14 files changed, 398 insertions, 84 deletions

diff --git a/crates/hir_ty/src/display.rs b/crates/hir_ty/src/display.rs
index 64b68014d..f389c5a4b 100644
--- a/crates/hir_ty/src/display.rs
+++ b/crates/hir_ty/src/display.rs
@@ -380,20 +380,34 @@ impl HirDisplay for ApplicationTy {
                     write!(f, ">")?;
                 }
             }
+            TypeCtor::ForeignType(type_alias) => {
+                let type_alias = f.db.type_alias_data(type_alias);
+                write!(f, "{}", type_alias.name)?;
+                if self.parameters.len() > 0 {
+                    write!(f, "<")?;
+                    f.write_joined(&*self.parameters.0, ", ")?;
+                    write!(f, ">")?;
+                }
+            }
             TypeCtor::OpaqueType(opaque_ty_id) => {
-                let bounds = match opaque_ty_id {
+                match opaque_ty_id {
                     OpaqueTyId::ReturnTypeImplTrait(func, idx) => {
                         let datas =
                             f.db.return_type_impl_traits(func).expect("impl trait id without data");
                         let data = (*datas)
                             .as_ref()
                             .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
-                        data.subst(&self.parameters)
+                        let bounds = data.subst(&self.parameters);
+                        write!(f, "impl ")?;
+                        write_bounds_like_dyn_trait(&bounds.value, f)?;
+                        // FIXME: it would maybe be good to distinguish this from the alias type (when debug printing), and to show the substitution
                     }
-                };
-                write!(f, "impl ")?;
-                write_bounds_like_dyn_trait(&bounds.value, f)?;
-                // FIXME: it would maybe be good to distinguish this from the alias type (when debug printing), and to show the substitution
+                    OpaqueTyId::AsyncBlockTypeImplTrait(..) => {
+                        write!(f, "impl Future<Output = ")?;
+                        self.parameters[0].hir_fmt(f)?;
+                        write!(f, ">")?;
+                    }
+                }
             }
             TypeCtor::Closure { .. } => {
                 let sig = self.parameters[0].callable_sig(f.db);
@@ -474,18 +488,21 @@ impl HirDisplay for Ty {
                 write_bounds_like_dyn_trait(predicates, f)?;
             }
             Ty::Opaque(opaque_ty) => {
-                let bounds = match opaque_ty.opaque_ty_id {
+                match opaque_ty.opaque_ty_id {
                     OpaqueTyId::ReturnTypeImplTrait(func, idx) => {
                         let datas =
                             f.db.return_type_impl_traits(func).expect("impl trait id without data");
                         let data = (*datas)
                             .as_ref()
                             .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
-                        data.subst(&opaque_ty.parameters)
+                        let bounds = data.subst(&opaque_ty.parameters);
+                        write!(f, "impl ")?;
+                        write_bounds_like_dyn_trait(&bounds.value, f)?;
+                    }
+                    OpaqueTyId::AsyncBlockTypeImplTrait(..) => {
+                        write!(f, "{{async block}}")?;
                     }
                 };
-                write!(f, "impl ")?;
-                write_bounds_like_dyn_trait(&bounds.value, f)?;
             }
             Ty::Unknown => write!(f, "{{unknown}}")?,
             Ty::Infer(..) => write!(f, "_")?,
diff --git a/crates/hir_ty/src/infer/expr.rs b/crates/hir_ty/src/infer/expr.rs
index a2f849d02..0a141b9cb 100644
--- a/crates/hir_ty/src/infer/expr.rs
+++ b/crates/hir_ty/src/infer/expr.rs
@@ -17,8 +17,8 @@ use crate::{
     autoderef, method_resolution, op,
     traits::{FnTrait, InEnvironment},
     utils::{generics, variant_data, Generics},
-    ApplicationTy, Binders, CallableDefId, InferTy, IntTy, Mutability, Obligation, Rawness, Substs,
-    TraitRef, Ty, TypeCtor,
+    ApplicationTy, Binders, CallableDefId, InferTy, IntTy, Mutability, Obligation, OpaqueTyId,
+    Rawness, Substs, TraitRef, Ty, TypeCtor,
 };
 
