Raw syntax for lifetimes and loop labels

[traviscross]

We don't currently accept:

pub fn label() {
    'r#async: loop {
        break 'r#async;
    }
}

pub fn lifetime<'r#async>() {}

Should we? This has relevance to edition migrations.

See:

• keyword-idents-2024 unable to migrate loop labels or lifetimes #125986

[traviscross]

@rustbot labels -I-lang-nominated

We discussed this in the lang triage call today. Our consensus was that this should be allowed and that it seems to have been an oversight that it wasn't already, given RFC 3101 and other related work.

[compiler-errors]

I'll put up a PR for this tomorrow. I've got a draft, just want to make sure it's actually correct.

[traviscross]

This has been fixed by #126452, so we can close this.