Macro overloadable::overloadable

macro_rules! overloadable {
    ($v:vis $name:ident as
    $(
        $(#[$($m:tt)*])*
        fn
            $(
                <$($lt:lifetime,)*
                 $($gen:ident),*$(,)?>
            )?
            (
                $($param:ident : $param_type:ty$(,)?)*
            )
            $( -> $ret:ty)?
            $(where [$($cons:tt)*])?
        $code:block
    )*) => { ... };
}