This appears to be a common issue with little to zero known resolutions over the years.... Appears to happen with previous versions of Xcode.
Does Apple or the community have a fix?
I've checked out the sources in a new location from my github - Same/similar issue.
I've started a completely new project from scratch and then dragged my source into it... same/similar issue.
I've killed the swift-frontend process & closed reopened Xcode. I've cleaned the build folder / delete DerivedData & restarted the computer... same/similar issue.
Any ideas?