rw [Nat.add_zero]
α : Type u_1
as bs : Array α
start stop : Nat
hstart : start ≤ stop
hstop : stop ≤ bs.size
heq : start = stop
⊢ as.size = as.size + 0

case hstop
α : Type u_1
as bs : Array α
start stop : Nat
hstart : start ≤ stop
hstop : stop ≤ bs.size
heq : start = stop
⊢ stop ≤ bs.size
case hstop
α : Type u_1
as bs : Array α
start stop : Nat
hstart : start ≤ stop
hstop : stop ≤ bs.size
heq : start = stop
⊢ stop ≤ bs.size