20 files changed, 538 insertions, 133 deletions

diff --git a/crates/hir_ty/src/chalk_db.rs b/crates/hir_ty/src/chalk_db.rs
index b108fd559..4e042bf42 100644
--- a/crates/hir_ty/src/chalk_db.rs
+++ b/crates/hir_ty/src/chalk_db.rs
@@ -383,7 +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 = generic_params.bound_vars_subst(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);
@@ -396,8 +396,10 @@ pub(crate) fn associated_ty_data_query(
         .filter_map(|pred| generic_predicate_to_inline_bound(db, &pred, &self_ty))
         .collect();
 
-    let where_clauses = convert_where_clauses(db, type_alias.into(), &bound_vars);
-    let bound_data = rust_ir::AssociatedTyDatumBound { bounds, where_clauses };
+    // FIXME: Re-enable where clauses on associated types when an upstream chalk bug is fixed.
+    //        (rust-analyzer#9052)
+    // let where_clauses = convert_where_clauses(db, type_alias.into(), &bound_vars);
+    let bound_data = rust_ir::AssociatedTyDatumBound { bounds, where_clauses: vec![] };
     let datum = AssociatedTyDatum {
         trait_id: to_chalk_trait_id(trait_),
         id,
diff --git a/crates/hir_ty/src/diagnostics.rs b/crates/hir_ty/src/diagnostics.rs
index 84fc8ce14..7598e2193 100644
--- a/crates/hir_ty/src/diagnostics.rs
+++ b/crates/hir_ty/src/diagnostics.rs
@@ -8,12 +8,14 @@ use std::{any::Any, fmt};
 
 use base_db::CrateId;
 use hir_def::{DefWithBodyId, ModuleDefId};
-use hir_expand::diagnostics::{Diagnostic, DiagnosticCode, DiagnosticSink};
 use hir_expand::{name::Name, HirFileId, InFile};
 use stdx::format_to;
 use syntax::{ast, AstPtr, SyntaxNodePtr};
 
-use crate::db::HirDatabase;
+use crate::{
+    db::HirDatabase,
+    diagnostics_sink::{Diagnostic, DiagnosticCode, DiagnosticSink},
+};
 
 pub use crate::diagnostics::expr::{record_literal_missing_fields, record_pattern_missing_fields};
 
@@ -446,15 +448,13 @@ impl Diagnostic for ReplaceFilterMapNextWithFindMap {
 mod tests {
     use base_db::{fixture::WithFixture, FileId, SourceDatabase, SourceDatabaseExt};
     use hir_def::{db::DefDatabase, AssocItemId, ModuleDefId};
-    use hir_expand::{
-        db::AstDatabase,
-        diagnostics::{Diagnostic, DiagnosticSinkBuilder},
-    };
+    use hir_expand::db::AstDatabase;
     use rustc_hash::FxHashMap;
     use syntax::{TextRange, TextSize};
 
     use crate::{
         diagnostics::{validate_body, validate_module_item},
+        diagnostics_sink::{Diagnostic, DiagnosticSinkBuilder},
         test_db::TestDB,
     };
 
diff --git a/crates/hir_ty/src/diagnostics/decl_check.rs b/crates/hir_ty/src/diagnostics/decl_check.rs
index 075dc4131..ef982cbcd 100644
--- a/crates/hir_ty/src/diagnostics/decl_check.rs
+++ b/crates/hir_ty/src/diagnostics/decl_check.rs
@@ -19,10 +19,7 @@ use hir_def::{
     src::HasSource,
     AdtId, AttrDefId, ConstId, EnumId, FunctionId, Lookup, ModuleDefId, StaticId, StructId,
 };
-use hir_expand::{
-    diagnostics::DiagnosticSink,
-    name::{AsName, Name},
-};
+use hir_expand::name::{AsName, Name};
 use stdx::{always, never};
 use syntax::{
     ast::{self, NameOwner},
@@ -32,6 +29,7 @@ use syntax::{
 use crate::{
     db::HirDatabase,
     diagnostics::{decl_check::case_conv::*, CaseType, IdentType, IncorrectCase},
+    diagnostics_sink::DiagnosticSink,
 };
 
 mod allow {
diff --git a/crates/hir_ty/src/diagnostics/expr.rs b/crates/hir_ty/src/diagnostics/expr.rs
index 53c4ee9da..86f82e3fa 100644
--- a/crates/hir_ty/src/diagnostics/expr.rs
+++ b/crates/hir_ty/src/diagnostics/expr.rs
@@ -5,7 +5,7 @@
 use std::sync::Arc;
 
 use hir_def::{expr::Statement, path::path, resolver::HasResolver, AssocItemId, DefWithBodyId};
-use hir_expand::{diagnostics::DiagnosticSink, name};
+use hir_expand::name;
 use rustc_hash::FxHashSet;
 use syntax::{ast, AstPtr};
 
@@ -16,6 +16,7 @@ use crate::{
         MismatchedArgCount, MissingFields, MissingMatchArms, MissingOkOrSomeInTailExpr,
         MissingPatFields, RemoveThisSemicolon,
     },
+    diagnostics_sink::DiagnosticSink,
     AdtId, InferenceResult, Interner, TyExt, TyKind,
 };
 
@@ -181,7 +182,7 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
         for (id, expr) in body.exprs.iter() {
             if let Expr::MethodCall { receiver, .. } = expr {
                 let function_id = match self.infer.method_resolution(id) {
-                    Some(id) => id,
+                    Some((id, _)) => id,
                     None => continue,
                 };
 
@@ -239,15 +240,11 @@ impl<'a, 'b> ExprValidator<'a, 'b> {
                     return;
                 }
 
