 either. In such case,
          assignment to an <span class="emphasis"><em>uninitialized </em></span> <code class="computeroutput"><span class="identifier">optional</span><span class="special">&lt;</span><span class="identifier">T</span><span class="special">&amp;&gt;</span></code> shall be prohibited. It is quite
          possible that in such a scenario it is a precondition that the lvalue must
          be already initialized. If it isn't, then binding for the first time is
          OK while rebindin