[vm] Ignore differences in generic-covariant-impl flags of type parameters when doing a subtype check

We might get different flags on lhs and rhs of a subtype check as
lhs might come from a tear-off which has generic-covariant-impl type
parameters and rhs is a standalone function type.

TEST=language/regress/regress46816_test
Fixes dart-lang/sdk#46816

Change-Id: Ic0f1b4a9fdf0f4c9ae65c8c372d12c1e51ad8050
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/209265
Reviewed-by: Tess Strickland <[email protected]>
Commit-Queue: Alexander Markov <[email protected]>

Author: alexmarkov

runtime/vm/object.cc

@@ -8949,9 +8949,11 @@ bool FunctionType::HasSameTypeParametersAndBounds(const FunctionType& other,
         }
       }
     }
-    // Compare flags (IsGenericCovariantImpl).
-    if (!Array::Equals(type_params.flags(), other_type_params.flags())) {
-      return false;
+    if (kind != TypeEquality::kInSubtypeTest) {
+      // Compare flags (IsGenericCovariantImpl).
+      if (!Array::Equals(type_params.flags(), other_type_params.flags())) {
+        return false;
+      }
     }
   }
   return true;

tests/language/regress/regress46816_test.dart

@@ -0,0 +1,18 @@
+// Copyright (c) 2021, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:expect/expect.dart';
+
+class A<X extends num> {
+  void f<Y extends X>(Y y) {}
+}
+
+typedef Func = void Function<Y extends int>(Y);
+
+main() {
+  A<num> a = new A<int>();
+  dynamic f = (a as A<int>).f;
+  Expect.isTrue(f is Func);
+  print(f as Func);
+}

tests/language_2/regress/regress46816_test.dart

@@ -0,0 +1,20 @@
+// Copyright (c) 2021, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// @dart=2.9
+
+import 'package:expect/expect.dart';
+
+class A<X extends num> {
+  void f<Y extends X>(Y y) {}
+}
+
+typedef Func = void Function<Y extends int>(Y);
+
+main() {
+  A<num> a = new A<int>();
+  dynamic f = (a as A<int>).f;
+  Expect.isTrue(f is Func);
+  print(f as Func);
+}