gh-109409: Fix inheritance of frozen dataclass from non-frozen dataclass mixins

[sobolevn]

• Issue: frozen dataclass inheritance is not strictly checked in multiple inheritance #109409

[ericvsmith]

I've added this to my list of things to do during the core dev sprint in October. I'll review it then.

[ericvsmith]

This looks good, thanks!

@sobolevn : I can't merge because your branch is out of date. Can you merge from main? Then I'll accept this.

I could probably do it myself, but I don't know the implications for the PR, so it's probably best if you do it.

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot AMD64 FreeBSD 3.x has failed when building commit b6000d2.

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/all/#builders/1223/builds/442) and take a look at the build logs.
4. Check if the failure is related to this commit (b6000d2) 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/all/#builders/1223/builds/442

Failed tests:

• test_interpreters

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

==

Click to see traceback logs

remote: Enumerating objects: 22, done.        
remote: Counting objects:   4% (1/22)        
remote: Counting objects:   9% (2/22)        
remote: Counting objects:  13% (3/22)        
remote: Counting objects:  18% (4/22)        
remote: Counting objects:  22% (5/22)        
remote: Counting objects:  27% (6/22)        
remote: Counting objects:  31% (7/22)        
remote: Counting objects:  36% (8/22)        
remote: Counting objects:  40% (9/22)        
remote: Counting objects:  45% (10/22)        
remote: Counting objects:  50% (11/22)        
remote: Counting objects:  54% (12/22)        
remote: Counting objects:  59% (13/22)        
remote: Counting objects:  63% (14/22)        
remote: Counting objects:  68% (15/22)        
remote: Counting objects:  72% (16/22)        
remote: Counting objects:  77% (17/22)        
remote: Counting objects:  81% (18/22)        
remote: Counting objects:  86% (19/22)        
remote: Counting objects:  90% (20/22)        
remote: Counting objects:  95% (21/22)        
remote: Counting objects: 100% (22/22)        
remote: Counting objects: 100% (22/22), done.        
remote: Compressing objects:  10% (1/10)        
remote: Compressing objects:  20% (2/10)        
remote: Compressing objects:  30% (3/10)        
remote: Compressing objects:  40% (4/10)        
remote: Compressing objects:  50% (5/10)        
remote: Compressing objects:  60% (6/10)        
remote: Compressing objects:  70% (7/10)        
remote: Compressing objects:  80% (8/10)        
remote: Compressing objects:  90% (9/10)        
remote: Compressing objects: 100% (10/10)        
remote: Compressing objects: 100% (10/10), done.        
remote: Total 12 (delta 10), reused 3 (delta 2), pack-reused 0        
From https://github.com/python/cpython
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HEAD is now at b6000d2874 gh-109409: Fix inheritance of frozen dataclass from non-frozen dataclass mixins (gh-109437)
Switched to and reset branch 'main'