. next i_out_of_bounds =>
  exfalso
  exact i_out_of_bounds i_in_bounds
case isFalse
α : Type u_1
a : Array α
i : Nat
i_in_bounds : i < a.size
f : α → α
h✝ : ¬i < a.size
⊢ (a.set ⟨i, ⋯⟩ (f (a.get ⟨i, ⋯⟩)))[i] = f a[i]
no goals