fact: Definition t0 {A} (v : t A O) : v = nil := match v in t _ m return (match m return t A m -> Type with O => fun v => v = nil | S k => fun _ => Unit end) v with nil => 1%path | cons _ _ _ => tt end.
imports: Coq(ssreflect) HoTT(HoTT) HoTT_additions Hierarchy Param_nat