{"ast_node_type":"other","tokens":[{"end":99,"kind":"keyword","start":0,"text":"(FeatureStability::Unstable"}]}
            (FeatureStability::Unstable { .. }, Some((FeatureStability::AcceptedSince(_), _))) => {
            }
                self.tcx.dcx().emit_err(FeaturePreviouslyDeclared {