span> <span class="keyword">operator</span><span class="special">()(</span><span class="keyword">int</span><span class="special">)</span> <span class="keyword">const</span> <span class="special">{</span> <span class="keyword">return</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">string</span><span class="special">();</span> <span class="special">}};</span>
    <span class="keyword">struct</span>  <span class="identifier">test5</span> <span class="special">{