 the result of <code>21 - 50</code> is
less than zero, the minimum representable <code>UInt8</code> value:</p>
<pre><code class="language-swift">var x: UInt8 = 21
x - 50
// Overflow error
</code></pre>
<blockquote>
<p>Note:
Overflow checking is not performed in <code>-Ounchecked</code> builds.</p>
</blockquote>
</div><div class="intro-declaration"><code class="language-swift">func -=(lhs:rhs:)(lhs: inout UInt32, rhs: UInt32)</code></div><div class="discussion comment"><p>Subtracts the second value from the 