intro ⟨_, h⟩
α : Type u_1
as : Array α
⊢ (∃ a, (if h : 0 < size as then some as[0] else none) = some a) → ¬size as = 0
α : Type u_1
as : Array α
w✝ : α
h : (if h : 0 < size as then some as[0] else none) = some w✝
⊢ ¬size as = 0