PEP 709 behavior change around mangling

[JelleZijlstra]

Another bug with comprehension inlining.

I made the fuzzer (carljm/compgenerator#1) use __a and __b as names in the hope of finding bugs around name mangling and got this one:

class __a:
 __a = (1)[[__a for __b in [1]]] = 1

On #104602:

>>> class __a:
... __a = (1)[[__a for __b in [1]]] = 1
... 
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
 File "<stdin>", line 2, in __a
TypeError: 'int' object does not support item assignment

On 3.11:

>>> class __a:
... __a = (1)[[__a for __b in [1]]] = 1
... 
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
 File "<stdin>", line 2, in __a
 File "<stdin>", line 2, in <listcomp>
NameError: name '_a__a' is not defined. Did you mean: '_a__b'?

I think that means we're missing some name mangling, but haven't thought too deeply about this yet.

[JelleZijlstra]

cc @carljm

[JelleZijlstra]

Actually this is just the class scoping change. It doesn't reproduce any more after #104528; looks like I forgot to merge that in before starting the fuzzer. Sorry for the noise.