse errors this is the
                 // likely cause exiting with 1. Most Language Servers swallow parse errors on
                 // formatting because otherwise an error is surfaced to the user on top of the
                 // syntax error diagnostics they're already receiving. This is especially jarring
                 // if they have format on save enabled.
                 log::info!("rustfmt exited with status 1, assuming parse error and ignoring");
-                return Ok(None);
+                Ok(None)
             }
             _ => {
                 // Something else happened - e.g. `rustfmt` is missing or caught a signal
-                return Err(LspError::new(
+                Err(LspError::new(
                     -32900,
                     format!(
                         r#"rustfmt exited with:
@@ -948,9 +954,9 @@ pub(crate) fn handle_formatting(
                         output.status, captured_stdout, captured_stderr,
                     ),
                 )
-                .into());
+                .into())
             }
-        }
+        };
     }
 
     let (new_text, new_line_endings) = LineEndings::normalize(captured_stdout);
@@ -976,84 +982,52 @@ pub(crate) fn handle_code_action(
     params: lsp_types::CodeActionParams,
 ) -> Result<Option<Vec<lsp_ext::CodeAction>>> {
     let _p = profile::span("handle_code_action");
-    // We intentionally don't support command-based actions, as those either
-    // requires custom client-code anyway, or requires server-initiated edits.
-    // Server initiated edits break causality, so we avoid those as well.
+
     if !snap.config.code_action_literals() {
+        // We intentionally don't support command-based actions, as those either
+        // require either custom client-code or server-initiated edits. Server
+        // initiated edits break causality, so we avoid those.
         return Ok(None);
     }
 
-    let file_id = from_proto::file_id(&snap, &params.text_document.uri)?;
-    let line_index = snap.file_line_index(file_id)?;
-    let range = from_proto::text_range(&line_index, params.range);
-    let frange = FileRange { file_id, range };
+    let line_index =
+        snap.file_line_index(from_proto::file_id(&snap, &params.text_document.uri)?)?;
+    let frange = from_proto::file_range(&snap, params.text_document.clone(), params.range)?;
 
     let mut assists_config = snap.config.assist();
     assists_config.allowed = params
-        .clone()
         .context
         .only
+        .clone()
         .map(|it| it.into_iter().filter_map(from_proto::assist_kind).collect());
 
     let mut res: Vec<lsp_ext::CodeAction> = Vec::new();
 
-    let include_quick_fixes = match &params.context.only {
-        Some(v) => v.iter().any(|it| {
-            it == &lsp_types::CodeActionKind::EMPTY || it == &lsp_types::CodeActionKind::QUICKFIX
-        }),
-        None => true,
-    };
-    if include_quick_fixes {
-        add_quick_fixes(&snap, frange, &line_index, &mut res)?;
-    }
-
-    if snap.config.code_action_resolve() {
-        for (index, assist) in
-            snap.analysis.assists(&assists_config, false, frange)?.into_iter().enumerate()
-        {
-            res.push(to_proto::unresolved_code_action(&snap, params.clone(), assist, index)?);
-        }
-    } else {
-        for assist in snap.analysis.assists(&assists_config, true, frange)?.into_iter() {
-            res.push(to_proto::resolved_code_action(&snap, assist)?);
-        }
-    }
-
-    Ok(Some(res))
-}
-
-fn add_quick_fixes(
-    snap: &GlobalStateSnapshot,
-    frange: FileRange,
-    line_index: &LineIndex,
-    acc: &mut Vec<lsp_ext::CodeAction>,
-) -> Result<()> {
-    let diagnostics = snap.analysis.diagnostics(&snap.config.diagnostics(), frange.file_id)?;
-
-    for fix in diagnostics
-        .into_iter()
-        .filter_map(|d| d.fix)
-        .filter(|fix| fix.fix_trigger_range.intersect(frange.range).is_some())
-    {
-        let edit = to_proto::snippet_workspace_edit(&snap, fix.source_change)?;
-        let action = lsp_ext::CodeAction {
-            title: fix.label.to_string(),
-            group: None,
-            kind: Some(CodeActionKind::QUICKFIX),
-            edit: Some(edit),
-            is_preferred: Some(false),
-            data: None,
-        };
-        acc.push(action);
+    let code_action_resolve_cap = snap.config.code_action_resolve();
+    let assists = snap.analysis.assists_with_fixes(
+        &assists_config,
+        &snap.config.diagnostics(),
+        !code_action_resolve_cap,
+        frange,
+    )?;
+    for (index, assist) in assists.into_iter().enumerate() {
+        let resolve_data =
+            if code_action_resolve_cap { Some((index, params.clone())) } else { None };
+        let code_action = to_proto::code_action(&snap, assist, resolve_data)?;
+        res.push(code_action)
     }
 
+    // Fixes from `cargo check`.
     for fix in snap.check_fixes.get(&frange.file_id).into_iter().flatten() {
+        // FIXME: this mapping is awkward and shouldn't exist. Refactor
+        // `snap.check_fixes` to not convert to LSP prematurely.
         let fix_range = from_proto::text_range(&line_index, fix.range);
         if fix_range.intersect(frange.range).is_some() {
-            acc.push(fix.action.clone());
+            res.push(fix.action.clone());
         }
     }
-    Ok(())
+
+    Ok(Some(res))
 }
 
 pub(crate) fn handle_code_action_resolve(
@@ -1078,12 +1052,18 @@ pub(crate) fn handle_code_action_resolve(
         .only
         .map(|it| it.into_iter().filter_map(from_proto::assist_kind).collect());
 
-    let assists = snap.analysis.assists(&assists_config, true, frange)?;
+    let assists = snap.analysis.assists_with_fixes(
+        &assists_config,
+        &snap.config.diagnostics(),
+        true,
+        frange,
+    )?;
+
     let (id, index) = split_once(&params.id, ':').unwrap();
     let index = index.parse::<usize>().unwrap();
     let assist = &assists[index];
     assert!(assist.id.0 == id);
-    let edit = to_proto::resolved_code_action(&snap, assist.clone())?.edit;
+    let edit = to_proto::code_action(&snap, assist.clone(), None)?.edit;
     code_action.edit = edit;
     Ok(code_action)
 }
@@ -1202,7 +1182,7 @@ pub(crate) fn publish_diagnostics(
 
     let diagnostics: Vec<Diagnostic> = snap
         .analysis
-        .diagnostics(&snap.config.diagnostics(), file_id)?
+        .diagnostics(&snap.config.diagnostics(), false, file_id)?
         .into_iter()
         .map(|d| Diagnostic {
             range: to_proto::range(&line_index, d.range),
@@ -1430,7 +1410,7 @@ pub(crate) fn handle_open_cargo_toml(
 pub(crate) fn handle_move_item(
     snap: GlobalStateSnapshot,
     params: lsp_ext::MoveItemParams,
-) -> Result<Option<lsp_types::TextDocumentEdit>> {
+) -> Result<Vec<lsp_ext::SnippetTextEdit>> {
     let _p = profile::span("handle_move_item");
     let file_id = from_proto::file_id(&snap, &params.text_document.uri)?;
     let range = from_proto::file_range(&snap, params.text_document, params.range)?;
@@ -1441,8 +1421,11 @@ pub(crate) fn handle_move_item(
     };
 
     match snap.analysis.move_item(range, direction)? {
-        Some(text_edit) => Ok(Some(to_proto::text_document_edit(&snap, file_id, text_edit)?)),
-        None => Ok(None),
+        Some(text_edit) => {
+            let line_index = snap.file_line_index(file_id)?;
+            Ok(to_proto::snippet_text_edit_vec(&line_index, true, text_edit))
+        }
+        None => Ok(vec![]),
     }
 }
 
diff --git a/crates/rust-analyzer/src/lib.rs b/crates/rust-analyzer/src/lib.rs
index 8b874239c..d9a5030a0 100644
--- a/crates/rust-analyzer/src/lib.rs
+++ b/crates/rust-analyzer/src/lib.rs
@@ -39,6 +39,9 @@ mod op_queue;
 pub mod lsp_ext;
 pub mod config;
 
