match this with
| AA.OneOfThree.first (_ : sgn p ≃ 0) =>
  have : p ≃ 0 := sgn_zero.mpr ‹sgn p ≃ 0›
  have : abs p ≃ p := calc
    _ ≃ abs p := eqv_refl
    _ ≃ 0     := abs_zero.mpr ‹p ≃ 0›
    _ ≃ p     := eqv_symm ‹p ≃ 0›
  exact (Or.inl this)
| AA.OneOfThree.second (_ : sgn p ≃ 1) =>
  have : abs p ≃ p := abs_positive ‹sgn p ≃ 1›
  exact (Or.inl this)
| AA.OneOfThree.third (_ : sgn p ≃ -1) =>
  have : abs p ≃ -p := abs_negative ‹sgn p ≃ -1›
  exact (Or.inr this)
ℕ ℤ ℚ : Type
inst✝¹² : Natural ℕ
inst✝¹¹ : Integer ℤ
inst✝¹⁰ : Core ℚ
inst✝⁹ : Addition ℚ
inst✝⁸ : Negation ℚ
inst✝⁷ : Subtraction ℚ
inst✝⁶ : Multiplication ℚ
inst✝⁵ : Reciprocation ℚ
inst✝⁴ : Division ℚ
inst✝³ : Sign ℚ
inst✝² : Order ℚ
inst✝¹ : MinMax ℚ
inst✝ : Metric ℚ
p : ℚ
this : AA.OneOfThree (sgn p ≃ 0) (sgn p ≃ 1) (sgn p ≃ -1)
⊢ abs p ≃ p ∨ abs p ≃ -p
no goals