Union of legit types is also a legit type

[sassanh]

Is there anyway in Python's typing system to have something like this work:

class OriginalType: ...
class SubclassOne(OriginalType): ...
class SubclassTwo(OriginalType): ...
UnionType = SubclassOne | SubclassTwo

def some_function(_: type[OriginalType]): ...

some_function(UnionType)

I want to be able to limit the argument of my function to a specific union of arbitrary subclasses of the base class. A real life usage of such function is here: https://github.com/sassanh/python-redux/blob/main/tests/test_features.py#L127

Context: microsoft/pyright#8390

Is it not possible until https://peps.python.org/pep-0747/ is done?

[JelleZijlstra]

Yes, this is a use case for PEP-747. A union is not an instance of type, so it is not assignable to type[].