pan></code> does whenever it is
          initialized; but in the case when <code class="computeroutput"><span class="identifier">U</span></code>
          is <code class="computeroutput"><span class="identifier">T</span><span class="special">&amp;</span></code>,
          doing so would result in inconsistent behavior w.r.t to the lvalue initialization
          state.
        </p>
<p>
          Imagine <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><s