Oh TIL: Non-frozen non-dataclass subclasses of a frozen dataclass superclass are unfrozen: https://github.com/python/cpython/pull/6148

I think you read that wrong. Only non-dataclass subclasses of a frozen dataclass are unfrozen. If the subclass is a dataclass it must match the super class’s frozeness--is how I read it at least… 🙂

Oops that's just a typo

?

In my PR I'm making it a frozen dataclass, but the derived vanilla class isn't frozen