Overloading function issues (incompatible with supertype).

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#3,750 3 comments 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
25/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Tech stack
python
Domain
devtools

Research direction

Start by reproducing the report from test.py with the stated mypy command and Python 3.6 settings. Inspect the overloaded pop definitions in CIDict.py and the reported MutableMapping compatibility errors. Done means determining the expected diagnostic or corrected typing behavior and covering it with a regression test.

Written by the indexing model from the issue text.

Description

bug priority-1-normal topic-overloads topic-usability 
mypy 0.530-dev-417e925b16bcd63ba594f5a85c54b2407bd8831d

KeyTy = TypeVar("KeyTy")
ValTy = TypeVar("ValTy")
TempTy = TypeVar("TempTy")

class CIDict(Dict[KeyTy, ValTy]):
    @overload
    def pop(self, key: KeyTy) -> ValTy:
        pass

    @overload
    def pop(self, key: KeyTy, default: Union[ValTy, TempTy]) \
            -> Union[ValTy, TempTy]:
        pass

    def pop(self, key: KeyTy, default: Optional[Union[ValTy, TempTy]] = None) \
            -> Union[ValTy, TempTy]:
        pass

Running mypy with:

mypy test.py --strict-optional --ignore-missing-imports --disallow-untyped-calls --python-version 3.6

Issues:

CIDict.py:31: error: Signature of "pop" incompatible with supertype "MutableMapping"
CIDict.py:40: error: Overloaded function implementation does not accept all possible arguments of signature 2

Line number differ because the code above is only a snippet.

What am I missing here?

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