title: Rvalue reference to lvalue reference - ub?
body: <p>This is not a duplicate of <a href="https://stackoverflow.com/questions/23629745/rvalue-reference-to-lvalue-reference">Rvalue reference to lvalue reference</a></p>
  
  <p>Since I'm asking this for C++17: does the following still invoke undefined behavior (if the reference is used, of course) due to a dangling reference?</p>
  
  <pre><code>template &lt;typename T&gt;
  constexpr T&amp; to_lvalue(T&amp;&amp; r) noexcept { return r; }
  int main()
  {
      int ten = 10;
      int&amp; ref = to_lvalue(ten+8);
      // Is ref a dangling reference in C++17?
  }
  </code></pre>