Macro variadic_generics::va_invoke_with_nil

macro_rules! va_invoke_with_nil {
    ($mac : ident $($cur_args : tt) *) => { ... };
}

Like va_invoke, but with lists of up to 32 elements and also includes an “empty list”.

va_invoke_more!(mymacro arg1 arg2);

will be expanded to

mymacro!(arg1 arg2 (0) () ());
mymacro!(arg1 arg2 (1) (_Va0) (0));
mymacro!(arg1 arg2 (2) (_Va0, _Va1) (0, 1));
// ...
mymacro!(arg1 arg2 (12) (_Va0, ..., _Va11) (0, ..., 11));