Bug report

% cat leak.py def f():    __foo = 1    class X[T]: ...    return __foof()% python3.12 leak.pyTraceback (most recent call last):  File "/Users/jelle/py/cpython/leak.py", line 5, in <module>    f()  File "/Users/jelle/py/cpython/leak.py", line 4, in f    return __foo           ^^^^^NameError: name '_X__foo' is not defined. Did you mean: '__foo'?

The PEP 695 implementation of generic classes turns on name mangling for the type parameter scope, but never turns it off afterwards. As a result, all code that appears syntactically after the PEP 695 scope also gets mangling applied to it.

I have a fix for this, but I believe applying it requires updating the magic number, and I'm not sure we can afford to to do that on the 3.12 branch.

Linked PRs

• gh-119395: Fix leaky mangling after generic classes #119399