functools.wraps does not work on class methods

We recently hit an error using @wraps on a class method in Trio: https://github.com/python-trio/trio/issues/2775#issuecomment-1702892474 when checked with pyright. It works fine on mypy, but I'm guessing they might be special-casing wraps usage while pyright doesn't.

Minimal repro (python 3.11):

from functools import wraps
from typing import assert_type


def foo(param: int) -> str:
    """docstring"""
    return ""

@wraps(foo)
def my_function(blah: int) -> str:
    return 'foo'

# works fine
assert_type(my_function(5), str)

class MyOtherClass:
    def bar(self, param: int) -> str:
        """docstring"""
        return ""

class MyClass:
    @wraps(MyOtherClass.bar)
    def my_method(self, blah: int) -> str:
        return 'foo'

instance = MyClass()
# works in mypy, but not pyright
assert_type(instance.my_method(5), str)

mypy 1.5.1 works without any issue, pyright 1.1.325 gives

./test.py
  ./test.py:26:13 - error: Argument missing for parameter "blah" (reportGeneralTypeIssues)
  ./test.py:26:13 - error: "assert_type" mismatch: expected "str" but received "Unknown" (reportGeneralTypeIssues)
2 errors, 0 warnings, 0 informations 

This smells a lot like the problem with getting functools.cache to work both with methods and functions, see e.g. https://github.com/python/typeshed/issues/6347

Beginne damit, die minimale Python 3.11-Reproduktion mit pyright auszuführen und sie mit mypy zu vergleichen. Untersuche dann den typeshed-Stub für functools.wraps und konzentriere dich darauf, wie er dekorierte Funktionen und Methoden darstellt. Erledigt ist die Aufgabe, wenn das Beispiel mit der Klassenmethode einer Typprüfung standhält und assert_type(instance.my_method(5), str) keine Fehler meldet.