∀ {α : Type u} {r : Std.Rci α} [inst : LT α] [DecidableLT α] [inst_2 : Std.PRange.UpwardEnumerable α]
  [inst_3 : Std.PRange.LawfulUpwardEnumerable α] [Std.PRange.LawfulUpwardEnumerableLT α]
  [inst : Std.Rxi.IsAlwaysFinite α] {i : ℕ}, i < r.toArray.size → (Std.PRange.succMany? i r.lower).isSome = true