commit bcc0a79a810df7f6caebaa56bdd4c2602289194a
author bors <bors@rust-lang.org> Sun Jul 13 18:34:13 2025 +0000
committer bors <bors@rust-lang.org> Sun Jul 13 18:34:13 2025 +0000
tree 754e19dfe080d2b340340be1c77ea052bba8bf2c
parent f9f09e54d0d4f8cb3234f35400290dccae341fbb
parent 7d6f447a4d5b5b2558d88ea1cf0f3de22e7512c9

Auto merge of #143461 - folkertdev:cfg-select-builtin-macro, r=petrochenkov

make `cfg_select` a builtin macro

tracking issue: https://github.com/rust-lang/rust/issues/115585

This parses mostly the same as the `macro cfg_select` version, except:

1. wrapping in double brackets is no longer supported (or needed): `cfg_select {{ /* ... */ }}` is now rejected.
2. in an expression context, the rhs is no longer wrapped in a block, so that this now works:
  ```rust
  fn main() {
      println!(cfg_select! {
          unix => { "foo" }
          _ => { "bar" }
      });
  }
  ```
3. a single wildcard rule is now supported: `cfg_select { _ => 1 }` now works

I've also added an error if none of the rules evaluate to true, and warnings for any arms that follow the `_` wildcard rule.

cc `@traviscross` if I'm missing any feature that should/should not be included
r? `@petrochenkov` for the macro logic details