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Do not push partial types to the binder #20202

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57a2586
Do not push partial types to binder
sterliakov Nov 7, 2025
f8ad206
Remove unrelated attempt
sterliakov Nov 7, 2025
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6 changes: 5 additions & 1 deletion mypy/checker.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3413,7 +3413,11 @@ def check_assignment(
and lvalue_type is not None
):
lvalue.node.type = remove_instance_last_known_values(lvalue_type)
elif self.options.allow_redefinition_new and lvalue_type is not None:
elif (
self.options.allow_redefinition_new
and lvalue_type is not None
and not isinstance(lvalue_type, PartialType)
):
# TODO: Can we use put() here?
self.binder.assign_type(lvalue, lvalue_type, lvalue_type)

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10 changes: 10 additions & 0 deletions test-data/unit/check-redefine2.test
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Expand Up @@ -369,6 +369,16 @@ class C4:
reveal_type(self.x) # N: Revealed type is "builtins.list[builtins.str]"

reveal_type(C4().x) # N: Revealed type is "builtins.list[builtins.str]"

class C5:
def __init__(self) -> None:
if int():
self.x = None
return
self.x = [""]
reveal_type(self.x) # N: Revealed type is "builtins.list[builtins.str]"

reveal_type(C5().x) # N: Revealed type is "Union[builtins.list[builtins.str], None]"
[builtins fixtures/list.pyi]

[case testNewRedefinePartialGenericTypes]
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