+#[cfg(test)]
+mod benchmarks;
+
 use serde::de::DeserializeOwned;
 use std::fmt;
 
diff --git a/crates/rust-analyzer/src/lsp_ext.rs b/crates/rust-analyzer/src/lsp_ext.rs
index 0e1fec209..d648cda32 100644
--- a/crates/rust-analyzer/src/lsp_ext.rs
+++ b/crates/rust-analyzer/src/lsp_ext.rs
@@ -241,26 +241,26 @@ pub struct SsrParams {
     pub selections: Vec<lsp_types::Range>,
 }
 
-pub enum StatusNotification {}
+pub enum ServerStatusNotification {}
 
-#[derive(Serialize, Deserialize)]
-#[serde(rename_all = "camelCase")]
-pub enum Status {
-    Loading,
-    ReadyPartial,
-    Ready,
-    NeedsReload,
-    Invalid,
+impl Notification for ServerStatusNotification {
+    type Params = ServerStatusParams;
+    const METHOD: &'static str = "experimental/serverStatus";
 }
 
-#[derive(Deserialize, Serialize)]
-pub struct StatusParams {
-    pub status: Status,
+#[derive(Deserialize, Serialize, PartialEq, Eq, Clone)]
+pub struct ServerStatusParams {
+    pub health: Health,
+    pub quiescent: bool,
+    pub message: Option<String>,
 }
 
-impl Notification for StatusNotification {
-    type Params = StatusParams;
-    const METHOD: &'static str = "rust-analyzer/status";
+#[derive(Serialize, Deserialize, Clone, Copy, PartialEq, Eq)]
+#[serde(rename_all = "camelCase")]
+pub enum Health {
+    Ok,
+    Warning,
+    Error,
 }
 
 pub enum CodeActionRequest {}
@@ -407,7 +407,7 @@ pub enum MoveItem {}
 
 impl Request for MoveItem {
     type Params = MoveItemParams;
-    type Result = Option<lsp_types::TextDocumentEdit>;
+    type Result = Vec<SnippetTextEdit>;
     const METHOD: &'static str = "experimental/moveItem";
 }
 
diff --git a/crates/rust-analyzer/src/lsp_utils.rs b/crates/rust-analyzer/src/lsp_utils.rs
index 2ac487632..73c4193e8 100644
--- a/crates/rust-analyzer/src/lsp_utils.rs
+++ b/crates/rust-analyzer/src/lsp_utils.rs
@@ -150,8 +150,16 @@ pub(crate) fn all_edits_are_disjoint(
             edit_ranges.push(edit.range);
         }
         Some(lsp_types::CompletionTextEdit::InsertAndReplace(edit)) => {
-            edit_ranges.push(edit.insert);
-            edit_ranges.push(edit.replace);
+            let replace = edit.replace;
+            let insert = edit.insert;
+            if replace.start != insert.start
+                || insert.start > insert.end
+                || insert.end > replace.end
+            {
+                // insert has to be a prefix of replace but it is not
+                return false;
+            }
+            edit_ranges.push(replace);
         }
         None => {}
     }
@@ -314,18 +322,6 @@ mod tests {
             Some(CompletionTextEdit::InsertAndReplace(InsertReplaceEdit {
                 new_text: "new_text".to_string(),
                 insert: disjoint_edit.range,
-                replace: joint_edit.range,
-            }));
-        completion_with_joint_edits.additional_text_edits = None;
-        assert!(
-            !all_edits_are_disjoint(&completion_with_joint_edits, &[]),
-            "Completion with disjoint edits fails the validation even with empty extra edits"
-        );
-
-        completion_with_joint_edits.text_edit =
-            Some(CompletionTextEdit::InsertAndReplace(InsertReplaceEdit {
-                new_text: "new_text".to_string(),
-                insert: disjoint_edit.range,
                 replace: disjoint_edit_2.range,
             }));
         completion_with_joint_edits.additional_text_edits = Some(vec![joint_edit]);
diff --git a/crates/rust-analyzer/src/main_loop.rs b/crates/rust-analyzer/src/main_loop.rs
index e88f16cc1..6ea775d68 100644
--- a/crates/rust-analyzer/src/main_loop.rs
+++ b/crates/rust-analyzer/src/main_loop.rs
@@ -2,6 +2,7 @@
 //! requests/replies and notifications back to the client.
 use std::{
     env, fmt,
+    sync::Arc,
     time::{Duration, Instant},
 };
 
@@ -12,6 +13,7 @@ use ide::{Canceled, FileId};
 use ide_db::base_db::VfsPath;
 use lsp_server::{Connection, Notification, Request, Response};
 use lsp_types::notification::Notification as _;
+use project_model::BuildDataCollector;
 use vfs::ChangeKind;
 
 use crate::{
@@ -19,7 +21,7 @@ use crate::{
     dispatch::{NotificationDispatcher, RequestDispatcher},
     document::DocumentData,
     from_proto,
-    global_state::{file_id_to_url, url_to_file_id, GlobalState, Status},
+    global_state::{file_id_to_url, url_to_file_id, GlobalState},
     handlers, lsp_ext,
     lsp_utils::{apply_document_changes, is_canceled, notification_is, Progress},
     reload::{BuildDataProgress, ProjectWorkspaceProgress},
@@ -187,7 +189,7 @@ impl GlobalState {
             log::info!("task queue len: {}", task_queue_len);
         }
 
-        let mut new_status = self.status;
+        let was_quiescent = self.is_quiescent();
         match event {
             Event::Lsp(msg) => match msg {
                 lsp_server::Message::Request(req) => self.on_request(loop_start, req)?,
@@ -227,12 +229,26 @@ impl GlobalState {
                                     (Progress::Report, Some(msg))
                                 }
                                 ProjectWorkspaceProgress::End(workspaces) => {
-                                    self.fetch_workspaces_completed();
-                                    self.switch_workspaces(workspaces, None);
+                                    self.fetch_workspaces_completed(workspaces);
+
+                                    let old = Arc::clone(&self.workspaces);
+                                    self.switch_workspaces();
+                                    let workspaces_updated = !Arc::ptr_eq(&old, &self.workspaces);
+
+                                    if self.config.run_build_scripts() && workspaces_updated {
+                                        let mut collector =
+                                            BuildDataCollector::new(self.config.wrap_rustc());
+                                        for ws in self.workspaces.iter() {
+                                            ws.collect_build_data_configs(&mut collector);
+                                        }
+                                        self.fetch_build_data_request(collector)
+                                    }
+
                                     (Progress::End, None)
                                 }
                             };
-                            self.report_progress("fetching", state, msg, None);
+
+                            self.report_progress("Fetching", state, msg, None);
                         }
                         Task::FetchBuildData(progress) => {
                             let (state, msg) = match progress {
@@ -240,19 +256,21 @@ impl GlobalState {
                                 BuildDataProgress::Report(msg) => {
                                     (Some(Progress::Report), Some(msg))
                                 }
-                                BuildDataProgress::End(collector) => {
-                                    self.fetch_build_data_completed();
-                                    let workspaces =
-                                        (*self.workspaces).clone().into_iter().map(Ok).collect();
-                                    self.switch_workspaces(workspaces, Some(collector));
+                                BuildDataProgress::End(build_data_result) => {
+                                    self.fetch_build_data_completed(build_data_result);
+
+                                    self.switch_workspaces();
+
                                     (Some(Progress::End), None)
                                 }
                             };
+
                             if let Some(state) = state {
-                                self.report_progress("loading", state, msg, None);
+                                self.report_progress("Loading", state, msg, None);
                             }
                         }
                     }
+
                     // Coalesce multiple task events into one loop turn
                     task = match self.task_pool.receiver.try_recv() {
                         Ok(task) => task,
@@ -280,7 +298,7 @@ impl GlobalState {
                         }
                     };
 
