{"ast_node_type":"variable","tokens":[{"end":65,"kind":"keyword","start":0,"text":"let"}]}
        let sig = tcx.instantiate_bound_regions_with_erased(sig);
        let sig = tcx.fn_sig(def_id).instantiate(tcx, &[self_ty.into()]);
        let span = tcx.def_span(def_id);