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Rollup merge of #138393 - oli-obk:pattern-type-in-pattern, r=BoxyUwU

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Allow const patterns of matches to contain pattern types

Trying to pattern match on a type containing a pattern type will currently fail with an ICE

```rust
error: internal compiler error: compiler/rustc_mir_build/src/builder/matches/test.rs:459:18: invalid type for non-scalar compare: (u32) is 1..
  --> src/main.rs:22:5
   |
22 |     TWO => {}
   |     ^^^
```

because the compiler tries to generate a MIR `BinOp(Eq)` operation on a pattern type, which is not supported. While we could support that, there are side effects of allowing this (none that would compile, but the compiler would simultaneously think it could `==` pattern types and that it could not because `PartialEq` is not implemented. So instead I change the logic for pattern matching to transmute pattern types to their base type before comparing.

r? ```@BoxyUwU```

cc #123646 ```@scottmcm``` ```@joshtriplett```
This commit is contained in:
Stuart Cook 2025-04-15 15:47:25 +10:00 • committed by GitHub
commit aa9a80cc34
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9 changed files with 233 additions and 9 deletions
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14
compiler/rustc_borrowck/src/type_check/mod.rs
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@ -1557,11 +1557,15 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
}
}
CastKind::Transmute => {
span_mirbug!(
self,
rvalue,
"Unexpected CastKind::Transmute, which is not permitted in Analysis MIR",
);
let ty_from = op.ty(self.body, tcx);
match ty_from.kind() {
ty::Pat(base, _) if base == ty => {}
_ => span_mirbug!(
self,
rvalue,
"Unexpected CastKind::Transmute {ty_from:?} -> {ty:?}, which is not permitted in Analysis MIR",
),
}
}
}
}