Macro defmacro

macro_rules! defmacro {
    {$id:ty { $(
        ($($generics:tt)*) { $($args:tt)* } => { $($out:tt)* };
    )* }} => { ... };
}

Setup a new macro function, and some match arms for implementation

The only difference between this and defun_nocalc! is that the arguments are provided un-evaluated, which means you’re matching on syntax instead of results. It therefore provides the opportunity to short-circuit evaluation of some arguments.