typing tests: test_overload_on_compiled_functions() may not work on alternative Python implementations

[AlexWaygood]

Bug report

A few weeks ago, the typing_extensions backport library received a bug report that test_overload_on_compiled_functions(), a recently added test, failed when run on PyPy: python/typing_extensions#83. This is due to the fact that builtins.sum() and builtins.print() are not compiled functions on PyPy.

The same test exists in the CPython test suite (the test was ported over to typing_extensions in python/typing_extensions#73 after being added to the CPython test suite in #96479):

cpython/Lib/test/test_typing.py

Lines 4638 to 4650 in de69816

	def test_overload_on_compiled_functions(self):
	with patch("typing._overload_registry",
	defaultdict(lambda: defaultdict(dict))):
	# The registry starts out empty:
	self.assertEqual(typing._overload_registry, {})
	# This should just not fail:
	overload(sum)
	overload(print)
	# No overloads are recorded (but, it still has a side-effect):
	self.assertEqual(typing.get_overloads(sum), [])
	self.assertEqual(typing.get_overloads(print), [])

.

I think the test should probably be marked with the @test.support.cpython_only decorator in the CPython test suite.

(Cc. @sobolevn, who added the test.)

[sobolevn]

Yes, I will send a PR for that!

[AlexWaygood]

Thanks for the fix @sobolevn!