-                    self.report_progress("indexing", state, message, Some(fraction));
+                    self.report_progress("Indexing", state, message, Some(fraction));
                 }
             }
             Event::Vfs(mut task) => {
@@ -298,30 +316,25 @@ impl GlobalState {
                         }
                         vfs::loader::Message::Progress { n_total, n_done, config_version } => {
                             always!(config_version <= self.vfs_config_version);
-                            if n_total == 0 {
-                                new_status = Status::Invalid;
+
+                            self.vfs_progress_config_version = config_version;
+                            self.vfs_progress_n_total = n_total;
+                            self.vfs_progress_n_done = n_done;
+
+                            let state = if n_done == 0 {
+                                Progress::Begin
+                            } else if n_done < n_total {
+                                Progress::Report
                             } else {
-                                let state = if n_done == 0 {
-                                    new_status = Status::Loading;
-                                    Progress::Begin
-                                } else if n_done < n_total {
-                                    Progress::Report
-                                } else {
-                                    assert_eq!(n_done, n_total);
-                                    new_status = Status::Ready {
-                                        partial: self.config.run_build_scripts()
-                                            && self.workspace_build_data.is_none()
-                                            || config_version < self.vfs_config_version,
-                                    };
-                                    Progress::End
-                                };
-                                self.report_progress(
-                                    "roots scanned",
-                                    state,
-                                    Some(format!("{}/{}", n_done, n_total)),
-                                    Some(Progress::fraction(n_done, n_total)),
-                                )
-                            }
+                                assert_eq!(n_done, n_total);
+                                Progress::End
+                            };
+                            self.report_progress(
+                                "Roots Scanned",
+                                state,
+                                Some(format!("{}/{}", n_done, n_total)),
+                                Some(Progress::fraction(n_done, n_total)),
+                            )
                         }
                     }
                     // Coalesce many VFS event into a single loop turn
@@ -397,18 +410,14 @@ impl GlobalState {
         }
 
         let state_changed = self.process_changes();
-        let prev_status = self.status;
-        if prev_status != new_status {
-            self.transition(new_status);
-        }
-        let is_ready = matches!(self.status, Status::Ready { .. });
-        if prev_status == Status::Loading && is_ready {
+
+        if self.is_quiescent() && !was_quiescent {
             for flycheck in &self.flycheck {
                 flycheck.update();
             }
         }
 
-        if is_ready && (state_changed || prev_status == Status::Loading) {
+        if self.is_quiescent() && (!was_quiescent || state_changed) {
             self.update_file_notifications_on_threadpool();
 
             // Refresh semantic tokens if the client supports it.
@@ -437,9 +446,13 @@ impl GlobalState {
             }
         }
 
-        self.fetch_workspaces_if_needed();
+        if self.config.cargo_autoreload() {
+            self.fetch_workspaces_if_needed();
+        }
         self.fetch_build_data_if_needed();
 
+        self.report_new_status_if_needed();
+
         let loop_duration = loop_start.elapsed();
         if loop_duration > Duration::from_millis(100) {
             log::warn!("overly long loop turn: {:?}", loop_duration);
@@ -466,18 +479,23 @@ impl GlobalState {
             return Ok(());
         }
 
-        if self.status == Status::Loading && req.method != "shutdown" {
+        // Avoid flashing a bunch of unresolved references during initial load.
+        if self.workspaces.is_empty() && !self.is_quiescent() {
             self.respond(lsp_server::Response::new_err(
                 req.id,
                 // FIXME: i32 should impl From<ErrorCode> (from() guarantees lossless conversion)
                 lsp_server::ErrorCode::ContentModified as i32,
-                "Rust Analyzer is still loading...".to_owned(),
+                "waiting for cargo metadata or cargo check".to_owned(),
             ));
             return Ok(());
         }
 
         RequestDispatcher { req: Some(req), global_state: self }
-            .on_sync::<lsp_ext::ReloadWorkspace>(|s, ()| Ok(s.fetch_workspaces_request()))?
+            .on_sync::<lsp_ext::ReloadWorkspace>(|s, ()| {
+                s.fetch_workspaces_request();
+                s.fetch_workspaces_if_needed();
+                Ok(())
+            })?
             .on_sync::<lsp_ext::JoinLines>(|s, p| handlers::handle_join_lines(s.snapshot(), p))?
             .on_sync::<lsp_ext::OnEnter>(|s, p| handlers::handle_on_enter(s.snapshot(), p))?
             .on_sync::<lsp_types::request::Shutdown>(|s, ()| {
diff --git a/crates/rust-analyzer/src/op_queue.rs b/crates/rust-analyzer/src/op_queue.rs
index 761b9ad39..1d612a933 100644
--- a/crates/rust-analyzer/src/op_queue.rs
+++ b/crates/rust-analyzer/src/op_queue.rs
@@ -1,29 +1,43 @@
-//! Bookkeeping to make sure only one long-running operation is executed.
+//! Bookkeeping to make sure only one long-running operation is being executed
+//! at a time.
 
-pub(crate) struct OpQueue<D> {
-    op_scheduled: Option<D>,
+pub(crate) struct OpQueue<Args, Output> {
+    op_requested: Option<Args>,
     op_in_progress: bool,
+    last_op_result: Output,
 }
 
-impl<D> Default for OpQueue<D> {
+impl<Args, Output: Default> Default for OpQueue<Args, Output> {
     fn default() -> Self {
-        Self { op_scheduled: None, op_in_progress: false }
+        Self { op_requested: None, op_in_progress: false, last_op_result: Default::default() }
     }
 }
 
-impl<D> OpQueue<D> {
-    pub(crate) fn request_op(&mut self, data: D) {
-        self.op_scheduled = Some(data);
+impl<Args, Output> OpQueue<Args, Output> {
+    pub(crate) fn request_op(&mut self, data: Args) {
+        self.op_requested = Some(data);
     }
-    pub(crate) fn should_start_op(&mut self) -> Option<D> {
+    pub(crate) fn should_start_op(&mut self) -> Option<Args> {
         if self.op_in_progress {
             return None;
         }
-        self.op_in_progress = self.op_scheduled.is_some();
-        self.op_scheduled.take()
+        self.op_in_progress = self.op_requested.is_some();
+        self.op_requested.take()
     }
-    pub(crate) fn op_completed(&mut self) {
+    pub(crate) fn op_completed(&mut self, result: Output) {
         assert!(self.op_in_progress);
         self.op_in_progress = false;
+        self.last_op_result = result;
+    }
+
+    #[allow(unused)]
+    pub(crate) fn last_op_result(&self) -> &Output {
+        &self.last_op_result
+    }
+    pub(crate) fn op_in_progress(&self) -> bool {
+        self.op_in_progress
+    }
+    pub(crate) fn op_requested(&self) -> bool {
+        self.op_requested.is_some()
     }
 }
diff --git a/crates/rust-analyzer/src/reload.rs b/crates/rust-analyzer/src/reload.rs
index 76fdbcddd..e51532d88 100644
--- a/crates/rust-analyzer/src/reload.rs
+++ b/crates/rust-analyzer/src/reload.rs
@@ -9,11 +9,10 @@ use vfs::{file_set::FileSetConfig, AbsPath, AbsPathBuf, ChangeKind};
 
 use crate::{
     config::{Config, FilesWatcher, LinkedProject},
-    global_state::{GlobalState, Status},
+    global_state::GlobalState,
     lsp_ext,
     main_loop::Task,
 };
-use lsp_ext::StatusParams;
 
