diff options
| -rw-r--r-- | compiler/rustc_mir_build/src/thir/cx/expr.rs | 32 |
1 files changed, 13 insertions, 19 deletions
diff --git a/compiler/rustc_mir_build/src/thir/cx/expr.rs b/compiler/rustc_mir_build/src/thir/cx/expr.rs index 0535ea24b82..ccaa996a070 100644 --- a/compiler/rustc_mir_build/src/thir/cx/expr.rs +++ b/compiler/rustc_mir_build/src/thir/cx/expr.rs @@ -191,11 +191,16 @@ impl<'tcx> Cx<'tcx> { source: self.mirror_expr(source), cast: PointerCoercion::ArrayToPointer, } - } else { - // check whether this is casting an enum variant discriminant - // to prevent cycles, we refer to the discriminant initializer + } else if let hir::ExprKind::Path(ref qpath) = source.kind + && let res = self.typeck_results().qpath_res(qpath, source.hir_id) + && let ty = self.typeck_results().node_type(source.hir_id) + && let ty::Adt(adt_def, args) = ty.kind() + && let Res::Def(DefKind::Ctor(CtorOf::Variant, CtorKind::Const), variant_ctor_id) = res + { + // Check whether this is casting an enum variant discriminant. + // To prevent cycles, we refer to the discriminant initializer, // which is always an integer and thus doesn't need to know the - // enum's layout (or its tag type) to compute it during const eval + // enum's layout (or its tag type) to compute it during const eval. // Example: // enum Foo { // A, @@ -204,21 +209,6 @@ impl<'tcx> Cx<'tcx> { // The correct solution would be to add symbolic computations to miri, // so we wouldn't have to compute and store the actual value - let hir::ExprKind::Path(ref qpath) = source.kind else { - return ExprKind::Cast { source: self.mirror_expr(source) }; - }; - - let res = self.typeck_results().qpath_res(qpath, source.hir_id); - let ty = self.typeck_results().node_type(source.hir_id); - let ty::Adt(adt_def, args) = ty.kind() else { - return ExprKind::Cast { source: self.mirror_expr(source) }; - }; - - let Res::Def(DefKind::Ctor(CtorOf::Variant, CtorKind::Const), variant_ctor_id) = res - else { - return ExprKind::Cast { source: self.mirror_expr(source) }; - }; - let idx = adt_def.variant_index_with_ctor_id(variant_ctor_id); let (discr_did, discr_offset) = adt_def.discriminant_def_for_variant(idx); @@ -255,6 +245,10 @@ impl<'tcx> Cx<'tcx> { }; ExprKind::Cast { source } + } else { + // Default to `ExprKind::Cast` for all explicit casts. + // MIR building then picks the right MIR casts based on the types. + ExprKind::Cast { source: self.mirror_expr(source) } } } |