><span class='macro'>!</span>(<span class='string'>&quot;{}&quot;</span>, <span class='ident'>s</span>);

<span class='ident'>s</span>.<span class='ident'>push_str</span>(<span class='string'>&quot;, world.&quot;</span>);
<span class='macro'>println</span><span class='macro'>!</span>(<span class='string'>&quot;{}&quot;</span>, <span class='ident'>s</span>);</pre>

<!-- `String`s will coerce into `&str` with an `&`: -->

<p><code>String</code> は <code>&amp;</code> によって <code>&amp;str</code> に型