37 files changed, 3676 insertions, 3851 deletions

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)
+    }
+}