macro_rules! msg_send {
    (super($obj:expr, $superclass:expr), $name:ident) => { ... };
    (super($obj:expr, $superclass:expr), $($name:ident : $arg:expr)+) => { ... };
    ($obj:expr, $name:ident) => { ... };
    ($obj:expr, $($name:ident : $arg:expr)+) => { ... };
}