-                // FIXME: note that we erase information about substs here. This
-                // is not right, but, luckily, doesn't matter as we care only
-                // about the number of params
-                let callee = match self.infer.method_resolution(call_id) {
-                    Some(callee) => callee,
+                let (callee, subst) = match self.infer.method_resolution(call_id) {
+                    Some(it) => it,
                     None => return,
                 };
-                let sig =
-                    db.callable_item_signature(callee.into()).into_value_and_skipped_binders().0;
+                let sig = db.callable_item_signature(callee.into()).substitute(&Interner, &subst);
 
                 (sig, args)
             }
diff --git a/crates/hir_ty/src/diagnostics/unsafe_check.rs b/crates/hir_ty/src/diagnostics/unsafe_check.rs
index ed97dc0e3..c3c483425 100644
--- a/crates/hir_ty/src/diagnostics/unsafe_check.rs
+++ b/crates/hir_ty/src/diagnostics/unsafe_check.rs
@@ -9,10 +9,10 @@ use hir_def::{
     resolver::{resolver_for_expr, ResolveValueResult, ValueNs},
     DefWithBodyId,
 };
-use hir_expand::diagnostics::DiagnosticSink;
 
 use crate::{
-    db::HirDatabase, diagnostics::MissingUnsafe, InferenceResult, Interner, TyExt, TyKind,
+    db::HirDatabase, diagnostics::MissingUnsafe, diagnostics_sink::DiagnosticSink, InferenceResult,
+    Interner, TyExt, TyKind,
 };
 
 pub(super) struct UnsafeValidator<'a, 'b: 'a> {
@@ -105,7 +105,7 @@ fn walk_unsafe(
         Expr::MethodCall { .. } => {
             if infer
                 .method_resolution(current)
-                .map(|func| db.function_data(func).is_unsafe())
+                .map(|(func, _)| db.function_data(func).is_unsafe())
                 .unwrap_or(false)
             {
                 unsafe_exprs.push(UnsafeExpr { expr: current, inside_unsafe_block });
diff --git a/crates/hir_ty/src/diagnostics_sink.rs b/crates/hir_ty/src/diagnostics_sink.rs
new file mode 100644
index 000000000..084fa8b06
--- /dev/null
+++ b/crates/hir_ty/src/diagnostics_sink.rs
@@ -0,0 +1,109 @@
+//! Semantic errors and warnings.
+//!
+//! The `Diagnostic` trait defines a trait object which can represent any
+//! diagnostic.
+//!
+//! `DiagnosticSink` struct is used as an emitter for diagnostic. When creating
+//! a `DiagnosticSink`, you supply a callback which can react to a `dyn
+//! Diagnostic` or to any concrete diagnostic (downcasting is used internally).
+//!
+//! Because diagnostics store file offsets, it's a bad idea to store them
+//! directly in salsa. For this reason, every hir subsytem defines it's own
+//! strongly-typed closed set of diagnostics which use hir ids internally, are
+//! stored in salsa and do *not* implement the `Diagnostic` trait. Instead, a
+//! subsystem provides a separate, non-query-based API which can walk all stored
+//! values and transform them into instances of `Diagnostic`.
+
+use std::{any::Any, fmt};
+
+use hir_expand::InFile;
+use syntax::SyntaxNodePtr;
+
+#[derive(Copy, Clone, Debug, PartialEq)]
+pub struct DiagnosticCode(pub &'static str);
+
+impl DiagnosticCode {
+    pub fn as_str(&self) -> &str {
+        self.0
+    }
+}
+
+pub trait Diagnostic: Any + Send + Sync + fmt::Debug + 'static {
+    fn code(&self) -> DiagnosticCode;
+    fn message(&self) -> String;
+    /// Source element that triggered the diagnostics.
+    ///
+    /// Note that this should reflect "semantics", rather than specific span we
+    /// want to highlight. When rendering the diagnostics into an error message,
+    /// the IDE will fetch the `SyntaxNode` and will narrow the span
+    /// appropriately.
+    fn display_source(&self) -> InFile<SyntaxNodePtr>;
+    fn as_any(&self) -> &(dyn Any + Send + 'static);
+    fn is_experimental(&self) -> bool {
+        false
+    }
+}
+
+pub struct DiagnosticSink<'a> {
+    callbacks: Vec<Box<dyn FnMut(&dyn Diagnostic) -> Result<(), ()> + 'a>>,
+    filters: Vec<Box<dyn FnMut(&dyn Diagnostic) -> bool + 'a>>,
+    default_callback: Box<dyn FnMut(&dyn Diagnostic) + 'a>,
+}
+
+impl<'a> DiagnosticSink<'a> {
+    pub fn push(&mut self, d: impl Diagnostic) {
+        let d: &dyn Diagnostic = &d;
+        self._push(d);
+    }
+
+    fn _push(&mut self, d: &dyn Diagnostic) {
+        for filter in &mut self.filters {
+            if !filter(d) {
+                return;
+            }
+        }
+        for cb in &mut self.callbacks {
+            match cb(d) {
+                Ok(()) => return,
+                Err(()) => (),
+            }
+        }
+        (self.default_callback)(d)
+    }
+}
+
+pub struct DiagnosticSinkBuilder<'a> {
+    callbacks: Vec<Box<dyn FnMut(&dyn Diagnostic) -> Result<(), ()> + 'a>>,
+    filters: Vec<Box<dyn FnMut(&dyn Diagnostic) -> bool + 'a>>,
+}
+
+impl<'a> DiagnosticSinkBuilder<'a> {
+    pub fn new() -> Self {
+        Self { callbacks: Vec::new(), filters: Vec::new() }
+    }
+
+    pub fn filter<F: FnMut(&dyn Diagnostic) -> bool + 'a>(mut self, cb: F) -> Self {
+        self.filters.push(Box::new(cb));
+        self
+    }
+
+    pub fn on<D: Diagnostic, F: FnMut(&D) + 'a>(mut self, mut cb: F) -> Self {
+        let cb = move |diag: &dyn Diagnostic| match diag.as_any().downcast_ref::<D>() {
+            Some(d) => {
+                cb(d);
+                Ok(())
+            }
+            None => Err(()),
+        };
+        self.callbacks.push(Box::new(cb));
+        self
+    }
+
+    pub fn build<F: FnMut(&dyn Diagnostic) + 'a>(self, default_callback: F) -> DiagnosticSink<'a> {
+        DiagnosticSink {
+            callbacks: self.callbacks,
+            filters: self.filters,
+            default_callback: Box::new(default_callback),
+        }
+    }
+}
diff --git a/crates/hir_ty/src/display.rs b/crates/hir_ty/src/display.rs
index 7bbd1a1f7..44f843bf3 100644
--- a/crates/hir_ty/src/display.rs
+++ b/crates/hir_ty/src/display.rs
@@ -13,6 +13,7 @@ use hir_def::{
     db::DefDatabase,
     find_path,
     generics::TypeParamProvenance,
+    intern::{Internable, Interned},
     item_scope::ItemInNs,
     path::{Path, PathKind},
     type_ref::{TypeBound, TypeRef},
@@ -256,6 +257,12 @@ impl<T: HirDisplay> HirDisplay for &'_ T {
     }
 }
 