 #[derive(Debug)]
 pub(crate) enum ProjectWorkspaceProgress {
@@ -30,6 +29,13 @@ pub(crate) enum BuildDataProgress {
 }
 
 impl GlobalState {
+    pub(crate) fn is_quiescent(&self) -> bool {
+        !(self.fetch_workspaces_queue.op_in_progress()
+            || self.fetch_build_data_queue.op_in_progress()
+            || self.vfs_progress_config_version < self.vfs_config_version
+            || self.vfs_progress_n_done < self.vfs_progress_n_total)
+    }
+
     pub(crate) fn update_configuration(&mut self, config: Config) {
         let _p = profile::span("GlobalState::update_configuration");
         let old_config = mem::replace(&mut self.config, Arc::new(config));
@@ -46,25 +52,17 @@ impl GlobalState {
         if !changes.iter().any(|(path, kind)| is_interesting(path, *kind)) {
             return;
         }
-        match self.status {
-            Status::Loading | Status::NeedsReload => return,
-            Status::Ready { .. } | Status::Invalid => (),
-        }
         log::info!(
-            "Reloading workspace because of the following changes: {}",
+            "Requesting workspace reload because of the following changes: {}",
             itertools::join(
                 changes
                     .iter()
                     .filter(|(path, kind)| is_interesting(path, *kind))
-                    .map(|(path, kind)| format!("{}/{:?}", path.display(), kind)),
+                    .map(|(path, kind)| format!("{}: {:?}", path.display(), kind)),
                 ", "
             )
         );
-        if self.config.cargo_autoreload() {
-            self.fetch_workspaces_request();
-        } else {
-            self.transition(Status::NeedsReload);
-        }
+        self.fetch_workspaces_request();
 
         fn is_interesting(path: &AbsPath, change_kind: ChangeKind) -> bool {
             const IMPLICIT_TARGET_FILES: &[&str] = &["build.rs", "src/main.rs", "src/lib.rs"];
@@ -101,46 +99,41 @@ impl GlobalState {
             false
         }
     }
-    pub(crate) fn transition(&mut self, new_status: Status) {
-        self.status = new_status;
-        if self.config.status_notification() {
-            let lsp_status = match new_status {
-                Status::Loading => lsp_ext::Status::Loading,
-                Status::Ready { partial: true } => lsp_ext::Status::ReadyPartial,
-                Status::Ready { partial: false } => lsp_ext::Status::Ready,
-                Status::Invalid => lsp_ext::Status::Invalid,
-                Status::NeedsReload => lsp_ext::Status::NeedsReload,
-            };
-            self.send_notification::<lsp_ext::StatusNotification>(StatusParams {
-                status: lsp_status,
-            });
+    pub(crate) fn report_new_status_if_needed(&mut self) {
+        let mut status = lsp_ext::ServerStatusParams {
+            health: lsp_ext::Health::Ok,
+            quiescent: self.is_quiescent(),
+            message: None,
+        };
+
+        if let Some(error) = self.build_data_error() {
+            status.health = lsp_ext::Health::Warning;
+            status.message = Some(error)
+        }
+        if !self.config.cargo_autoreload()
+            && self.is_quiescent()
+            && self.fetch_workspaces_queue.op_requested()
+        {
+            status.health = lsp_ext::Health::Warning;
+            status.message = Some("Workspace reload required".to_string())
         }
-    }
 
-    pub(crate) fn fetch_build_data_request(&mut self, build_data_collector: BuildDataCollector) {
-        self.fetch_build_data_queue.request_op(build_data_collector);
-    }
+        if let Some(error) = self.fetch_workspace_error() {
+            status.health = lsp_ext::Health::Error;
+            status.message = Some(error)
+        }
 
-    pub(crate) fn fetch_build_data_if_needed(&mut self) {
-        let mut build_data_collector = match self.fetch_build_data_queue.should_start_op() {
-            Some(it) => it,
-            None => return,
-        };
-        self.task_pool.handle.spawn_with_sender(move |sender| {
-            sender.send(Task::FetchBuildData(BuildDataProgress::Begin)).unwrap();
+        if self.last_reported_status.as_ref() != Some(&status) {
+            self.last_reported_status = Some(status.clone());
 
-            let progress = {
-                let sender = sender.clone();
-                move |msg| {
-                    sender.send(Task::FetchBuildData(BuildDataProgress::Report(msg))).unwrap()
-                }
-            };
-            let res = build_data_collector.collect(&progress);
-            sender.send(Task::FetchBuildData(BuildDataProgress::End(res))).unwrap();
-        });
-    }
-    pub(crate) fn fetch_build_data_completed(&mut self) {
-        self.fetch_build_data_queue.op_completed()
+            if let (lsp_ext::Health::Error, Some(message)) = (status.health, &status.message) {
+                self.show_message(lsp_types::MessageType::Error, message.clone());
+            }
+
+            if self.config.server_status_notification() {
+                self.send_notification::<lsp_ext::ServerStatusNotification>(status);
+            }
+        }
     }
 
     pub(crate) fn fetch_workspaces_request(&mut self) {
@@ -194,54 +187,69 @@ impl GlobalState {
             }
         });
     }
-    pub(crate) fn fetch_workspaces_completed(&mut self) {
-        self.fetch_workspaces_queue.op_completed()
+    pub(crate) fn fetch_workspaces_completed(
+        &mut self,
+        workspaces: Vec<anyhow::Result<ProjectWorkspace>>,
+    ) {
+        self.fetch_workspaces_queue.op_completed(workspaces)
+    }
+
+    pub(crate) fn fetch_build_data_request(&mut self, build_data_collector: BuildDataCollector) {
+        self.fetch_build_data_queue.request_op(build_data_collector);
     }
+    pub(crate) fn fetch_build_data_if_needed(&mut self) {
+        let mut build_data_collector = match self.fetch_build_data_queue.should_start_op() {
+            Some(it) => it,
+            None => return,
+        };
+        self.task_pool.handle.spawn_with_sender(move |sender| {
+            sender.send(Task::FetchBuildData(BuildDataProgress::Begin)).unwrap();
 
-    pub(crate) fn switch_workspaces(
+            let progress = {
+                let sender = sender.clone();
+                move |msg| {
+                    sender.send(Task::FetchBuildData(BuildDataProgress::Report(msg))).unwrap()
+                }
+            };
+            let res = build_data_collector.collect(&progress);
+            sender.send(Task::FetchBuildData(BuildDataProgress::End(res))).unwrap();
+        });
+    }
+    pub(crate) fn fetch_build_data_completed(
         &mut self,
-        workspaces: Vec<anyhow::Result<ProjectWorkspace>>,
-        workspace_build_data: Option<anyhow::Result<BuildDataResult>>,
+        build_data: anyhow::Result<BuildDataResult>,
     ) {
-        let _p = profile::span("GlobalState::switch_workspaces");
-        log::info!("will switch workspaces: {:?}", workspaces);
+        self.fetch_build_data_queue.op_completed(Some(build_data))
+    }
 
-        let mut has_errors = false;
-        let workspaces = workspaces
-            .into_iter()
-            .filter_map(|res| {
-                res.map_err(|err| {
-                    has_errors = true;
-                    log::error!("failed to load workspace: {:#}", err);
-                    if self.workspaces.is_empty() {
-                        self.show_message(
-                            lsp_types::MessageType::Error,
-                            format!("rust-analyzer failed to load workspace: {:#}", err),
-                        );
-                    }
-                })
-                .ok()
-            })
-            .collect::<Vec<_>>();
+    pub(crate) fn switch_workspaces(&mut self) {
+        let _p = profile::span("GlobalState::switch_workspaces");
+        log::info!("will switch workspaces");
 
-        let workspace_build_data = match workspace_build_data {
-            Some(Ok(it)) => Some(it),
-            Some(Err(err)) => {
-                log::error!("failed to fetch build data: {:#}", err);
-                self.show_message(
-                    lsp_types::MessageType::Error,
-                    format!("rust-analyzer failed to fetch build data: {:#}", err),
-                );
+        if let Some(error_message) = self.fetch_workspace_error() {
+            log::error!("failed to switch workspaces: {}", error_message);
+            if !self.workspaces.is_empty() {
                 return;
             }
-            None => None,
-        };
+        }
 
-        if *self.workspaces == workspaces && self.workspace_build_data == workspace_build_data {
-            return;
+        if let Some(error_message) = self.build_data_error() {
+            log::error!("failed to switch build data: {}", error_message);
         }
 
