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

Reproduce the report with the paired mod.py and mod.pyi examples and run PYTHONPATH=$PWD stubtest mod. Compare how stubtest handles T.c and the alias T.d, then verify the change against this reproduction; done means the command succeeds without output or errors.