False positive W0231 when using typing.overload.

[mrshannon]

Steps to reproduce

Minimum failing example.

from typing import Union, overload


class Parent:

    def __init__(self, num: int) -> None:
        self.number = num


class Child(Parent):

    @overload
    def __init__(self, num: int) -> None:
        ...

    @overload
    def __init__(self, num: float) -> None:
        ...

    def __init__(self, num: Union[int, float]):
        super().__init__(round(num))

Run pylint on the above example code.

Current behavior

pylint_init_bug.py:13:4: W0231: __init__ method from base class 'Parent' is not called (super-init-not-called)
pylint_init_bug.py:17:4: W0231: __init__ method from base class 'Parent' is not called (super-init-not-called)

Expected behavior

The methods decorated with typing.overload should not be required to call the base __init__ as they are "for the benefit of the type checker only" as indicated at https://docs.python.org/3/library/typing.html#typing.overload.

pylint --version output

pylint 2.3.1
astroid 2.2.5
Python 3.7.3 (default, Apr  3 2019, 19:16:38) 
[GCC 8.0.1 20180414 (experimental) [trunk revision 259383]]

Same bug exists on the master branch which includes #2927.

pylint 2.4.0-dev0
astroid 2.3.0
Python 3.7.3 (default, Apr  3 2019, 19:16:38) 
[GCC 8.0.1 20180414 (experimental) [trunk revision 259383]]

[PCManticore]

Thanks, this definitely makes sense.

[gyermolenko]

I can try and take a look

[gyermolenko]

@mrshannon

def __init__(self, num: Union[int, float]):
    super().__init__(round(num))

I think you don't need to put type annotations here, it was the sole purpose of overload methods to do that.
Also, for some time now It is not required to specify return type of __init__.

[mrshannon]

@gyermolenko
You are correct about the return value of __init__. However, the Union is required. The CPython documentation for the typing module is incorrect in several areas (see python/mypy#5466).

However, none of these changes prevent the original warnings from pylint.

[gyermolenko]

However, none of these changes prevent the original warnings from pylint

Well, to fix the issue I've created PR :)

[mrshannon]

@gyermolenko
I think I see now. While the above is technically valid it's not required since __init__ always has the same return type. My mistake