+impl<T: HirDisplay + Internable> HirDisplay for Interned<T> {
+    fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
+        HirDisplay::hir_fmt(self.as_ref(), f)
+    }
+}
+
 impl HirDisplay for ProjectionTy {
     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
         if f.should_truncate() {
@@ -771,8 +778,10 @@ fn write_bounds_like_dyn_trait(
             }
             WhereClause::AliasEq(alias_eq) if is_fn_trait => {
                 is_fn_trait = false;
-                write!(f, " -> ")?;
-                alias_eq.ty.hir_fmt(f)?;
+                if !alias_eq.ty.is_unit() {
+                    write!(f, " -> ")?;
+                    alias_eq.ty.hir_fmt(f)?;
+                }
             }
             WhereClause::AliasEq(AliasEq { ty, alias }) => {
                 // in types in actual Rust, these will always come
diff --git a/crates/hir_ty/src/infer.rs b/crates/hir_ty/src/infer.rs
index f1cebbdb9..7a4268819 100644
--- a/crates/hir_ty/src/infer.rs
+++ b/crates/hir_ty/src/infer.rs
@@ -28,17 +28,18 @@ use hir_def::{
     AdtId, AssocItemId, DefWithBodyId, EnumVariantId, FieldId, FunctionId, HasModule, Lookup,
     TraitId, TypeAliasId, VariantId,
 };
-use hir_expand::{diagnostics::DiagnosticSink, name::name};
+use hir_expand::name::name;
 use la_arena::ArenaMap;
 use rustc_hash::FxHashMap;
 use stdx::impl_from;
 use syntax::SmolStr;
 
 use super::{DomainGoal, InEnvironment, ProjectionTy, TraitEnvironment, TraitRef, Ty};
+use crate::diagnostics_sink::DiagnosticSink;
 use crate::{
     db::HirDatabase, fold_tys, infer::diagnostics::InferenceDiagnostic,
-    lower::ImplTraitLoweringMode, to_assoc_type_id, AliasEq, AliasTy, Goal, Interner, TyBuilder,
-    TyExt, TyKind,
+    lower::ImplTraitLoweringMode, to_assoc_type_id, AliasEq, AliasTy, Goal, Interner, Substitution,
+    TyBuilder, TyExt, TyKind,
 };
 
 // This lint has a false positive here. See the link below for details.
@@ -132,7 +133,7 @@ impl Default for InternedStandardTypes {
 #[derive(Clone, PartialEq, Eq, Debug, Default)]
 pub struct InferenceResult {
     /// For each method call expr, records the function it resolves to.
-    method_resolutions: FxHashMap<ExprId, FunctionId>,
+    method_resolutions: FxHashMap<ExprId, (FunctionId, Substitution)>,
     /// For each field access expr, records the field it resolves to.
     field_resolutions: FxHashMap<ExprId, FieldId>,
     /// For each struct literal or pattern, records the variant it resolves to.
@@ -152,8 +153,8 @@ pub struct InferenceResult {
 }
 
 impl InferenceResult {
-    pub fn method_resolution(&self, expr: ExprId) -> Option<FunctionId> {
-        self.method_resolutions.get(&expr).copied()
+    pub fn method_resolution(&self, expr: ExprId) -> Option<(FunctionId, Substitution)> {
+        self.method_resolutions.get(&expr).cloned()
     }
     pub fn field_resolution(&self, expr: ExprId) -> Option<FieldId> {
         self.field_resolutions.get(&expr).copied()
@@ -284,14 +285,17 @@ impl<'a> InferenceContext<'a> {
         self.table.propagate_diverging_flag();
         let mut result = std::mem::take(&mut self.result);
         for ty in result.type_of_expr.values_mut() {
-            *ty = self.table.resolve_ty_completely(ty.clone());
+            *ty = self.table.resolve_completely(ty.clone());
         }
         for ty in result.type_of_pat.values_mut() {
-            *ty = self.table.resolve_ty_completely(ty.clone());
+            *ty = self.table.resolve_completely(ty.clone());
         }
         for mismatch in result.type_mismatches.values_mut() {
-            mismatch.expected = self.table.resolve_ty_completely(mismatch.expected.clone());
-            mismatch.actual = self.table.resolve_ty_completely(mismatch.actual.clone());
+            mismatch.expected = self.table.resolve_completely(mismatch.expected.clone());
+            mismatch.actual = self.table.resolve_completely(mismatch.actual.clone());
+        }
+        for (_, subst) in result.method_resolutions.values_mut() {
+            *subst = self.table.resolve_completely(subst.clone());
         }
         result
     }
@@ -300,8 +304,8 @@ impl<'a> InferenceContext<'a> {
         self.result.type_of_expr.insert(expr, ty);
     }
 
