Potential Redundant `issubclass` type checks that are always True

[rc4typecheck]

When statically analyzing and manually reviewing the code, I noticed a potential logic redundancy in /Lib/test/test_typechecks.py as follows:

def testSubclassBehavior(self):
    self.assertEqual(issubclass(SubInt, Integer), True)
    self.assertEqual(issubclass(SubInt, (Integer,)), True)
    self.assertEqual(issubclass(SubInt, SubInt), True)
    ......

The check 'issubclass(SubInt, Integer)' is always True, as SubInt is explicitly a subtype of Integer. And The check 'issubclass(SubInt, SubInt)' is indeed a self-check, which will always evaluate to True as any class is considered a subclass of itself.

There are several similar subclass self-checking cases in /Lib/test/test_isinstance.py:

self.assertEqual(True, issubclass(Super, Super))
self.assertEqual(True, issubclass(Child, Child))
self.assertEqual(True, issubclass(AbstractSuper, AbstractSuper))
self.assertEqual(True, issubclass(AbstractChild, AbstractChild))

I am not sure whether the code is intentional or it is an issue warranting a refactoring or fixing.

[aisk]

Hi, this repo is the implementation of Python itself, so these tests are just to ensure the behavior of issubclass works correctly. I think it's not redundant.

[StanFromIreland]

These are tests, they may always be true in theory, but we still have to ensure they are always true in practice (i.e. we don't break something ;-).