anchor.diff:    const _DigitCharMatcher();
   
     @override
  -  bool call(int value) => 48 <= value && value <= 57;
  +  bool match(int value) => 48 <= value && value <= 57;
   
   }
   
  
positive.code:   const _LetterCharMatcher();
  
    @override
    bool call(int value) => (65 <= value && value <= 90) || (97 <= value && value <= 122);
  
  }
  
  
negative.code:   const _RangeCharMatcher(this._start, this._stop);
  
    @override
    bool match(int value) => _start <= value && value <= _stop;
  
  }
  
  