title: In C++ is there a proposed type traits helper for "copying" reference category and cv-qualification?
body: <p>For the SFINAE in the hypothetical call operator in <a href="https://stackoverflow.com/a/71404857/1505451">this answer</a> I need a type trait that &quot;copies&quot; reference category and const/volatile qualifications from one type to another:</p>
  <pre class="lang-cpp prettyprint-override"><code>template &lt;typename T, typename U&gt;
  using copy_category_and_qualifications_t = [...];
  
  copy_category_and_qualifications_t&lt;int, char&gt;             // char
  copy_category_and_qualifications_t&lt;const int&amp;, char&gt;      // const char&amp;
  copy_category_and_qualifications_t&lt;volatile int&amp;&amp;, char&gt;  // volatile char&amp;&amp;
  </code></pre>
  <p>I seem to recall some proposed addition to <code>type_traits</code> for this. Does anybody have a reference to this proposal, or know if it was added for C++20 or C++23?</p>