code: protected void _reportInvalidToken(String matchedPart, String msg)
              throws IOException, JsonParseException
      {
          StringBuilder sb = new StringBuilder(matchedPart);
          /* Let's just try to find what appears to be the token, using
           * regular Java identifier character rules. It's just a heuristic,
           * nothing fancy here.
           */
          while (true) {
              if (_inputPtr >= _inputEnd) {
                  if (!loadMore()) {
                      break;
                  }
              }
              char c = _inputBuffer[_inputPtr];
              if (!IdentifierUtils.isIdCharLenient(c)) {
                  break;
              }
              ++_inputPtr;
              sb.append(c);
          }
          _reportError("Unrecognized token '"+sb.toString()+"': was expecting ");
      }
docs: /*
  ********************************************************
  /* Error reporting
  ********************************************************