diff --git a/mypy/plugins/dataclasses.py b/mypy/plugins/dataclasses.py index acb785aad70a..90c983b0bacd 100644 --- a/mypy/plugins/dataclasses.py +++ b/mypy/plugins/dataclasses.py @@ -965,6 +965,9 @@ def dataclass_tag_callback(ctx: ClassDefContext) -> None: def dataclass_class_maker_callback(ctx: ClassDefContext) -> bool: """Hooks into the class typechecking process to add support for dataclasses.""" + if any(i.is_named_tuple for i in ctx.cls.info.mro): + ctx.api.fail("A NamedTuple cannot be a dataclass", ctx=ctx.cls.info) + return True transformer = DataclassTransformer( ctx.cls, ctx.reason, _get_transform_spec(ctx.reason), ctx.api ) diff --git a/test-data/unit/check-dataclasses.test b/test-data/unit/check-dataclasses.test index 26c81812ab62..9109b2b7c36d 100644 --- a/test-data/unit/check-dataclasses.test +++ b/test-data/unit/check-dataclasses.test @@ -2576,3 +2576,20 @@ reveal_type(m.b) # N: Revealed type is "builtins.int" m.a = 1 # E: Cannot assign to final attribute "a" m.b = 2 # E: Cannot assign to final attribute "b" [builtins fixtures/tuple.pyi] + +[case testNoCrashForDataclassNamedTupleCombination] +# flags: --python-version 3.13 +from dataclasses import dataclass +from typing import NamedTuple + +@dataclass +class A(NamedTuple): # E: A NamedTuple cannot be a dataclass + i: int + +class B1(NamedTuple): + i: int +@dataclass +class B2(B1): # E: A NamedTuple cannot be a dataclass + pass + +[builtins fixtures/tuple.pyi]