anchor.diff:      }
     }
   
  -  void _addHelpTask(String helpTaskName) {
  -    assert(_helpTaskName == null);
  -    addTask(helpTaskName, _getHelpTask());
  -    _helpTaskName = helpTaskName;
  -  }
  -
     void freeze() {
       require(!isFrozen, "Already frozen.");
       final list = new List<String>.from(_tasks.keys);
  
positive.code:   void doPrint(Object value) {
      print(value);
    }
  }
  
negative.code:     return _tasks.containsKey(taskName);
    }
  
    void addSync(String name, Func1<TaskContext, bool> func) {
      addTask(name, new Task.sync(func));
    }
  