 use super::{
@@ -146,6 +146,13 @@ impl<'a> InferenceContext<'a> {
                 // FIXME should be std::result::Result<{inner}, _>
                 Ty::Unknown
             }
+            Expr::Async { body } => {
+                // Use the first type parameter as the output type of future.
+                // existenail type AsyncBlockImplTrait<InnerType>: Future<Output = InnerType>
+                let inner_ty = self.infer_expr(*body, &Expectation::none());
+                let opaque_ty_id = OpaqueTyId::AsyncBlockTypeImplTrait(self.owner, *body);
+                Ty::apply_one(TypeCtor::OpaqueType(opaque_ty_id), inner_ty)
+            }
             Expr::Loop { body, label } => {
                 self.breakables.push(BreakableContext {
                     may_break: false,
diff --git a/crates/hir_ty/src/infer/pat.rs b/crates/hir_ty/src/infer/pat.rs
index dde38bc39..cde2ab82b 100644
--- a/crates/hir_ty/src/infer/pat.rs
+++ b/crates/hir_ty/src/infer/pat.rs
@@ -209,6 +209,18 @@ impl<'a> InferenceContext<'a> {
                 end_ty
             }
             Pat::Lit(expr) => self.infer_expr(*expr, &Expectation::has_type(expected.clone())),
+            Pat::Box { inner } => match self.resolve_boxed_box() {
+                Some(box_adt) => {
+                    let inner_expected = match expected.as_adt() {
+                        Some((adt, substs)) if adt == box_adt => substs.as_single(),
+                        _ => &Ty::Unknown,
+                    };
+
+                    let inner_ty = self.infer_pat(*inner, inner_expected, default_bm);
+                    Ty::apply_one(TypeCtor::Adt(box_adt), inner_ty)
+                }
+                None => Ty::Unknown,
+            },
             Pat::Missing => Ty::Unknown,
         };
         // use a new type variable if we got Ty::Unknown here
@@ -236,6 +248,6 @@ fn is_non_ref_pat(body: &hir_def::body::Body, pat: PatId) -> bool {
             Expr::Literal(Literal::String(..)) => false,
             _ => true,
         },
-        Pat::Wild | Pat::Bind { .. } | Pat::Ref { .. } | Pat::Missing => false,
+        Pat::Wild | Pat::Bind { .. } | Pat::Ref { .. } | Pat::Box { .. } | Pat::Missing => false,
     }
 }
diff --git a/crates/hir_ty/src/lib.rs b/crates/hir_ty/src/lib.rs
index 1e748476a..768d95eff 100644
--- a/crates/hir_ty/src/lib.rs
+++ b/crates/hir_ty/src/lib.rs
@@ -129,10 +129,14 @@ pub enum TypeCtor {
 
     /// 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. As with that one,
-    /// these are only produced by Chalk.
+    /// 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),
 
+    /// Represents a foreign type declared in external blocks.
+    ForeignType(TypeAliasId),
+
     /// The type of a specific closure.
     ///
     /// The closure signature is stored in a `FnPtr` type in the first type
@@ -167,12 +171,18 @@ impl TypeCtor {
                 let generic_params = generics(db.upcast(), type_alias.into());
                 generic_params.len()
             }
+            TypeCtor::ForeignType(type_alias) => {
+                let generic_params = generics(db.upcast(), type_alias.into());
+                generic_params.len()
+            }
             TypeCtor::OpaqueType(opaque_ty_id) => {
                 match opaque_ty_id {
                     OpaqueTyId::ReturnTypeImplTrait(func, _) => {
                         let generic_params = generics(db.upcast(), func.into());
                         generic_params.len()
                     }
+                    // 1 param representing Future::Output type.
+                    OpaqueTyId::AsyncBlockTypeImplTrait(..) => 1,
                 }
             }
             TypeCtor::FnPtr { num_args, is_varargs: _ } => num_args as usize + 1,
@@ -201,10 +211,14 @@ impl TypeCtor {
             TypeCtor::AssociatedType(type_alias) => {
                 Some(type_alias.lookup(db.upcast()).module(db.upcast()).krate)
             }
+            TypeCtor::ForeignType(type_alias) => {
+                Some(type_alias.lookup(db.upcast()).module(db.upcast()).krate)
+            }
             TypeCtor::OpaqueType(opaque_ty_id) => match opaque_ty_id {
                 OpaqueTyId::ReturnTypeImplTrait(func, _) => {
                     Some(func.lookup(db.upcast()).module(db.upcast()).krate)
                 }
+                OpaqueTyId::AsyncBlockTypeImplTrait(def, _) => Some(def.module(db.upcast()).krate),
             },
         }
     }
@@ -227,6 +241,7 @@ impl TypeCtor {
             TypeCtor::Adt(adt) => Some(adt.into()),
             TypeCtor::FnDef(callable) => Some(callable.into()),
             TypeCtor::AssociatedType(type_alias) => Some(type_alias.into()),
+            TypeCtor::ForeignType(type_alias) => Some(type_alias.into()),
             TypeCtor::OpaqueType(_impl_trait_id) => None,
         }
     }
@@ -843,6 +858,29 @@ impl Ty {
 
     pub fn impl_trait_bounds(&self, db: &dyn HirDatabase) -> Option<Vec<GenericPredicate>> {
         match self {
+            Ty::Apply(ApplicationTy { ctor: TypeCtor::OpaqueType(opaque_ty_id), .. }) => {
+                match opaque_ty_id {
+                    OpaqueTyId::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 = GenericPredicate::Implemented(TraitRef {
+                                trait_: future_trait,
+                                substs: Substs::empty(),
+                            });
+                            Some(vec![impl_bound])
+                        } else {
+                            None
+                        }
+                    }
+                    OpaqueTyId::ReturnTypeImplTrait(..) => None,
+                }
+            }
             Ty::Opaque(opaque_ty) => {
                 let predicates = match opaque_ty.opaque_ty_id {
                     OpaqueTyId::ReturnTypeImplTrait(func, idx) => {
@@ -853,6 +891,8 @@ impl Ty {
                             data.subst(&opaque_ty.parameters)
                         })
                     }
+                    // It always has an parameter for Future::Output type.
+                    OpaqueTyId::AsyncBlockTypeImplTrait(..) => unreachable!(),
                 };
 
