Fix crash overriding partial-type attribute with method #12943
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Attributes can still be partially typed (e.g. `<partial list[?]>`) after a parent-class definition if the block they are declared in is deferred. The first pass for child classes might then encounter this type when considering method overrides, which could cause a crash when attempting to determine subtype compatibility.
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According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉 |
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Hi all - apologies for the bump, I just wanted to ask if this bug fix is being considered? Thanks! |
JukkaL
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Jul 8, 2022
Gobot1234
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Aug 12, 2022
Attributes can still be partially typed (e.g. `<partial list[?]>`) after a parent-class definition if the block they are declared in is deferred. The first pass for child classes might then encounter this type when considering method overrides, which could cause a crash when attempting to determine subtype compatibility. Fixes python#11686 Fixes python#11981
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Description
Attributes can still be partially typed (e.g.
<partial list[?]>) aftera parent-class definition if the block they are declared in is deferred.
The first pass for child classes might then encounter this type when
considering method overrides, which could cause a crash when attempting
to determine subtype compatibility.
This patch causes the subtype checker to defer the override test if the original type is still partial, avoiding the crash. The correct error messages are still reported after this. This is the same approach as suggested by #11686 (comment), but the test case is different to the original issue. The original reproducer involved
@property, which runs afoul of #4125, and a full fix there is likely better part of #7724. The behaviour is not caused by@propertyitself, though, but any method overriding a value with partially inferred type.Fixes #11686
Fixes #11981
Test Plan
Added test case to
check-classes.test.