I have posted about a similar issue beforehand, where I encountered a compiler error that only popped-up during CI on GitHub using Swift for Linux. Back then, the solution was to replace occurrences of:
guard let x = x else { }
with
guard let x = self.x else { }
In other words: introducing scope was a workaround. But even then, guard let x = x else { } would work most of the time and it only would fail sometimes.
The New Problem
Now I am facing this problem again in this context:
let (x, y) = myMethod(z)
guard let x = x else { return self }
which results in the following error:
... error: definition conflicts with previous value
guard let x = x else { return self }
^
... note: previous definition of 'x' is here
let (x, y) = myMethod(z)
This works fine in Xcode 13.1 with Swift 5.5.1, but fails again in the GitHub CI workflow where Linux is running. Obviously, in this context I cannot fall back to use scope to tell the compiler which symbol I am talking about and I am forced to use a different name for x in the first line. If I have time, then I might be able to get around to try to replicate this using Docker on my laptop where I could play around with different Linux-versions of the Swift compiler.
The main issue (for me) is not that I have to provide scope and/or rename a symbol, but that the compiler behavior differs across platforms and that it sometimes works fine and fails seemingly randomly.