Repository navigation
Unexpected name mangling behavior with generics #119311
Description
Bug report
Bug description:
Name mangling behaves inconsistently when used with generics. Here’s the code to reproduce the issue:
class __Foo(type):
pass
class Bar[T](metaclass=__Foo):
passThis raises NameError: name '_Bar__Foo' is not defined. However, removing the [T] results in the error disappearing. This suggests that the name mangling behavior is inconsistent when generics are involved. This behavior seems to be a bug, as it would be expected for the name mangling to either always occur or never occur, regardless of whether generics are used.
CPython versions tested on:
3.12
Operating systems tested on:
Linux
Activity
JelleZijlstra commentedon May 22, 2024
I agree this is a bug. We apply name mangling to all names that appear in the type parameter scope for the generic class (and also to all code after it, which is a separate bug: #119395). In the example, this means
__Fooin the bases gets mangled to_Bar__Foo.We could instead not do any mangling in the type parameter scope. That would fix this bug and simplify the code. However, it would break cases like this:
If we didn't do mangling in the type parameter scope, the second use of
__Twould get mangled, but the first one wouldn't, so the second use of__Twould fail to resolve.Fortunately, the set of names that can appear in a type parameter scope is very limited. I think it should be possible to mangle only the type parameter names defined in the scope but nothing else. This would make both my example and the OP's example work, but it adds some complexity to the symtable.
pythongh-119311: Fix name mangling with PEP 695 generic classes
gh-119311: Fix name mangling with PEP 695 generic classes (#119464)
pythongh-119311: Fix name mangling with PEP 695 generic classes (pyth…
[3.12] pythongh-119311: Fix name mangling with PEP 695 generic classes (
[3.13] gh-119311: Fix name mangling with PEP 695 generic classes (#11…
[3.12] gh-119311: Fix name mangling with PEP 695 generic classes (#11…
pythongh-119311: Fix name mangling with PEP 695 generic classes (pyth…
gh-119311: Add missing magic number (3571) for 3.13.0b1 (#125771)
pythongh-119311: Add missing magic number (3571) for 3.13.0b1 (python…