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