outside of borrowck, do not provide an implicit_region_bound

see comment added to the field in `VerifyBoundCx`.

compiler/rustc_trait_selection/src/traits/auto_trait.rs

@@ -220,7 +220,7 @@ impl<'tcx> AutoTraitFinder<'tcx> {
                 .map(|&(id, _)| (id, vec![]))
                 .collect();
 
-            infcx.process_registered_region_obligations(&body_id_map, None, full_env);
+            infcx.process_registered_region_obligations(&body_id_map, full_env);
 
             let region_data = infcx
                 .inner

compiler/rustc_trait_selection/src/traits/coherence.rs

@@ -407,11 +407,7 @@ fn resolve_negative_obligation<'cx, 'tcx>(
     // function bodies with closures).
     outlives_env.save_implied_bounds(CRATE_HIR_ID);
 
-    infcx.process_registered_region_obligations(
-        outlives_env.region_bound_pairs_map(),
-        Some(tcx.lifetimes.re_root_empty),
-        param_env,
-    );
+    infcx.process_registered_region_obligations(outlives_env.region_bound_pairs_map(), param_env);
 
     let errors = infcx.resolve_regions(region_context, &outlives_env);