span class="identifier">x3</span><span class="special">::</span><span class="identifier">int_</span><span class="special">;</span>
    <span class="keyword">using</span> <span class="identifier">x3</span><span class="special">::</span><span class="identifier">lit</span><span class="special">;</span>
    <span class="keyword">using</span> <span class="identifier">x3</span><span class="special">::</span><span class="identifier">double_</span><span class="special">;</span>
    <span class="keyword">using</span