-    fn write_method_resolution(&mut self, expr: ExprId, func: FunctionId) {
-        self.result.method_resolutions.insert(expr, func);
+    fn write_method_resolution(&mut self, expr: ExprId, func: FunctionId, subst: Substitution) {
+        self.result.method_resolutions.insert(expr, (func, subst));
     }
 
     fn write_field_resolution(&mut self, expr: ExprId, field: FieldId) {
@@ -554,7 +558,13 @@ impl<'a> InferenceContext<'a> {
 
             self.infer_pat(*pat, &ty, BindingMode::default());
         }
-        let return_ty = self.make_ty_with_mode(&data.ret_type, ImplTraitLoweringMode::Disallowed); // FIXME implement RPIT
+        let error_ty = &TypeRef::Error;
+        let return_ty = if data.is_async() {
+            data.async_ret_type.as_deref().unwrap_or(error_ty)
+        } else {
+            &*data.ret_type
+        };
+        let return_ty = self.make_ty_with_mode(return_ty, ImplTraitLoweringMode::Disallowed); // FIXME implement RPIT
         self.return_ty = return_ty;
     }
 
@@ -575,9 +585,14 @@ impl<'a> InferenceContext<'a> {
     }
 
     fn resolve_ops_try_ok(&self) -> Option<TypeAliasId> {
+        // FIXME resolve via lang_item once try v2 is stable
         let path = path![core::ops::Try];
         let trait_ = self.resolver.resolve_known_trait(self.db.upcast(), &path)?;
-        self.db.trait_data(trait_).associated_type_by_name(&name![Ok])
+        let trait_data = self.db.trait_data(trait_);
+        trait_data
+            // FIXME remove once try v2 is stable
+            .associated_type_by_name(&name![Ok])
+            .or_else(|| trait_data.associated_type_by_name(&name![Output]))
     }
 
     fn resolve_ops_neg_output(&self) -> Option<TypeAliasId> {
@@ -790,11 +805,11 @@ impl std::ops::BitOrAssign for Diverges {
 
 mod diagnostics {
     use hir_def::{expr::ExprId, DefWithBodyId};
-    use hir_expand::diagnostics::DiagnosticSink;
 
     use crate::{
         db::HirDatabase,
         diagnostics::{BreakOutsideOfLoop, NoSuchField},
+        diagnostics_sink::DiagnosticSink,
     };
 
     #[derive(Debug, PartialEq, Eq, Clone)]
diff --git a/crates/hir_ty/src/infer/coerce.rs b/crates/hir_ty/src/infer/coerce.rs
index 765a02b1c..03b97e7db 100644
--- a/crates/hir_ty/src/infer/coerce.rs
+++ b/crates/hir_ty/src/infer/coerce.rs
@@ -76,17 +76,17 @@ impl<'a> InferenceContext<'a> {
         // way around first would mean we make the type variable `!`, instead of
         // just marking it as possibly diverging.
         if self.coerce(&ty2, &ty1) {
-            ty1.clone()
+            ty1
         } else if self.coerce(&ty1, &ty2) {
-            ty2.clone()
+            ty2
         } else {
             if let Some(id) = id {
                 self.result
                     .type_mismatches
-                    .insert(id.into(), TypeMismatch { expected: ty1.clone(), actual: ty2.clone() });
+                    .insert(id.into(), TypeMismatch { expected: ty1.clone(), actual: ty2 });
             }
             cov_mark::hit!(coerce_merge_fail_fallback);
-            ty1.clone()
+            ty1
         }
     }
 
@@ -183,7 +183,7 @@ impl<'a> InferenceContext<'a> {
         // details of coercion errors though, so I think it's useful to leave
         // the structure like it is.
 
-        let canonicalized = self.canonicalize(from_ty.clone());
+        let canonicalized = self.canonicalize(from_ty);
         let autoderef = autoderef::autoderef(
             self.db,
             self.resolver.krate(),
@@ -389,7 +389,7 @@ impl<'a> InferenceContext<'a> {
                 // The CoerceUnsized trait should have two generic params: Self and T.
                 return Err(TypeError);
             }
-            b.push(coerce_from.clone()).push(to_ty.clone()).build()
+            b.push(coerce_from).push(to_ty.clone()).build()
         };
 
         let goal: InEnvironment<DomainGoal> =
diff --git a/crates/hir_ty/src/infer/expr.rs b/crates/hir_ty/src/infer/expr.rs
index 08c05c67c..41ef45326 100644
--- a/crates/hir_ty/src/infer/expr.rs
+++ b/crates/hir_ty/src/infer/expr.rs
@@ -44,7 +44,7 @@ impl<'a> InferenceContext<'a> {
             if !could_unify {
                 self.result.type_mismatches.insert(
                     tgt_expr.into(),
-                    TypeMismatch { expected: expected_ty.clone(), actual: ty.clone() },
+                    TypeMismatch { expected: expected_ty, actual: ty.clone() },
                 );
             }
         }
@@ -57,15 +57,14 @@ impl<'a> InferenceContext<'a> {
         let ty = self.infer_expr_inner(expr, &expected);
         let ty = if let Some(target) = expected.only_has_type(&mut self.table) {
             if !self.coerce(&ty, &target) {
-                self.result.type_mismatches.insert(
-                    expr.into(),
-                    TypeMismatch { expected: target.clone(), actual: ty.clone() },
-                );
+                self.result
+                    .type_mismatches
+                    .insert(expr.into(), TypeMismatch { expected: target, actual: ty.clone() });
                 // Return actual type when type mismatch.
                 // This is needed for diagnostic when return type mismatch.
                 ty
             } else {
-                target.clone()
+                target
             }
         } else {
             ty
@@ -120,7 +119,7 @@ impl<'a> InferenceContext<'a> {
     }
 
