The relative path of a test file is just its name, even if it's in a
module.
Diagnostics in IR are mapped to the file path and so it's reported on
all files with the same path, i.e. name.
This doesn't happen in production code because no two files can have
the same path.
The proper fix would be to prefix the test files' paths with the module
name.
Unfortunately, this breaks a bunch of test runners that rely on the
current behavior.
Especially, some JS runners turned out to be hard to fix.
The linked YouTrack issue contains a WIP, incomplete patch of fixing
some runners.
#KT-61592 Fixed
#KT-63252
Kirill Rakhman
eba1fdec1d