Print region in case of ICE

Author: sinkuu

src/librustc/infer/error_reporting/mod.rs

@@ -181,7 +181,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
                 self.msg_span_from_early_bound_and_free_regions(region)
             },
             ty::ReStatic => ("the static lifetime".to_owned(), None),
-            _ => bug!(),
+            _ => bug!("{:?}", region),
         }
     }