Emit [mutable-override] for covariant override of attribute with method by brianschubert · Pull Request #18058 · python/mypy (original) (raw)

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Fixes #18052

Given:

flags: --enable-error-code=mutable-override

from typing import Callable

class Parent: func: Callable[[str], None]

class Child(Parent): def func(self, x: object) -> None: pass

Before:

Success: no issues found in 1 source file

After:

main.py:7 error: Covariant override of a mutable attribute (base class "Parent" defined the type as "Callable[[str], None]", override has type "Callable[[object], None]")
Found 1 error in 1 file (checked 1 source file)

According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅

2 participants