cppcoro/detail/get_awaiter.hpp

0001 ///////////////////////////////////////////////////////////////////////////////
0002 // Copyright (c) Lewis Baker
0003 // Licenced under MIT license. See LICENSE.txt for details.
0004 ///////////////////////////////////////////////////////////////////////////////
0005 #ifndef CPPCORO_DETAIL_GET_AWAITER_HPP_INCLUDED
0006 #define CPPCORO_DETAIL_GET_AWAITER_HPP_INCLUDED
0007
0008 #include <cppcoro/detail/is_awaiter.hpp>
0009 #include <cppcoro/detail/any.hpp>
0010
0011 namespace cppcoro
0012 {
0013     namespace detail
0014     {
0015         template<typename T>
0016         auto get_awaiter_impl(T&& value, int)
0017             noexcept(noexcept(static_cast<T&&>(value).operator co_await()))
0018             -> decltype(static_cast<T&&>(value).operator co_await())
0019         {
0020             return static_cast<T&&>(value).operator co_await();
0021         }
0022
0023         template<typename T>
0024         auto get_awaiter_impl(T&& value, long)
0025             noexcept(noexcept(operator co_await(static_cast<T&&>(value))))
0026             -> decltype(operator co_await(static_cast<T&&>(value)))
0027         {
0028             return operator co_await(static_cast<T&&>(value));
0029         }
0030
0031         template<
0032             typename T,
0033             std::enable_if_t<cppcoro::detail::is_awaiter<T&&>::value, int> = 0>
0034         T&& get_awaiter_impl(T&& value, cppcoro::detail::any) noexcept
0035         {
0036             return static_cast<T&&>(value);
0037         }
0038
0039         template<typename T>
0040         auto get_awaiter(T&& value)
0041             noexcept(noexcept(detail::get_awaiter_impl(static_cast<T&&>(value), 123)))
0042             -> decltype(detail::get_awaiter_impl(static_cast<T&&>(value), 123))
0043         {
0044             return detail::get_awaiter_impl(static_cast<T&&>(value), 123);
0045         }
0046     }
0047 }
0048
0049 #endif