anchor.diff:    /// to files generated by Bazel.
     ///
     /// Might be `null` if watching Bazel files is not enabled.
  -  BazelFileWatcherService bazelWatcherService;
  +  BazelFileWatcherService? bazelWatcherService;
   
     /// The subscription to changes in the files watched by [bazelWatcherService].
     ///
     /// Might be `null` if watching Bazel files is not enabled.
  -  StreamSubscription<List<WatchEvent>> bazelWatcherSubscription;
  +  StreamSubscription<List<WatchEvent>>? bazelWatcherSubscription;
   
     /// For each [Folder] store which files are being watched. This allows us to
     /// clean up when we destroy a context.
  
positive.code:   final InstrumentationService _instrumentationService;
  
    @override
    ContextManagerCallbacks callbacks;
  
    @override
    final Map<Folder, AnalysisDriver> driverMap =
  
negative.code:   void _createAnalysisContexts() {
      _destroyAnalysisContexts();
  
      var collection = _collection = AnalysisContextCollectionImpl(
        includedPaths: includedPaths,
        excludedPaths: excludedPaths,
        byteStore: _byteStore,
  