// function arguments can never be outside of limits</span>
<span class="keyword">auto</span> <span class="identifier">f</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">safe_t</span> <span class="special">&amp;</span> <span class="identifier">x</span><span class="special">,</span> <span class="keyword">const</span> <span class="identifier">safe_t</span> <span class="special">&amp;</span> <span class="identifier">y</span><span class="special">)</span><span clas