anchor.diff:          string += _parseEscapedStringFragment();
         } else {
           string += character;
  -      }
  -      _index++;
  +        _index++;
  +      }
         if (_index == _json.length) {
           throw new LexerException("Invalid json fragment encountered: $string");
         }
  
positive.code:   String _parseEscapedStringFragment() {
      _index++;
      String character = _json[_index];
      switch (character) {
        case '"':
        case r'\':
  
negative.code:       case 'u':
          int remainingLength = _json.length - _index;
          if (remainingLength >= 4) {
            var hexString = _json.substring(_index, _index + 4);
            _index += 4;
            var hexInt = int.parse(hexString, radix: 16);
            return UTF8.decode([hexInt]);
  