UP008 should only apply when the `__class__` cell exists

[dscorbett]

Summary

super-call-with-parameters (UP008) should only apply when super is a global variable or __class__ is a nonlocal variable. Expressions that are merely equal to super aren’t good enough. Otherwise, the zero-argument super call doesn’t work. One solution is for the autofix to rewrite the super-equivalent expression to super, although that won’t work in all contexts. Example:

$ cat >up008.py <<'# EOF'
import builtins
class A:
    def f(self):
        print("!")
class B(A):
    def f(self):
        builtins.super(B, self).f()
B().f()
# EOF

$ python up008.py
!

$ ruff --isolated check up008.py --select UP008 --unsafe-fixes --fix
Found 1 error (1 fixed, 0 remaining).

$ cat up008.py
import builtins
class A:
    def f(self):
        print("!")
class B(A):
    def f(self):
        builtins.super().f()
B().f()

$ python up008.py 2>&1 | tail -n 1
RuntimeError: super(): __class__ cell not found

Note that the expression that UP008 rewrites can still use builtins.super (or other expressions that equal super but are not literally super) but super or __class__ just needs to be mentioned somewhere in the method in order for the __class__ cell, which the zero-argument super uses, to be created. True positive example with super:

$ cat >up008_super.py <<'# EOF'
import builtins
super = None  # It still works even if `super` is shadowed!
class A:
    def f(self):
        print("!")
class B(A):
    def f(self):
        if False: super
        builtins.super(B, self).f()
B().f()
# EOF

$ ruff --isolated check up008_super.py --select UP008 --unsafe-fixes --fix
Found 1 error (1 fixed, 0 remaining).

$ python up008_super.py
!

True positive example with __class__:

$ cat >up008_class.py <<'# EOF'
import builtins
class A:
    def f(self):
        print("!")
class B(A):
    def f(self):
        if False: __class__
        builtins.super(B, self).f()
B().f()
# EOF

$ ruff --isolated check up008_class.py --select UP008 --unsafe-fixes --fix
Found 1 error (1 fixed, 0 remaining).

$ python up008_class.py
!

Version

ruff 0.12.3 (5bc81f2 2025-07-11)