[resolver] Apply type storage class uses via return types

Change-Id: I16cf23af7f6a792d22268e6af45c77d4faeb6918
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/46460
Commit-Queue: James Price <jrprice@google.com>
Auto-Submit: James Price <jrprice@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>

src/resolver/resolver.cc

@@ -321,6 +321,14 @@ bool Resolver::Function(ast::Function* func) {
 
   if (auto* str =
           func->return_type()->UnwrapAliasIfNeeded()->As<type::Struct>()) {
+    if (!ApplyStorageClassUsageToType(ast::StorageClass::kNone, str,
+                                      func->source())) {
+      diagnostics_.add_note("while instantiating return type for " +
+                                builder_->Symbols().NameFor(func->symbol()),
+                            func->source());
+      return false;
+    }
+
     auto* info = Structure(str);
     if (!info) {
       return false;

src/resolver/struct_storage_class_use_test.cc

@@ -49,6 +49,19 @@ TEST_F(ResolverStorageClassUseTest, StructReachableFromParameter) {
               UnorderedElementsAre(ast::StorageClass::kNone));
 }
 
+TEST_F(ResolverStorageClassUseTest, StructReachableFromReturnType) {
+  auto* s = Structure("S", {Member("a", ty.f32())});
+
+  Func("f", {}, s, {Return(Construct(s))}, {});
+
+  ASSERT_TRUE(r()->Resolve()) << r()->error();
+
+  auto* sem = Sem().Get(s);
+  ASSERT_NE(sem, nullptr);
+  EXPECT_THAT(sem->StorageClassUsage(),
+              UnorderedElementsAre(ast::StorageClass::kNone));
+}
+
 TEST_F(ResolverStorageClassUseTest, StructReachableFromGlobal) {
   auto* s = Structure("S", {Member("a", ty.f32())});