ActorRef passing is somewhat limited.

[pct-cclausen]

Currently ActorRefs can be passed to Actor calls, but when using forked or threaded actors, this only is correctly handled for a few cases:

• As a method parameter value
• As a value in customParameters.

Nesting is not supported at all, so passing a method parameter of types {a: ActorRef, b: ActorRef} fails.
Additionally you can also not return ActorRefs from actor methods.
There are workaround, but they are cumbersome.
I think bus messages also cannot transport ActorRefs.

It would make some scenarios easier to handle to add handling in more cases.