{"ast_node_type":"variable","tokens":[{"end":60,"kind":"keyword","start":0,"text":"let"}]}
        let sig = tcx.fn_sig(def_id).instantiate_identity();
    enter_wf_checking_ctxt(tcx, def_id, |wfcx| {
        check_fn_or_method(wfcx, sig, decl, def_id);