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gh-143969: Fix frozen+slotted dataclass __setattr__ crash ambiguity #143971

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gh-143969: Fix frozen+slotted dataclass __setattr__ crash ambiguity #143971

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d3b62e4
gh-143969: Fix frozen+slotted dataclass __setattr__ crash ambiguity
dawdameet Jan 17, 2026
34cfdda
gh-143969: Fix crash in frozen slots dataclasses by patching closure …
dawdameet Jan 17, 2026
9f255ac
Update Misc/NEWS.d/next/Library/2026-01-17-23-15-55.gh-issue-143969.W…
dawdameet Jan 18, 2026
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8 changes: 8 additions & 0 deletions Lib/test/test_dataclasses/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3404,6 +3404,14 @@ class C:

c = C('hello')
self.assertEqual(deepcopy(c), c)
def test_frozen_slots_setattr(self):
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@picnixz picnixz Jan 18, 2026

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Suggested change
def test_frozen_slots_setattr(self):
def test_frozen_slots_setattr(self):

# gh-143969: Ensure frozen+slots uses object.__setattr__
@dataclass(frozen=True, slots=True)
class A:
x: int
a = A(1)
with self.assertRaisesRegex(FrozenInstanceError, 'cannot assign to field'):
a.x = 2


class TestSlots(unittest.TestCase):
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2026-01-17-23-15-55.gh-issue-143969.Waq8zN.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Fixed a crash in frozen slotted dataclasses where assigning to an attribute
could raise an internal TypeError instead of failing cleanly.
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