="identifier">child_c</span><span class="special">&lt;</span><span class="number">0</span><span class="special">&gt;</span><span class="special">::</span><span class="identifier">type</span><span class="special">,</span>
      <span class="special">...</span>
      <span class="keyword">typename</span> <span class="identifier">proto</span><span class="special">::</span><span class="identifier">result_of</span><span class="special">::</span><span class="identifier">child_c</span><span class="special">&lt;</s