                 predicates.map(|it| it.value)
@@ -1065,6 +1105,7 @@ impl<T: TypeWalk> TypeWalk for Vec<T> {
 #[derive(Copy, Clone, PartialEq, Eq, Debug, Hash)]
 pub enum OpaqueTyId {
     ReturnTypeImplTrait(hir_def::FunctionId, u16),
+    AsyncBlockTypeImplTrait(hir_def::DefWithBodyId, ExprId),
 }
 
 #[derive(Clone, PartialEq, Eq, Debug, Hash)]
diff --git a/crates/hir_ty/src/lower.rs b/crates/hir_ty/src/lower.rs
index cd574e983..708e2af0f 100644
--- a/crates/hir_ty/src/lower.rs
+++ b/crates/hir_ty/src/lower.rs
@@ -1101,10 +1101,14 @@ fn type_for_type_alias(db: &dyn HirDatabase, t: TypeAliasId) -> Binders<Ty> {
     let resolver = t.resolver(db.upcast());
     let ctx =
         TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
-    let type_ref = &db.type_alias_data(t).type_ref;
     let substs = Substs::bound_vars(&generics, DebruijnIndex::INNERMOST);
-    let inner = Ty::from_hir(&ctx, type_ref.as_ref().unwrap_or(&TypeRef::Error));
-    Binders::new(substs.len(), inner)
+    if db.type_alias_data(t).is_extern {
+        Binders::new(substs.len(), Ty::apply(TypeCtor::ForeignType(t), substs))
+    } else {
+        let type_ref = &db.type_alias_data(t).type_ref;
+        let inner = Ty::from_hir(&ctx, type_ref.as_ref().unwrap_or(&TypeRef::Error));
+        Binders::new(substs.len(), inner)
+    }
 }
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
diff --git a/crates/hir_ty/src/method_resolution.rs b/crates/hir_ty/src/method_resolution.rs
index ec59145c7..8961df404 100644
--- a/crates/hir_ty/src/method_resolution.rs
+++ b/crates/hir_ty/src/method_resolution.rs
@@ -250,6 +250,14 @@ impl Ty {
                 TypeCtor::Adt(def_id) => {
                     return Some(std::iter::once(def_id.module(db.upcast()).krate).collect())
                 }
+                TypeCtor::ForeignType(type_alias_id) => {
+                    return Some(
+                        std::iter::once(
+                            type_alias_id.lookup(db.upcast()).module(db.upcast()).krate,
+                        )
+                        .collect(),
+                    )
+                }
                 TypeCtor::Bool => lang_item_crate!("bool"),
                 TypeCtor::Char => lang_item_crate!("char"),
                 TypeCtor::Float(f) => match f.bitness {
diff --git a/crates/hir_ty/src/tests/method_resolution.rs b/crates/hir_ty/src/tests/method_resolution.rs
index 23b2601e6..0f17ff151 100644
--- a/crates/hir_ty/src/tests/method_resolution.rs
+++ b/crates/hir_ty/src/tests/method_resolution.rs
@@ -1051,3 +1051,39 @@ fn dyn_trait_super_trait_not_in_scope() {
         "#]],
     );
 }
+
+#[test]
+fn method_resolution_foreign_opaque_type() {
+    check_infer(
+        r#"
+        extern "C" {
+            type S;
+            fn f() -> &'static S;
+        }
+
+        impl S {
+            fn foo(&self) -> bool {
+                true
+            }
+        }
+
+        fn test() {
+            let s = unsafe { f() };
+            s.foo();
+        }
+        "#,
+        expect![[r#"
+            75..79 'self': &S
+            89..109 '{     ...     }': bool
+            99..103 'true': bool
+            123..167 '{     ...o(); }': ()
+            133..134 's': &S
+            137..151 'unsafe { f() }': &S
+            144..151 '{ f() }': &S
+            146..147 'f': fn f() -> &S
+            146..149 'f()': &S
+            157..158 's': &S
+            157..164 's.foo()': bool
+        "#]],
+    );
+}
diff --git a/crates/hir_ty/src/tests/patterns.rs b/crates/hir_ty/src/tests/patterns.rs
index aeb191c79..6a965ac4f 100644
--- a/crates/hir_ty/src/tests/patterns.rs
+++ b/crates/hir_ty/src/tests/patterns.rs
@@ -654,3 +654,28 @@ fn slice_tail_pattern() {
         "#]],
     );
 }
+
+#[test]
+fn box_pattern() {
+    check_infer(
+        r#"
+        #[lang = "owned_box"]
+        pub struct Box<T>(T);
+
+        fn foo(params: Box<i32>) {
+            match params {
+                box integer => {}
+            }
+        }
+        "#,
+        expect![[r#"
+            52..58 'params': Box<i32>
+            70..124 '{     ...   } }': ()
+            76..122 'match ...     }': ()
+            82..88 'params': Box<i32>
+            99..110 'box integer': Box<i32>
+            103..110 'integer': i32
+            114..116 '{}': ()
+        "#]],
+    );
+}
diff --git a/crates/hir_ty/src/tests/simple.rs b/crates/hir_ty/src/tests/simple.rs
index 48db23a34..5b07948f3 100644
--- a/crates/hir_ty/src/tests/simple.rs
+++ b/crates/hir_ty/src/tests/simple.rs
@@ -1889,31 +1889,40 @@ fn fn_pointer_return() {
 fn effects_smoke_test() {
     check_infer(
         r#"
-        fn main() {
+        async fn main() {
             let x = unsafe { 92 };
             let y = async { async { () }.await };
             let z = try { () };
             let t = 'a: { 92 };
         }
+
+        #[prelude_import] use future::*;
+
+        mod future {
+            #[lang = "future_trait"]
+            pub trait Future { type Output; }
+        }
         "#,
         expect![[r#"
-            10..130 '{     ...2 }; }': ()
-            20..21 'x': i32
-            24..37 'unsafe { 92 }': i32
-            31..37 '{ 92 }': i32
-            33..35 '92': i32
-            47..48 'y': {unknown}
-            57..79 '{ asyn...wait }': {unknown}
-            59..77 'async ....await': {unknown}
-            65..71 '{ () }': ()
-            67..69 '()': ()
-            89..90 'z': {unknown}
-            93..103 'try { () }': {unknown}
-            97..103 '{ () }': ()
-            99..101 '()': ()
-            113..114 't': i32
-            121..127 '{ 92 }': i32
-            123..125 '92': i32
+            16..136 '{     ...2 }; }': ()
+            26..27 'x': i32
+            30..43 'unsafe { 92 }': i32
+            37..43 '{ 92 }': i32
+            39..41 '92': i32
+            53..54 'y': impl Future<Output = ()>
+            57..85 'async ...wait }': impl Future<Output = ()>
+            63..85 '{ asyn...wait }': ()
+            65..77 'async { () }': impl Future<Output = ()>
+            65..83 'async ....await': ()
+            71..77 '{ () }': ()
+            73..75 '()': ()
+            95..96 'z': {unknown}
+            99..109 'try { () }': {unknown}
+            103..109 '{ () }': ()
+            105..107 '()': ()
+            119..120 't': i32
+            127..133 '{ 92 }': i32
+            129..131 '92': i32
         "#]],
     )
 }
diff --git a/crates/hir_ty/src/tests/traits.rs b/crates/hir_ty/src/tests/traits.rs
index 1f1056962..41d097519 100644
--- a/crates/hir_ty/src/tests/traits.rs
+++ b/crates/hir_ty/src/tests/traits.rs
@@ -86,6 +86,46 @@ mod future {
 }
 
