Allow lifetimes in macros

[mikeyhew]

This is a resurrection of PR #33135.

@sgrif can you take a look at the following diffs from #33135, and see if those changes are still necessary?

• src/libsyntax/ext/tt/transcribe.rs This was refactored by @jseyfried, so he may be able to weigh in.
• src/libsyntax/parse/parser.rs

Still to do:

• Make sure CI passes
• Get approval from @sgrif, since he wrote the code
• Feature gate

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @pnkfelix (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

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[shepmaster]

Thanks @mikeyhew! We'll get @pnkfelix to take a look at this PR shortly!

[kennytm]

All three tests failed, "expected one of >, identifier, or lifetime, found 'a".

---

BTW, could you add some tests to show that the patch handles labels?

#![allow(unreachable_code)]

macro_rules! x {
    ($a:lifetime) => {
        $a: loop {
            break $a;
            panic!("failed");
        }
    }
}
macro_rules! br {
    ($a:lifetime) => {
        break $a;
    }
}
macro_rules! br2 {
    ($b:lifetime) => {
        'b: loop {
            break $b; // this $b should refer to the outer loop.
        }
    }
}
fn main() {
    x!('a);
    'c: loop {
        br!('c);
        panic!("failed");
    }
    'b: loop {
        br2!('b);
        panic!("failed");
    }
}

[mikeyhew]

Thanks @kennytm, and sure, I'll add those tests. What is the quickest way to run tests for libsyntax? Anything with --stage 1 seems to take forever to build.

[petrochenkov]

@mikeyhew

Anything with --stage 1 seems to take forever to build.

Do you include LLVM build and similar in "forever"? It only needs to be done once.
"Development cycle" includes only build from modifying libsyntax to running stage 1 tests.
The only way to speed it up that I know is to set codegen-units = 0 in config.toml, with it time ../x.py test --stage 1 src/test/run-pass --test-args macroxxx gives real 4m14.233s. Slow, but not forever (I'm on a relatively fast desktop machine though).
You can also try to add --incremental to the x.py command line (I haven't measured time for it because it breaks the build on my machine.).

[bors]

☔ The latest upstream changes (presumably #42049) made this pull request unmergeable. Please resolve the merge conflicts.

[mikeyhew]

I'm too busy with school right now, and I still don't really understand the code in this PR so I'm going to give up. Someone else will have to take over for this to get implemented.