pkg/front_end/testcases/nnbd/nsm_from_opt_in_lib.dart

// 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.

class A {
  int method(int? i) => i ?? 0;
}

abstract class B1 extends A implements C1 {
  @override
  noSuchMethod(Invocation invocation) {
    return super.noSuchMethod(invocation);
  }
}

abstract class C1 {
  int method(int? i, {optional});
}