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BUG: typings: a - b returns NoReturn instead of ndarray #20265

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nschloe opened this issue Nov 1, 2021 · 4 comments
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BUG: typings: a - b returns NoReturn instead of ndarray #20265

nschloe opened this issue Nov 1, 2021 · 4 comments
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00 - Bug 41 - Static typing 50 - Duplicate

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@nschloe
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nschloe commented Nov 1, 2021 •
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Describe the issue:

Running

pyright foo.py

on

import numpy as np


def myfun(x: np.ndarray, b: np.ndarray):
    v = b - x
    v.copy()

gives

  /tmp/dummy.py:6:7 - error: Cannot access member "copy" for type "NoReturn"
    Member "copy" is unknown (reportGeneralTypeIssues)

The vector operations +, *, / work fine.

NumPy/Python version information:

1.21.3 3.9.7 (default, Sep 10 2021, 14:59:43)
[GCC 11.2.0]
@BvB93
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BvB93 commented Nov 1, 2021

Duplicate of #20099 and (to some extent) #20072.

Interestingly, it appears that this bug is not limited to mypy (xref python/mypy#11347).
Annoying as it is, I'm wondering if it might be best to temporarily remove the dunder overloads...

@nschloe
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nschloe commented Nov 1, 2021

It's funny that only - is concerned, not +, *, or /.

@BvB93
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BvB93 commented Nov 1, 2021

It's funny that only - is concerned, not +, *, or /.

The problem is that self annotations are ignored when a Any-parametrized object is passed to an overload method.
So what happens is that np.ndarray (or equivalently np.ndarray[Any, Any]) will just pick whatever happens to be the first overload, which turns out to be to NoReturn overload used for boolean arrays:

numpy/numpy/__init__.pyi

Lines 2013 to 2014 in fa397e9

@overload
def __sub__(self: NDArray[bool_], other: _ArrayLikeBool_co) -> NoReturn: ...

@BvB93
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BvB93 commented Nov 1, 2021

Closing this in favor of #20099

@BvB93 BvB93 closed this as completed Nov 1, 2021
This was referenced Nov 1, 2021
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