False-negative `unneeded-not` when using `hash` function

[Moisan]

Bug description

Line of the type not hash(x) == hash(y) does not trigger unneeded-not.

More complete example:

def test_unneeded_not():
    first_string = '123'
    second_string = '456'
    assert not first_string == second_string
    assert not hash(first_string) == hash(second_string)
    assert not int(first_string) == int(second_string)

Configuration

No response

Command used

pylint test.py

Pylint output

************* Module test
test.py:1:0: C0114: Missing module docstring (missing-module-docstring)
test.py:1:0: C0116: Missing function or method docstring (missing-function-docstring)
test.py:4:11: C0113: Consider changing "not first_string == second_string" to "first_string != second_string" (unneeded-not)
test.py:6:11: C0113: Consider changing "not int(first_string) == int(second_string)" to "int(first_string) != int(second_string)" (unneeded-not)

Expected behavior

To trigger not-unneeded on the assert not hash(first_string) == hash(second_string) line.

Pylint version

pylint 2.15.5
astroid 2.12.12
Python 3.9.13 | packaged by conda-forge | (main, May 27 2022, 17:01:00)
[Clang 13.0.1 ]

OS / Environment

No response

Additional dependencies

No response

[clavedeluna]

This is inference-related. When the node is a call to hash, it seems to not be able to infer and this tuple is (None, None)

Wonder if passing context to the infer call could help?

edit: turns out astroid doesn't seem to be able to infer a call to hash

>>> import astroid
>>> node = astroid.extract_node("hash(1)")
>>> [x for x in node.infer()]
Traceback (most recent call last):
  File "/Users/dani/astroid/astroid/decorators.py", line 140, in raise_if_nothing_inferred
    yield next(generator)
StopIteration

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 1, in <listcomp>
  File "/Users/dani/astroid/astroid/nodes/node_ng.py", line 169, in infer
    yield from self._infer(context=context, **kwargs)
  File "/Users/dani/astroid/astroid/decorators.py", line 146, in raise_if_nothing_inferred
    raise InferenceError(
astroid.exceptions.InferenceError: StopIteration raised without any error information.

so seems like a fix in the astroid repo?

[mbyrnepr2]

Hi folks. I wanted to check a detail before opening a MR for this in astroid. Sorry for tagging @cdce8p @DanielNoord @jacobtylerwalls but I know you spend time in the astroid repo & don't want to lose out on your insights.

Would it be preferable to add an inference function, infer_hash which always returns nodes.Const(0) similar to the infer_str function or would you prefer to try to do something like infer_bool which would require defining a hash_value function on specific nodes like for example the Dict node ?

[DanielNoord]

I think infer_bool makes more sense as it actually allows us to try and start inferring hashes instead of always returning the same.