Nullness :: Improvement :: Overrides of generic methods with nullable type instantiations #18337
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T-Gro
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psfinaki
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Feb 24, 2025
abonie
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T-Gro
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Fixes #17988
In the object model, overrides for originally nullable slots can narrow the return type from nullable to not-null.
This was added especially in the context of
ToString(), which is by default nullable, but most common implementation just return string.However, the relaxation from a
Withnullreturn type to a nullness inference variable has been done even for generic code, one that has been explicitely instantiated with a nullable type in place forT.This changes the "nullable relaxation for overrides" to stop applying in the case of generic return types (i.e. it will not attempt to relax those, and instead keep the exact type which was passed in.).