If the basedmypy version differs from the mypy, things depending on basedmypy will break

[KotlinIsland]

Apart from swapping the versions around (__version__ as the upstream version and a separate __based_version__). There is an issue of the mypy version not being 'correct'. If the mypy version doesn't match the exact format that release versions contain then anything looking at it could break (like pydantic expecting the version string to be float-like). But if the version is "0.940" it wouldn't be true (because it's not 0.940 release edition).

Perhaps just have __version__ look like it's release and include some extra version info like:

version_info = version_info(major=1, minor=2, patch=2, mypy="0.940", mypy_releaselevel="dev", mypy_hash="123abc")

[KotlinIsland]

resolved in #214