Classmethod bound with an additional name trigger stubtest errors

Bug Report

Classmethods bound with an additional name trigger stubtest errors.

To Reproduce

Consider the following trivial module and companion typing stub file

# mod.py
class T:
    def a(self): pass
    b = a
    @classmethod
    def c(cls): pass
    d = c

# mod.pyi
class T:
    def a(self) -> None: pass
    b = a
    @classmethod
    def c(cls) -> None: pass
    d = c

then run stubtest the following way:

PYTHONPATH=$PWD stubtest mod

Expected Behavior

stubtest succeeds with no output printed

Actual Behavior

error: mod.T.d variable differs from runtime type def () -> Any
Stub: in file /home/dalcinl/tmp/pkg/mod.pyi:6
def (cls: Type[mod.T])
Runtime: in file /tmp/mod.py:4
<bound method T.c of <class 'mod.T'>>

Found 1 error (checked 1 module)

Please note that the issue comes from a @classmethod, a regular method does not trigger the error.

Your Environment

• Mypy version used: 1.4.1
• Mypy command-line flags: none
• Mypy configuration options from mypy.ini (and other config files): none
• Python version used: 3.11.4

Riproduci il problema riportato con gli esempi abbinati mod.py e mod.pyi ed esegui PYTHONPATH=$PWD stubtest mod. Confronta il modo in cui stubtest gestisce T.c e l'alias T.d, quindi verifica la modifica con questa riproduzione; la modifica è completata quando il comando viene eseguito correttamente senza output né errori.