∀ {motive : Turing.ToPartrec.Code → Sort u} (t : Turing.ToPartrec.Code)
  (F_1 : (t : Turing.ToPartrec.Code) → Turing.ToPartrec.Code.below t → motive t),
  Turing.ToPartrec.Code.brecOn t F_1 = F_1 t (Turing.ToPartrec.Code.brecOn.go t F_1).2