Macro stakker::ret_to

macro_rules! ret_to {
    ([$cx:expr], |$this:pat_param, $cxid:pat_param, $arg:ident : Option<$t:ty>| $($body:tt)+) => { ... };
    ([$cx:expr], move | $($x:tt)*) => { ... };
    ($($x:tt)*) => { ... };
}

Create a Ret instance for actor calls

This is guaranteed to be called exactly once. So it will be called even if the Ret is dropped. (The guarantee can be broken by leaking memory using mem::forget, though, so don’t do that!) The message is passed as Some(msg) if called normally, or as None if the Ret instance was dropped, e.g. if it couldn’t be delivered somewhere. The underlying closure is a FnOnce, so non-Copy types can be passed. The syntax is the same as for fwd_to!, and the message types are specified as normal. However the message is received in a single argument on the receiving method, either Option<type> for a single type, or else Option<(type1, type2...)>.

See ret_some_to! instead if you’re only interested in the Some(msg) case.

ret_to!(...arguments-as-for-fwd_to-macro...);

The closure form must use a single Option as above as the argument type, containing all the types passed from the Ret.

Implemented using Ret::to_actor or Ret::to_actor_prep.