span><span class="special">&lt;</span> <span class="identifier">return_t</span> <span class="special">&gt;(</span> <span class="identifier">chanp</span><span class="special">,</span>
                                         <span class="identifier">std</span><span class="special">::</span><span class="identifier">forward</span><span class="special">&lt;</span> <span class="identifier">Fn</span> <span class="special">&gt;(</span> <span class="identifier">function</span><span class="special">),</span>
       