Macro bastion::receive

macro_rules! receive {
    ( $msg:expr, $($rest:tt)* ) => { ... };
    (@private $msg:expr, ($recvty:ty => $clo:expr, _ => $fallback:expr) -> ($($parsed:tt)*) ) => { ... };
    (@private $msg:expr, ($recvty:ty => $clo:expr, $($rest:tt)*) -> ($($parsed:tt)*) ) => { ... };
    (@private $msg:expr, () -> ($(($recvty:ty => $clo:expr))*) $fallback:expr ) => { ... };
}