I tried all of these, but to no avail - nothing worked. My situation is I have a Swift class "A" that after performing a large merge into my branch could no longer see several other Swift files ("B" - "F") that were located in a different Group from within my project.
What's interesting is "A" belongs to both the main project Target, but also to the UnitTest Target whereas "B", "C", "D", "E", and "F" ONLY belonged to the main project Target.
By including them for membership with the UnitTests also all of a
sudden Xcode can now see those classes correctly - must be members in the same Targets, perhaps?
The fixed a couple of things:
1) Code completion now works.
2) The little red error markers that are next to the line numbers ("unresolved identifier" errors) cleared up too. This last one was very annoying to me as when you CMD-B to build they clear up and the code compiles just fine / runs just fine. But, make ANY change (add a single white space, for example) and these reappeared all the time (and, of course, Code Completion would stop working again as well).
Not sure if this is a Swift or Xcode issue but this is what fixed it for me.