diff options
| -rw-r--r-- | compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs | 23 |
1 files changed, 19 insertions, 4 deletions
diff --git a/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs b/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs index 37f5d5f6cc3..a203b3a1428 100644 --- a/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs +++ b/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs @@ -63,8 +63,23 @@ struct ConstToPat<'a, 'tcx> { include_lint_checks: bool, } -#[derive(Debug)] -struct FallbackToConstRef; +mod fallback_to_const_ref { + #[derive(Debug)] + /// This error type signals that we encountered a non-struct-eq situation behind a reference. + /// We bubble this up in order to get back to the reference destructuring and make that emit + /// a const pattern instead of a deref pattern. This allows us to simply call `PartialEq::eq` + /// on such patterns (since that function takes a reference) and not have to jump through any + /// hoops to get a reference to the value. + pub(super) struct FallbackToConstRef(()); + + pub(super) fn fallback_to_const_ref<'a, 'tcx>( + c2p: &super::ConstToPat<'a, 'tcx>, + ) -> FallbackToConstRef { + assert!(c2p.behind_reference.get()); + FallbackToConstRef(()) + } +} +use fallback_to_const_ref::{fallback_to_const_ref, FallbackToConstRef}; impl<'a, 'tcx> ConstToPat<'a, 'tcx> { fn new( @@ -314,7 +329,7 @@ impl<'a, 'tcx> ConstToPat<'a, 'tcx> { // Since we are behind a reference, we can just bubble the error up so we get a // constant at reference type, making it easy to let the fallback call // `PartialEq::eq` on it. - return Err(FallbackToConstRef); + return Err(fallback_to_const_ref(self)); } ty::Adt(adt_def, _) if !self.type_marked_structural(cv.ty) => { debug!("adt_def {:?} has !type_marked_structural for cv.ty: {:?}", adt_def, cv.ty); @@ -447,7 +462,7 @@ impl<'a, 'tcx> ConstToPat<'a, 'tcx> { // very hard to invoke `PartialEq::eq` on it as a fallback. let val = match self.recur(tcx.deref_const(self.param_env.and(cv)), false) { Ok(subpattern) => PatKind::Deref { subpattern }, - Err(FallbackToConstRef) => PatKind::Constant { value: cv }, + Err(_) => PatKind::Constant { value: cv }, }; self.behind_reference.set(old); val |