anchor.diff:  
     Iterable<String> get subtasks => _subtasks.keys;
   
  -  int getSubtaskTime(String subtask) => _subtasks[subtask].timing;
  -
  -  bool getSubtaskIsRunning(String subtask) => _subtasks[subtask].isRunning;
  +  int getSubtaskTime(String subtask) => _subtasks[subtask]!.timing;
  +
  +  bool getSubtaskIsRunning(String subtask) => _subtasks[subtask]!.isRunning;
   
     /// Returns the metrics for this task.
     Metrics get metrics => Metrics.none();
  
positive.code: 
    int get timing {
      if (_isDisabled) return 0;
      int total = _watch.elapsedMilliseconds;
      for (GenericTask subtask in _subtasks.values) {
        total += subtask.timing;
      }
  
negative.code:   /// Call this before returning to the eventloop.
    void startAsyncWallClock() {
      if (_currentAsyncTask != null) {
        _currentAsyncTask!._watch?.start();
      } else {
        _asyncWallClock.start();
      }
  