rw [String.decEq_refl a]
a b : String
n : ℕ
nab : ¬a = b
⊢ Ø ⋁
    ∀ₛ b ;
      (match String.decEq a a with
          | isTrue h => fromNat n
          | isFalse h => _ a) +ₛ
          _ b =ₛ
        _ b +ₛ
          match String.decEq a a with
          | isTrue h => fromNat n
          | isFalse h => _ a
a b : String
n : ℕ
nab : ¬a = b
⊢ Ø ⋁
    ∀ₛ b ;
      (match isTrue (_ : a = a) with
          | isTrue h => fromNat n
          | isFalse h => _ a) +ₛ
          _ b =ₛ
        _ b +ₛ
          match isTrue (_ : a = a) with
          | isTrue h => fromNat n
          | isFalse h => _ a