{"ast_node_type":"variable","tokens":[{"end":45,"kind":"keyword","start":0,"text":"let"}]}
    let variances = tcx.variances_of(def_id);
fn format_variances(tcx: TyCtxt<'_>, def_id: LocalDefId) -> String {
    let generics = GenericArgs::identity_for_item(tcx, def_id);