macro_rules! fwd {
([ $fwd:expr ], $arg:expr) => { ... };
([ $fwd:expr ] $(, $arg:expr)*) => { ... };
}
Forward data via a Fwd
instance
fwd!([fwd2zz], arg1, arg2...);
There may be zero or more arguments, and they must match the
message type. Implemented using Fwd::fwd