| // Copyright (c) 2023, 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. | |
| extension type Missing() {} // Error | |
| extension type Multiple(bool instanceField1, int instanceField2) {} // Error | |
| extension type Duplicate(bool instanceField, int instanceField) {} // Error |