// Copyright (c) 2020, 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 In an unmigrated library, override checking is done using legacy
 * types. This means that an unmigrated library can bring together otherwise
 * incompatible methods. When choosing the most specific signature during
 * interface computation, all nullability and requiredness annotations are
 * ignored, and the [Never] type is treated as [Null].
 *
 * @description Check that if legacy class extends legacy class and implements
 * opted-in class, legacy method can return [null] if parent method returns
 * non-nullable.
 *
 * @author iarkh@unipro.ru
 */
// Requirements=nnbd-weak
// @dart=2.6

import "dart:async";
import "../../../../Utils/expect.dart";
import "override_checking_A01_opted_in_lib.dart";

class A extends B implements OPTED_NONNULLABLE_RETURN {}

class B {
  int           getInt()         => null;
  Object        getObject()      => null;
  Function      getFunction()    => null;
  FutureOr<int> getFutureOrInt() => null;
}

main() {
  A a = A();

  Expect.isNull(a.getInt());
  Expect.isNull(a.getObject());
  Expect.isNull(a.getFutureOrInt());
  Expect.isNull(a.getFunction());
}