{"ast_node_type":"variable","tokens":[{"end":47,"kind":"keyword","start":0,"text":"let"}]}
        let lang_items = self.tcx.lang_items();
    fn map_trait_to_async_trait(&self, def_id: DefId) -> Option<DefId> {
        match self.tcx.fn_trait_kind_from_def_id(def_id)? {