gh-124445: Allow specializing generic ParamSpec aliases

[tomasr8]

I think I more or less understood how this is supposed to work, but please let me know if I missed something :)
Also, if you think I should add more tests.

• Issue: Alias that is generic over a ParamSpec cannot be further specialized #124445

[tomasr8]

Just trying to debug this weird error now:

Objects/tupleobject.c:408: _PyObject_GC_TRACK: Assertion "!_PyObject_GC_IS_TRACKED(((PyObject*)(op)))" failed: object already tracked by the garbage collector Fatal Python error: Segmentation fault

Unfortunately seems to only happen when running the tests, not when I run the test case as a script :/

[tomasr8]

Ready for another round :)

[tomasr8]

ping @JelleZijlstra in case you forgot about this 🙂

[JelleZijlstra]

Looks good but I'm going to run refleak tests locally to make sure I'm not missing something.

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot x86 Debian Installed with X 3.x (no tier) has failed when building commit bbf1979.

What do you need to do:

1. Don't panic.
2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/#/builders/1244/builds/4460) and take a look at the build logs.
4. Check if the failure is related to this commit (bbf1979) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/#/builders/1244/builds/4460

Failed tests:

• test.test_concurrent_futures.test_process_pool

Failed subtests:

• test_force_shutdown_workers - test.test_concurrent_futures.test_process_pool.ProcessPoolForkserverProcessPoolExecutorTest.test_force_shutdown_workers

Summary of the results of the build (if available):

==

Click to see traceback logs

Traceback (most recent call last):
File "/buildbot/buildarea/3.x.ware-debian-x86.installed/build/target/lib/python3.14/test/test_importlib/metadata/fixtures.py", line 391, in _inner
func(self, **args)
~~~~^^^^^^^^^^^^^^
File "/buildbot/buildarea/3.x.ware-debian-x86.installed/build/target/lib/python3.14/test/test_concurrent_futures/test_process_pool.py", line 281, in test_force_shutdown_workersself.assertEqual(worker_process.exitcode, -signal.SIGKILL)
~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^AssertionError: 255 != -9

[tomasr8]

Buildbot failure seems unrelated