anchor.diff:    const _NotCharMatcher(this._matcher);
   
     @override
  -  bool call(int value) => !_matcher(value);
  +  bool match(int value) => !_matcher.match(value);
   
   }
   
  
positive.code:   const _LowercaseCharMatcher();
  
    @override
    bool call(int value) => 97 <= value && value <= 122;
  
  }
  
  
negative.code:  * Internal abstract character matcher class.
   */
  abstract class _CharMatcher {
    bool match(int value);
  }
  
  /**
  