catch2/include/internal/catch_meta.hpp

/*
 *  Created by Jozef on 02/12/2018.
 *  Copyright 2018 Two Blue Cubes Ltd. All rights reserved.
 *
 *  Distributed under the Boost Software License, Version 1.0. (See accompanying
 *  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 */

#ifndef TWOBLUECUBES_CATCH_META_HPP_INCLUDED
#define TWOBLUECUBES_CATCH_META_HPP_INCLUDED

#include <type_traits>

namespace Catch {
    template<typename T>
    struct always_false : std::false_type {};

    template <typename> struct true_given : std::true_type {};
    struct is_callable_tester {
        template <typename Fun, typename... Args>
        true_given<decltype(std::declval<Fun>()(std::declval<Args>()...))> static test(int);
        template <typename...>
        std::false_type static test(...);
    };

    template <typename T>
    struct is_callable;

    template <typename Fun, typename... Args>
    struct is_callable<Fun(Args...)> : decltype(is_callable_tester::test<Fun, Args...>(0)) {};


#if defined(__cpp_lib_is_invocable) && __cpp_lib_is_invocable >= 201703
    // std::result_of is deprecated in C++17 and removed in C++20. Hence, it is
    // replaced with std::invoke_result here. Also *_t format is preferred over
    // typename *::type format.
    template <typename Func, typename U>
    using FunctionReturnType = std::remove_reference_t<std::remove_cv_t<std::invoke_result_t<Func, U>>>;
#else
    template <typename Func, typename U>
    using FunctionReturnType = typename std::remove_reference<typename std::remove_cv<typename std::result_of<Func(U)>::type>::type>::type;
#endif

} // namespace Catch

namespace mpl_{
    struct na;
}

#endif // TWOBLUECUBES_CATCH_META_HPP_INCLUDED