Why can I not use a type alias in #[repr()] on an enum?

[raphaelcohn]

I'd like to use a type alias, in this case c_int, as the repr of an enum. For example, in this code snippet:-

extern crate libc;
use self::libc::c_int;

#[repr(c_int)]
pub enum Facility
{
    LOG_KERN = self::libc::LOG_KERN,
    // ... Omitted ...
}

(Note, LOG_KERN is not yet defined in libc, but I'm working on a PR for it). The type alias for LOG_KERN is c_int, which resolves to i32 on Mac OS X.

Whilst I can use a repr of i32, I'd rather not. Whilst in this particular case it's very highly unlikely that the definition of c_int will every change or vary across platforms (16-bit rust, anyone), one loses expressiveness and introduces a little more need to understand what's going on - limiting the usefulness of a type alias...

I've raised this as an issue, not a RFC or anything like that (a) because I'm new to all of this and (b) because what I just did was what I thought would be logical - it's the very first time I tried to use repr, and it didn't work as seemed obvious. Obviously if there's a better forum I'll move this.

[steveklabnik]

(a) because I'm new to all of this

Welcome!

Obviously if there's a better forum I'll move this.

So, in general, question-type things are best posted to https://users.rust-lang.org/ or http://internals.rust-lang.org/ , I would say this leans more internals. We try to keep the bug tracker for bugs only.

However, as it just so happens, an RFC was opened a few days ago for this exact issue, so I'd suggest you get involved over there!

Thanks :)

[raphaelcohn]

Thank you. I'll get on to the RFC...