Use Box instead of Rc for polonius_output.

Refcounting isn't needed.

Author: nnethercote

compiler/rustc_borrowck/src/consumers.rs

@@ -79,7 +79,7 @@ pub struct BodyWithBorrowckFacts<'tcx> {
     pub input_facts: Option<Box<PoloniusInput>>,
     /// Polonius output facts. Populated when using
     /// [`ConsumerOptions::PoloniusOutputFacts`].
-    pub output_facts: Option<Rc<PoloniusOutput>>,
+    pub output_facts: Option<Box<PoloniusOutput>>,
 }
 
 /// This function computes borrowck facts for the given body. The [`ConsumerOptions`]

compiler/rustc_borrowck/src/lib.rs

@@ -586,7 +586,7 @@ struct MirBorrowckCtxt<'a, 'infcx, 'tcx> {
     next_region_name: RefCell<usize>,
 
     /// Results of Polonius analysis.
-    polonius_output: Option<Rc<PoloniusOutput>>,
+    polonius_output: Option<Box<PoloniusOutput>>,
 
     diags: diags::BorrowckDiags<'infcx, 'tcx>,
     move_errors: Vec<MoveError<'tcx>>,

compiler/rustc_borrowck/src/nll.rs

@@ -42,7 +42,7 @@ pub(crate) struct NllOutput<'tcx> {
     pub regioncx: RegionInferenceContext<'tcx>,
     pub opaque_type_values: FxIndexMap<LocalDefId, OpaqueHiddenType<'tcx>>,
     pub polonius_input: Option<Box<AllFacts>>,
-    pub polonius_output: Option<Rc<PoloniusOutput>>,
+    pub polonius_output: Option<Box<PoloniusOutput>>,
     pub opt_closure_req: Option<ClosureRegionRequirements<'tcx>>,
     pub nll_errors: RegionErrors<'tcx>,
 }
@@ -184,7 +184,7 @@ pub(crate) fn compute_regions<'a, 'tcx>(
             let algorithm = Algorithm::from_str(&algorithm).unwrap();
             debug!("compute_regions: using polonius algorithm {:?}", algorithm);
             let _prof_timer = infcx.tcx.prof.generic_activity("polonius_analysis");
-            Some(Rc::new(Output::compute(all_facts, algorithm, false)))
+            Some(Box::new(Output::compute(all_facts, algorithm, false)))
         } else {
             None
         }

compiler/rustc_borrowck/src/region_infer/mod.rs

@@ -637,7 +637,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         &mut self,
         infcx: &InferCtxt<'tcx>,
         body: &Body<'tcx>,
-        polonius_output: Option<Rc<PoloniusOutput>>,
+        polonius_output: Option<Box<PoloniusOutput>>,
     ) -> (Option<ClosureRegionRequirements<'tcx>>, RegionErrors<'tcx>) {
         let mir_def_id = body.source.def_id();
         self.propagate_constraints();
@@ -663,7 +663,9 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             self.check_polonius_subset_errors(
                 outlives_requirements.as_mut(),
                 &mut errors_buffer,
-                polonius_output.expect("Polonius output is unavailable despite `-Z polonius`"),
+                polonius_output
+                    .as_ref()
+                    .expect("Polonius output is unavailable despite `-Z polonius`"),
             );
         } else {
             self.check_universal_regions(outlives_requirements.as_mut(), &mut errors_buffer);
@@ -1411,7 +1413,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         &self,
         mut propagated_outlives_requirements: Option<&mut Vec<ClosureOutlivesRequirement<'tcx>>>,
         errors_buffer: &mut RegionErrors<'tcx>,
-        polonius_output: Rc<PoloniusOutput>,
+        polonius_output: &PoloniusOutput,
     ) {
         debug!(
             "check_polonius_subset_errors: {} subset_errors",