{α : Type u_1} →
  {motive : Array.PrefixTable α → Sort u} →
    (t : Array.PrefixTable α) →
      ((toArray : Array (α × ℕ)) →
          (valid : ∀ {i : ℕ} (h : i < toArray.size), toArray[i].2 ≤ i) →
            motive { toArray := toArray, valid := valid }) →
        motive t