How to pass in a generic template to macro_rules?

1 
struct X {}

macro_rules! test {
    ($tmpl: path) => {
        impl $tmpl<usize> for X {
            type Output = ();
            fn add(self, b: usize) -> () {}
        }
    };
}

test!(std::ops::Add);

This code doesn't compile:

error: expected `::`, found keyword `for`
  --> src/lib.rs:5:27
   |
5  |         impl $tmpl<usize> for X {
   |                           ^^^ expected `::`
...
12 | test!(std::ops::Add);
   | -------------------- in this macro invocation
   |
   = note: this error originates in the macro `test` (in Nightly builds, run with -Z macro-backtrace for more info)

I really can't figure out how to fix this; the LLMs don't emit anything useful. I want to be able to implement multiple operations and I cannot pass in std::ops::Add - because in my real code I have more than one types that I want to put inside std::ops::Add, in the same macro expansion (in this example I only showed one).

2

Is this adequate or do you need to pass in something more complicated?

3

Interesting, thanks a lot!! Looks like tt is really useful. I do need to take two more parameters, but I was able to do that by requiring that the tt group be enclosed by a ().