     fn infer_expr_inner(&mut self, tgt_expr: ExprId, expected: &Expectation) -> Ty {
-        self.db.check_canceled();
+        self.db.unwind_if_cancelled();
 
         let body = Arc::clone(&self.body); // avoid borrow checker problem
         let ty = match &body[tgt_expr] {
@@ -805,7 +804,7 @@ impl<'a> InferenceContext<'a> {
                     None => self.table.new_float_var(),
                 },
             },
-            Expr::MacroStmts { tail } => self.infer_expr(*tail, expected),
+            Expr::MacroStmts { tail } => self.infer_expr_inner(*tail, expected),
         };
         // use a new type variable if we got unknown here
         let ty = self.insert_type_vars_shallow(ty);
@@ -891,17 +890,21 @@ impl<'a> InferenceContext<'a> {
                 method_name,
             )
         });
-        let (derefed_receiver_ty, method_ty, def_generics) = match resolved {
+        let (derefed_receiver_ty, method_ty, substs) = match resolved {
             Some((ty, func)) => {
                 let ty = canonicalized_receiver.decanonicalize_ty(ty);
-                self.write_method_resolution(tgt_expr, func);
-                (ty, self.db.value_ty(func.into()), Some(generics(self.db.upcast(), func.into())))
+                let generics = generics(self.db.upcast(), func.into());
+                let substs = self.substs_for_method_call(generics, generic_args, &ty);
+                self.write_method_resolution(tgt_expr, func, substs.clone());
+                (ty, self.db.value_ty(func.into()), substs)
             }
-            None => (receiver_ty, Binders::empty(&Interner, self.err_ty()), None),
+            None => (
+                receiver_ty,
+                Binders::empty(&Interner, self.err_ty()),
+                Substitution::empty(&Interner),
+            ),
         };
-        let substs = self.substs_for_method_call(def_generics, generic_args, &derefed_receiver_ty);
         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) {
             Some(sig) => {
@@ -950,23 +953,21 @@ impl<'a> InferenceContext<'a> {
 
     fn substs_for_method_call(
         &mut self,
-        def_generics: Option<Generics>,
+        def_generics: Generics,
         generic_args: Option<&GenericArgs>,
         receiver_ty: &Ty,
     ) -> Substitution {
         let (parent_params, self_params, type_params, impl_trait_params) =
-            def_generics.as_ref().map_or((0, 0, 0, 0), |g| g.provenance_split());
+            def_generics.provenance_split();
         assert_eq!(self_params, 0); // method shouldn't have another Self param
         let total_len = parent_params + type_params + impl_trait_params;
         let mut substs = Vec::with_capacity(total_len);
         // Parent arguments are unknown, except for the receiver type
-        if let Some(parent_generics) = def_generics.as_ref().map(|p| p.iter_parent()) {
-            for (_id, param) in parent_generics {
-                if param.provenance == hir_def::generics::TypeParamProvenance::TraitSelf {
-                    substs.push(receiver_ty.clone());
-                } else {
-                    substs.push(self.err_ty());
-                }
+        for (_id, param) in def_generics.iter_parent() {
+            if param.provenance == hir_def::generics::TypeParamProvenance::TraitSelf {
+                substs.push(receiver_ty.clone());
+            } else {
+                substs.push(self.table.new_type_var());
             }
         }
         // handle provided type arguments
@@ -989,7 +990,7 @@ impl<'a> InferenceContext<'a> {
         };
         let supplied_params = substs.len();
         for _ in supplied_params..total_len {
-            substs.push(self.err_ty());
+            substs.push(self.table.new_type_var());
         }
         assert_eq!(substs.len(), total_len);
         Substitution::from_iter(&Interner, substs)
diff --git a/crates/hir_ty/src/infer/pat.rs b/crates/hir_ty/src/infer/pat.rs
index 9c8e3b6ae..83e0a7a9e 100644
--- a/crates/hir_ty/src/infer/pat.rs
+++ b/crates/hir_ty/src/infer/pat.rs
@@ -196,7 +196,7 @@ impl<'a> InferenceContext<'a> {
                 let inner_ty = if let Some(subpat) = subpat {
                     self.infer_pat(*subpat, &expected, default_bm)
                 } else {
-                    expected.clone()
+                    expected
                 };
                 let inner_ty = self.insert_type_vars_shallow(inner_ty);
 
@@ -266,10 +266,9 @@ impl<'a> InferenceContext<'a> {
         // use a new type variable if we got error type here
         let ty = self.insert_type_vars_shallow(ty);
         if !self.unify(&ty, &expected) {
-            self.result.type_mismatches.insert(
-                pat.into(),
-                TypeMismatch { expected: expected.clone(), actual: ty.clone() },
-            );
+            self.result
+                .type_mismatches
+                .insert(pat.into(), TypeMismatch { expected: expected, actual: ty.clone() });
         }
         self.write_pat_ty(pat, ty.clone());
         ty
diff --git a/crates/hir_ty/src/infer/unify.rs b/crates/hir_ty/src/infer/unify.rs
index f8233cac3..ea5684229 100644
--- a/crates/hir_ty/src/infer/unify.rs
+++ b/crates/hir_ty/src/infer/unify.rs
@@ -295,8 +295,11 @@ impl<'a> InferenceTable<'a> {
         .expect("fold failed unexpectedly")
     }
 
