span><span class="special">::</span><span class="identifier">type</span> <span class="identifier">as_child</span><span class="special">(</span><span class="identifier">T</span> <span class="special">&amp;</span> t<span class="special">)</span><span class="special">;</span>
<span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> <a class="link" href="../../Domain.html" title="Concept Domain">Domain</a><span class="special">,</span> <span class="keyword">typ