intro h ha
case h.mp
α : Type u
inst✝ : DecidableEq α
as : Array α
a : α
⊢ (∀ (a_1 : α), a_1 ∈ as → a_1 ≠ a) → ¬a ∈ as
case h.mp
α : Type u
inst✝ : DecidableEq α
as : Array α
a : α
h : ∀ (a_1 : α), a_1 ∈ as → a_1 ≠ a
ha : a ∈ as
⊢ False