title: What is the type of an 'auto' return type when returning *this in an anonymous class?
body: <p>In this code:</p>
  <pre><code>struct
  {
      auto operator[](const char*)
      {
          return *this;
      }
  
  } m_some_class;
  </code></pre>
  <p>What is type of <code>auto</code> in here?</p>