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/** Determine if `T` meets the requirements of @b CompletionHandler.

    This trait checks whether a type meets the requirements for a completion
    handler, and is also callable with the specified signature.
    Metafunctions are used to perform compile time checking of template
    types. This type will be `std::true_type` if `T` meets the requirements,
    else the type will be `std::false_type`. 

    @par Example

    Use with `static_assert`:

    @code
    struct handler
    {
        void operator()(error_code&);
    };

    static_assert(is_completion_handler<handler, void(error_code&)>::value,
        "Not a completion handler");
    @endcode
*/
template<class T, class Signature>
using is_completion_handler = std::integral_constant<bool, __see_below__>;

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