|  | // Copyright (c) 2019, 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 Class { | 
|  | int field; | 
|  | } | 
|  |  | 
|  | extension Extension on Class { | 
|  | int get property => field; | 
|  | void set property(int value) { | 
|  | field = value; | 
|  | } | 
|  | int method() => field; | 
|  | } | 
|  |  | 
|  | main() { | 
|  | Class c; | 
|  | c?.property ?? 0; | 
|  | Extension(c)?.property ?? 0; | 
|  | c?.property = 42 ?? 0; | 
|  | Extension(c)?.property = 42 ?? 0; | 
|  | (c?.property = 42) ?? 0; | 
|  | (Extension(c)?.property = 42) ?? 0; | 
|  | c?.method() ?? 0; | 
|  | Extension(c)?.method() ?? 0; | 
|  | c = new Class(); | 
|  | c.property ?? 0; | 
|  | Extension(c).property ?? 0; | 
|  | } |