 #[test]
+fn infer_async_block() {
+    check_types(
+        r#"
+//- /main.rs crate:main deps:core
+async fn test() {
+    let a = async { 42 };
+    a;
+//  ^ impl Future<Output = i32>
+    let x = a.await;
+    x;
+//  ^ i32
+    let b = async {}.await;
+    b;
+//  ^ ()
+    let c = async {
+        let y = Option::None;
+        y
+    //  ^ Option<u64>
+    };
+    let _: Option<u64> = c.await;
+    c;
+//  ^ impl Future<Output = Option<u64>>
+}
+
+enum Option<T> { None, Some(T) }
+
+//- /core.rs crate:core
+#[prelude_import] use future::*;
+mod future {
+    #[lang = "future_trait"]
+    trait Future {
+        type Output;
+    }
+}
+
+"#,
+    );
+}
+
+#[test]
 fn infer_try() {
     check_types(
         r#"
diff --git a/crates/hir_ty/src/traits/chalk.rs b/crates/hir_ty/src/traits/chalk.rs
index 01b5717a3..27f0ed628 100644
--- a/crates/hir_ty/src/traits/chalk.rs
+++ b/crates/hir_ty/src/traits/chalk.rs
@@ -11,6 +11,7 @@ use hir_def::{
     lang_item::{lang_attr, LangItemTarget},
     AssocContainerId, AssocItemId, HasModule, Lookup, TypeAliasId,
 };
+use hir_expand::name::name;
 
