rd">template</span><span class="special">&lt;</span>
    <span class="keyword">class</span><span class="special">...</span> <span class="identifier">Args</span><span class="special">&gt;</span>
<span class="keyword">void</span>
<span class="keyword">operator</span><span class="special">()(</span>
    <span class="identifier">error_code</span> <span class="identifier">ec</span><span class="special">,</span>
    <span class="identifier">Args</span><span class="special">&amp;&amp;</span> <span class="special">