Make Mapping covariant. #512
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| @@ -226,16 +226,18 @@ class ValuesView(MappingView, Iterable[_VT_co], Generic[_VT_co]): | |||
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| # TODO: ContextManager (only if contextlib.AbstractContextManager exists) | |||
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| class Mapping(Iterable[_KT], Container[_KT], Sized, Generic[_KT, _VT]): | |||
| class Mapping(Iterable[_KT_co], Container[_KT_co], Sized, Generic[_KT_co, _VT_co]): | |||
| # TODO: Value type should be covariant, but currently we can't give a good signature for | |||
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Thanks, pushed a fix deleting the comment.
Fixes #510. This requires a `# type: ignore` on `__getitem__` and `get` because mypy complains about covariant parameters. FWIW typing.py needs to be changed too. (It was covariant in the value but invariant in the key -- typeshed was invariant in both.)
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OK, as a compromise I am making it covariant in the value only. (It was already that way in typing.py.) There's still a |
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Fixes #510.
This requires a
# type: ignoreon__getitem__andgetbecausemypy complains about covariant parameters.
FWIW typing.py needs to be changed too. (It was covariant in the
value but invariant in the key -- typeshed was invariant in both.)
See also python/typing#273.