Jul 12, 2023 · Jul 12, 2023 · Jul 12, 2023 · Jul 12, 2023 · Jul 12, 2023
diff --git a/mypy/plugins/dataclasses.py b/mypy/plugins/dataclasses.py
                self._cls,
            )
            return

        info.slots = generated_slots

        # Now, insert `.__slots__` attribute to class namespace:
        slots_type = TupleType(
            [self._api.named_type("builtins.str") for _ in generated_slots],
            self._api.named_type("builtins.tuple"),
        )
        add_attribute_to_class(self._api, self._cls, "__slots__", slots_type)

    def reset_init_only_vars(self, info: TypeInfo, attributes: list[DataclassAttribute]) -> None:
        """Remove init-only vars from the class and reset init var declarations."""
        for attr in attributes:
diff --git a/test-data/unit/check-dataclasses.test b/test-data/unit/check-dataclasses.test
 [builtins fixtures/dataclasses.pyi]


 [case testDataclassWithSlotsRuntimeAttr]
 # flags: --python-version 3.10
 from dataclasses import dataclass

 @dataclass(slots=True)
 class Some:
    x: int
    y: str
    z: bool

 reveal_type(Some.__slots__)  # N: Revealed type is "Tuple[builtins.str, builtins.str, builtins.str]"

 @dataclass(slots=True)
 class Other:
    x: int
    y: str

 reveal_type(Other.__slots__)  # N: Revealed type is "Tuple[builtins.str, builtins.str]"


 @dataclass
 class NoSlots:
    x: int
    y: str

 NoSlots.__slots__  # E: "Type[NoSlots]" has no attribute "__slots__"
 [builtins fixtures/dataclasses.pyi]


 [case testSlotsDefinitionWithTwoPasses1]
 # flags: --python-version 3.10
 # https://github.com/python/mypy/issues/11821
Original file line number	Diff line number	Diff line change
Expand Up		@@ -469,9 +469,15 @@ def add_slots(
		self._cls,
		)
		return

		info.slots = generated_slots

		# Now, insert `.__slots__` attribute to class namespace:
		slots_type = TupleType(
		[self._api.named_type("builtins.str") for _ in generated_slots],
Copy link Member JelleZijlstraJul 12, 2023 Choose a reason for hiding this comment The reason will be displayed to describe this comment to others.Learn more. Is it worth creating Literal types here? So the inferred type in the test cases would be`tuple[Literal["x"], Literal["y"], Literal["z"]]`. Copy link MemberAuthor sobolevnJul 12, 2023 Choose a reason for hiding this comment The reason will be displayed to describe this comment to others.Learn more. No, because regular classes produce the same result: classA:__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. Copy link Member JelleZijlstraJul 12, 2023 Choose a reason for hiding this comment The reason will be displayed to describe this comment to others.Learn more. 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.
		self._api.named_type("builtins.tuple"),
		)
		add_attribute_to_class(self._api, self._cls, "__slots__", slots_type)

		def reset_init_only_vars(self, info: TypeInfo, attributes: list[DataclassAttribute]) -> None:
		"""Remove init-only vars from the class and reset init var declarations."""
		for attr in attributes:
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Original file line number	Diff line number	Diff line change
Expand Up		@@ -1547,6 +1547,35 @@ class Other:
		[builtins fixtures/dataclasses.pyi]


		[case testDataclassWithSlotsRuntimeAttr]
		# flags: --python-version 3.10
		from dataclasses import dataclass

		@dataclass(slots=True)
		class Some:
		x: int
		y: str
		z: bool

		reveal_type(Some.__slots__) # N: Revealed type is "Tuple[builtins.str, builtins.str, builtins.str]"

		@dataclass(slots=True)
		class Other:
		x: int
		y: str

		reveal_type(Other.__slots__) # N: Revealed type is "Tuple[builtins.str, builtins.str]"


		@dataclass
		class NoSlots:
		x: int
		y: str

		NoSlots.__slots__ # E: "Type[NoSlots]" has no attribute "__slots__"
		[builtins fixtures/dataclasses.pyi]


		[case testSlotsDefinitionWithTwoPasses1]
		# flags: --python-version 3.10
		# https://github.com/python/mypy/issues/11821
Expand Down