https://svn.boost.org/trac10/ticket/7378 <p> <code>boost::lookup_one_property&lt;PropertyList,Tag&gt;::found</code> does not compile if <code>Tag</code> is not found in the <code>PropertyList</code>. </p> <p> The problem originates from the <code>lookup(...)</code> function definition in the template specialization </p> <pre class="wiki"> template &lt;typename Tag, typename T, typename Base, typename PropName&gt; struct lookup_one_property_internal&lt;boost::property&lt;Tag, T, Base&gt;, PropName&gt;: lookup_one_property_internal&lt;Base, PropName&gt; { private: typedef lookup_one_property_internal&lt;Base, PropName&gt; base_type; public: template &lt;typename PL&gt; static typename enable_if&lt;is_same&lt;PL, boost::property&lt;Tag, T, Base&gt; &gt;, typename base_type::type&amp;&gt;::type lookup(PL&amp; prop, const PropName&amp; tag) </pre><p> which requires the base class to provide a <code>type</code> member. </p> <p> If the tag is not found the unspecialized template </p> <pre class="wiki"> template &lt;typename PList, typename PropName, typename Enable = void&gt; struct lookup_one_property_internal {BOOST_STATIC_CONSTANT(bool, found = false);}; </pre><p> will be instantiated as Base where the compiler can't find any <code>type</code> member. </p> en-us /htdocs/site/boost.png https://svn.boost.org/trac10/ticket/7378 Trac 1.4.3 Andreas Hehn <hehn@…> Fri, 14 Sep 2012 15:42:37 GMT https://svn.boost.org/trac10/ticket/7378 https://svn.boost.org/trac10/ticket/7378 <ul> <li><strong>attachment</strong> → <span class="trac-field-new">example.cpp</span> </li> </ul> <p> demonstration code </p> Ticket Jeremiah Willcock Fri, 14 Sep 2012 15:45:53 GMT https://svn.boost.org/trac10/ticket/7378#comment:1 https://svn.boost.org/trac10/ticket/7378#comment:1 <ul> <li><strong>status</strong> <span class="trac-field-old">new</span> → <span class="trac-field-new">closed</span> </li> <li><strong>resolution</strong> → <span class="trac-field-new">wontfix</span> </li> <li><strong>component</strong> <span class="trac-field-old">property_map</span> → <span class="trac-field-new">graph</span> </li> </ul> <p> That change was made on purpose; it greatly helps error messages for using nonexistent property maps from graphs. </p> Ticket Andreas Hehn <hehn@…> Fri, 14 Sep 2012 15:45:56 GMT https://svn.boost.org/trac10/ticket/7378 https://svn.boost.org/trac10/ticket/7378 <ul> <li><strong>attachment</strong> → <span class="trac-field-new">property.hpp.patch</span> </li> </ul> <p> patch </p> Ticket Andreas Hehn <hehn@…> Fri, 14 Sep 2012 15:52:52 GMT https://svn.boost.org/trac10/ticket/7378#comment:9 https://svn.boost.org/trac10/ticket/7378#comment:9 <ul> <li><strong>status</strong> <span class="trac-field-old">closed</span> → <span class="trac-field-new">reopened</span> </li> <li><strong>resolution</strong> <span class="trac-field-deleted">wontfix</span> </li> </ul> <p> This was also my first approach, but unfortunately it doesn't solve the problem. </p> <p> Since the return type of <code>lookup(...)</code> is <code>type&amp;</code> the compiler will complain if <code>type</code> is <code>void</code>, as you can see if you try to compile my example code. </p> Ticket Jeremiah Willcock Fri, 14 Sep 2012 21:41:09 GMT https://svn.boost.org/trac10/ticket/7378#comment:10 https://svn.boost.org/trac10/ticket/7378#comment:10 <ul> <li><strong>status</strong> <span class="trac-field-old">reopened</span> → <span class="trac-field-new">closed</span> </li> <li><strong>resolution</strong> → <span class="trac-field-new">fixed</span> </li> </ul> <p> (In <a class="changeset" href="https://svn.boost.org/trac10/changeset/80528" title="Using lazy_enable_if to avoid &#34;reference to void&#34; errors for ...">[80528]</a>) Using lazy_enable_if to avoid "reference to void" errors for properties that are not found; fixes <a class="closed ticket" href="https://svn.boost.org/trac10/ticket/7378" title="#7378: Bugs: lookup_one_property fails if property tag not found (closed: fixed)">#7378</a> </p> Ticket Andreas Hehn <hehn@…> Sat, 15 Sep 2012 11:50:06 GMT