fun {α : Type} (motive : List α → List α → Type) (h1 : Unit → motive [] []) (h2 : (x : List α) → motive x [])
  (h3 : (x x_1 : List α) → motive x x_1) =>
  match [], [] with 
  | [], [] => h1 Unit.unit
  | x, [] => h2 x
  | x, x_1 =>
    h3 x
      x_1 : {α : Type} →
  (motive : List α → List α → Type) →
    (Unit → motive [] []) → ((x : List α) → motive x []) → ((x x_1 : List α) → motive x x_1) → motive [] []