f. We have therefore
created a reference whose lifetime outlives its referent, which is <em>literally</em>
the first thing we said that references can&#39;t do. The compiler rightfully blows
up in our face.</p>

<p>To make this more clear, we can expand the example:</p>

<span class='rusttest'>fn as_str&lt;&#39;a&gt;(data: &amp;&#39;a u32) -&gt; &amp;&#39;a str {
    &#39;b: {
        let s = format!(&quot;{}&quot;, data);
        return &amp;&#39;a s
    }
}

fn main() {
    &#39;c: {
        let x: u32 = 