title: Can a default function return auto?
body: <p>Consider the following class:</p>
  <pre><code>class example
  {
  public:
      auto &amp; operator =(const example &amp;) = default;
      auto &amp; operator =(example &amp;&amp;) = default;
  };
  </code></pre>
  <p>Are those declarations considered legal?</p>