pan class="ident">usize</span>
{
    <span class="ident">func</span>(<span class="number">1</span>)
}

<span class="kw">let</span> <span class="ident">double</span> <span class="op">=</span> <span class="op">|</span><span class="ident">x</span><span class="op">|</span> <span class="ident">x</span> <span class="op">*</span> <span class="number">2</span>;
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">call_with_one</span>(<span class="ident">double</span>), <span class="n