Converts a move-constructible type `U` that provides a value of type `T` via `T& operator*() const;` method into `std::shared_ptr<const T>`.

to_shared_ptr.cc

// Converts a move-constructible type `U` that provides a value of type `T` via
// `T& operator*() const;` method into `std::shared_ptr<const T>`.
template <typename U,
          typename T = typename std::remove_reference<decltype(
              *std::declval<typename std::add_const<U>::type>())>::type>
std::shared_ptr<T> ToSharedPtr(U container) {
  static_assert(std::is_move_constructible<U>::value,
                "The container type U must be move-constructible");
  const U* on_heap = new U(std::move(container));
  return std::shared_ptr<T>(&**on_heap, [on_heap](T*) { delete on_heap; });
}