// 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.

/**
 * @assertion
 * NORM(FutureOr<T>) =
 *  let S be NORM(T)
 *  if S is a top type then S
 *  if S is Object then S
 *  if S is Object* then S
 *  if S is Never then Future<Never>
 *  if S is Null then Future<Null>?
 *  else FutureOr<S>
 *
 * @description Checks that if NORM(T) is Null then
 * NORM(FutureOr<T>) = Future<Null>?
 *
 * @author sgrekhov@unipro.ru
 */
// Requirements=nnbd-weak
import 'dart:async';

class A<X> {}
class B<X> implements A<X> {}

class C extends B<FutureOr<Null>> implements A<Future<Null>?> {}

main() {
  new C();
}