anchor.diff:    /**
      * Parses a "true" literal starting at [position].
      *
  -   * [:source[position]:] must be "t".
  +   * The character `source[position]` must be "t".
      */
     int parseTrue(int position) {
       assert(getChar(position) == CHAR_t);
  
positive.code:     assert(start < chunkEnd);
      int length = chunkEnd - start;
      var buffer = new _NumberBuffer(length);
      copyCharsToList(start, chunkEnd, buffer.list);
      buffer.length = length;
      return buffer;
    }
  
negative.code:    *
     * Used for number buffer (always copies ASCII, so encoding is not important).
     */
    void copyCharsToList(int start, int end, List<int> target, int offset);
  
    /**
     * Build a string using input code units.
  