Frame.parseFirefox constructor Null safety

Implementation

factory Frame.parseFirefox(String frame) => _catchFormatException(frame, () {
      var match = _firefoxSafariFrame.firstMatch(frame);
      if (match == null) return UnparsedFrame(frame);

      if (match[3]!.contains(' line ')) {
        return Frame._parseFirefoxEval(frame);
      }

      // Normally this is a URI, but in a jsshell trace it can be a path.
      var uri = _uriOrPathToUri(match[3]!);

      var member = match[1];
      if (member != null) {
        member +=
            List.filled('/'.allMatches(match[2]!).length, '.<fn>').join();
        if (member == '') member = '<fn>';

        // Some Firefox members have initial dots. We remove them for
        // consistency with other platforms.
        member = member.replaceFirst(_initialDot, '');
      } else {
        member = '<fn>';
      }

      var line = match[4] == '' ? null : int.parse(match[4]!);
      var column =
          match[5] == null || match[5] == '' ? null : int.parse(match[5]!);
      return Frame(uri, line, column, member);
    });