anchor.diff:      LsonToken token;
       var expectValue = true;
       var key;
  -    
  +
       var isKey = true;
   
       while ((token = lexer.nextToken()) != null) {
  
positive.code:           }
  
            token.end = _pos;
            token.value = buff.toString();
            return token;
          } else {
            buff.write(read);
  
negative.code:           previousChar();
          }
        }
  
        var content = buff.toString();
        if (possibleTokenType.matching(content)) {
          return new LsonToken(LsonTokenType.BLOCK_COMMENT, content, start, _pos);
  