-    pub(crate) fn resolve_ty_completely(&mut self, ty: Ty) -> Ty {
-        self.resolve_with_fallback(ty, |_, _, d, _| d)
+    pub(crate) fn resolve_completely<T>(&mut self, t: T) -> T::Result
+    where
+        T: HasInterner<Interner = Interner> + Fold<Interner>,
+    {
+        self.resolve_with_fallback(t, |_, _, d, _| d)
     }
 
     /// Unify two types and register new trait goals that arise from that.
diff --git a/crates/hir_ty/src/lib.rs b/crates/hir_ty/src/lib.rs
index ef021978a..50e0d6333 100644
--- a/crates/hir_ty/src/lib.rs
+++ b/crates/hir_ty/src/lib.rs
@@ -21,6 +21,7 @@ mod utils;
 mod walk;
 pub mod db;
 pub mod diagnostics;
+pub mod diagnostics_sink;
 pub mod display;
 pub mod method_resolution;
 pub mod primitive;
diff --git a/crates/hir_ty/src/lower.rs b/crates/hir_ty/src/lower.rs
index 8a375b973..c83933c73 100644
--- a/crates/hir_ty/src/lower.rs
+++ b/crates/hir_ty/src/lower.rs
@@ -10,6 +10,7 @@ use std::{iter, sync::Arc};
 
 use base_db::CrateId;
 use chalk_ir::{cast::Cast, fold::Shift, interner::HasInterner, Mutability, Safety};
+use hir_def::intern::Interned;
 use hir_def::{
     adt::StructKind,
     body::{Expander, LowerCtx},
@@ -843,7 +844,7 @@ impl<'a> TyLoweringContext<'a> {
             })
     }
 
-    fn lower_impl_trait(&self, bounds: &[TypeBound]) -> ReturnTypeImplTrait {
+    fn lower_impl_trait(&self, bounds: &[Interned<TypeBound>]) -> ReturnTypeImplTrait {
         cov_mark::hit!(lower_rpit);
         let self_ty =
             TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0)).intern(&Interner);
@@ -1025,7 +1026,7 @@ pub(crate) fn trait_environment_query(
     };
     if let Some(AssocContainerId::TraitId(trait_id)) = container {
         // add `Self: Trait<T1, T2, ...>` to the environment in trait
-        // function default implementations (and hypothetical code
+        // function default implementations (and speculative code
         // inside consts or type aliases)
         cov_mark::hit!(trait_self_implements_self);
         let substs = TyBuilder::type_params_subst(db, trait_id);
diff --git a/crates/hir_ty/src/tests.rs b/crates/hir_ty/src/tests.rs
index cc819373c..9d726b024 100644
--- a/crates/hir_ty/src/tests.rs
+++ b/crates/hir_ty/src/tests.rs
@@ -7,6 +7,7 @@ mod traits;
 mod method_resolution;
 mod macros;
 mod display_source_code;
+mod incremental;
 
 use std::{env, sync::Arc};
 
@@ -317,50 +318,6 @@ fn ellipsize(mut text: String, max_len: usize) -> String {
     text
 }
 
-#[test]
-fn typing_whitespace_inside_a_function_should_not_invalidate_types() {
-    let (mut db, pos) = TestDB::with_position(
-        "
-        //- /lib.rs
-        fn foo() -> i32 {
-            $01 + 1
-        }
-    ",
-    );
-    {
-        let events = db.log_executed(|| {
-            let module = db.module_for_file(pos.file_id);
-            let crate_def_map = module.def_map(&db);
-            visit_module(&db, &crate_def_map, module.local_id, &mut |def| {
-                db.infer(def);
-            });
-        });
-        assert!(format!("{:?}", events).contains("infer"))
-    }
-
-    let new_text = "
-        fn foo() -> i32 {
-            1
-            +
-            1
-        }
-    "
-    .to_string();
-
-    db.set_file_text(pos.file_id, Arc::new(new_text));
-
-    {
-        let events = db.log_executed(|| {
-            let module = db.module_for_file(pos.file_id);
-            let crate_def_map = module.def_map(&db);
-            visit_module(&db, &crate_def_map, module.local_id, &mut |def| {
-                db.infer(def);
-            });
-        });
-        assert!(!format!("{:?}", events).contains("infer"), "{:#?}", events)
-    }
-}
-
 fn check_infer(ra_fixture: &str, expect: Expect) {
     let mut actual = infer(ra_fixture);
     actual.push('\n');
diff --git a/crates/hir_ty/src/tests/coercion.rs b/crates/hir_ty/src/tests/coercion.rs
index bb568ea37..6dac7e103 100644
--- a/crates/hir_ty/src/tests/coercion.rs
+++ b/crates/hir_ty/src/tests/coercion.rs
@@ -832,11 +832,9 @@ fn coerce_unsize_super_trait_cycle() {
     );
 }
 
