title: 'auto' not allowed in function prototype with Clang
body: <p>Using Clang 3.5, 3.6, or 3.7, with the flag <code>std=c++1y</code> the following code does not compile :</p>
  
  <pre><code>#include &lt;iostream&gt;
  auto foo(auto bar) { return bar; }
  int main() {
    std::cout &lt;&lt; foo(5.0f) &lt;&lt; std::endl;
  }
  </code></pre>
  
  <p>The error given is :</p>
  
  <blockquote>
    <p>error: 'auto' not allowed in function prototype</p>
  </blockquote>
  
  <p>I do not have errors using g++ 4.9.
  Is this error produced because Clang has not yet implemented this functionnality yet or is it because I am not allowed to do that and GCC somehow permits it ?</p>