exact ⟨domain m, by simp, rfl, fun x hx ↦ by
  rcases hm x hx with ⟨y, hy, uniq⟩
  exact ⟨y, lt_of_mem_rng hy, hy, fun y' _ h' ↦ uniq y' h'⟩⟩
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* 𝐈𝚺₁
m : M
hm : IsMapping m
⊢ ∃ d ≤ 2 * m, d = domain m ∧ ∀ x ∈ d, ∃ y < m, ⟪x, y⟫ ∈ m ∧ ∀ y' < m, ⟪x, y'⟫ ∈ m → y' = y
no goals