 class="kw">where</span> <span class="ident">F</span>: <span class="ident">FnOnce</span>() <span class="op">-&gt;</span> <span class="ident">String</span>
{
    <span class="comment">// `func` consumes its captured variables, so it cannot be run more</span>
    <span class="comment">// than once</span>
    <span class="macro">println</span><span class="macro">!</span>(<span class="string">&quot;Consumed: {}&quot;</span>, <span class="ident">func</span>());

    <span class="macro">println</span><span class=