Incorrect slot check: typo in `__dictoffset__`

[sobolevn]

Bug report

I made a typo that made it into the final code:

cpython/Lib/dataclasses.py

Lines 1211 to 1212 in 00ffdf2

	if getattr(cls, '__dictrefoffset__', -1) != 0:
	slots.append('__dict__')

It should had been __dictoffset__ not __dictrefoffset__.

Fixing plan:

• Add tests for C types with __dictoffset__, so it won't happen again :)
• Fix the typo

Linked PRs

• gh-123935: Fix typo in _get_slots in dataclasses.py #123941
• [3.13] gh-123935: Fix typo in _get_slots in dataclasses.py (GH-123941) #123991
• [3.12] gh-123935: Fix typo in _get_slots in dataclasses.py (GH-123941) #123992

[picnixz]

Out of curiosity... how did you find it?

[sobolevn]

I have a telegram channel, where I post different Python-related posts. Today I posted about how slots work in dataclasses. And one of my readers found this typo :)