title: Xcode autocomplete does not show STL header files without .h file ending
body: <p>I'm working with C++ in Xcode 12.5.1. Suddenly Xcode stopped showing me autocomplete for including typical STL header files such as chrono, algorithm or string. I still get autocomplete for includes with <code>.h</code> file endings like <code>math.h</code> but not <code>cmath</code> although both reside in the same directory. It's also not dependent on a specific project, it stopped working everywhere.
  <a href="https://i.stack.imgur.com/ncIFJ.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ncIFJ.png" alt="enter image description here" /></a></p>
  <p>It previously worked without issues and as far as I know I didn't change anything. The only thing I could imagine, is that I downloaded the Xcode 13 beta but haven't opened it before that happened.</p>
  <p>I already deleted everything in the <code>Derived Data</code> dir, updated and reinstalled Xcode (both from App Store and download from developer portal).</p>
  <p>Any suggestions what causes the problem or what I could do to fix this?</p>