This is mainly for Serhiy's planned refactoring (see GH-27196). I did not backport any of the new features, only the code refactoring.

Hmm I don't understand the failure in Tests / Check if the ABI has changed (pull_request):

2 Removed functions:

  'function PyObject* _Py_make_parameters(PyObject*)'    {_Py_make_parameters}
  'function PyObject* _Py_subs_parameters(PyObject*, PyObject*, PyObject*, PyObject*)'    {_Py_subs_parameters}

These functions are newly added, how can they be removed?

I do not think it is needed for backporting of GH-27196. GH-27196 almost do not touch genericaliasobject.c, so conflicts are minimal.

It would nice to backport indexing.

I do not think it is needed for backporting of GH-27196. GH-27196 almost do not touch genericaliasobject.c, so conflicts are minimal.

You're right that most things should backport cleanly. It's only required if you want to backport shifting or using _Py_subs_parameters and _Py_make_parameters. Those don't exist in 3.10 currently.

It would nice to backport indexing.

Yup. Maybe if you review and approve GH-26980, Pablo will allow us to backport it to 3.10.

Closing this since GH-27207 has been approved.