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//
// Copyright (c) 2016-2019 Vinnie Falco (vinnie dot falco at gmail dot com)
//
// 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)
//
// Official repository: https://github.com/boostorg/beast
//
#ifndef BOOST_BEAST_DETAIL_IS_INVOCABLE_HPP
#define BOOST_BEAST_DETAIL_IS_INVOCABLE_HPP
#include <boost/asio/async_result.hpp>
#include <boost/type_traits/make_void.hpp>
#include <type_traits>
#include <utility>
namespace boost {
namespace beast {
namespace detail {
template<class R, class C, class ...A>
auto
is_invocable_test(C&& c, int, A&& ...a)
-> decltype(std::is_convertible<
decltype(c(std::forward<A>(a)...)), R>::value ||
std::is_same<R, void>::value,
std::true_type());
template<class R, class C, class ...A>
std::false_type
is_invocable_test(C&& c, long, A&& ...a);
/** Metafunction returns `true` if F callable as R(A...)
Example:
@code
is_invocable<T, void(std::string)>::value
@endcode
*/
/** @{ */
template<class C, class F>
struct is_invocable : std::false_type
{
};
template<class C, class R, class ...A>
struct is_invocable<C, R(A...)>
: decltype(is_invocable_test<R>(
std::declval<C>(), 1, std::declval<A>()...))
{
};
/** @} */
template<class CompletionToken, class Signature, class = void>
struct is_completion_token_for : std::false_type
{
};
struct any_initiation
{
template<class...AnyArgs>
void operator()(AnyArgs&&...);
};
template<class CompletionToken, class R, class...Args>
struct is_completion_token_for<
CompletionToken, R(Args...), boost::void_t<decltype(
boost::asio::async_initiate<CompletionToken, R(Args...)>(
any_initiation(), std::declval<CompletionToken&>())
)>> : std::true_type
{
};
} // detail
} // beast
} // boost
#endif
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