{"ast_node_type":"variable","tokens":[{"end":72,"kind":"keyword","start":0,"text":"let"}]}
                    let ty = tcx.type_of(def_id).instantiate_identity();
                res = res.and(enter_wf_checking_ctxt(tcx, def_id, |wfcx| {
                    let span = tcx.def_span(def_id);