case mp =>
  intro (_ : a ≤ b)
  show a < b ∨ a ≃ b
  have : Decidable (a ≃ b) := eqv? a b
  have : a < b ∨ a ≃ b := match this with
  | isTrue (_ : a ≃ b) =>
    Or.inr ‹a ≃ b›
  | isFalse (_ : a ≄ b) =>
    have : a < b := lt_iff_le_neqv.mpr (And.intro ‹a ≤ b› ‹a ≄ b›)
    Or.inl ‹a < b›
  exact this
ℕ : Type
inst✝⁷ : Natural ℕ
ℤ : Type
inst✝⁶ : Core ℤ
inst✝⁵ : Addition ℤ
inst✝⁴ : Multiplication ℤ
inst✝³ : Negation ℤ
inst✝² : Subtraction ℤ
inst✝¹ : Sign ℤ
inst✝ : Order ℤ
a b : ℤ
⊢ a ≤ b → a < b ∨ a ≃ b
no goals