| // 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. |
| |
| /// A class that's used as a default argument to detect whether an argument was |
| /// passed. |
| /// |
| /// We use a custom class for this rather than just `const Object()` so that |
| /// callers can't accidentally pass the placeholder value. |
| class _Placeholder { |
| const _Placeholder(); |
| } |
| |
| /// A placeholder to use as a default argument value to detect whether an |
| /// argument was passed. |
| const placeholder = const _Placeholder(); |