      <span class="kw">if</span> <span class="ident">state</span> {
                <span class="ident">led</span>.<span class="ident">on</span>();
            } <span class="kw">else</span> {
                <span class="ident">led</span>.<span class="ident">off</span>();
            }
        }
    });

    <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">loopback</span> <span class="op">=</span> (<span class="kw">move</span> <span class="op">|</span><span class="op">|</span> 