I have noticed a problem in several projects where Xcode will flag a C or Obj-C header file as not found, marking the #import or #include line with a red error flag and putting an error symbol in the status area up top. Sometimes cleaning the build folder will resolve this. Other times, the problem remains until I compile, after which it goes away. But then it might come back again later on while editing/coding even though I have done nothing to the header file in question.
I have seen this on old projects and projects that were started new with Xcode 11. I assume something changed in the way Xcode parses headers on the fly while doing live syntax checking, etc, and for some reason it's not finding the headers or it's erroneously showing them as missing. All of these headers are in the main source root folder of the projects (and for old projects, have been that way for years without issues).
Obviously the compiler finds the headers, otherwise compilation would fail.
Anybody else seen this or have suggestions?