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

首先使用 pyright 執行最小的 Python 3.11 重現，並將其與 mypy 比較。接著檢查 functools.wraps 的 typeshed stub，著重了解它如何表示經裝飾的函式與方法。當類別方法範例通過型別檢查，且 assert_type(instance.my_method(5), str) 未回報任何錯誤時，即表示完成。