/span><span class="special">&lt;</span><span class="identifier">AsyncReadStream</span><span class="special">&gt;::</span><span class="identifier">value</span><span class="special">,</span>
        <span class="string">"AsyncReadStream type requirements not met"</span><span class="special">);</span>
<span class="special">...</span>
</pre>
<p>
        Use with <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">enable_if</span></code> (SFINAE