-        if !self.workspaces.is_empty() && has_errors {
+        let workspaces = self
+            .fetch_workspaces_queue
+            .last_op_result()
+            .iter()
+            .filter_map(|res| res.as_ref().ok().cloned())
+            .collect::<Vec<_>>();
+
+        let workspace_build_data = match self.fetch_build_data_queue.last_op_result() {
+            Some(Ok(it)) => Some(it.clone()),
+            None | Some(Err(_)) => None,
+        };
+
+        if *self.workspaces == workspaces && self.workspace_build_data == workspace_build_data {
             return;
         }
 
@@ -337,14 +345,6 @@ impl GlobalState {
         };
         change.set_crate_graph(crate_graph);
 
-        if self.config.run_build_scripts() && workspace_build_data.is_none() {
-            let mut collector = BuildDataCollector::default();
-            for ws in &workspaces {
-                ws.collect_build_data_configs(&mut collector);
-            }
-            self.fetch_build_data_request(collector)
-        }
-
         self.source_root_config = project_folders.source_root_config;
         self.workspaces = Arc::new(workspaces);
         self.workspace_build_data = workspace_build_data;
@@ -355,6 +355,32 @@ impl GlobalState {
         log::info!("did switch workspaces");
     }
 
+    fn fetch_workspace_error(&self) -> Option<String> {
+        let mut buf = String::new();
+
+        for ws in self.fetch_workspaces_queue.last_op_result() {
+            if let Err(err) = ws {
+                stdx::format_to!(buf, "rust-analyzer failed to load workspace: {:#}\n", err);
+            }
+        }
+
+        if buf.is_empty() {
+            return None;
+        }
+
+        Some(buf)
+    }
+
+    fn build_data_error(&self) -> Option<String> {
+        match self.fetch_build_data_queue.last_op_result() {
+            Some(Err(err)) => {
+                Some(format!("rust-analyzer failed to fetch build data: {:#}\n", err))
+            }
+            Some(Ok(data)) => data.error(),
+            None => None,
+        }
+    }
+
     fn reload_flycheck(&mut self) {
         let _p = profile::span("GlobalState::reload_flycheck");
         let config = match self.config.flycheck() {
diff --git a/crates/rust-analyzer/src/semantic_tokens.rs b/crates/rust-analyzer/src/semantic_tokens.rs
index a3c5e9ccf..adc059817 100644
--- a/crates/rust-analyzer/src/semantic_tokens.rs
+++ b/crates/rust-analyzer/src/semantic_tokens.rs
@@ -39,7 +39,9 @@ macro_rules! define_semantic_token_types {
 
 define_semantic_token_types![
     (ANGLE, "angle"),
+    (ARITHMETIC, "arithmetic"),
     (ATTRIBUTE, "attribute"),
+    (BITWISE, "bitwise"),
     (BOOLEAN, "boolean"),
     (BRACE, "brace"),
     (BRACKET, "bracket"),
@@ -47,6 +49,7 @@ define_semantic_token_types![
     (CHAR_LITERAL, "characterLiteral"),
     (COLON, "colon"),
     (COMMA, "comma"),
+    (COMPARISION, "comparision"),
     (CONST_PARAMETER, "constParameter"),
     (DOT, "dot"),
     (ESCAPE_SEQUENCE, "escapeSequence"),
@@ -54,6 +57,8 @@ define_semantic_token_types![
     (GENERIC, "generic"),
     (LABEL, "label"),
     (LIFETIME, "lifetime"),
+    (LOGICAL, "logical"),
+    (OPERATOR, "operator"),
     (PARENTHESIS, "parenthesis"),
     (PUNCTUATION, "punctuation"),
     (SELF_KEYWORD, "selfKeyword"),
@@ -88,6 +93,7 @@ define_semantic_token_modifiers![
     (CONSUMING, "consuming"),
     (UNSAFE, "unsafe"),
     (ATTRIBUTE_MODIFIER, "attribute"),
+    (TRAIT_MODIFIER, "trait"),
     (CALLABLE, "callable"),
     (INTRA_DOC_LINK, "intraDocLink"),
 ];
diff --git a/crates/rust-analyzer/src/to_proto.rs b/crates/rust-analyzer/src/to_proto.rs
index 530c8a5a4..1a1f65f3b 100644
--- a/crates/rust-analyzer/src/to_proto.rs
+++ b/crates/rust-analyzer/src/to_proto.rs
@@ -7,9 +7,9 @@ use std::{
 use ide::{
     Annotation, AnnotationKind, Assist, AssistKind, CallInfo, CompletionItem, CompletionItemKind,
     CompletionRelevance, Documentation, FileId, FileRange, FileSystemEdit, Fold, FoldKind,
-    Highlight, HlMod, HlPunct, HlRange, HlTag, Indel, InlayHint, InlayKind, InsertTextFormat,
-    Markup, NavigationTarget, ReferenceAccess, RenameError, Runnable, Severity, SourceChange,
-    StructureNodeKind, SymbolKind, TextEdit, TextRange, TextSize,
+    Highlight, HlMod, HlOperator, HlPunct, HlRange, HlTag, Indel, InlayHint, InlayKind,
+    InsertTextFormat, Markup, NavigationTarget, ReferenceAccess, RenameError, Runnable, Severity,
+    SourceChange, StructureNodeKind, SymbolKind, TextEdit, TextRange, TextSize,
 };
 use itertools::Itertools;
 use serde_json::to_value;
@@ -145,6 +145,23 @@ pub(crate) fn text_edit(line_index: &LineIndex, indel: Indel) -> lsp_types::Text
     lsp_types::TextEdit { range, new_text }
 }
 
+pub(crate) fn completion_text_edit(
+    line_index: &LineIndex,
+    insert_replace_support: Option<lsp_types::Position>,
+    indel: Indel,
+) -> lsp_types::CompletionTextEdit {
+    let text_edit = text_edit(line_index, indel);
+    match insert_replace_support {
+        Some(cursor_pos) => lsp_types::InsertReplaceEdit {
+            new_text: text_edit.new_text,
+            insert: lsp_types::Range { start: text_edit.range.start, end: cursor_pos },
+            replace: text_edit.range,
+        }
+        .into(),
+        None => text_edit.into(),
+    }
+}
+
 pub(crate) fn snippet_text_edit(
     line_index: &LineIndex,
     is_snippet: bool,
@@ -179,6 +196,7 @@ pub(crate) fn snippet_text_edit_vec(
 }
 
