message_format::message_args_aux!

macro_rules! message_args_aux {
    ($prev:expr, $name:ident => $value:expr) => { ... };
    ($prev:expr, $name:ident) => { ... };
    ($prev:expr, $name:ident, $($rest:tt)*) => { ... };
    ($prev:expr, $name:ident => $value:expr, $($rest:tt)*) => { ... };
}