encapsulate access to member constraints

Author: lqd

compiler/rustc_borrowck/src/dataflow.rs

@@ -330,7 +330,6 @@ impl<'tcx> PoloniusOutOfScopePrecomputer<'_, 'tcx> {
         // region that outlives free regions via outlives constraints.)
 
         let sccs = self.regioncx.constraint_sccs();
-        let member_constraints = &self.regioncx.member_constraints;
 
         let issuing_region_scc = sccs.scc(issuing_region);
         self.reachability_stack.push(issuing_region_scc);
@@ -352,15 +351,15 @@ impl<'tcx> PoloniusOutOfScopePrecomputer<'_, 'tcx> {
             //
             // If the issuing region outlives such a region, its loan escapes the function and
             // cannot go out of scope. We can early return.
-            if member_constraints.indices(scc).next().is_some()
+            if self.regioncx.scc_has_member_constraints(scc)
                 || self.sccs_live_at_all_points.contains(&scc)
             {
                 self.reachability_stack.clear();
                 self.reachability.clear();
                 return;
             }
 
-            // 3. Via outlives successors, which we want to record and traverse, so we add them
+            // 3. Via outlives successors, which we want to record and traverse: we add them
             //    to the worklist stack
             for &succ_scc in sccs.successors(scc) {
                 if self.reachability.insert(succ_scc) {

compiler/rustc_borrowck/src/region_infer/mod.rs

@@ -79,7 +79,7 @@ pub struct RegionInferenceContext<'tcx> {
     rev_scc_graph: Option<ReverseSccGraph>,
 
     /// The "R0 member of [R1..Rn]" constraints, indexed by SCC.
-    pub(crate) member_constraints: Rc<MemberConstraintSet<'tcx, ConstraintSccIndex>>,
+    member_constraints: Rc<MemberConstraintSet<'tcx, ConstraintSccIndex>>,
 
     /// Records the member constraints that we applied to each scc.
     /// This is useful for error reporting. Once constraint
@@ -2289,6 +2289,11 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     pub(crate) fn liveness_values(&self) -> &LivenessValues<RegionVid> {
         &self.liveness_constraints
     }
+
+    /// Returns whether the given SCC has any member constraints.
+    pub(crate) fn scc_has_member_constraints(&self, scc: ConstraintSccIndex) -> bool {
+        self.member_constraints.indices(scc).next().is_some()
+    }
 }
 
 impl<'tcx> RegionDefinition<'tcx> {