{"ast_node_type":"other","tokens":[{"end":100,"kind":"keyword","start":0,"text":"tcx.dcx().emit_err(errors::DuplicateFeatureErr"}]}
            tcx.dcx().emit_err(errors::DuplicateFeatureErr { span: *attr_sp, feature: *gate_name });
            // Warn if the user enables a lang feature multiple times.
        }