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> {
 pubinput_facts:Option<Box<PoloniusInput>>,
 /// Polonius output facts. Populated when using
 /// [`ConsumerOptions::PoloniusOutputFacts`].
-puboutput_facts:Option<Rc<PoloniusOutput>>,
+puboutput_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> {
 pubregioncx:RegionInferenceContext<'tcx>,
 pubopaque_type_values:FxIndexMap<LocalDefId,OpaqueHiddenType<'tcx>>,
 pubpolonius_input:Option<Box<AllFacts>>,
-pubpolonius_output:Option<Rc<PoloniusOutput>>,
+pubpolonius_output:Option<Box<PoloniusOutput>>,
 pubopt_closure_req:Option<ClosureRegionRequirements<'tcx>>,
 pubnll_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> {
 &mutself,
 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,
 mutpropagated_outlives_requirements:Option<&mutVec<ClosureOutlivesRequirement<'tcx>>>,
 errors_buffer:&mutRegionErrors<'tcx>,
-polonius_output:Rc<PoloniusOutput>,
+polonius_output:&PoloniusOutput,
 ){
 debug!(
 "check_polonius_subset_errors: {} subset_errors",