Bug report

Bug description:

typing._UnionGenericAlias) became unshable somewhere between 3.13 and 3.14.0b1 (most likely ingh-105511)

importtypinghash(typing._UnionGenericAlias)

Traceback (most recent call last):  File"<python-input-0>", line2, in<module>hash(typing._UnionGenericAlias)~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^TypeError:unhashable type: '_UnionGenericAliasMeta'

This was hit in a doctest fromastropy: xrefastropy/astropy#18126
To be clear, the test in question doesn't necessarily correspond to a real-life application; we're testing that ouritersubclasses utility function works in a very broad case where we try to retrieve all defined subclasses ofobject, and do a bit of internal book-keeping using aset of already-visited classes. This used to work in Python 3.13 (and seems to have worked with no interruption for 10+ years), so it still seemed worth a shot to see if that would be considered a bug here. Otherwise, it should be possible to fix the function on our side to either special case this exact class, ignore any unhashable class, or avoid reequiring hashability altogether.

CPython versions tested on:

3.14

Operating systems tested on:

Linux

Linked PRs

• gh-133925: Make typing._UnionGenericAlias hashable #133929
• [3.14] gh-133925: Make typing._UnionGenericAlias hashable (GH-133929) #133936