Auto merge of #142707 - ashivaram23:drop_wildcard, r=dianqk

Apply effects to `otherwise` edge in dataflow analysis

This allows `ElaborateDrops` to remove drops when a `match` wildcard arm covers multiple no-Drop enum variants. It modifies dataflow analysis to update the `MaybeUninitializedPlaces` and `MaybeInitializedPlaces` data for a block reached through an `otherwise` edge.

Fixes rust-lang/rust#142705.

2 files changed, 7 insertions, 5 deletions

diff --git a/compiler/rustc_mir_dataflow/src/framework/direction.rs b/compiler/rustc_mir_dataflow/src/framework/direction.rs
index e955e38ad10..cb647476db8 100644
--- a/compiler/rustc_mir_dataflow/src/framework/direction.rs
+++ b/compiler/rustc_mir_dataflow/src/framework/direction.rs
@@ -112,12 +112,13 @@ impl Direction for Backward {
                     propagate(pred, &tmp);
                 }
 
-                mir::TerminatorKind::SwitchInt { targets: _, ref discr } => {
+                mir::TerminatorKind::SwitchInt { ref targets, ref discr } => {
                     if let Some(mut data) = analysis.get_switch_int_data(block, discr) {
                         let mut tmp = analysis.bottom_value(body);
                         for &value in &body.basic_blocks.switch_sources()[&(block, pred)] {
                             tmp.clone_from(exit_state);
-                            analysis.apply_switch_int_edge_effect(&mut data, &mut tmp, value);
+                            analysis
+                                .apply_switch_int_edge_effect(&mut data, &mut tmp, value, targets);
                             propagate(pred, &tmp);
                         }
                     } else {
@@ -290,20 +291,20 @@ impl Direction for Forward {
                     for (value, target) in targets.iter() {
                         tmp.clone_from(exit_state);
                         let value = SwitchTargetValue::Normal(value);
-                        analysis.apply_switch_int_edge_effect(&mut data, &mut tmp, value);
+                        analysis.apply_switch_int_edge_effect(&mut data, &mut tmp, value, targets);
                         propagate(target, &tmp);
                     }
 
                     // Once we get to the final, "otherwise" branch, there is no need to preserve
                     // `exit_state`, so pass it directly to `apply_switch_int_edge_effect` to save
                     // a clone of the dataflow state.
-                    let otherwise = targets.otherwise();
                     analysis.apply_switch_int_edge_effect(
                         &mut data,
                         exit_state,
                         SwitchTargetValue::Otherwise,
+                        targets,
                     );
-                    propagate(otherwise, exit_state);
+                    propagate(targets.otherwise(), exit_state);
                 } else {
                     for target in targets.all_targets() {
                         propagate(*target, exit_state);
diff --git a/compiler/rustc_mir_dataflow/src/framework/mod.rs b/compiler/rustc_mir_dataflow/src/framework/mod.rs
index 9cadec100b5..b6a56036019 100644
--- a/compiler/rustc_mir_dataflow/src/framework/mod.rs
+++ b/compiler/rustc_mir_dataflow/src/framework/mod.rs
@@ -224,6 +224,7 @@ pub trait Analysis<'tcx> {
         _data: &mut Self::SwitchIntData,
         _state: &mut Self::Domain,
         _value: SwitchTargetValue,
+        _targets: &mir::SwitchTargets,
     ) {
         unreachable!();
     }