Type changes in decorators are not detected

[olirice]

When a decorator changes the return type of a function, that change is not detected.

Steps to reproduce

from typing import Callable
from functools import wraps

def cast_to_str(func) -> Callable[..., str]:
    @wraps(func)
    def wrapper(*args, **kwargs):
        return str(func(*args, **kwargs))
    return wrapper

@cast_to_str
def get_num() -> int:
    return 5

get_num().strip()
# [no-member] Instance of 'int' has no 'strip' member 

Current behavior

Return type of decorated function is set by the function declaration

Expected behavior

Return type of the function set by decorator

pylint --version output

pylint 2.1.1
astroid 2.0.4
Python 3.6.5 (default, May 14 2018, 11:01:09)
[GCC 4.2.1 Compatible Apple LLVM 9.1.0 (clang-902.0.39.1)]

[PCManticore]

Thanks for creating an issue! pylint doesn't currently correctly understand decorators, which is why it does not infer the new type.

[moi90]

Is there any roadmap towards this?

[PCManticore]

No, there isn't. pylint is a volunteer driven project and the roadmap tends to be the things that volunteers are mostly interested in working on. For now this is not a priority but hopefully we'll get to it at some point.

[moi90]

I understand. Is there already any discussion about this or is this issue the right place to start one?

[PCManticore]

This is the right place to start one. :)

[Pierre-Sassoulas]

A lot of similar issues were listed in #8332