Xcode 10 Objective-C #import filename completion not working

Question

I've upgraded to Xcode 10 and realized that filename completion in #import statements are not working properly. Here is a small part of my project:

Here is what happens when I try to complete a filename:

I've restarted my Mac, cleaned build folders, did all the common "fixes", though nothing changed.

When I type the filename manually, I don't get any errors, everything compiles correctly, and code completion works perfectly too.

What might be wrong? Is there anything that I can do or is Xcode 10 inherently broken?

UPDATE: I'm on Xcode 10.1 and it's still broken.

Answer 1

As "zhysan" pointed out on https://forums.developer.apple.com/thread/108523 this seems to be caused by the new build system.

This works for me:

File -> Project Settings... -> Build system -> Legacy build system.