docs: private boolean isFastPath(String regex) {
          char ch;
          return (((regex.length() == 1 && ".$|()[{^?*+\\".indexOf(ch = regex.charAt(0)) == -1) || (regex.length() == 2
                  && regex.charAt(0) == '\\' && (((ch = regex.charAt(1)) - '0') | ('9' - ch)) < 0 && ((ch - 'a') | ('z' - ch)) < 0 && ((ch - 'A') | ('Z' - ch)) < 0)) && (ch < Character.MIN_HIGH_SURROGATE || ch > Character.MAX_LOW_SURROGATE));
      }