(motive : ℕ → String.Pos.Raw → ℕ → Sort u_1) →
  (x : ℕ) →
    (x_1 : String.Pos.Raw) →
      (x_2 : ℕ) →
        ((x : String.Pos.Raw) → (utf16pos : ℕ) → motive 0 x utf16pos) →
          ((cp : ℕ) → (utf8pos : String.Pos.Raw) → (utf16pos : ℕ) → motive cp.succ utf8pos utf16pos) → motive x x_1 x_2