Make mark_inactive_variants_as_uninit configurable

Author: ecstatic-morse

src/librustc_mir/borrow_check/mod.rs

@@ -204,6 +204,7 @@ fn do_mir_borrowck<'a, 'tcx>(
     let mdpe = MoveDataParamEnv { move_data, param_env };
 
     let mut flow_inits = MaybeInitializedPlaces::new(tcx, &body, &mdpe)
+        .mark_inactive_variants_as_uninit(true)
         .into_engine(tcx, &body, def.did.to_def_id())
         .iterate_to_fixpoint()
         .into_results_cursor(&body);

src/librustc_mir/dataflow/impls/mod.rs

@@ -71,11 +71,17 @@ pub struct MaybeInitializedPlaces<'a, 'tcx> {
     tcx: TyCtxt<'tcx>,
     body: &'a Body<'tcx>,
     mdpe: &'a MoveDataParamEnv<'tcx>,
+    mark_inactive_variants_as_uninit: bool,
 }
 
 impl<'a, 'tcx> MaybeInitializedPlaces<'a, 'tcx> {
     pub fn new(tcx: TyCtxt<'tcx>, body: &'a Body<'tcx>, mdpe: &'a MoveDataParamEnv<'tcx>) -> Self {
-        MaybeInitializedPlaces { tcx, body, mdpe }
+        MaybeInitializedPlaces { tcx, body, mdpe, mark_inactive_variants_as_uninit: false }
+    }
+
+    pub fn mark_inactive_variants_as_uninit(mut self, yes: bool) -> Self {
+        self.mark_inactive_variants_as_uninit = yes;
+        self
     }
 }
 
@@ -138,8 +144,8 @@ impl<'a, 'tcx> MaybeUninitializedPlaces<'a, 'tcx> {
     ///
     /// This is correct in a vacuum but is not the default because it causes problems in the borrow
     /// checker, where this information gets propagated along `FakeEdge`s.
-    pub fn mark_inactive_variants_as_uninit(mut self) -> Self {
-        self.mark_inactive_variants_as_uninit = true;
+    pub fn mark_inactive_variants_as_uninit(mut self, yes: bool) -> Self {
+        self.mark_inactive_variants_as_uninit = yes;
         self
     }
 }
@@ -362,6 +368,10 @@ impl<'tcx> GenKillAnalysis<'tcx> for MaybeInitializedPlaces<'_, 'tcx> {
         _adt: &ty::AdtDef,
         variant: VariantIdx,
     ) {
+        if !self.mark_inactive_variants_as_uninit {
+            return;
+        }
+
         // Kill all move paths that correspond to variants we know to be inactive along this
         // particular outgoing edge of a `SwitchInt`.
         drop_flag_effects::on_all_inactive_variants(

src/librustc_mir/transform/elaborate_drops.rs

@@ -42,13 +42,14 @@ impl<'tcx> MirPass<'tcx> for ElaborateDrops {
             let dead_unwinds = find_dead_unwinds(tcx, body, def_id, &env);
 
             let inits = MaybeInitializedPlaces::new(tcx, body, &env)
+                .mark_inactive_variants_as_uninit(true)
                 .into_engine(tcx, body, def_id)
                 .dead_unwinds(&dead_unwinds)
                 .iterate_to_fixpoint()
                 .into_results_cursor(body);
 
             let uninits = MaybeUninitializedPlaces::new(tcx, body, &env)
-                .mark_inactive_variants_as_uninit()
+                .mark_inactive_variants_as_uninit(true)
                 .into_engine(tcx, body, def_id)
                 .dead_unwinds(&dead_unwinds)
                 .iterate_to_fixpoint()
@@ -82,6 +83,7 @@ fn find_dead_unwinds<'tcx>(
     // reach cleanup blocks, which can't have unwind edges themselves.
     let mut dead_unwinds = BitSet::new_empty(body.basic_blocks().len());
     let mut flow_inits = MaybeInitializedPlaces::new(tcx, body, &env)
+        .mark_inactive_variants_as_uninit(true)
         .into_engine(tcx, body, def_id)
         .iterate_to_fixpoint()
         .into_results_cursor(body);