I mean, it wouldn’t be an anonymous type at all, it has an obvious name.
I’m really on the fence here.
This definitely has some utility - defining inner classes is not uncommon and not just in Python, and given that the original definition is valid Python already, the barrier to doing this is definitely going to be lower.
But on the other hand, the engineering task of moving the inner class definition up a couple of lines is tiny.
If it were up to me, I’d encourage someone who wanted to try to put this feature in, but I personally wouldn’t spend my time on it unless I wanted to find out more about how Python type checking internals worked anyway.