intro i h _
case h₂
α : Type u_1
a : Array α
hemp : ¬a.isEmpty = true
this : 0 < a.size
⊢ ∀ (i : Nat) (hi₁ hi₂ : i < a.size), (a.pop.push (a.back' hemp))[i] = a[i]
case h₂
α : Type u_1
a : Array α
hemp : ¬a.isEmpty = true
this : 0 < a.size
i : Nat
h hi₂✝ : i < a.size
⊢ (a.pop.push (a.back' hemp))[i] = a[i]