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Description
mypy --python-version=3.6 --strict-optional --check-untyped-defs --disallow-incomplete-defs --warn-incomplete-stub --warn-redundant-casts --warn-no-return --warn-return-any --no-incremental
This (simplified) code generates a warning: Returning Any from function declared to return "_SelfType" (for context, this code implements a base class similar to namedtuple but using regular classes instead of tuple):
class PlainOldData:
__slots__ = () # type: Sequence[str]
_SelfType = TypeVar('_SelfType', bound='PlainOldData')
def _replace(self: _SelfType, **kwargs: Dict[Text, Any]) -> _SelfType: # pylint: disable=undefined-variable
"""Make a new object, replacing fields with new values."""
new_attrs = {
k: kwargs.pop(k) if k in kwargs else getattr(self, k)
for k in self.__slots__
}
if kwargs:
raise ValueError('Unknown field names: {!r}'.format(list(kwargs)))
return self.__class__(**new_attrs)
When I change the return statement to return cast(self._SelfType, self.__class__(**new_attrs)), I get Redundant cast to self._SelfType?