In commit c33ed02 (issue #279) a new Spawn trait was introduced. It comes with three generic parameters S (Supervisor), NA (NewActor) and RT (either ThreadLocal or ThreadSafe). This was required because spawn of thread-safe actors requires, S, NA and NA::Actor to be Send + Sync, while thread-local actors don't have this requirement. However when using async function as actor we can't name NA or NA::Actor, making this trait impossible to use with it.

My initial idea was to split the two traits: Spawn and SpawnLocal, but types like TcpServer need a single trait otherwise we have to implement that twice as well.