[nelson137]

Objective

Fix #25407. Supersedes first attempt #26190.

Solution

Implement Alice's fix.

Testing

Bring over the tests from the first attempt along with a couple new regression tests that cover the heart of the bug.

[nelson137]

I want to call attention to the last commit on this branch, (which I kept separate from the other changes so it can be easily reverted if anyone disagrees with it). Applying the fix meant parenthesized_tokens() and bracketed_tokens() had no callers so I deleted them. That left just braced_tokens(), which I then deleted in the last commit. Reading through the history it looks like group_tokens() is newer, and given that it, like the others, maintains autocomplete support in the macro body, as well as being the fix for call sites, it felt like the better util to be using.

[alice-i-cecile]

Thanks for taking a crack at this :) CI has caught the problems, but the reason it's failing is that the fix is applied too widely. You only need group_tokens on the TypeFunction | Function arm. Your other uses are resulting in double braces :)

[nelson137]

Hmm CI is still failing on extra brackets. I think I need to further narrow this fix in the input.peek(Brace) branch to when maybe_macro.is_some().