brunal commented on PR #9454:
URL: https://github.com/apache/arrow-rs/pull/9454#issuecomment-3977496362
About each arm:
| Arm # | Accepts | Turns into | Comment |
| - | - | - | - |
| 1 | `foo => thing(),` | `foo => { thing() }` | |
| 2 | `(foo, bar) => thing(),` | `foo, bar => { thing() }` | Not sure why
the parentheses around args get removed |
| 3 | `foo, bar => { thing() }` | `(foo, bar) => { thing() }` | |
| 4 | `(foo, bar) => { thing() }` | another macro | |
I think we can update (2) to avoid the trip through (3).
I don't really understand the point of the pattern (3) apart from catching
what's emitted by (2).
> I'm pretty sure we can simplify the macro to just two arms, because
$e:expr actually matches {...} just fine, and macro expansion handles the comma
vs {} thing automagically:
https://play.rust-lang.org/?version=stable&mode=debug&edition=2024&gist=cddb9bf00fca4bb2f3a77df3c84def8d
I'm not sure what you mean here. In your example you cannot skip the comma
after `{ 20 }`. I don't think we can have a single arm for `thing(),` and `{
thing() }`.
OK for restoring the explicit syntax in the 4th arm.
OK for turning `$(if $pred:expr)*` into `$(if $pred:expr)?`.
I've now updated the changes. Recap:
1. Use a muncher in recursive macro calls. That's much lighter on
compilation/rust-analyzer.
2. Accept a single `if pred` (multiple lead to invalid generated code anyway)
3. Don't unwrap `(foo, bar)` into `foo, bar` that gets wrapper back later on.
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