title: Const references in std::vector elements
body: <p>Is it only my compiler or is it forbidden to use cons references in std::vector elements. Consider following structure:</p>
  
  <pre><code>struct Y
  {
    const int &amp; x;
  
    Y(const int &amp; p_x):
          x(p_x)
    {
    }
  };
  </code></pre>
  
  <p>Now, when I try to push such object onto vector:</p>
  
  <pre><code>std::vector&lt;Y&gt; yv;
  int x = 5;
  Y y(x);
  yv.push_back(y);
  </code></pre>
  
  <p>I get compiler error: "error: non-static reference member `const int&amp;Y::x', can't use default assignment operator". Shouldn't copy ctor be enough?</p>