 use super::ChalkContext;
 use crate::{
@@ -18,10 +19,12 @@ use crate::{
     display::HirDisplay,
     method_resolution::{TyFingerprint, ALL_FLOAT_FPS, ALL_INT_FPS},
     utils::generics,
-    CallableDefId, DebruijnIndex, FnSig, GenericPredicate, Substs, Ty, TypeCtor,
+    BoundVar, CallableDefId, DebruijnIndex, FnSig, GenericPredicate, ProjectionPredicate,
+    ProjectionTy, Substs, TraitRef, Ty, TypeCtor,
 };
 use mapping::{
-    convert_where_clauses, generic_predicate_to_inline_bound, make_binders, TypeAliasAsValue,
+    convert_where_clauses, generic_predicate_to_inline_bound, make_binders, TypeAliasAsAssocType,
+    TypeAliasAsValue,
 };
 
 pub use self::interner::*;
@@ -166,27 +169,88 @@ impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
     fn opaque_ty_data(&self, id: chalk_ir::OpaqueTyId<Interner>) -> Arc<OpaqueTyDatum> {
         let interned_id = crate::db::InternedOpaqueTyId::from(id);
         let full_id = self.db.lookup_intern_impl_trait_id(interned_id);
-        let (func, idx) = match full_id {
-            crate::OpaqueTyId::ReturnTypeImplTrait(func, idx) => (func, idx),
-        };
-        let datas =
-            self.db.return_type_impl_traits(func).expect("impl trait id without impl traits");
-        let data = &datas.value.impl_traits[idx as usize];
-        let bound = OpaqueTyDatumBound {
-            bounds: make_binders(
-                data.bounds
-                    .value
-                    .iter()
-                    .cloned()
-                    .filter(|b| !b.is_error())
-                    .map(|b| b.to_chalk(self.db))
-                    .collect(),
-                1,
-            ),
-            where_clauses: make_binders(vec![], 0),
+        let bound = match full_id {
+            crate::OpaqueTyId::ReturnTypeImplTrait(func, idx) => {
+                let datas = self
+                    .db
+                    .return_type_impl_traits(func)
+                    .expect("impl trait id without impl traits");
+                let data = &datas.value.impl_traits[idx as usize];
+                let bound = OpaqueTyDatumBound {
+                    bounds: make_binders(
+                        data.bounds
+                            .value
+                            .iter()
+                            .cloned()
+                            .filter(|b| !b.is_error())
+                            .map(|b| b.to_chalk(self.db))
+                            .collect(),
+                        1,
+                    ),
+                    where_clauses: make_binders(vec![], 0),
+                };
+                let num_vars = datas.num_binders;
+                make_binders(bound, num_vars)
+            }
+            crate::OpaqueTyId::AsyncBlockTypeImplTrait(..) => {
+                if let Some((future_trait, future_output)) = self
+                    .db
+                    .lang_item(self.krate, "future_trait".into())
+                    .and_then(|item| item.as_trait())
+                    .and_then(|trait_| {
+                        let alias =
+                            self.db.trait_data(trait_).associated_type_by_name(&name![Output])?;
+                        Some((trait_, alias))
+                    })
+                {
+                    // Making up `AsyncBlock<T>: Future<Output = T>`
+                    //
+                    // |--------------------OpaqueTyDatum-------------------|
+                    //        |-------------OpaqueTyDatumBound--------------|
+                    // for<T> <Self> [Future<Self>, Future::Output<Self> = T]
+                    //     ^1  ^0            ^0                    ^0      ^1
+                    let impl_bound = GenericPredicate::Implemented(TraitRef {
+                        trait_: future_trait,
+                        // Self type as the first parameter.
+                        substs: Substs::single(Ty::Bound(BoundVar {
+                            debruijn: DebruijnIndex::INNERMOST,
+                            index: 0,
+                        })),
+                    });
+                    let proj_bound = GenericPredicate::Projection(ProjectionPredicate {
+                        // The parameter of the opaque type.
+                        ty: Ty::Bound(BoundVar { debruijn: DebruijnIndex::ONE, index: 0 }),
+                        projection_ty: ProjectionTy {
+                            associated_ty: future_output,
+                            // Self type as the first parameter.
+                            parameters: Substs::single(Ty::Bound(BoundVar::new(
+                                DebruijnIndex::INNERMOST,
+                                0,
+                            ))),
+                        },
+                    });
+                    let bound = OpaqueTyDatumBound {
+                        bounds: make_binders(
+                            vec![impl_bound.to_chalk(self.db), proj_bound.to_chalk(self.db)],
+                            1,
+                        ),
+                        where_clauses: make_binders(vec![], 0),
+                    };
+                    // The opaque type has 1 parameter.
+                    make_binders(bound, 1)
+                } else {
+                    // If failed to find `Future::Output`, return empty bounds as fallback.
+                    let bound = OpaqueTyDatumBound {
+                        bounds: make_binders(vec![], 0),
+                        where_clauses: make_binders(vec![], 0),
+                    };
+                    // The opaque type has 1 parameter.
+                    make_binders(bound, 1)
+                }
+            }
         };
-        let num_vars = datas.num_binders;
-        Arc::new(OpaqueTyDatum { opaque_ty_id: id, bound: make_binders(bound, num_vars) })
+
+        Arc::new(OpaqueTyDatum { opaque_ty_id: id, bound })
     }
 
