{α : Type u_1} →
  (motive : Ordnode α → Sort u_2) →
    (x : Ordnode α) →
      (Unit → motive Ordnode.nil) →
        ((size : ℕ) → (l : Ordnode α) → (x : α) → (r : Ordnode α) → motive (Ordnode.node size l x r)) → motive x