case mpr =>
  intro (_ : a < b ∨ a ≃ b)
  show a ≤ b
  have : a ≤ b := match ‹a < b ∨ a ≃ b› with
  | Or.inl (_ : a < b) =>
    have (And.intro (_ : a ≤ b) _) := lt_iff_le_neqv.mp ‹a < b›
    ‹a ≤ b›
  | Or.inr (_ : a ≃ b) =>
    have : a ≤ a := le_refl
    have : a ≤ b := AA.substRFn ‹a ≃ b› ‹a ≤ a›
    ‹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