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Class attribute that duplicates a base class attribute is not flagged #1338
Description
The following is not an error currently:
class C:
a = None # type: int
class D(C):
a = None # type: int # No error
(Even though repeating the definition in C does cause an error.)
Worse, there's not even a check that the types match:
class C:
a = None # type: int
class D(C):
a = None # type: str # Still no error
Activity
JukkaL commentedon Apr 7, 2016
Mypy should verify that class attributes are compatible with any definitions in a base class. The latter is clearly a bug. The first one should be disallowed as well, for consistency with other variable definitions. However, just an assignment without a declared type should be okay even if the attribute is defined in a base class, but mypy should verify that the assigned value is compatible with the base class definition.
gvanrossum commentedon Apr 7, 2016
I wonder if it's worth a note or warning if you redefine an attribute (with the same type) in a subclass? When seen as documentation, I found this confusing.
For class variables, lookup type in base classes (#1338, #2022, #2211) (
Revert "For class variables, lookup type in base classes (#1338, #2022,
Revert "For class variables, lookup type in base classes (#1338, #2022,
For class variables, lookup type in base classes (#1338, #2022, #2211) (
gvanrossum commentedon Jan 27, 2017
Fixed by #2510.