Revert to only using opportunistic_resolve_vars for existing places

3 files changed, 33 insertions, 9 deletions

diff --git a/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs b/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs
index 27ac817463f..337b8365d8c 100644
--- a/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs
+++ b/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs
@@ -322,7 +322,22 @@ impl<'cx, 'tcx> TypeFolder<'tcx> for Canonicalizer<'cx, 'tcx> {
                 }
             }
 
-            ty::ReVar(_) => self.canonicalize_region_mode.canonicalize_free_region(self, r),
+            ty::ReVar(vid) => {
+                let resolved_vid = self
+                    .infcx
+                    .unwrap()
+                    .inner
+                    .borrow_mut()
+                    .unwrap_region_constraints()
+                    .opportunistic_resolve_var(vid);
+                debug!(
+                    "canonical: region var found with vid {:?}, \
+                     opportunistically resolved to {:?}",
+                    vid, r
+                );
+                let r = self.tcx.reuse_or_mk_region(r, ty::ReVar(resolved_vid));
+                self.canonicalize_region_mode.canonicalize_free_region(self, r)
+            }
 
             ty::ReStatic
             | ty::ReEarlyBound(..)
diff --git a/compiler/rustc_infer/src/infer/region_constraints/mod.rs b/compiler/rustc_infer/src/infer/region_constraints/mod.rs
index dfbb82bd657..d46a91b6a77 100644
--- a/compiler/rustc_infer/src/infer/region_constraints/mod.rs
+++ b/compiler/rustc_infer/src/infer/region_constraints/mod.rs
@@ -623,6 +623,10 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
         }
     }
 
+    pub fn opportunistic_resolve_var(&mut self, rid: ty::RegionVid) -> ty::RegionVid {
+        self.unification_table().find(rid).vid
+    }
+
     pub fn opportunistic_resolve_region(
         &mut self,
         tcx: TyCtxt<'tcx>,
@@ -692,8 +696,7 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
         &self,
         value_count: usize,
     ) -> (Range<RegionVid>, Vec<RegionVariableOrigin>) {
-        let range = RegionVid::from(value_count as u32)
-            ..RegionVid::from(self.unification_table.len() as u32);
+        let range = RegionVid::from(value_count)..RegionVid::from(self.unification_table.len());
         (
             range.clone(),
             (range.start.index()..range.end.index())
diff --git a/compiler/rustc_infer/src/infer/resolve.rs b/compiler/rustc_infer/src/infer/resolve.rs
index 4eec65b3d96..48b8ee17594 100644
--- a/compiler/rustc_infer/src/infer/resolve.rs
+++ b/compiler/rustc_infer/src/infer/resolve.rs
@@ -84,12 +84,18 @@ impl<'a, 'tcx> TypeFolder<'tcx> for OpportunisticRegionResolver<'a, 'tcx> {
     }
 
     fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
-        let tcx = self.tcx();
-        self.infcx
-            .inner
-            .borrow_mut()
-            .unwrap_region_constraints()
-            .opportunistic_resolve_region(tcx, r)
+        match *r {
+            ty::ReVar(rid) => {
+                let resolved = self
+                    .infcx
+                    .inner
+                    .borrow_mut()
+                    .unwrap_region_constraints()
+                    .opportunistic_resolve_var(rid);
+                self.tcx().reuse_or_mk_region(r, ty::ReVar(resolved))
+            }
+            _ => r,
+        }
     }
 
     fn fold_const(&mut self, ct: &'tcx ty::Const<'tcx>) -> &'tcx ty::Const<'tcx> {