typechecked not compatible with class property decorator

[Jonas1312]

Things to check first

• I have searched the existing issues and didn't find my bug already reported there

• I have checked that my bug is still present in the latest release

Typeguard version

4

Bug is not present with typeguard v2

Python version

3.7

What happened?

The code below raises:

    obj.a = "2"
TypeError: a() takes 1 positional argument but 2 were given

How can we reproduce the bug?

from typeguard import typechecked


class MyClass:
    def __init__(self) -> None:
        self._a = "1"

    @property
    def a(self) -> str:
        return self._a

    @a.setter
    @typechecked
    def a(self, a: str) -> None:
        self._a = a


obj = MyClass()
print(obj.a)
obj.a = "2"
print(obj.a)

[agronholm]

It appears that this is caused by the fact that @typechecked looks up the target function based on the fully qualified name, which would be the same for both the getter and the setter. The fix would be to improve the accuracy of the targeting by specifying the target line number as well. The only workarounds I can think of right now are to either use the import hook or check_type() instead.

[agronholm]

I'm finally making some progress with this. It can be reproduced w/o getters/setters, like this:

from typeguard import typechecked


@typechecked
def func(value: int) -> None:
    print("first")

first_func = func

@typechecked
def func(value: int) -> None:
    print("second")

first_func(1)
func(1)

The above code prints first twice. Once I figure out why it's replacing the second function with the code of the first, I can fix this.