diff options
| -rw-r--r-- | compiler/rustc_middle/src/mir/interpret/queries.rs | 19 | ||||
| -rw-r--r-- | tests/ui/const-generics/const_eval_unchecked_doesnt_fire_patterns.rs | 23 |
2 files changed, 33 insertions, 9 deletions
diff --git a/compiler/rustc_middle/src/mir/interpret/queries.rs b/compiler/rustc_middle/src/mir/interpret/queries.rs index 4222a68e544..e5d1dda3aa0 100644 --- a/compiler/rustc_middle/src/mir/interpret/queries.rs +++ b/compiler/rustc_middle/src/mir/interpret/queries.rs @@ -115,15 +115,16 @@ impl<'tcx> TyCtxt<'tcx> { // @lcnr believes that successfully evaluating even though there are // used generic parameters is a bug of evaluation, so checking for it // here does feel somewhat sensible. - if !self.features().generic_const_exprs() && ct.args.has_non_region_param() { - let def_kind = self.def_kind(instance.def_id()); - assert!( - matches!( - def_kind, - DefKind::InlineConst | DefKind::AnonConst | DefKind::AssocConst - ), - "{cid:?} is {def_kind:?}", - ); + if !self.features().generic_const_exprs() + && ct.args.has_non_region_param() + // We only FCW for anon consts as repeat expr counts with anon consts are the only place + // that we have a back compat hack for. We don't need to check this is a const argument + // as only anon consts as const args should get evaluated "for the type system". + // + // If we don't *only* FCW anon consts we can wind up incorrectly FCW'ing uses of assoc + // consts in pattern positions. #140447 + && self.def_kind(instance.def_id()) == DefKind::AnonConst + { let mir_body = self.mir_for_ctfe(instance.def_id()); if mir_body.is_polymorphic { let Some(local_def_id) = ct.def.as_local() else { return }; diff --git a/tests/ui/const-generics/const_eval_unchecked_doesnt_fire_patterns.rs b/tests/ui/const-generics/const_eval_unchecked_doesnt_fire_patterns.rs new file mode 100644 index 00000000000..fae2d16f430 --- /dev/null +++ b/tests/ui/const-generics/const_eval_unchecked_doesnt_fire_patterns.rs @@ -0,0 +1,23 @@ +//@ check-pass + +// Previously the `CONST_EVALUATABLE_UNCHECKED` FCW would fire on const evaluation of +// associated consts. This is unnecessary as the FCW only needs to apply for repeat expr +// counts which are anon consts with generic parameters provided. #140447 + +pub struct Foo<const N: usize>; + +impl<const N: usize> Foo<N> { + const UNUSED_PARAM: usize = { + let _: [(); N]; + 3 + }; + + pub fn bar() { + match 1 { + Self::UNUSED_PARAM => (), + _ => (), + } + } +} + +fn main() {} |