cppargs/include/cppargs/group/simple_group.inl

#pragma once

#include <cppargs/group/simple_group.h>

namespace cppargs
{

    template<typename T_arg>
    struct simple_verify_and_forward
    {
        template<typename T, typename T_enable = void>
        struct check
        {
            template<typename X>
            constexpr X&& operator()(X&& x) const
                { static_assert(sizeof(X) == -1, "invalid group or option type"); }
        };

        template<typename T>
        struct check<
            std::unique_ptr<T>,
            utl::mp::enable_if<utl::mp::is_base_of<simple_group, T>>>
        {
            template<typename X>
            constexpr X&& operator()(X&& x) const
                { return std::forward<X>(x); }
        };

        template<typename T>
        struct check<
            std::unique_ptr<T>,
            utl::mp::enable_if<utl::mp::is_base_of<simple_option, T>>>
        {
            template<typename X>
            constexpr X&& operator()(X&& x) const
                { return std::forward<X>(x); }
        };

        template<typename X>
        constexpr decltype(auto) operator()(X&& x) const
            { return check<T_arg> { } (std::forward<X>(x)); }
    };

    template<typename... T_args>
    simple_group::simple_group(
        const group_meta& p_meta,
        T_args&&... p_args)
        : group(p_meta, simple_verify_and_forward<T_args> { } (std::forward<T_args>(p_args))...)
        { }

}