ident">Error</span> <span class="op">=</span> <span class="ident">Void</span><span class="op">&gt;</span>
<span class="kw">where</span>
    <span class="ident">T</span>: <span class="ident">hal</span>::<span class="ident">timer</span>::<span class="ident">CountDown</span>,
{
    <span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">timer</span> <span class="op">=</span> <span class="prelude-val">Some</span>(<span class="ident">timer</span>);
    <span class="ident">future</span>::<sp