∀ {α : Type u_3} {β : α → Type u_1} (a : α) (motive : Option (β a) → Sort u_2) (b : β a) (h_1 : Unit → motive none)
  (h_2 : (b : β a) → motive (some b)),
  (match some b with
    | none => h_1 ()
    | some b => h_2 b) =
    h_2 b