anchor.diff:      int hostPort,
       bool ipv6,
       bool disableServiceAuthCodes, {
  -    @required Logger logger,
  +    required Logger logger,
     }) async {
       final Uri ddsUri = Uri(
         scheme: 'http',
  
positive.code:         io.InternetAddress.loopbackIPv6 :
          io.InternetAddress.loopbackIPv4
        ).host,
        port: hostPort ?? 0,
      );
      logger.printTrace(
        'Launching a Dart Developer Service (DDS) instance at $ddsUri, '
  
negative.code:           enableAuthCodes: !disableServiceAuthCodes,
            ipv6: ipv6,
          );
        unawaited(_ddsInstance?.done.whenComplete(() {
          if (!_completer.isCompleted) {
            _completer.complete();
          }
        }));
        logger.printTrace('DDS is listening at ${_ddsInstance?.uri}.');
      } on dds.DartDevelopmentServiceException catch (e) {
        logger.printTrace('Warning: Failed to start DDS: ${e.message}');
        if (e.errorCode == dds.DartDevelopmentServiceException.existingDdsInstanceError) {
  