I thought about that, but basically we no longer have direct access to injector internals and the injector marking is done with a String name (injectors can be named). Even if someone manually created an injector with the 'SHADOW_INJECTOR' name and passed it to the blockFactory it should not cause issues because at the shadow injector we would be 2 layers of injectors below that injector, so from the shadow injector we would walk up once and always find the nameless injector created in _instantiateDirectives.

I should add a test for it. If you still have concerns about it we can chat about it tomorrow.