have : 0 < b := by
  by_contra e
  have : a = 0 := by simpa [show b = 0 from by simpa using e] using h
  rcases this with rfl
  simpa using ha.pos
M : Type u_1
inst✝⁵ : Zero M
inst✝⁴ : One M
inst✝³ : Add M
inst✝² : Mul M
inst✝¹ : LT M
inst✝ : M ⊧ₘ* 𝐈open
a b : M
h : b ∣ a
ha : Pow2 a
⊢ Pow2 b
M : Type u_1
inst✝⁵ : Zero M
inst✝⁴ : One M
inst✝³ : Add M
inst✝² : Mul M
inst✝¹ : LT M
inst✝ : M ⊧ₘ* 𝐈open
a b : M
h : b ∣ a
ha : Pow2 a
this : 0 < b
⊢ Pow2 b