no_result_value.hpp

// Copyright (C) 2022 by Camden Mannett.
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE or copy at https://www.boost.org/LICENSE_1_0.txt)
 
#pragma once
 
#include "arg_router/policy/policy.hpp"
 
namespace arg_router::policy
{
template <typename = void>  // This is needed due so it can be used in
struct no_result_value {    // template template parameters
};
 
template <typename T>
using has_no_result_value = std::is_base_of<no_result_value<>, T>;
 
template <typename T>
constexpr bool has_no_result_value_v = has_no_result_value<T>::value;
 
template <>
struct is_policy<no_result_value<>> : std::true_type {
};
}  // namespace arg_router::policy