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Mirraz opened this issue Aug 31, 2022 · 2 comments
Open

False positive error "incompatible type" #13566

Mirraz opened this issue Aug 31, 2022 · 2 comments
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bug mypy got something wrong topic-inheritance Inheritance and incompatible overrides

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@Mirraz
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Mirraz commented Aug 31, 2022

For this code:

from typing import Any, Generic, TypeVar

T = TypeVar('T')


class EtcdValueWatcherTyped(Generic[T]):
    def __init__(self):
        pass


class EtcdValueWatcher(EtcdValueWatcherTyped[dict[str, Any]]):
    pass


class SettingsWatcher(EtcdValueWatcher):
    def __init__(self, arg1: str):
        self.__arg1 = arg1
        EtcdValueWatcher.__init__(self)


def main():
    watcher = SettingsWatcher('/v1/qwe')

mypy outputs error:

test.py: note: In member "__init__" of class "SettingsWatcher":
test.py:19: error: Argument 1 to "__init__" has incompatible type "SettingsWatcher"; expected "EtcdValueWatcherTyped[T]"  [arg-type]
            EtcdValueWatcher.__init__(self)
                                      ^
Found 1 error in 1 file (checked 1 source file)

which is false positive.

  • Mypy version used: mypy 0.971 (compiled: yes)
  • Mypy command-line flags: mypy --config-file ./mypy.ini ./test.py
  • Mypy configuration options from mypy.ini (and other config files):
[mypy]
ignore_missing_imports = True
show_error_codes = True
show_error_context = True
pretty = True
no_site_packages = False
  • Python version used: Python 3.10.6
  • Operating system and version: Fedora 35
@Mirraz Mirraz added the bug mypy got something wrong label Aug 31, 2022
@AlexWaygood AlexWaygood added the topic-inheritance Inheritance and incompatible overrides label Sep 2, 2022
@asqui
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asqui commented Nov 25, 2022

We've run in to this problem too...

Is there an easy way to work around this in the meantime until a fix is released?

@leandro-lucarella-frequenz
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leandro-lucarella-frequenz commented Feb 24, 2023 •
edited
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Same here, I think this is a more reduced test case (mypy-playground):

EDIT: Is not the same case actually, my case involves constraints.

from typing import Generic, TypeVar

T = TypeVar("T", float, int)


class C(Generic[T]):
    def __init__(self, i: T) -> None:
        self.i: T = i


class B(C[T]):
    def __init__(self, i: T) -> None:
        super().__init__(i)
main.py: note: In member "__init__" of class "B":
main.py:13:26: error: Argument 1 to "__init__" of "C" has incompatible type "float"; expected "T"  [arg-type]
main.py:13:26: error: Argument 1 to "__init__" of "C" has incompatible type "int"; expected "T"  [arg-type]
Found 2 errors in 1 file (checked 1 source file)

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@asqui @Mirraz @AlexWaygood @leandro-lucarella-frequenz