 pub(crate) fn completion_item(
+    insert_replace_support: Option<lsp_types::Position>,
     line_index: &LineIndex,
     item: CompletionItem,
 ) -> Vec<lsp_types::CompletionItem> {
@@ -190,7 +208,7 @@ pub(crate) fn completion_item(
     for indel in item.text_edit().iter() {
         if indel.delete.contains_range(source_range) {
             text_edit = Some(if indel.delete == source_range {
-                self::text_edit(line_index, indel.clone())
+                self::completion_text_edit(line_index, insert_replace_support, indel.clone())
             } else {
                 assert!(source_range.end() == indel.delete.end());
                 let range1 = TextRange::new(indel.delete.start(), source_range.start());
@@ -198,7 +216,7 @@ pub(crate) fn completion_item(
                 let indel1 = Indel::replace(range1, String::new());
                 let indel2 = Indel::replace(range2, indel.insert.clone());
                 additional_text_edits.push(self::text_edit(line_index, indel1));
-                self::text_edit(line_index, indel2)
+                self::completion_text_edit(line_index, insert_replace_support, indel2)
             })
         } else {
             assert!(source_range.intersect(indel.delete).is_none());
@@ -213,7 +231,7 @@ pub(crate) fn completion_item(
         detail: item.detail().map(|it| it.to_string()),
         filter_text: Some(item.lookup().to_string()),
         kind: item.kind().map(completion_item_kind),
-        text_edit: Some(text_edit.into()),
+        text_edit: Some(text_edit),
         additional_text_edits: Some(additional_text_edits),
         documentation: item.documentation().map(documentation),
         deprecated: Some(item.deprecated()),
@@ -445,7 +463,13 @@ fn semantic_token_type_and_modifiers(
         HlTag::FormatSpecifier => semantic_tokens::FORMAT_SPECIFIER,
         HlTag::Keyword => lsp_types::SemanticTokenType::KEYWORD,
         HlTag::None => semantic_tokens::GENERIC,
-        HlTag::Operator => lsp_types::SemanticTokenType::OPERATOR,
+        HlTag::Operator(op) => match op {
+            HlOperator::Bitwise => semantic_tokens::BITWISE,
+            HlOperator::Arithmetic => semantic_tokens::ARITHMETIC,
+            HlOperator::Logical => semantic_tokens::LOGICAL,
+            HlOperator::Comparision => semantic_tokens::COMPARISION,
+            HlOperator::Other => semantic_tokens::OPERATOR,
+        },
         HlTag::StringLiteral => lsp_types::SemanticTokenType::STRING,
         HlTag::UnresolvedReference => semantic_tokens::UNRESOLVED_REFERENCE,
         HlTag::Punctuation(punct) => match punct {
@@ -474,6 +498,7 @@ fn semantic_token_type_and_modifiers(
             HlMod::Callable => semantic_tokens::CALLABLE,
             HlMod::Static => lsp_types::SemanticTokenModifier::STATIC,
             HlMod::IntraDocLink => semantic_tokens::INTRA_DOC_LINK,
+            HlMod::Trait => semantic_tokens::TRAIT_MODIFIER,
             HlMod::Associated => continue,
         };
         mods |= modifier;
@@ -492,7 +517,12 @@ pub(crate) fn folding_range(
         FoldKind::Comment => Some(lsp_types::FoldingRangeKind::Comment),
         FoldKind::Imports => Some(lsp_types::FoldingRangeKind::Imports),
         FoldKind::Region => Some(lsp_types::FoldingRangeKind::Region),
-        FoldKind::Mods | FoldKind::Block | FoldKind::ArgList => None,
+        FoldKind::Mods
+        | FoldKind::Block
+        | FoldKind::ArgList
+        | FoldKind::Consts
+        | FoldKind::Statics
+        | FoldKind::Array => None,
     };
 
     let range = range(line_index, fold.range);
@@ -658,18 +688,6 @@ pub(crate) fn goto_definition_response(
     }
 }
 
-pub(crate) fn text_document_edit(
-    snap: &GlobalStateSnapshot,
-    file_id: FileId,
-    edit: TextEdit,
-) -> Result<lsp_types::TextDocumentEdit> {
-    let text_document = optional_versioned_text_document_identifier(snap, file_id);
-    let line_index = snap.file_line_index(file_id)?;
-    let edits =
-        edit.into_iter().map(|it| lsp_types::OneOf::Left(text_edit(&line_index, it))).collect();
-    Ok(lsp_types::TextDocumentEdit { text_document, edits })
-}
-
 pub(crate) fn snippet_text_document_edit(
     snap: &GlobalStateSnapshot,
     is_snippet: bool,
@@ -819,40 +837,31 @@ pub(crate) fn code_action_kind(kind: AssistKind) -> lsp_types::CodeActionKind {
     }
 }
 
-pub(crate) fn unresolved_code_action(
+pub(crate) fn code_action(
     snap: &GlobalStateSnapshot,
-    code_action_params: lsp_types::CodeActionParams,
     assist: Assist,
-    index: usize,
+    resolve_data: Option<(usize, lsp_types::CodeActionParams)>,
 ) -> Result<lsp_ext::CodeAction> {
-    assert!(assist.source_change.is_none());
-    let res = lsp_ext::CodeAction {
+    let mut res = lsp_ext::CodeAction {
         title: assist.label.to_string(),
         group: assist.group.filter(|_| snap.config.code_action_group()).map(|gr| gr.0),
         kind: Some(code_action_kind(assist.id.1)),
         edit: None,
         is_preferred: None,
-        data: Some(lsp_ext::CodeActionData {
-            id: format!("{}:{}", assist.id.0, index.to_string()),
-            code_action_params,
-        }),
-    };
-    Ok(res)
-}
-
-pub(crate) fn resolved_code_action(
-    snap: &GlobalStateSnapshot,
-    assist: Assist,
-) -> Result<lsp_ext::CodeAction> {
-    let change = assist.source_change.unwrap();
-    let res = lsp_ext::CodeAction {
-        edit: Some(snippet_workspace_edit(snap, change)?),
-        title: assist.label.to_string(),
-        group: assist.group.filter(|_| snap.config.code_action_group()).map(|gr| gr.0),
-        kind: Some(code_action_kind(assist.id.1)),
-        is_preferred: None,
         data: None,
     };
+    match (assist.source_change, resolve_data) {
+        (Some(it), _) => res.edit = Some(snippet_workspace_edit(snap, it)?),
+        (None, Some((index, code_action_params))) => {
+            res.data = Some(lsp_ext::CodeActionData {
+                id: format!("{}:{}", assist.id.0, index.to_string()),
+                code_action_params,
+            });
+        }
+        (None, None) => {
+            stdx::never!("assist should always be resolved if client can't do lazy resolving")
+        }
+    };
     Ok(res)
 }
 
@@ -1130,7 +1139,7 @@ mod tests {
             .unwrap()
             .into_iter()
             .filter(|c| c.label().ends_with("arg"))
-            .map(|c| completion_item(&line_index, c))
+            .map(|c| completion_item(None, &line_index, c))
             .flat_map(|comps| comps.into_iter().map(|c| (c.label, c.sort_text)))
             .collect();
         expect_test::expect![[r#"
diff --git a/crates/rust-analyzer/tests/rust-analyzer/main.rs b/crates/rust-analyzer/tests/rust-analyzer/main.rs
index 4442cbff6..52a2674d5 100644
--- a/crates/rust-analyzer/tests/rust-analyzer/main.rs
+++ b/crates/rust-analyzer/tests/rust-analyzer/main.rs
@@ -340,7 +340,6 @@ fn main() {}
                 }
               ]
             },
-            "isPreferred": false,
             "kind": "quickfix",
             "title": "Create module"
         }]),
@@ -411,7 +410,6 @@ fn main() {{}}
                 }
               ]
             },
-            "isPreferred": false,
             "kind": "quickfix",
             "title": "Create module"
         }]),
@@ -527,7 +525,7 @@ version = \"0.0.0\"
 #[test]
 fn out_dirs_check() {
     if skip_slow_tests() {
-        return;
+        // return;
     }
 
     let server = Project::with_fixture(
diff --git a/crates/rust-analyzer/tests/rust-analyzer/support.rs b/crates/rust-analyzer/tests/rust-analyzer/support.rs
index 95bf26f01..75e677762 100644
--- a/crates/rust-analyzer/tests/rust-analyzer/support.rs
+++ b/crates/rust-analyzer/tests/rust-analyzer/support.rs
@@ -32,8 +32,12 @@ impl<'a> Project<'a> {
             tmp_dir: None,
             roots: vec![],
             config: serde_json::json!({
-                // Loading standard library is costly, let's ignore it by default
-                "cargo": { "noSysroot": true }
+                "cargo": {
+                    // Loading standard library is costly, let's ignore it by default
+                    "noSysroot": true,
+                    // Can't use test binary as rustc wrapper.
+                    "useRustcWrapperForBuildScripts": false,
+                }
             }),
         }
     }
@@ -49,7 +53,17 @@ impl<'a> Project<'a> {
     }
 
     pub(crate) fn with_config(mut self, config: serde_json::Value) -> Project<'a> {
-        self.config = config;
+        fn merge(dst: &mut serde_json::Value, src: serde_json::Value) {
+            match (dst, src) {
+                (Value::Object(dst), Value::Object(src)) => {
+                    for (k, v) in src {
+                        merge(dst.entry(k).or_insert(v.clone()), v)
+                    }
+                }
+                (dst, src) => *dst = src,
+            }
+        }
+        merge(&mut self.config, config);
         self
     }
 
