Use Ty::apply instead of simple and fix method resolution.

Author: crlf0710

crates/hir_ty/src/lower.rs

@@ -1102,13 +1102,13 @@ fn type_for_type_alias(db: &dyn HirDatabase, t: TypeAliasId) -> Binders<Ty> {
     let ctx =
         TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
     let substs = Substs::bound_vars(&generics, DebruijnIndex::INNERMOST);
-    let inner = if db.type_alias_data(t).is_extern {
-        Ty::simple(TypeCtor::ForeignType(t))
+    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;
-        Ty::from_hir(&ctx, type_ref.as_ref().unwrap_or(&TypeRef::Error))
-    };
-    Binders::new(substs.len(), inner)
+        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)]

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 {

crates/hir_ty/src/tests/method_resolution.rs

@@ -1072,7 +1072,6 @@ fn method_resolution_foreign_opaque_type() {
             s.foo();
         }
         "#,
-        // FIXME: 's.foo()' should be `bool`.
         expect![[r#"
             75..79 'self': &S
             89..109 '{     ...     }': bool
@@ -1084,8 +1083,7 @@ fn method_resolution_foreign_opaque_type() {
             146..147 'f': fn f() -> &S
             146..149 'f()': &S
             157..158 's': &S
-            157..164 's.foo()': {unknown}
+            157..164 's.foo()': bool
         "#]],
     );
 }
-