∀ {α : Type u_1} [inst : Std.PRange.Least? α] [inst_1 : LT α] [inst_2 : DecidableLT α]
  [inst_3 : Std.PRange.UpwardEnumerable α] [inst_4 : Std.Rxo.IsAlwaysFinite α]
  [inst_5 : Std.PRange.LawfulUpwardEnumerable α] {xs : Std.Rio α}, xs.toList ++ [] = xs.toList