anchor.diff:    }
   
     @override
  -  Core<CoreContext>? makeCoreInstance(int typeKey) {
  -    return null;
  -  }
  +  Core<CoreContext>? makeCoreInstance(int typeKey) =>
  +      RiveCoreContext.makeCoreInstance(typeKey);
   
     @override
     void dirty(void Function() dirt) {
  
positive.code:     _redraw.notify();
    }
  
    Artboard? instance() {
      var artboard = RuntimeArtboard();
      artboard.copy(this);
      artboard._objects.add(artboard);
      // First copy the objects ensuring onAddedDirty can later find them in the
      // _objects list.
      for (final object in _objects.skip(1)) {
        Core? clone = object?.clone();
        artboard._objects.add(clone);
      }
  
      // Then run the onAddedDirty loop.
  
negative.code:       }
        object?.onAddedDirty();
      }
      animations.forEach(artboard.animations.add);
      for (final object in artboard.objects.toList(growable: false)) {
        if (object == null) {
          continue;
        }
        object.onAdded();
        InternalCoreHelper.markValid(object);
      }
      artboard.clean();
      return artboard;
    }
  }
  