NonEmpty type for C++

NonEmpty.h

template<typename T, typename Container = std::vector<T>>
struct NonEmpty {
    using iterator = typename Container::iterator;
    using const_iterator = typename Container::const_iterator;

    iterator begin()
    {
        return c_.begin();
    }
    iterator end()
    {
        return c_.end();
    }
    const_iterator begin() const
    {
        return c_.begin();
    }
    const_iterator end() const
    {
        return c_.end();
    }
    size_t size() const { return c_.size(); }

    private:
        Container c_;

        NonEmpty(Container const & c) : c_(c) {}
        NonEmpty(Container &&c) : c_(std::move(c)) {}

        friend boost::optional<NonEmpty<T, Container>> nonEmpty(Container const &) {}
        //friend boost::optional<NonEmpty<T, Container>> nonEmpty(Container &&) {}
};

template<typename T, typename Container = std::vector<T>>
inline boost::optional<NonEmpty<T, Container>> nonEmpty(Container const & vs) {
    return vs.size() > 0 ? NonEmpty<T, Container>(vs) : boost::optional<NonEmpty<T, Container>>();
}