Concrete regions can show up in mir borrowck if the originated from there.

We used to not encounter them here, because we took regions from typeck's opaque type resolution by renumbering them. We don't do that anymore.

diff --git a/compiler/rustc_mir/src/borrow_check/region_infer/opaque_types.rs b/compiler/rustc_mir/src/borrow_check/region_infer/opaque_types.rs
index e9ab62e1664f972778fa884a8b46a9f53f6f62cd..12fceeff0884c92a8f4f8ada963004d36b86c8f8 100644 (file)
--- a/compiler/rustc_mir/src/borrow_check/region_infer/opaque_types.rs
+++ b/compiler/rustc_mir/src/borrow_check/region_infer/opaque_types.rs
@@ -82,15 +82,7 @@ pub(in crate::borrow_check) fn infer_opaque_types(
                             .find(|ur_vid| self.eval_equal(vid, **ur_vid))
                             .and_then(|ur_vid| self.definitions[*ur_vid].external_name)
                             .unwrap_or(infcx.tcx.lifetimes.re_root_empty),
-                        ty::ReLateBound(..) => region,
-                        ty::ReStatic => region,
-                        _ => {
-                            infcx.tcx.sess.delay_span_bug(
-                                span,
-                                &format!("unexpected concrete region in borrowck: {:?}", region),
-                            );
-                            region
-                        }
+                        _ => region,
                     });
 
                 debug!(?universal_concrete_type, ?universal_substs);