attrs: wrong type inferred from Factory attribute (using auto_attribs)

[belm0]

Steps to reproduce

attrs allows this form for factory, but pylint doesn't understand it:

import attr
from functools import partial
import numpy as np

@attr.attrs(auto_attribs=True)
class Foo:
    position: np.ndarray = attr.Factory(partial(np.zeros, 3))
    # position: np.ndarray = attr.attrib(default=attr.Factory(partial(np.zeros, 3)))  # this works

    def bar(self):
        return -self.position

Current behavior

 E1130: bad operand type for unary -: Factory (invalid-unary-operand-type)

Expected behavior

no error

pylint --version output

Result of pylint --version output:

pylint 2.7.2
astroid 2.5.1
Python 3.7.7 (default, Oct  5 2020, 09:18:33)
[Clang 9.0.0 (clang-900.0.39.2)]

Additional dependencies:

attrs=20.2.0

[hippo91]

@belm0 thanks for your report. Would it be possible to have smaller reproducer? For example without numpy dependency?
It would be clearer if this false positive arises from our handling of attr or numpy.

[belm0]

confirmed it's not related to numpy:

import attr

@attr.attrs(auto_attribs=True)
class Foo:
    position: int = attr.Factory(lambda: 3)
    #position: int = attr.attrib(default=attr.Factory(lambda: 3))  # this works

    def bar(self):
        return -self.position

E1130: bad operand type for unary -: Factory (invalid-unary-operand-type)

[hippo91]

@belm0 thanks for this update!