simp [List.length] at i
α : Type u_1
inst✝ : BEq α
i j✝ : Fin (List.length [])
a✝ : List.get [] i = List.get [] j✝
⊢ i = j✝
α : Type u_1
inst✝ : BEq α
i : Fin 0
j✝ : Fin (List.length [])
a✝ : List.get [] i = List.get [] j✝
⊢ i = j✝