@@ -103,7 +117,7 @@ impl<'a> Project<'a> {
                     ..Default::default()
                 }),
                 experimental: Some(json!({
-                    "statusNotification": true,
+                    "serverStatusNotification": true,
                 })),
                 ..Default::default()
             },
@@ -154,6 +168,7 @@ impl Server {
         self.send_notification(r)
     }
 
+    #[track_caller]
     pub(crate) fn request<R>(&self, params: R::Params, expected_resp: Value)
     where
         R: lsp_types::request::Request,
@@ -213,13 +228,12 @@ impl Server {
     }
     pub(crate) fn wait_until_workspace_is_loaded(self) -> Server {
         self.wait_for_message_cond(1, &|msg: &Message| match msg {
-            Message::Notification(n) if n.method == "rust-analyzer/status" => {
+            Message::Notification(n) if n.method == "experimental/serverStatus" => {
                 let status = n
                     .clone()
-                    .extract::<lsp_ext::StatusParams>("rust-analyzer/status")
-                    .unwrap()
-                    .status;
-                matches!(status, lsp_ext::Status::Ready)
+                    .extract::<lsp_ext::ServerStatusParams>("experimental/serverStatus")
+                    .unwrap();
+                status.quiescent
             }
             _ => false,
         })
diff --git a/crates/stdx/src/lib.rs b/crates/stdx/src/lib.rs
index d26be4853..b0a18d58d 100644
--- a/crates/stdx/src/lib.rs
+++ b/crates/stdx/src/lib.rs
@@ -178,6 +178,7 @@ where
     start..start + len
 }
 
+#[repr(transparent)]
 pub struct JodChild(pub process::Child);
 
 impl ops::Deref for JodChild {
@@ -200,6 +201,13 @@ impl Drop for JodChild {
     }
 }
 
+impl JodChild {
+    pub fn into_inner(self) -> process::Child {
+        // SAFETY: repr transparent
+        unsafe { std::mem::transmute::<JodChild, process::Child>(self) }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/crates/syntax/Cargo.toml b/crates/syntax/Cargo.toml
index 9f01acc26..a8c1a8075 100644
--- a/crates/syntax/Cargo.toml
+++ b/crates/syntax/Cargo.toml
@@ -13,10 +13,10 @@ doctest = false
 [dependencies]
 cov-mark = { version = "1.1", features = ["thread-local"] }
 itertools = "0.10.0"
-rowan = "0.13.0-pre.3"
-rustc_lexer = { version = "710.0.0", package = "rustc-ap-rustc_lexer" }
+rowan = "=0.13.0-pre.3"
+rustc_lexer = { version = "714.0.0", package = "rustc-ap-rustc_lexer" }
 rustc-hash = "1.1.0"
-arrayvec = "0.6"
+arrayvec = "0.7"
 once_cell = "1.3.1"
 indexmap = "1.4.0"
 smol_str = { version = "0.1.15", features = ["serde"] }
diff --git a/crates/syntax/src/ast/make.rs b/crates/syntax/src/ast/make.rs
index c6a7b99b7..94d4f2cf0 100644
--- a/crates/syntax/src/ast/make.rs
+++ b/crates/syntax/src/ast/make.rs
@@ -29,9 +29,13 @@ pub fn ty(text: &str) -> ast::Type {
 pub fn ty_unit() -> ast::Type {
     ty("()")
 }
-// FIXME: handle types of length == 1
 pub fn ty_tuple(types: impl IntoIterator<Item = ast::Type>) -> ast::Type {
-    let contents = types.into_iter().join(", ");
+    let mut count: usize = 0;
+    let mut contents = types.into_iter().inspect(|_| count += 1).join(", ");
+    if count == 1 {
+        contents.push(',');
+    }
+
     ty(&format!("({})", contents))
 }
 // FIXME: handle path to type
@@ -292,11 +296,13 @@ pub fn wildcard_pat() -> ast::WildcardPat {
 
 /// Creates a tuple of patterns from an iterator of patterns.
 ///
-/// Invariant: `pats` must be length > 1
-///
-/// FIXME handle `pats` length == 1
+/// Invariant: `pats` must be length > 0
 pub fn tuple_pat(pats: impl IntoIterator<Item = ast::Pat>) -> ast::TuplePat {
-    let pats_str = pats.into_iter().map(|p| p.to_string()).join(", ");
+    let mut count: usize = 0;
+    let mut pats_str = pats.into_iter().inspect(|_| count += 1).join(", ");
+    if count == 1 {
+        pats_str.push(',');
+    }
     return from_text(&format!("({})", pats_str));
 
     fn from_text(text: &str) -> ast::TuplePat {
diff --git a/crates/test_utils/src/assert_linear.rs b/crates/test_utils/src/assert_linear.rs
new file mode 100644
index 000000000..6ecc232e1
--- /dev/null
+++ b/crates/test_utils/src/assert_linear.rs
@@ -0,0 +1,112 @@
+//! Checks that a set of measurements looks like a linear function rather than
+//! like a quadratic function. Algorithm:
+//!
+//! 1. Linearly scale input to be in [0; 1)
+//! 2. Using linear regression, compute the best linear function approximating
+//!    the input.
+//! 3. Compute RMSE and  maximal absolute error.
+//! 4. Check that errors are within tolerances and that the constant term is not
+//!    too negative.
+//!
+//! Ideally, we should use a proper "model selection" to directly compare
+//! quadratic and linear models, but that sounds rather complicated:
+//!
+//!     https://stats.stackexchange.com/questions/21844/selecting-best-model-based-on-linear-quadratic-and-cubic-fit-of-data
+//!
+//! We might get false positives on a VM, but never false negatives. So, if the
+//! first round fails, we repeat the ordeal three more times and fail only if
+//! every time there's a fault.
+use stdx::format_to;
+
+#[derive(Default)]
+pub struct AssertLinear {
+    rounds: Vec<Round>,
+}
+
+#[derive(Default)]
+struct Round {
+    samples: Vec<(f64, f64)>,
+    plot: String,
+    linear: bool,
+}
+
+impl AssertLinear {
+    pub fn next_round(&mut self) -> bool {
+        if let Some(round) = self.rounds.last_mut() {
+            round.finish();
+        }
+        if self.rounds.iter().any(|it| it.linear) || self.rounds.len() == 4 {
+            return false;
+        }
+        self.rounds.push(Round::default());
+        true
+    }
+
+    pub fn sample(&mut self, x: f64, y: f64) {
+        self.rounds.last_mut().unwrap().samples.push((x, y))
+    }
+}
+
+impl Drop for AssertLinear {
+    fn drop(&mut self) {
+        assert!(!self.rounds.is_empty());
+        if self.rounds.iter().all(|it| !it.linear) {
+            for round in &self.rounds {
+                eprintln!("\n{}", round.plot);
+            }
+            panic!("Doesn't look linear!")
+        }
+    }
+}
+
+impl Round {
+    fn finish(&mut self) {
+        let (mut xs, mut ys): (Vec<_>, Vec<_>) = self.samples.iter().copied().unzip();
+        normalize(&mut xs);
+        normalize(&mut ys);
+        let xy = xs.iter().copied().zip(ys.iter().copied());
+
+        // Linear regression: finding a and b to fit y = a + b*x.
+
+        let mean_x = mean(&xs);
+        let mean_y = mean(&ys);
+
+        let b = {
+            let mut num = 0.0;
+            let mut denom = 0.0;
+            for (x, y) in xy.clone() {
+                num += (x - mean_x) * (y - mean_y);
+                denom += (x - mean_x).powi(2);
+            }
+            num / denom
+        };
+
+        let a = mean_y - b * mean_x;
+
+        self.plot = format!("y_pred = {:.3} + {:.3} * x\n\nx     y     y_pred\n", a, b);
+
+        let mut se = 0.0;
+        let mut max_error = 0.0f64;
+        for (x, y) in xy {
+            let y_pred = a + b * x;
+            se += (y - y_pred).powi(2);
+            max_error = max_error.max((y_pred - y).abs());
+
+            format_to!(self.plot, "{:.3} {:.3} {:.3}\n", x, y, y_pred);
+        }
+
+        let rmse = (se / xs.len() as f64).sqrt();
+        format_to!(self.plot, "\nrmse = {:.3} max error = {:.3}", rmse, max_error);
+
+        self.linear = rmse < 0.05 && max_error < 0.1 && a > -0.1;
+
+        fn normalize(xs: &mut Vec<f64>) {
+            let max = xs.iter().copied().max_by(|a, b| a.partial_cmp(b).unwrap()).unwrap();
+            xs.iter_mut().for_each(|it| *it /= max);
+        }
+
+        fn mean(xs: &[f64]) -> f64 {
+            xs.iter().copied().sum::<f64>() / (xs.len() as f64)
+        }
+    }
+}
diff --git a/crates/test_utils/src/bench_fixture.rs b/crates/test_utils/src/bench_fixture.rs
index 3a37c4473..979156263 100644
--- a/crates/test_utils/src/bench_fixture.rs
+++ b/crates/test_utils/src/bench_fixture.rs
@@ -8,7 +8,10 @@ use crate::project_root;
 
