Generic functions with "C" ABI

[o11c]

I need to pass a callback function pointer to C, and there's no reason a generic function shouldn't be able to do this. The only problem with generic functions is that they would mangle all to the same name, but I don't care about the mangling.

[huonw]

(Updated the title to be more descriptive.)

[steveklabnik]

Triage; no change here.

[Mark-Simulacrum]

The below compiles, so at least basically, this does work. I'm uncertain if the code I came up with is what the author wants, but due to the age of this request and the lack of a code sample within the request, I will close this. Please reopen with a code sample that fails to work (or indicate why mine doesn't) if necessary.

fn main() {}

extern "C" fn foo<F: Fn(i32) -> usize>(f: F) -> usize {
    f(10)
}

extern "C" fn bar<T: Clone>(f: fn(i32) -> usize) -> usize {
    f(10)
}