{"ast_node_type":"variable","tokens":[{"end":43,"kind":"keyword","start":0,"text":"let"}]}
        let referent_ty = match ty.kind() {
    fn is_fn_ref(ty: Ty<'tcx>) -> Option<(DefId, GenericArgsRef<'tcx>)> {
            ty::Ref(_, referent_ty, _) => Some(referent_ty),