pkg/front_end/testcases/general/issue47728_4.dart

// 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.

typedef A = Function()?;

mixin B {}

class C = A with B;

main() {}