anchor.diff:      _logger.printTrace('dart ${command.skip(1).join(' ')}');
       _process = await _processManager.start(command);
       // This callback hookup can't throw.
  -    unawaited(_process.exitCode.whenComplete(() => _process = null));
  -
  -    final Stream<String> errorStream = _process.stderr
  +    unawaited(_process!.exitCode.whenComplete(() => _process = null));
  +
  +    final Stream<String> errorStream = _process!.stderr
           .transform<String>(utf8.decoder)
           .transform<String>(const LineSplitter());
       errorStream.listen(_logger.printError);
   
  -    final Stream<String> inStream = _process.stdout
  +    final Stream<String> inStream = _process!.stdout
           .transform<String>(utf8.decoder)
           .transform<String>(const LineSplitter());
       inStream.listen(_handleServerResponse);
  
positive.code:       case AnalysisSeverity.none:
          return writtenError.severity;
      }
      return null;
    }
  
    String get type => writtenError.type;
  
negative.code:   AnalysisServer(
      this.sdkPath,
      this.directories, {
      required FileSystem fileSystem,
      required ProcessManager processManager,
      required Logger logger,
      required Platform platform,
      required Terminal terminal,
      String? protocolTrafficLog,
    }) : _fileSystem = fileSystem,
         _processManager = processManager,
         _logger = logger,
  