[functools] Allow method override with @cache decorator
#15238
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Signed-off-by: Emmanuel Ferdman <emmanuelferdman@gmail.com>
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According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉 |
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PR Summary
When you use the
@cachedecorator on a method and then override that method in a subclass with a more specific return type, mypy incorrectly rejects it. For example, if a parent class has a cached method returningFruitand a child class overrides it to returnApple(a subclass ofFruit), this should be valid but wasn't. The fix changes_lru_cache_wrapperto use a covariant type parameter, which is safe because the type only appears in return positions. This matches howcached_propertyalready works in the same file.Fixes #15139.