{m : Type u → Type u} →
  {α : Type u} →
    {motive_1 : MLList.MLListImpl✝ m α → Sort u_1} →
      (t : MLList.MLListImpl✝¹ m α) →
        MLList.MLListImpl.ctorIdx✝ t = 2 →
          ((a : Thunk (MLList.MLListImpl✝² m α)) → motive_1 (MLList.MLListImpl.thunk✝ a)) → motive_1 t