Add runtime __slots__ attribute to dataclasses
#15649
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| info.slots = generated_slots | ||
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| # Now, insert `.__slots__` attribute to class namespace: | ||
| slots_type = TupleType( | ||
| [self._api.named_type("builtins.str") for _ in generated_slots], |
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Is it worth creating Literal types here? So the inferred type in the test cases would be tuple[Literal["x"], Literal["y"], Literal["z"]].
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No, because regular classes produce the same result:
class A:
__slots__ = ('a', 'b')
reveal_type(A.__slots__) # N: Revealed type is "tuple[builtins.str, builtins.str]"__match_args__ attribute needs Literal to handle match kwargs correctly, but __slots__ does not need it at all.
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Thanks, I feel like we might get an issue at some point asking that we use the literal types, but it's fine if we're consistent with how explicit __slots__ works.
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According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅ |
gertvdijk
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Aug 10, 2023
Observed before this change with mypy==1.5.0:
error: Trying to assign name "[...]" that is not in "__slots__" of type
"purepythonmilter.server.session.MtaMilterSession" [misc]
Mypy gained this feature to learn __slots__ for dataclasses (here via
attrs classes) in python/mypy#15649.
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Closes #15647