anchor.diff:    dynamic get value => throw new ParserError(this);
   
     @override
  -  String get message => _message;
  +  final String message;
   
     @override
  -  String toString() => 'Failure[${toPositionString()}]: $_message';
  +  String toString() => 'Failure[${toPositionString()}]: $message';
   
   }
   
  
positive.code:  */
  class Context {
  
    final dynamic _buffer;
    final int _position;
  
    const Context(this._buffer, this._position);
  
    /**
     * The buffer we are working on.
     */
    dynamic get buffer => _buffer;
  
    /**
     * The current position in the buffer.
     */
    int get position => _position;
  
    /**
     * Returns [true] if this result indicates a parse success.
  
negative.code:    * Returns a result indicating a parse success.
     */
    Result success(dynamic result, [int position]) {
      return new Success(buffer, position == null ? this.position : position, result);
    }
  
    /**
     * Returns a result indicating a parse failure.
     */
    Result failure(String message, [int position]) {
      return new Failure(buffer, position == null ? this.position : position, message);
    }
  
    /**
  