{"ast_node_type":"other","tokens":[{"end":92,"kind":"keyword","start":0,"text":"predicates.insert((ty::ClauseKind::UnstableFeature(*feat_name).upcast(tcx),"}]}
        predicates.insert((ty::ClauseKind::UnstableFeature(*feat_name).upcast(tcx), *span));
    for (feat_name, span) in allow_unstable_feature_attr {
    }