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Fix variant index / discriminant confusion in uninhabited enum branching #89764

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merged 3 commits into from
Jan 20, 2022
+6 −11
Merged

Fix variant index / discriminant confusion in uninhabited enum branching #89764

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763703c
Remove redundant check for promoteds
tmiasko Oct 11, 2021
d5a91f3
Use `IndexVec::indices` instead of reimplementing it
tmiasko Oct 11, 2021
c3e71d8
Fix a variant index and variant discriminant confusion
tmiasko Oct 11, 2021
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17 changes: 6 additions & 11 deletions compiler/rustc_mir_transform/src/uninhabited_enum_branching.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,8 +3,7 @@
use crate::MirPass;
use rustc_data_structures::stable_set::FxHashSet;
use rustc_middle::mir::{
BasicBlock, BasicBlockData, Body, Local, Operand, Rvalue, StatementKind, SwitchTargets,
TerminatorKind,
BasicBlockData, Body, Local, Operand, Rvalue, StatementKind, SwitchTargets, TerminatorKind,
};
use rustc_middle::ty::layout::TyAndLayout;
use rustc_middle::ty::{Ty, TyCtxt};
Expand Down Expand Up @@ -56,7 +55,10 @@ fn variant_discriminants<'tcx>(
match &layout.variants {
Variants::Single { index } => {
let mut res = FxHashSet::default();
res.insert(index.as_u32() as u128);
res.insert(
ty.discriminant_for_variant(tcx, *index)
.map_or(index.as_u32() as u128, |discr| discr.val),
);
res
}
Variants::Multiple { variants, .. } => variants
Expand All @@ -71,16 +73,9 @@ fn variant_discriminants<'tcx>(

impl<'tcx> MirPass<'tcx> for UninhabitedEnumBranching {
fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
if body.source.promoted.is_some() {
return;
}

trace!("UninhabitedEnumBranching starting for {:?}", body.source);

let basic_block_count = body.basic_blocks().len();

for bb in 0..basic_block_count {
let bb = BasicBlock::from_usize(bb);
for bb in body.basic_blocks().indices() {
trace!("processing block {:?}", bb);

let Some(discriminant_ty) = get_switched_on_type(&body.basic_blocks()[bb], tcx, body) else {
Expand Down