{"ast_node_type":"variable","tokens":[{"end":52,"kind":"keyword","start":0,"text":"let"}]}
            let errno = unsafe { *libc::__error() };
            // 0: https://github.com/apple-oss-distributions/libpthread/blob/67e155c94093be9a204b69637d198eceff2c7c46/src/qos.c#L171-L177
            unreachable!("`pthread_get_qos_class_np` failed unexpectedly (os error {errno})");