∀ {α : Type u_2} [inst : LinearOrder α] [inst_1 : One α] [inst_2 : LocallyFiniteOrder α] [inst_3 : Add α]
  [SuccAddOrder α] {a b : α} [NoMaxOrder α], a ≤ b → Finset.Ioc a (b + 1) = insert (b + 1) (Finset.Ioc a b)