fact: Definition t0P A P (v : t A O) : P nil -> P v := match v in t _ m return (match m return t A m -> Type with O => fun v => P nil -> P v | S k => fun _ => Unit end) v with nil => id | cons _ _ _ => tt end.
imports: Coq(ssreflect) HoTT(HoTT) HoTT_additions Hierarchy Param_nat