anchor.diff:        assert(ancestor is InheritedElement);
         _dependencies ??= new HashSet<InheritedElement>();
         _dependencies.add(ancestor);
  -      ancestor._dependants.add(this);
  +      ancestor._dependents.add(this);
         return ancestor.widget;
       }
       return null;
  
positive.code:   @override
    void debugDeactivated() {
      assert(() {
        assert(_dependants.isEmpty);
        return true;
      });
      super.debugDeactivated();
  
negative.code:     assert(_active);
      if (_dependencies != null) {
        for (InheritedElement dependency in _dependencies)
          dependency._dependents.remove(this);
        _dependencies.clear();
      }
      _active = false;
  