-#[ignore]
 #[test]
 fn coerce_unsize_generic() {
-    // FIXME: Implement this
-    // https://doc.rust-lang.org/reference/type-coercions.html#unsized-coercions
+    // FIXME: fix the type mismatches here
     check_infer_with_mismatches(
         r#"
         #[lang = "unsize"]
@@ -854,8 +852,58 @@ fn coerce_unsize_generic() {
             let _: &Bar<[usize]> = &Bar(Foo { t: [1, 2, 3] });
         }
         "#,
-        expect![[r"
-        "]],
+        expect![[r#"
+            209..317 '{     ... }); }': ()
+            219..220 '_': &Foo<[usize]>
+            238..259 '&Foo {..., 3] }': &Foo<[usize]>
+            239..259 'Foo { ..., 3] }': Foo<[usize]>
+            248..257 '[1, 2, 3]': [usize; 3]
+            249..250 '1': usize
+            252..253 '2': usize
+            255..256 '3': usize
+            269..270 '_': &Bar<[usize]>
+            288..314 '&Bar(F... 3] })': &Bar<[i32; 3]>
+            289..292 'Bar': Bar<[i32; 3]>(Foo<[i32; 3]>) -> Bar<[i32; 3]>
+            289..314 'Bar(Fo... 3] })': Bar<[i32; 3]>
+            293..313 'Foo { ..., 3] }': Foo<[i32; 3]>
+            302..311 '[1, 2, 3]': [i32; 3]
+            303..304 '1': i32
+            306..307 '2': i32
+            309..310 '3': i32
+            248..257: expected [usize], got [usize; 3]
+            288..314: expected &Bar<[usize]>, got &Bar<[i32; 3]>
+        "#]],
+    );
+}
+
+#[test]
+fn coerce_unsize_apit() {
+    // FIXME: #8984
+    check_infer_with_mismatches(
+        r#"
+#[lang = "sized"]
+pub trait Sized {}
+#[lang = "unsize"]
+pub trait Unsize<T> {}
+#[lang = "coerce_unsized"]
+pub trait CoerceUnsized<T> {}
+
+impl<T: Unsize<U>, U> CoerceUnsized<&U> for &T {}
+
+trait Foo {}
+
+fn test(f: impl Foo) {
+    let _: &dyn Foo = &f;
+}
+        "#,
+        expect![[r#"
+            210..211 'f': impl Foo
+            223..252 '{     ... &f; }': ()
+            233..234 '_': &dyn Foo
+            247..249 '&f': &impl Foo
+            248..249 'f': impl Foo
+            247..249: expected &dyn Foo, got &impl Foo
+        "#]],
     );
 }
 
@@ -912,3 +960,46 @@ fn test() -> i32 {
         "#,
     )
 }
+
+#[test]
+fn panic_macro() {
+    check_infer_with_mismatches(
+        r#"
+mod panic {
+    #[macro_export]
+    pub macro panic_2015 {
+        () => (
+            $crate::panicking::panic()
+        ),
+    }
+}
+
+mod panicking {
+    pub fn panic() -> ! { loop {} }
+}
+
+#[rustc_builtin_macro = "core_panic"]
+macro_rules! panic {
+    // Expands to either `$crate::panic::panic_2015` or `$crate::panic::panic_2021`
+    // depending on the edition of the caller.
+    ($($arg:tt)*) => {
+        /* compiler built-in */
+    };
+}
+
+fn main() {
+    panic!()
+}
+        "#,
+        expect![[r#"
+            174..185 '{ loop {} }': !
+            176..183 'loop {}': !
+            181..183 '{}': ()
+            !0..24 '$crate...:panic': fn panic() -> !
+            !0..26 '$crate...anic()': !
+            !0..26 '$crate...anic()': !
+            !0..28 '$crate...015!()': !
+            454..470 '{     ...c!() }': ()
+        "#]],
+    );
+}
diff --git a/crates/hir_ty/src/tests/incremental.rs b/crates/hir_ty/src/tests/incremental.rs
new file mode 100644
index 000000000..3e08e83e8
--- /dev/null
+++ b/crates/hir_ty/src/tests/incremental.rs
@@ -0,0 +1,51 @@
+use std::sync::Arc;
+
+use base_db::{fixture::WithFixture, SourceDatabaseExt};
+
+use crate::{db::HirDatabase, test_db::TestDB};
+
+use super::visit_module;
+
+#[test]
+fn typing_whitespace_inside_a_function_should_not_invalidate_types() {
+    let (mut db, pos) = TestDB::with_position(
+        "
+        //- /lib.rs
+        fn foo() -> i32 {
+            $01 + 1
+        }
+    ",
+    );
+    {
+        let events = db.log_executed(|| {
+            let module = db.module_for_file(pos.file_id);
+            let crate_def_map = module.def_map(&db);
+            visit_module(&db, &crate_def_map, module.local_id, &mut |def| {
+                db.infer(def);
+            });
+        });
+        assert!(format!("{:?}", events).contains("infer"))
+    }
+
+    let new_text = "
+        fn foo() -> i32 {
+            1
+            +
+            1
+        }
+    "
+    .to_string();
+
+    db.set_file_text(pos.file_id, Arc::new(new_text));
+
+    {
+        let events = db.log_executed(|| {
+            let module = db.module_for_file(pos.file_id);
+            let crate_def_map = module.def_map(&db);
+            visit_module(&db, &crate_def_map, module.local_id, &mut |def| {
+                db.infer(def);
+            });
+        });
+        assert!(!format!("{:?}", events).contains("infer"), "{:#?}", events)
+    }
+}
diff --git a/crates/hir_ty/src/tests/macros.rs b/crates/hir_ty/src/tests/macros.rs
index 6588aa46c..7647bb08b 100644
--- a/crates/hir_ty/src/tests/macros.rs
+++ b/crates/hir_ty/src/tests/macros.rs
@@ -752,6 +752,24 @@ fn bar() -> u32 {0}
 }
 
