wg21/docs/lwg-defects.html#225">unqualified calls</a>.  If all we want is to
avoid unintentional argument-dependent lookup (ADL), we can
isolate <tt class="docutils literal">depth_first_search</tt> in a namespace containing no
types<a class="footnote-reference" href="#using" id="id8"><sup>6</sup></a>, but suppose we <em>want</em> it to found via ADL?</li>
</ol>
<p>It's usually a good idea to prevent functions from being considered
for overload resolution when the passed argument types aren't
appropriate.  T