Request for feedback: how to clean up actors

I'm building an actor library and have ran into a sticking point. For context, the library is powered by macros, so I have a lot of leeway in terms of generating or modifying the implementation for a given actor on top of the code provided by the user. However, two things I want to support in the design are: I want you to be able to implement traits on your actors and upcast them into trait objects (or equivalent) so the API to create an actor of type Actor hands out Arc<Actor>. I need to use A...