anchor.diff:  
     final Dynamic _result;
   
  -  Success(buffer, position, this._result) : super(buffer, position);
  +  const Success(buffer, position, this._result) : super(buffer, position);
   
     bool isSuccess() => true;
   
  
positive.code: 
    final String _message;
  
    Failure(buffer, position, this._message) : super(buffer, position);
  
    bool isFailure() => true;
  
  
negative.code:   final Dynamic _buffer;
    final int _position;
  
    const Context(this._buffer, this._position);
  
    /** The buffer we are working on. */
    Dynamic get buffer() => _buffer;
  