|  | // Copyright (c) 2018, 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. | 
|  |  | 
|  | class Base { | 
|  | void foo() {} | 
|  | } | 
|  |  | 
|  | mixin M1 { | 
|  | void foo({x}) {} | 
|  | } | 
|  |  | 
|  | class BaseWithM1 = Base with M1; | 
|  |  | 
|  | mixin M2 { | 
|  | void foo() {} | 
|  | } | 
|  |  | 
|  | class Derived extends BaseWithM1 with M2 {} | 
|  | //    ^^^^^^^ | 
|  | // [cfe] Applying the mixin 'M2' to 'BaseWithM1' introduces an erroneous override of 'foo'. | 
|  | //                                    ^^ | 
|  | // [analyzer] COMPILE_TIME_ERROR.INVALID_OVERRIDE | 
|  |  | 
|  | main() { | 
|  | new Derived().foo(); | 
|  | } |