//
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// Copyright (c) 2016-2019 Vinnie Falco (vinnie dot falco at gmail dot com)
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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// Official repository: https://github.com/boostorg/beast
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//
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#ifndef BOOST_BEAST_DETAIL_IS_INVOCABLE_HPP
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#define BOOST_BEAST_DETAIL_IS_INVOCABLE_HPP
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#include <boost/asio/async_result.hpp>
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#include <boost/type_traits/make_void.hpp>
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#include <type_traits>
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#include <utility>
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namespace boost {
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namespace beast {
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namespace detail {
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template<class R, class C, class ...A>
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auto
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is_invocable_test(C&& c, int, A&& ...a)
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-> decltype(std::is_convertible<
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decltype(c(std::forward<A>(a)...)), R>::value ||
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std::is_same<R, void>::value,
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std::true_type());
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template<class R, class C, class ...A>
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std::false_type
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is_invocable_test(C&& c, long, A&& ...a);
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/** Metafunction returns `true` if F callable as R(A...)
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Example:
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@code
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is_invocable<T, void(std::string)>::value
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@endcode
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*/
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/** @{ */
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template<class C, class F>
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struct is_invocable : std::false_type
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{
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};
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template<class C, class R, class ...A>
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struct is_invocable<C, R(A...)>
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: decltype(is_invocable_test<R>(
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std::declval<C>(), 1, std::declval<A>()...))
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{
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};
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/** @} */
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template<class CompletionToken, class Signature, class = void>
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struct is_completion_token_for : std::false_type
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{
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};
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struct any_initiation
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{
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template<class...AnyArgs>
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void operator()(AnyArgs&&...);
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};
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template<class CompletionToken, class R, class...Args>
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struct is_completion_token_for<
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CompletionToken, R(Args...), boost::void_t<decltype(
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boost::asio::async_initiate<CompletionToken, R(Args...)>(
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any_initiation(), std::declval<CompletionToken&>())
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)>> : std::true_type
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{
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};
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} // detail
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} // beast
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} // boost
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#endif
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