anchor.diff:        _evictionIsolateIsRunning = true;
         try {
           ReceivePort response = new ReceivePort();
  -        _cleanUpSendPort.send([_cachePath, _maxSizeBytes, response.sendPort]);
  +        _cleanUpSendPort.send(new CacheCleanUpRequest(
  +            _cachePath, _maxSizeBytes, response.sendPort));
           await response.first;
         } finally {
           _evictionIsolateIsRunning = false;
  
positive.code: 
  import 'package:analyzer/src/dart/analysis/byte_store.dart';
  import 'package:path/path.dart';
  
  /**
   * [ByteStore] that stores values as files.
  
negative.code:   static void _cacheCleanUpFunction(SendPort initialReplyTo) {
      ReceivePort port = new ReceivePort();
      initialReplyTo.send(port.sendPort);
      port.listen((request) async {
        if (request is CacheCleanUpRequest) {
          await _cleanUpFolder(request.cachePath, request.maxSizeBytes);
          // Let the client know that we're done.
          request.replyTo.send(true);
        }
      });
    }
  