{"ast_node_type":"variable","tokens":[{"end":75,"kind":"keyword","start":0,"text":"let"}]}
                let counter = *self.next_region_name.try_borrow().unwrap();
                // will increment the counter, "reserving" the number we just used.
                self.highlight_if_we_cannot_match_hir_ty(fr, return_ty, return_span, counter)