simp only [length, uniqueAux, h, ite_false]
case cons.inr
α : Type u_1
inst✝ : DecidableEq α
x : α
xs : List α
ih : ∀ (as : List α), length (uniqueAux xs as) ≤ length xs + length as
as : List α
h : ¬x ∈ as
⊢ length (uniqueAux (x :: xs) as) ≤ length (x :: xs) + length as
case cons.inr
α : Type u_1
inst✝ : DecidableEq α
x : α
xs : List α
ih : ∀ (as : List α), length (uniqueAux xs as) ≤ length xs + length as
as : List α
h : ¬x ∈ as
⊢ length (uniqueAux xs (x :: as)) ≤ length xs + 1 + length as