induction c generalizing xs x <;> simp_all [getSnoc?]
α : Type u_1
xs : List α
x : α
c : List α
⊢ c.getSnoc? = some (xs, x) ↔ c = xs ++ [x]
case cons
α : Type u_1
head✝ : α
tail✝ : List α
tail_ih✝ : ∀ {xs : List α} {x : α}, tail✝.getSnoc? = some (xs, x) ↔ tail✝ = xs ++ [x]
xs : List α
x : α
⊢ (match tail✝.getSnoc? with
      | none => some ([], head✝)
      | some (xs', x') => some (head✝ :: xs', x')) =
      some (xs, x) ↔
    head✝ :: tail✝ = xs ++ [x]