template<
    typename T,
    typename  = void,
    typename  = void,
    typename  = void,
    typename  = void,
    typename  = void,
    typename  = void,
    typename  = void,
    typename  = void,
    typename  = void>
struct is_async_operation

Requirements

Header: asio/async_result.hpp

Convenience header: asio.hpp