10 files changed, 150 insertions, 33 deletions

diff --git a/crates/hir_ty/Cargo.toml b/crates/hir_ty/Cargo.toml
index 7d02aaf95..bc86df2b1 100644
--- a/crates/hir_ty/Cargo.toml
+++ b/crates/hir_ty/Cargo.toml
@@ -17,9 +17,9 @@ ena = "0.14.0"
 log = "0.4.8"
 rustc-hash = "1.1.0"
 scoped-tls = "1"
-chalk-solve = { version = "0.25.0" }
-chalk-ir = { version = "0.25.0" }
-chalk-recursive = { version = "0.25.0" }
+chalk-solve = { version = "0.27.0" }
+chalk-ir = { version = "0.27.0" }
+chalk-recursive = { version = "0.27.0" }
 
 stdx = { path = "../stdx", version = "0.0.0" }
 hir_def = { path = "../hir_def", version = "0.0.0" }
diff --git a/crates/hir_ty/src/display.rs b/crates/hir_ty/src/display.rs
index efb48c7ee..f389c5a4b 100644
--- a/crates/hir_ty/src/display.rs
+++ b/crates/hir_ty/src/display.rs
@@ -380,6 +380,15 @@ 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) => {
                 match opaque_ty_id {
                     OpaqueTyId::ReturnTypeImplTrait(func, idx) => {
diff --git a/crates/hir_ty/src/lib.rs b/crates/hir_ty/src/lib.rs
index f16d1fc97..768d95eff 100644
--- a/crates/hir_ty/src/lib.rs
+++ b/crates/hir_ty/src/lib.rs
@@ -134,6 +134,9 @@ pub enum TypeCtor {
     /// 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
@@ -168,6 +171,10 @@ 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, _) => {
@@ -204,6 +211,9 @@ 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)
@@ -231,6 +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,
         }
     }
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/traits/chalk.rs b/crates/hir_ty/src/traits/chalk.rs
index 57d0a32df..27f0ed628 100644
--- a/crates/hir_ty/src/traits/chalk.rs
+++ b/crates/hir_ty/src/traits/chalk.rs
@@ -23,7 +23,8 @@ use crate::{
     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::*;
@@ -340,7 +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"),
@@ -394,8 +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));
@@ -433,6 +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",
     }
 }
 
@@ -576,7 +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)
@@ -611,9 +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 cb6b0fe81..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};
 
@@ -77,6 +77,10 @@ impl DebugContext<'_> {
                     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 {
@@ -119,7 +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,
@@ -153,7 +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,