pkg/front_end/testcases/general/constants/issue_43431.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.
// @dart=2.9
class Foo {
  const Foo({bool x: true});
  const x = Foo();
}

main() {}