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fix: prevent crash on dataclass with PEP695 TypeVarTuple on py3.13 #19565

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Merged
merged 2 commits into from
Aug 2, 2025
Merged

fix: prevent crash on dataclass with PEP695 TypeVarTuple on py3.13 #19565

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66bf1a0
Fix Instance creation
sterliakov Aug 1, 2025
12f892c
Move testcase to 3.12+
sterliakov Aug 1, 2025
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3 changes: 1 addition & 2 deletions mypy/plugins/dataclasses.py
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Original file line number Diff line number Diff line change
Expand Up @@ -410,13 +410,12 @@ def _add_dunder_replace(self, attributes: list[DataclassAttribute]) -> None:
for attr in attributes
if attr.is_in_init
]
type_vars = [tv for tv in self._cls.type_vars]
add_method_to_class(
self._api,
self._cls,
"__replace__",
args=args,
return_type=Instance(self._cls.info, type_vars),
return_type=fill_typevars(self._cls.info),
)

def _add_internal_replace_method(self, attributes: list[DataclassAttribute]) -> None:
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11 changes: 11 additions & 0 deletions test-data/unit/check-python312.test
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Expand Up @@ -2084,3 +2084,14 @@ reveal_type(A1().x) # N: Revealed type is "builtins.int"
reveal_type(A2().x) # N: Revealed type is "builtins.int"
reveal_type(A3().x) # N: Revealed type is "builtins.list[builtins.int]"
[builtins fixtures/tuple.pyi]

[case testDataclassWithTypeVarTuple]
# flags: --python-version 3.13
# https://github.com/python/mypy/issues/19559
from typing import Callable
from dataclasses import dataclass

@dataclass
class Test[*Ts, R]:
a: Callable[[*Ts], R]
[builtins fixtures/dict.pyi]
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