have : Positive n₂ := Signed.positive_defn.mpr ‹n₂ ≄ 0›
ℕ : Type
inst✝³ : Core ℕ
inst✝² : Induction ℕ
inst✝¹ : Addition ℕ
inst✝ : Sign ℕ
n₁ n₂ : ℕ
x✝¹ : n₁ ≃ n₂
x✝ : Positive n₁
this✝ : n₁ ≄ 0
this : n₂ ≄ 0
⊢ Positive n₂
ℕ : Type
inst✝³ : Core ℕ
inst✝² : Induction ℕ
inst✝¹ : Addition ℕ
inst✝ : Sign ℕ
n₁ n₂ : ℕ
x✝¹ : n₁ ≃ n₂
x✝ : Positive n₁
this✝¹ : n₁ ≄ 0
this✝ : n₂ ≄ 0
this : Positive n₂
⊢ Positive n₂