Initializing formals can't be optional parameters

runtime/bin/input_stream.dart

 // Copyright (c) 2011, 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.
 
 /**
  * Input is read from a given input stream. Such an input stream can
  * be an endpoint, e.g., a socket or a file, or another input stream.
  * Multiple input streams can be chained together to operate collaboratively
  * on a given input.
  */
@@ skipping 88 matching lines @@
 
   /**
    * Sets the handler that gets called when the underlying
    * communication channel gets into some kind of error situation.
    */
   void set errorHandler(void callback());
 }
 
 
 class StreamException implements Exception {
-  const StreamException([String this.message = ""]);
+  const StreamException([String msg = ""]) : message = msg;
   String toString() => "StreamException: $message";
   final String message;
 }