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