rd">typedef</span> <span class="keyword">typename</span> <span class="identifier">call_traits</span><span class="special">&lt;</span><span class="identifier">first_type</span><span class="special">&gt;::</span><span class="identifier">reference</span>        <span class="identifier">first_reference</span><span class="special">;</span>
    <span class="keyword">typedef</span> <span class="keyword">typename</span> <span class="identifier">call_traits</span><span class="special">&lt;</span><span class="identif