title: Xcode "Use of undeclared identifier" errors, compiles/runs just fine
body: <p>I've got an incredibly annoying issue that is hampering my workflow. In my project I have "User of undeclared identifier" errors all over. They are all in reference to a single class, specifically a Theme class. I checked for any circular referencing with my imports, none. I'm really confused.</p>
  
  <p>Here is a screenshot of the errors. I would post errors in the Build Log for more detail, but there aren't any. It builds and runs just fine...</p>
  
  <p><img src="https://i.stack.imgur.com/awqPR.png" alt="enter image description here"></p>
  
  <p>I've tried cleaning, deleting the derived data... Any ideas?</p>