     fn hidden_opaque_type(&self, _id: chalk_ir::OpaqueTyId<Interner>) -> chalk_ir::Ty<Interner> {
@@ -277,7 +341,7 @@ pub(crate) fn associated_ty_data_query(
     id: AssocTypeId,
 ) -> Arc<AssociatedTyDatum> {
     debug!("associated_ty_data {:?}", id);
-    let type_alias: TypeAliasId = from_chalk(db, id);
+    let type_alias: TypeAliasId = from_chalk::<TypeAliasAsAssocType, _>(db, id).0;
     let trait_ = match type_alias.lookup(db.upcast()).container {
         AssocContainerId::TraitId(t) => t,
         _ => panic!("associated type not in trait"),
@@ -331,8 +395,10 @@ pub(crate) fn trait_datum_query(
         fundamental: false,
     };
     let where_clauses = convert_where_clauses(db, trait_.into(), &bound_vars);
-    let associated_ty_ids =
-        trait_data.associated_types().map(|type_alias| type_alias.to_chalk(db)).collect();
+    let associated_ty_ids = trait_data
+        .associated_types()
+        .map(|type_alias| TypeAliasAsAssocType(type_alias).to_chalk(db))
+        .collect();
     let trait_datum_bound = rust_ir::TraitDatumBound { where_clauses };
     let well_known =
         lang_attr(db.upcast(), trait_).and_then(|name| well_known_trait_from_lang_attr(&name));
@@ -370,6 +436,7 @@ fn lang_attr_from_well_known_trait(attr: WellKnownTrait) -> &'static str {
         WellKnownTrait::FnMut => "fn_mut",
         WellKnownTrait::Fn => "fn",
         WellKnownTrait::Unsize => "unsize",
+        WellKnownTrait::Unpin => "unpin",
     }
 }
 
@@ -513,7 +580,7 @@ fn type_alias_associated_ty_value(
     let value_bound = rust_ir::AssociatedTyValueBound { ty: ty.value.to_chalk(db) };
     let value = rust_ir::AssociatedTyValue {
         impl_id: impl_id.to_chalk(db),
-        associated_ty_id: assoc_ty.to_chalk(db),
+        associated_ty_id: TypeAliasAsAssocType(assoc_ty).to_chalk(db),
         value: make_binders(value_bound, ty.num_binders),
     };
     Arc::new(value)
@@ -548,9 +615,11 @@ pub(crate) fn fn_def_datum_query(
     };
     let datum = FnDefDatum {
         id: fn_def_id,
-        abi: (),
-        safety: chalk_ir::Safety::Safe,
-        variadic: sig.value.is_varargs,
+        sig: chalk_ir::FnSig {
+            abi: (),
+            safety: chalk_ir::Safety::Safe,
+            variadic: sig.value.is_varargs,
+        },
         binders: make_binders(bound, sig.num_binders),
     };
     Arc::new(datum)
diff --git a/crates/hir_ty/src/traits/chalk/interner.rs b/crates/hir_ty/src/traits/chalk/interner.rs
index eb35db3ff..f9304b7d0 100644
--- a/crates/hir_ty/src/traits/chalk/interner.rs
+++ b/crates/hir_ty/src/traits/chalk/interner.rs
@@ -12,6 +12,7 @@ pub struct Interner;
 
