case mp =>
  intro (_ : Nonzero a) (_ : a ≃ 0)
  show False
  have : a ≃ 0 ∧ Nonzero a := And.intro ‹a ≃ 0› ‹Nonzero a›
  exact absurd ‹a ≃ 0 ∧ Nonzero a› ‹¬(a ≃ 0 ∧ Nonzero a)›
ℕ : Type
inst✝⁵ : Natural ℕ
ℤ : Type
inst✝⁴ : Core ℤ
inst✝³ : Addition ℤ
inst✝² : Multiplication ℤ
inst✝¹ : Negation ℤ
inst✝ : Sign ℤ
a : ℤ
left✝ : a ≃ 0 ∨ Nonzero a
right✝ : ¬(a ≃ 0 ∧ Nonzero a)
⊢ Nonzero a → a ≄ 0
no goals