SPM on Linux: Extension not visible from Tests

[mickeyl (Dr. Mickey Lauer)]

I don't know whether this is a compiler or a package manager issue, perhaps a bit of both. [SR-15462] Regression: Swift 5.5 on Linux doesn't see extension on `timeval_t` · Issue #57767 · apple/swift · GitHub describes a problem where an extension is not visible in the tests. On macOS this works, on Linux it fails.

Any idea how to circumvent that?

[SDGGiesbrecht (Jeremy David Giesbrecht)]

It is a general problem in the compiler. Have a look at some of the existing threads, such as this one:

How do we work around SR-15532?

Summary of SR-15532: On Linux. Swift >= 5.5 Public properties in Swift's extension of C structs such as in_addr cannot be used outside the module. How do we work around it? I have thought about that in my own way, but I have no idea to work around it (not to mention how to fix it).