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Rollup merge of #89764 - tmiasko:uninhabited-enums, r=wesleywiser
Fix variant index / discriminant confusion in uninhabited enum branching Fix confusion between variant index and variant discriminant. The pass incorrectly assumed that for `Variants::Single` variant index is the same as variant discriminant. r? `@wesleywiser`
2 parents 98cb338 + c3e71d8 commit d188287

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compiler/rustc_mir_transform/src/uninhabited_enum_branching.rs

+6-11
Original file line numberDiff line numberDiff line change
@@ -3,8 +3,7 @@
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use crate::MirPass;
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use rustc_data_structures::stable_set::FxHashSet;
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use rustc_middle::mir::{
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BasicBlock, BasicBlockData, Body, Local, Operand, Rvalue, StatementKind, SwitchTargets,
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TerminatorKind,
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BasicBlockData, Body, Local, Operand, Rvalue, StatementKind, SwitchTargets, TerminatorKind,
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};
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use rustc_middle::ty::layout::TyAndLayout;
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use rustc_middle::ty::{Ty, TyCtxt};
@@ -56,7 +55,10 @@ fn variant_discriminants<'tcx>(
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match &layout.variants {
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Variants::Single { index } => {
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let mut res = FxHashSet::default();
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res.insert(index.as_u32() as u128);
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res.insert(
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ty.discriminant_for_variant(tcx, *index)
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.map_or(index.as_u32() as u128, |discr| discr.val),
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);
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res
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}
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Variants::Multiple { variants, .. } => variants
@@ -75,16 +77,9 @@ impl<'tcx> MirPass<'tcx> for UninhabitedEnumBranching {
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}
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fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
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if body.source.promoted.is_some() {
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return;
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}
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trace!("UninhabitedEnumBranching starting for {:?}", body.source);
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let basic_block_count = body.basic_blocks().len();
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for bb in 0..basic_block_count {
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let bb = BasicBlock::from_usize(bb);
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for bb in body.basic_blocks().indices() {
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trace!("processing block {:?}", bb);
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let Some(discriminant_ty) = get_switched_on_type(&body.basic_blocks()[bb], tcx, body) else {

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