{"ast_node_type":"variable","tokens":[{"end":37,"kind":"keyword","start":0,"text":"let"}]}
                let prev_ast_id_map =
                    std::mem::replace(&mut self.span_map, db.span_map(self.current_file_id));
                    mem::replace(&mut self.ast_id_map, db.ast_id_map(self.current_file_id));