Auto merge of rust-lang#88533 - oli-obk:tait_🧊, r=spastorino

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. Instead mir borrock does all the logic, and it can handle concrete regions just fine, as long as it created them itself.

fixes rust-lang#83190 which was introduced by rust-lang#87287

r? `@spastorino`

Author: bors

compiler/rustc_mir/src/borrow_check/region_infer/opaque_types.rs

@@ -82,15 +82,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                             .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);