Can I apply must_use to a function result?
<p>I have a function that returns a <code>f64</code>. I'd like to ensure that the output from this function is used, rather than just ignored. Is there any way to do this?</p>

<p>The return type is not used for error handling so wrapping it in a <code>Result</code> or <code>Option</code> doesn't really make sense.</p>

<p>I'd like something similar to this:</p>

<pre><code>#[must_use]
fn calculate_the_thing(number: f64) -&gt; f64 {
    number * 2.0
}
</code></pre>