span class="o">&gt;</span> <span class="o">&amp;&amp;</span><span class="n">ch</span><span class="p">)</span>
        <span class="o">:</span> <span class="n">_handler</span><span class="p">(</span><span class="n">std</span><span class="o">::</span><span class="n">forward</span><span class="o">&lt;</span><span class="n">U</span><span class="o">&gt;</span><span class="p">(</span><span class="n">ch</span><span class="p">.</span><span class="n">token</span><span class="p">))</span>
    <span class="p">{</span>