∀ {α : Type u} [inst : LT α] [inst_1 : DecidableLT α] [inst_2 : Std.PRange.UpwardEnumerable α]
  [inst_3 : Std.Rxo.IsAlwaysFinite α] [inst_4 : Std.PRange.LawfulUpwardEnumerable α]
  [Std.PRange.LawfulUpwardEnumerableLT α] {a b : α}, (a<...b).toList.Nodup