This is probably more something to be added in an extension crate, but it would be cool to be able to define actors from closures:

let initial_state = 0u64;
xtra::actor::unbounded(initial_state)
  .handle(|name: String, ctx: &mut Context| async move {
     format!("Hello {name}")
  });

Not sure how nameable the actor type would be (some nested AndHandler<HandlerFn<String, String>, AndHandler<HandlerFn<u64, u64>>> stuff probably) so perhaps one would only be able to access such an actor through MessageChannels?