Merge #1032

1032: Fix apply_substs assertion failure r=matklad a=flodiebold

Fixes #1030.

Co-authored-by: Florian Diebold <flodiebold@gmail.com>

crates/ra_hir/src/ty/infer.rs

@@ -407,7 +407,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
 
                     let substs =
                         Ty::substs_from_path_segment(self.db, &self.resolver, segment, typable);
-                    self.db.type_for_def(typable, Namespace::Types).apply_substs(substs)
+                    self.db.type_for_def(typable, Namespace::Types).subst(&substs)
                 }
                 Resolution::LocalBinding(_) => {
                     // can't have a local binding in an associated item path
@@ -466,7 +466,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 let typable: Option<TypableDef> = def.into();
                 let typable = typable?;
                 let substs = Ty::substs_from_path(self.db, &self.resolver, path, typable);
-                let ty = self.db.type_for_def(typable, Namespace::Values).apply_substs(substs);
+                let ty = self.db.type_for_def(typable, Namespace::Values).subst(&substs);
                 let ty = self.insert_type_vars(ty);
                 Some(ty)
             }

crates/ra_hir/src/ty/tests.rs

@@ -1791,6 +1791,29 @@ fn test<R>(query_response: Canonical<QueryResponse<R>>) {
     );
 }
 
+#[test]
+fn bug_1030() {
+    assert_snapshot_matches!(infer(r#"
+struct HashSet<T, H>;
+struct FxHasher;
+type FxHashSet<T> = HashSet<T, FxHasher>;
+
+impl<T, H> HashSet<T, H> {
+    fn default() -> HashSet<T, H> {}
+}
+
+pub fn main_loop() {
+    FxHashSet::default();
+}
+"#),
+    @r###"
+[144; 146) '{}': ()
+[169; 198) '{     ...t(); }': ()
+[175; 193) 'FxHash...efault': fn default<{unknown}, {unknown}>() -> HashSet<T, H>
+[175; 195) 'FxHash...ault()': HashSet<{unknown}, {unknown}>"###
+    );
+}
+
 #[test]
 fn cross_crate_associated_method_call() {
     let (mut db, pos) = MockDatabase::with_position(