{"ast_node_type":"variable","tokens":[{"end":97,"kind":"keyword","start":0,"text":"let"}]}
        let old_span_map = mem::replace(&mut self.span_map, SpanMap::ExpansionSpanMap(span_map));
        let old_ast_id_map = mem::replace(&mut self.ast_id_map, self.db.ast_id_map(self.file_id));
        self.depth += 1;