 #[test]
+fn infer_builtin_macros_include_expression() {
+    check_types(
+        r#"
+//- /main.rs
+#[rustc_builtin_macro]
+macro_rules! include {() => {}}
+fn main() {
+    let i = include!("bla.rs");
+    i;
+  //^ i32
+}
+//- /bla.rs
+0
+        "#,
+    )
+}
+
+#[test]
 fn infer_builtin_macros_include_child_mod() {
     check_types(
         r#"
diff --git a/crates/hir_ty/src/tests/traits.rs b/crates/hir_ty/src/tests/traits.rs
index a5a2df54c..49add4ab9 100644
--- a/crates/hir_ty/src/tests/traits.rs
+++ b/crates/hir_ty/src/tests/traits.rs
@@ -161,6 +161,58 @@ mod result {
 }
 
 #[test]
+fn infer_try_trait_v2() {
+    check_types(
+        r#"
+//- /main.rs crate:main deps:core
+fn test() {
+    let r: Result<i32, u64> = Result::Ok(1);
+    let v = r?;
+    v;
+} //^ i32
+
+//- /core.rs crate:core
+mod ops {
+    mod try_trait {
+        pub trait Try: FromResidual {
+            type Output;
+            type Residual;
+        }
+        pub trait FromResidual<R = <Self as Try>::Residual> {}
+    }
+
+    pub use self::try_trait::FromResidual;
+    pub use self::try_trait::Try;
+}
+
+mov convert {
+    pub trait From<T> {}
+    impl<T> From<T> for T {}
+}
+
+#[prelude_import] use result::*;
+mod result {
+    use crate::convert::From;
+    use crate::ops::{Try, FromResidual};
+
+    pub enum Infallible {}
+    pub enum Result<O, E> {
+        Ok(O),
+        Err(E)
+    }
+
+    impl<O, E> Try for Result<O, E> {
+        type Output = O;
+        type Error = Result<Infallible, E>;
+    }
+
+    impl<T, E, F: From<E>> FromResidual<Result<Infallible, E>> for Result<T, F> {}
+}
+"#,
+    );
+}
+
+#[test]
 fn infer_for_loop() {
     check_types(
         r#"
@@ -3041,7 +3093,7 @@ fn infer_fn_trait_arg() {
 
 #[test]
 fn infer_box_fn_arg() {
-    // The type mismatch is a bug
+    // The type mismatch is because we don't define Unsize and CoerceUnsized
     check_infer_with_mismatches(
         r#"
 //- /lib.rs deps:std
@@ -3101,7 +3153,7 @@ fn foo() {
             555..557 'ps': {unknown}
             559..561 '{}': ()
             568..569 'f': Box<dyn FnOnce(&Option<i32>)>
-            568..573 'f(&s)': FnOnce::Output<dyn FnOnce(&Option<i32>), (&Option<i32>,)>
+            568..573 'f(&s)': ()
             570..572 '&s': &Option<i32>
             571..572 's': Option<i32>
             549..562: expected Box<dyn FnOnce(&Option<i32>)>, got Box<|{unknown}| -> ()>
@@ -3571,3 +3623,104 @@ fn main() {
         "#]],
     )
 }
+
+#[test]
+fn fn_returning_unit() {
+    check_infer_with_mismatches(
+        r#"
+#[lang = "fn_once"]
+trait FnOnce<Args> {
+    type Output;
+}
+
+fn test<F: FnOnce()>(f: F) {
+    let _: () = f();
+}"#,
+        expect![[r#"
+            82..83 'f': F
+            88..112 '{     ...f(); }': ()
+            98..99 '_': ()
+            106..107 'f': F
+            106..109 'f()': ()
+        "#]],
+    );
+}
+
+#[test]
+fn trait_in_scope_of_trait_impl() {
+    check_infer(
+        r#"
+mod foo {
+    pub trait Foo {
+        fn foo(self);
+        fn bar(self) -> usize { 0 }
+    }
+}
+impl foo::Foo for u32 {
+    fn foo(self) {
+        let _x = self.bar();
+    }
+}
+    "#,
+        expect![[r#"
+            45..49 'self': Self
+            67..71 'self': Self
+            82..87 '{ 0 }': usize
+            84..85 '0': usize
+            131..135 'self': u32
+            137..173 '{     ...     }': ()
+            151..153 '_x': usize
+            156..160 'self': u32
+            156..166 'self.bar()': usize
+        "#]],
+    );
+}
+
+#[test]
+fn infer_async_ret_type() {
+    check_types(
+        r#"
+//- /main.rs crate:main deps:core
+
+enum Result<T, E> {
+    Ok(T),
+    Err(E),
+}
+
+use Result::*;
+
+
+struct Fooey;
+
+impl Fooey {
+    fn collect<B: Convert>(self) -> B {
+        B::new()
+    }
+}
+
+trait Convert {
+    fn new() -> Self;
+}
+impl Convert for u32 {
+    fn new() -> Self {
+        0
+    }
+}
+
+async fn get_accounts() -> Result<u32, ()> {
+    let ret = Fooey.collect();
+    //                      ^ u32
+    Ok(ret)
+}
+
+//- /core.rs crate:core
+#[prelude_import] use future::*;
+mod future {
+    #[lang = "future_trait"]
+    trait Future {
+        type Output;
+    }
+}
+"#,
+    );
+}
diff --git a/crates/hir_ty/src/traits.rs b/crates/hir_ty/src/traits.rs
index 294cb531c..f589b314b 100644
--- a/crates/hir_ty/src/traits.rs
+++ b/crates/hir_ty/src/traits.rs
@@ -112,7 +112,7 @@ fn solve(
     let fuel = std::cell::Cell::new(CHALK_SOLVER_FUEL);
 
     let should_continue = || {
-        context.db.check_canceled();
+        db.unwind_if_cancelled();
         let remaining = fuel.get();
         fuel.set(remaining - 1);
         if remaining == 0 {