pkg/front_end/testcases/regress/issue_31183.dart

// Copyright (c) 2017, 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 C {
  operator unary- => 0;
}

main() {
  new C();
}