Rollup merge of rust-lang#134827 - compiler-errors:borrowck-nits, r=lqd

Some random region tweaks

Remove a redundant function and add an assertion that I think is useful

Author: dtolnay

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -140,6 +140,12 @@ pub(crate) fn type_check<'a, 'tcx>(
         &mut constraints,
     );
 
+    let pre_obligations = infcx.take_registered_region_obligations();
+    assert!(
+        pre_obligations.is_empty(),
+        "there should be no incoming region obligations = {pre_obligations:#?}",
+    );
+
     debug!(?normalized_inputs_and_output);
 
     let mut typeck = TypeChecker {

compiler/rustc_infer/src/infer/region_constraints/mod.rs

@@ -299,10 +299,6 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
         self.storage.var_infos.len()
     }
 
-    pub fn region_constraint_data(&self) -> &RegionConstraintData<'tcx> {
-        &self.storage.data
-    }
-
     /// Takes (and clears) the current set of constraints. Note that
     /// the set of variables remains intact, but all relationships
     /// between them are reset. This is used during NLL checking to

compiler/rustc_trait_selection/src/traits/auto_trait.rs

@@ -161,8 +161,7 @@ impl<'tcx> AutoTraitFinder<'tcx> {
         let outlives_env = OutlivesEnvironment::new(full_env);
         let _ = infcx.process_registered_region_obligations(&outlives_env, |ty, _| Ok(ty));
 
-        let region_data =
-            infcx.inner.borrow_mut().unwrap_region_constraints().region_constraint_data().clone();
+        let region_data = infcx.inner.borrow_mut().unwrap_region_constraints().data().clone();
 
         let vid_to_region = self.map_vid_to_region(&region_data);