 pub type AssocTypeId = chalk_ir::AssocTypeId<Interner>;
 pub type AssociatedTyDatum = chalk_solve::rust_ir::AssociatedTyDatum<Interner>;
+pub type ForeignDefId = chalk_ir::ForeignDefId<Interner>;
 pub type TraitId = chalk_ir::TraitId<Interner>;
 pub type TraitDatum = chalk_solve::rust_ir::TraitDatum<Interner>;
 pub type AdtId = chalk_ir::AdtId<Interner>;
diff --git a/crates/hir_ty/src/traits/chalk/mapping.rs b/crates/hir_ty/src/traits/chalk/mapping.rs
index d6bacba1d..d42f4bba9 100644
--- a/crates/hir_ty/src/traits/chalk/mapping.rs
+++ b/crates/hir_ty/src/traits/chalk/mapping.rs
@@ -34,9 +34,11 @@ impl ToChalk for Ty {
                     let substitution = apply_ty.parameters.to_chalk(db).shifted_in(&Interner);
                     chalk_ir::TyData::Function(chalk_ir::FnPointer {
                         num_binders: 0,
-                        abi: (),
-                        safety: chalk_ir::Safety::Safe,
-                        variadic: is_varargs,
+                        sig: chalk_ir::FnSig {
+                            abi: (),
+                            safety: chalk_ir::Safety::Safe,
+                            variadic: is_varargs,
+                        },
                         substitution,
                     })
                     .intern(&Interner)
@@ -48,7 +50,7 @@ impl ToChalk for Ty {
                 }
             },
             Ty::Projection(proj_ty) => {
-                let associated_ty_id = proj_ty.associated_ty.to_chalk(db);
+                let associated_ty_id = TypeAliasAsAssocType(proj_ty.associated_ty).to_chalk(db);
                 let substitution = proj_ty.parameters.to_chalk(db);
                 chalk_ir::AliasTy::Projection(chalk_ir::ProjectionTy {
                     associated_ty_id,
@@ -114,7 +116,8 @@ impl ToChalk for Ty {
                 Ty::Placeholder(db.lookup_intern_type_param_id(interned_id))
             }
             chalk_ir::TyData::Alias(chalk_ir::AliasTy::Projection(proj)) => {
-                let associated_ty = from_chalk(db, proj.associated_ty_id);
+                let associated_ty =
+                    from_chalk::<TypeAliasAsAssocType, _>(db, proj.associated_ty_id).0;
                 let parameters = from_chalk(db, proj.substitution);
                 Ty::Projection(ProjectionTy { associated_ty, parameters })
             }
@@ -125,7 +128,7 @@ impl ToChalk for Ty {
             }
             chalk_ir::TyData::Function(chalk_ir::FnPointer {
                 num_binders,
-                variadic,
+                sig: chalk_ir::FnSig { variadic, .. },
                 substitution,
                 ..
             }) => {
@@ -290,8 +293,9 @@ impl ToChalk for TypeCtor {
     fn to_chalk(self, db: &dyn HirDatabase) -> TypeName<Interner> {
         match self {
             TypeCtor::AssociatedType(type_alias) => {
-                let type_id = type_alias.to_chalk(db);
-                TypeName::AssociatedType(type_id)
+                let assoc_type = TypeAliasAsAssocType(type_alias);
+                let assoc_type_id = assoc_type.to_chalk(db);
+                TypeName::AssociatedType(assoc_type_id)
             }
 
             TypeCtor::OpaqueType(impl_trait_id) => {
@@ -299,6 +303,12 @@ impl ToChalk for TypeCtor {
                 TypeName::OpaqueType(id)
             }
 
+            TypeCtor::ForeignType(type_alias) => {
+                let foreign_type = TypeAliasAsForeignType(type_alias);
+                let foreign_type_id = foreign_type.to_chalk(db);
+                TypeName::Foreign(foreign_type_id)
+            }
+
             TypeCtor::Bool => TypeName::Scalar(Scalar::Bool),
             TypeCtor::Char => TypeName::Scalar(Scalar::Char),
             TypeCtor::Int(int_ty) => TypeName::Scalar(int_ty_to_chalk(int_ty)),
@@ -339,7 +349,9 @@ impl ToChalk for TypeCtor {
     fn from_chalk(db: &dyn HirDatabase, type_name: TypeName<Interner>) -> TypeCtor {
         match type_name {
             TypeName::Adt(struct_id) => TypeCtor::Adt(struct_id.0),
-            TypeName::AssociatedType(type_id) => TypeCtor::AssociatedType(from_chalk(db, type_id)),
+            TypeName::AssociatedType(type_id) => {
+                TypeCtor::AssociatedType(from_chalk::<TypeAliasAsAssocType, _>(db, type_id).0)
+            }
             TypeName::OpaqueType(opaque_type_id) => {
                 TypeCtor::OpaqueType(from_chalk(db, opaque_type_id))
             }
@@ -379,6 +391,10 @@ impl ToChalk for TypeCtor {
                 TypeCtor::Closure { def, expr }
             }
 
+            TypeName::Foreign(foreign_def_id) => {
+                TypeCtor::ForeignType(from_chalk::<TypeAliasAsForeignType, _>(db, foreign_def_id).0)
+            }
+
             TypeName::Error => {
                 // this should not be reached, since we don't represent TypeName::Error with TypeCtor
                 unreachable!()
@@ -488,15 +504,31 @@ impl ToChalk for CallableDefId {
     }
 }
 
-impl ToChalk for TypeAliasId {
+pub struct TypeAliasAsAssocType(pub TypeAliasId);
+
+impl ToChalk for TypeAliasAsAssocType {
     type Chalk = AssocTypeId;
 
     fn to_chalk(self, _db: &dyn HirDatabase) -> AssocTypeId {
-        chalk_ir::AssocTypeId(self.as_intern_id())
+        chalk_ir::AssocTypeId(self.0.as_intern_id())
+    }
+
+    fn from_chalk(_db: &dyn HirDatabase, assoc_type_id: AssocTypeId) -> TypeAliasAsAssocType {
+        TypeAliasAsAssocType(InternKey::from_intern_id(assoc_type_id.0))
+    }
+}
+
+pub struct TypeAliasAsForeignType(pub TypeAliasId);
+
+impl ToChalk for TypeAliasAsForeignType {
+    type Chalk = ForeignDefId;
+
+    fn to_chalk(self, _db: &dyn HirDatabase) -> ForeignDefId {
+        chalk_ir::ForeignDefId(self.0.as_intern_id())
     }
 
