Auto merge of #141396 - matthiaskrgr:rollup-feg050g, r=matthiaskrgr

Rollup of 7 pull requests

Successful merges:

 - #135562 (Add ignore value suggestion in closure body)
 - #139635 (Finalize repeat expr inference behaviour with inferred repeat counts)
 - #139668 (Handle regions equivalent to 'static in non_local_bounds)
 - #140218 (HIR ty lowering: Clean up & refactor the lowering of type-relative paths)
 - #140435 (use uX::from instead of _ as uX in non - const contexts)
 - #141130 (rustc_on_unimplemented cleanups)
 - #141286 (Querify `coroutine_hidden_types`)

Failed merges:

 - #140247 (Don't build `ParamEnv` and do trait solving in `ItemCtxt`s when lowering IATs)

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

compiler/rustc_borrowck/src/type_check/free_region_relations.rs

@@ -131,7 +131,8 @@ impl UniversalRegionRelations<'_> {
         assert!(self.universal_regions.is_universal_region(fr0));
 
         let mut external_parents = vec![];
-        let mut queue = vec![fr0];
+
+        let mut queue = vec![relation.minimal_scc_representative(fr0)];
 
         // Keep expanding `fr` into its parents until we reach
         // non-local regions.

compiler/rustc_data_structures/src/transitive_relation.rs

@@ -354,6 +354,20 @@ impl<T: Eq + Hash + Copy> TransitiveRelation<T> {
             .collect()
     }
 
+    /// Given an element A, elements B with the lowest index such that `A R B`
+    /// and `B R A`, or `A` if no such element exists.
+    pub fn minimal_scc_representative(&self, a: T) -> T {
+        match self.index(a) {
+            Some(a_i) => self.with_closure(|closure| {
+                closure
+                    .iter(a_i.0)
+                    .find(|i| closure.contains(*i, a_i.0))
+                    .map_or(a, |i| self.elements[i])
+            }),
+            None => a,
+        }
+    }
+
     fn with_closure<OP, R>(&self, op: OP) -> R
     where
         OP: FnOnce(&BitMatrix<usize, usize>) -> R,