anchor.diff:    CharMatcher operator | (CharMatcher other) => other;
   }
   
  -/** Matches a specifc character. */
  +/** Matches a character [char]. */
   CharMatcher isChar(char) {
     return new _SingleCharMatcher(_toCharCode(char));
   }
  
positive.code:   bool call(int value) => _value == value;
  }
  
  /** Matches a character range. */
  CharMatcher inRange(start, stop) {
    return new _RangeCharMatcher(_toCharCode(start), _toCharCode(stop));
  }
  
negative.code:   String toString() => 'WHITESPACE';
    bool call(int value) => (9 <= value && value <= 13) || (value == 32)
        || (value == 160) || (value == 5760) || (value == 6158)
        || (8192 <= value && value <= 8202) || (value == 8232)
        || (value == 8233) || (value == 8239) || (value == 8287)
        || (value == 12288);
  }
  
  /** Internal method to convert an element to a character code. */
  