lt;tag::error_of&lt; Feature &gt;&gt;">as_feature</a><span class="special">&lt;</span><span class="identifier">tag</span><span class="special">::</span><span class="identifier">error_of</span><span class="special">&lt;</span> <span class="identifier">Feature</span> <span class="special">&gt;</span><span class="special">&gt;</span> <span class="special">{</span>
  <span class="comment">// types</span>
  <span class="keyword">typedef</span> <a class="link" href="tag/error_of.html" title="Struct template error