3 files changed, 28 insertions, 18 deletions
diff --git a/compiler/rustc_borrowck/src/handle_placeholders.rs b/compiler/rustc_borrowck/src/handle_placeholders.rs
index 94379cdebf7..6be90994015 100644
--- a/compiler/rustc_borrowck/src/handle_placeholders.rs
+++ b/compiler/rustc_borrowck/src/handle_placeholders.rs
@@ -166,13 +166,9 @@ impl RegionTracker {
         }
     }
 
-    /// Determine if the tracked universes of the two SCCs are compatible.
-    pub(crate) fn universe_compatible_with(&self, other: Self) -> bool {
-        // HACK: We first check whether we can name the highest existential universe
-        // of `other`. This only exists to avoid errors in case that scc already
-        // depends on a placeholder it cannot name itself.
-        self.max_nameable_universe().can_name(other.max_nameable_universe())
-            || other.reachable_placeholders.can_be_named_by(self.max_nameable_universe())
+    /// Determine if we can name all the placeholders in `other`.
+    pub(crate) fn can_name_all_placeholders(&self, other: Self) -> bool {
+        other.reachable_placeholders.can_be_named_by(self.max_nameable_universe.0)
     }
 
     /// If this SCC reaches a placeholder it can't name, return it.
diff --git a/compiler/rustc_borrowck/src/region_infer/mod.rs b/compiler/rustc_borrowck/src/region_infer/mod.rs
index f57456949bb..5f4bfd9df48 100644
--- a/compiler/rustc_borrowck/src/region_infer/mod.rs
+++ b/compiler/rustc_borrowck/src/region_infer/mod.rs
@@ -571,11 +571,15 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         }
     }
 
-    /// Returns `true` if all the elements in the value of `scc_b` are nameable
+    /// Returns `true` if all the placeholders in the value of `scc_b` are nameable
     /// in `scc_a`. Used during constraint propagation, and only once
     /// the value of `scc_b` has been computed.
-    fn universe_compatible(&self, scc_b: ConstraintSccIndex, scc_a: ConstraintSccIndex) -> bool {
-        self.scc_annotations[scc_a].universe_compatible_with(self.scc_annotations[scc_b])
+    fn can_name_all_placeholders(
+        &self,
+        scc_a: ConstraintSccIndex,
+        scc_b: ConstraintSccIndex,
+    ) -> bool {
+        self.scc_annotations[scc_a].can_name_all_placeholders(self.scc_annotations[scc_b])
     }
 
     /// Once regions have been propagated, this method is used to see
@@ -964,16 +968,22 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             return true;
         }
 
+        let fr_static = self.universal_regions().fr_static;
+
         // If we are checking that `'sup: 'sub`, and `'sub` contains
         // some placeholder that `'sup` cannot name, then this is only
         // true if `'sup` outlives static.
-        if !self.universe_compatible(sub_region_scc, sup_region_scc) {
+        //
+        // Avoid infinite recursion if `sub_region` is already `'static`
+        if sub_region != fr_static
+            && !self.can_name_all_placeholders(sup_region_scc, sub_region_scc)
+        {
             debug!(
                 "sub universe `{sub_region_scc:?}` is not nameable \
                 by super `{sup_region_scc:?}`, promoting to static",
             );
 
-            return self.eval_outlives(sup_region, self.universal_regions().fr_static);
+            return self.eval_outlives(sup_region, fr_static);
         }
 
         // Both the `sub_region` and `sup_region` consist of the union
diff --git a/compiler/rustc_borrowck/src/type_check/canonical.rs b/compiler/rustc_borrowck/src/type_check/canonical.rs
index 2627ed899a9..aece0bda346 100644
--- a/compiler/rustc_borrowck/src/type_check/canonical.rs
+++ b/compiler/rustc_borrowck/src/type_check/canonical.rs
@@ -230,8 +230,14 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         location: impl NormalizeLocation,
     ) -> Ty<'tcx> {
         let tcx = self.tcx();
+        let body = self.body;
+
+        let cause = ObligationCause::misc(
+            location.to_locations().span(body),
+            body.source.def_id().expect_local(),
+        );
+
         if self.infcx.next_trait_solver() {
-            let body = self.body;
             let param_env = self.infcx.param_env;
             // FIXME: Make this into a real type op?
             self.fully_perform_op(
@@ -241,10 +247,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                     |ocx| {
                         let structurally_normalize = |ty| {
                             ocx.structurally_normalize_ty(
-                                &ObligationCause::misc(
-                                    location.to_locations().span(body),
-                                    body.source.def_id().expect_local(),
-                                ),
+                                &cause,
                                 param_env,
                                 ty,
                             )
@@ -253,6 +256,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
 
                         let tail = tcx.struct_tail_raw(
                             ty,
+                            &cause,
                             structurally_normalize,
                             || {},
                         );
@@ -265,7 +269,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             .unwrap_or_else(|guar| Ty::new_error(tcx, guar))
         } else {
             let mut normalize = |ty| self.normalize(ty, location);
-            let tail = tcx.struct_tail_raw(ty, &mut normalize, || {});
+            let tail = tcx.struct_tail_raw(ty, &cause, &mut normalize, || {});
             normalize(tail)
         }
     }