 pub fn big_struct() -> String {
     let n = 1_000;
+    big_struct_n(n)
+}
 
+pub fn big_struct_n(n: u32) -> String {
     let mut buf = "pub struct RegisterBlock {".to_string();
     for i in 0..n {
         format_to!(buf, "  /// Doc comment for {}.\n", i);
diff --git a/crates/test_utils/src/fixture.rs b/crates/test_utils/src/fixture.rs
index 6bc824e94..099baeca2 100644
--- a/crates/test_utils/src/fixture.rs
+++ b/crates/test_utils/src/fixture.rs
@@ -1,5 +1,65 @@
 //! Defines `Fixture` -- a convenient way to describe the initial state of
 //! rust-analyzer database from a single string.
+//!
+//! Fixtures are strings containing rust source code with optional metadata.
+//! A fixture without metadata is parsed into a single source file.
+//! Use this to test functionality local to one file.
+//!
+//! Simple Example:
+//! ```
+//! r#"
+//! fn main() {
+//!     println!("Hello World")
+//! }
+//! "#
+//! ```
+//!
+//! Metadata can be added to a fixture after a `//-` comment.
+//! The basic form is specifying filenames,
+//! which is also how to define multiple files in a single test fixture
+//!
+//! Example using two files in the same crate:
+//! ```
+//! "
+//! //- /main.rs
+//! mod foo;
+//! fn main() {
+//!     foo::bar();
+//! }
+//!
+//! //- /foo.rs
+//! pub fn bar() {}
+//! "
+//! ```
+//!
+//! Example using two crates with one file each, with one crate depending on the other:
+//! ```
+//! r#"
+//! //- /main.rs crate:a deps:b
+//! fn main() {
+//!     b::foo();
+//! }
+//! //- /lib.rs crate:b
+//! pub fn b() {
+//!     println!("Hello World")
+//! }
+//! "#
+//! ```
+//!
+//! Metadata allows specifying all settings and variables
+//! that are available in a real rust project:
+//! - crate names via `crate:cratename`
+//! - dependencies via `deps:dep1,dep2`
+//! - configuration settings via `cfg:dbg=false,opt_level=2`
+//! - environment variables via `env:PATH=/bin,RUST_LOG=debug`
+//!
+//! Example using all available metadata:
+//! ```
+//! "
+//! //- /lib.rs crate:foo deps:bar,baz cfg:foo=a,bar=b env:OUTDIR=path/to,OTHER=foo
+//! fn insert_source_code_here() {}
+//! "
+//! ```
 
 use rustc_hash::FxHashMap;
 use stdx::{lines_with_ends, split_once, trim_indent};
@@ -24,7 +84,7 @@ impl Fixture {
     ///  //- some meta
     ///  line 1
     ///  line 2
-    ///  // - other meta
+    ///  //- other meta
     ///  ```
     pub fn parse(ra_fixture: &str) -> Vec<Fixture> {
         let fixture = trim_indent(ra_fixture);
diff --git a/crates/test_utils/src/lib.rs b/crates/test_utils/src/lib.rs
index c5f859790..72466c957 100644
--- a/crates/test_utils/src/lib.rs
+++ b/crates/test_utils/src/lib.rs
@@ -8,6 +8,7 @@
 
 pub mod bench_fixture;
 mod fixture;
+mod assert_linear;
 
 use std::{
     convert::{TryFrom, TryInto},
@@ -22,7 +23,7 @@ use text_size::{TextRange, TextSize};
 pub use dissimilar::diff as __diff;
 pub use rustc_hash::FxHashMap;
 
-pub use crate::fixture::Fixture;
+pub use crate::{assert_linear::AssertLinear, fixture::Fixture};
 
 pub const CURSOR_MARKER: &str = "$0";
 pub const ESCAPED_CURSOR_MARKER: &str = "\\$0";
diff --git a/crates/vfs/Cargo.toml b/crates/vfs/Cargo.toml
index c318a68f7..894944b18 100644
--- a/crates/vfs/Cargo.toml
+++ b/crates/vfs/Cargo.toml
@@ -14,3 +14,4 @@ rustc-hash = "1.0"
 fst = "0.4"
 
 paths = { path = "../paths", version = "0.0.0" }
+indexmap = "1.6.2"
diff --git a/crates/vfs/src/path_interner.rs b/crates/vfs/src/path_interner.rs
index 2189e5e25..6e049f0d4 100644
--- a/crates/vfs/src/path_interner.rs
+++ b/crates/vfs/src/path_interner.rs
@@ -1,15 +1,22 @@
 //! Maps paths to compact integer ids. We don't care about clearings paths which
 //! no longer exist -- the assumption is total size of paths we ever look at is
 //! not too big.
-use rustc_hash::FxHashMap;
+use std::hash::BuildHasherDefault;
+
+use indexmap::IndexSet;
+use rustc_hash::FxHasher;
 
 use crate::{FileId, VfsPath};
 
 /// Structure to map between [`VfsPath`] and [`FileId`].
-#[derive(Default)]
 pub(crate) struct PathInterner {
-    map: FxHashMap<VfsPath, FileId>,
-    vec: Vec<VfsPath>,
+    map: IndexSet<VfsPath, BuildHasherDefault<FxHasher>>,
+}
+
+impl Default for PathInterner {
+    fn default() -> Self {
+        Self { map: IndexSet::default() }
+    }
 }
 
 impl PathInterner {
@@ -17,7 +24,7 @@ impl PathInterner {
     ///
     /// If `path` does not exists in `self`, returns [`None`].
     pub(crate) fn get(&self, path: &VfsPath) -> Option<FileId> {
-        self.map.get(path).copied()
+        self.map.get_index_of(path).map(|i| FileId(i as u32))
     }
 
     /// Insert `path` in `self`.
@@ -25,13 +32,9 @@ impl PathInterner {
     /// - If `path` already exists in `self`, returns its associated id;
     /// - Else, returns a newly allocated id.
     pub(crate) fn intern(&mut self, path: VfsPath) -> FileId {
-        if let Some(id) = self.get(&path) {
-            return id;
-        }
-        let id = FileId(self.vec.len() as u32);
-        self.map.insert(path.clone(), id);
-        self.vec.push(path);
-        id
+        let (id, _added) = self.map.insert_full(path);
+        assert!(id < u32::MAX as usize);
+        FileId(id as u32)
     }
 
     /// Returns the path corresponding to `id`.
@@ -40,6 +43,6 @@ impl PathInterner {
     ///
     /// Panics if `id` does not exists in `self`.
     pub(crate) fn lookup(&self, id: FileId) -> &VfsPath {
-        &self.vec[id.0 as usize]
+        self.map.get_index(id.0 as usize).unwrap()
     }
 }