Auto merge of #117881 - TaKO8Ki:rollup-n7jtmgj, r=TaKO8Ki

Rollup of 5 pull requests

Successful merges:

 - #117737 (Remove `-Zkeep-hygiene-data`.)
 - #117830 (Small improvements in object lifetime default code)
 - #117858 (Compute layout with spans for better cycle errors in coroutines)
 - #117863 (Remove some unused stuff from `rustc_index`)
 - #117872 (Cranelift isn't available on non-nightly channels)

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

compiler/rustc_trait_selection/src/traits/wf.rs

@@ -913,20 +913,15 @@ pub fn object_region_bounds<'tcx>(
     tcx: TyCtxt<'tcx>,
     existential_predicates: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
 ) -> Vec<ty::Region<'tcx>> {
-    // Since we don't actually *know* the self type for an object,
-    // this "open(err)" serves as a kind of dummy standin -- basically
-    // a placeholder type.
-    let open_ty = Ty::new_fresh(tcx, 0);
-
     let predicates = existential_predicates.iter().filter_map(|predicate| {
         if let ty::ExistentialPredicate::Projection(_) = predicate.skip_binder() {
             None
         } else {
-            Some(predicate.with_self_ty(tcx, open_ty))
+            Some(predicate.with_self_ty(tcx, tcx.types.trait_object_dummy_self))
         }
     });
 
-    required_region_bounds(tcx, open_ty, predicates)
+    required_region_bounds(tcx, tcx.types.trait_object_dummy_self, predicates)
 }
 
 /// Given a set of predicates that apply to an object type, returns