FWS_U
w->state = w->state >= FWS_R ? FWS_U : FWS_INIT;
w->state = w->state >= FWS_C ? FWS_U : FWS_INIT;
w->state = FWS_U;
w->state = FWS_U;
case FWS_U:
return w->node && !(w->state == FWS_U && w->node == w->root);