// 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 otherwise NORM(FutureOr<T>) = FutureOr<NORM(T)>.
/// Test that NORM(FutureOr<T??>) == FutureOr<T?> and
/// NORM(FutureOr<Never?>) == FutureOr<Null>
///
/// @author sgrekhov@unipro.ru

// Requirements=nnbd-weak
import 'dart:async';

class T {}
class A<X> {}
class B<X> implements A<FutureOr<X?>> {}
class D<X> implements A<X> {}

class C1 extends B<T?> implements A<FutureOr<T?>> {}
class C2 extends B<Never?> implements A<FutureOr<Null>> {}

main() {
  new C1();
  new C2();
}