-    fn from_chalk(_db: &dyn HirDatabase, type_alias_id: AssocTypeId) -> TypeAliasId {
-        InternKey::from_intern_id(type_alias_id.0)
+    fn from_chalk(_db: &dyn HirDatabase, foreign_def_id: ForeignDefId) -> TypeAliasAsForeignType {
+        TypeAliasAsForeignType(InternKey::from_intern_id(foreign_def_id.0))
     }
 }
 
@@ -580,7 +612,7 @@ impl ToChalk for ProjectionTy {
 
     fn to_chalk(self, db: &dyn HirDatabase) -> chalk_ir::ProjectionTy<Interner> {
         chalk_ir::ProjectionTy {
-            associated_ty_id: self.associated_ty.to_chalk(db),
+            associated_ty_id: TypeAliasAsAssocType(self.associated_ty).to_chalk(db),
             substitution: self.parameters.to_chalk(db),
         }
     }
@@ -590,7 +622,11 @@ impl ToChalk for ProjectionTy {
         projection_ty: chalk_ir::ProjectionTy<Interner>,
     ) -> ProjectionTy {
         ProjectionTy {
-            associated_ty: from_chalk(db, projection_ty.associated_ty_id),
+            associated_ty: from_chalk::<TypeAliasAsAssocType, _>(
+                db,
+                projection_ty.associated_ty_id,
+            )
+            .0,
             parameters: from_chalk(db, projection_ty.substitution),
         }
     }
@@ -789,7 +825,8 @@ pub(super) fn generic_predicate_to_inline_bound(
             let alias_eq_bound = rust_ir::AliasEqBound {
                 value: proj.ty.clone().to_chalk(db),
                 trait_bound: rust_ir::TraitBound { trait_id: trait_.to_chalk(db), args_no_self },
-                associated_ty_id: proj.projection_ty.associated_ty.to_chalk(db),
+                associated_ty_id: TypeAliasAsAssocType(proj.projection_ty.associated_ty)
+                    .to_chalk(db),
                 parameters: Vec::new(), // FIXME we don't support generic associated types yet
             };
             Some(rust_ir::InlineBound::AliasEqBound(alias_eq_bound))
diff --git a/crates/hir_ty/src/traits/chalk/tls.rs b/crates/hir_ty/src/traits/chalk/tls.rs
index db915625c..b4568cff6 100644
--- a/crates/hir_ty/src/traits/chalk/tls.rs
+++ b/crates/hir_ty/src/traits/chalk/tls.rs
@@ -4,7 +4,7 @@ use std::fmt;
 use chalk_ir::{AliasTy, GenericArg, Goal, Goals, Lifetime, ProgramClauseImplication, TypeName};
 use itertools::Itertools;
 
-use super::{from_chalk, Interner};
+use super::{from_chalk, Interner, TypeAliasAsAssocType};
 use crate::{db::HirDatabase, CallableDefId, TypeCtor};
 use hir_def::{AdtId, AssocContainerId, DefWithBodyId, Lookup, TypeAliasId};
 
@@ -73,7 +73,14 @@ impl DebugContext<'_> {
                 crate::OpaqueTyId::ReturnTypeImplTrait(func, idx) => {
                     write!(f, "{{impl trait {} of {:?}}}", idx, func)?;
                 }
+                crate::OpaqueTyId::AsyncBlockTypeImplTrait(def, idx) => {
+                    write!(f, "{{impl trait of async block {} of {:?}}}", idx.into_raw(), def)?;
+                }
             },
+            TypeCtor::ForeignType(type_alias) => {
+                let name = self.0.type_alias_data(type_alias).name.clone();
+                write!(f, "{}", name)?;
+            }
             TypeCtor::Closure { def, expr } => {
                 write!(f, "{{closure {:?} in ", expr.into_raw())?;
                 match def {
@@ -116,7 +123,7 @@ impl DebugContext<'_> {
         id: super::AssocTypeId,
         fmt: &mut fmt::Formatter<'_>,
     ) -> Result<(), fmt::Error> {
-        let type_alias: TypeAliasId = from_chalk(self.0, id);
+        let type_alias: TypeAliasId = from_chalk::<TypeAliasAsAssocType, _>(self.0, id).0;
         let type_alias_data = self.0.type_alias_data(type_alias);
         let trait_ = match type_alias.lookup(self.0.upcast()).container {
             AssocContainerId::TraitId(t) => t,
@@ -150,7 +157,8 @@ impl DebugContext<'_> {
         projection_ty: &chalk_ir::ProjectionTy<Interner>,
         fmt: &mut fmt::Formatter<'_>,
     ) -> Result<(), fmt::Error> {
-        let type_alias: TypeAliasId = from_chalk(self.0, projection_ty.associated_ty_id);
+        let type_alias: TypeAliasId =
+            from_chalk::<TypeAliasAsAssocType, _>(self.0, projection_ty.associated_ty_id).0;
         let type_alias_data = self.0.type_alias_data(type_alias);
         let trait_ = match type_alias.lookup(self.0.upcast()).container {
             AssocContainerId::TraitId(t) => t,