|  | // Copyright (c) 2012, 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. | 
|  |  | 
|  | import "package:expect/expect.dart"; | 
|  |  | 
|  | // It is a compile-time error if a named formal parameter begins with an '_' | 
|  |  | 
|  | class Foo { | 
|  | num _y; | 
|  | Foo.optional_private({this._y: 77}) {} | 
|  | } | 
|  |  | 
|  | main() { | 
|  | var obj; | 
|  | obj = new Foo.optional_private(_y: 222); | 
|  | Expect.equals(222, obj._y); | 
|  |  | 
|  | obj = new Foo.optional_private(); | 
|  | Expect.equals(77, obj._y); | 
|  | } |