{"ast_node_type":"variable","tokens":[{"end":48,"kind":"keyword","start":0,"text":"let"}]}
    let (cfg, feature, has_feature) = gated_cfg;
fn gate_cfg(gated_cfg: &GatedCfg, cfg_span: Span, sess: &Session, features: &Features) {
    if !has_feature(features) && !cfg_span.allows_unstable(*feature) {