Fix availability checking for stored properties and enum cases with associated values #36327
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@xymus I suspect there are some similar edge cases with SPI that need to be straightened out. |
…the deployment target
This cannot be supported for the same reasons struct and class stored properties with potential unavailability cannot be supported. It is possible that some users relied on this, because it worked in some cases where the type metadata for the potentially unavailable type was not actually needed for anything (eg, if the type was @Frozen and trivial, or a simple class reference). If this becomes an issue we can downgrade this to a warning. Note that just like the previous fix for stored properties, we do still allow writing an '@available' attribute on the enum element if the OS version is not any newer than the deployment target. This allows annotating APIs with the OS version where they were introduced.
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@swift-ci Please test |
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@swift-ci Please test source compatibility |
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Build failed |
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@swift-ci Please test Linux |
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I believe the second commit message should say "as new as the enclosing availability context"? |
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In swiftlang#36327, trying to compile library code where a struct has an unavailable stored property or an enum with an unavailable case with associated values was made into a hard error. Update the docs to reflect this limitation for library authors shipping new versions of dylibs to older OSes.
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@slavapestov Why It Not work in Xcode14-beta now?
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The old behavior:
@availableat all.@availablewithout restriction.When computing the in-memory layout of a type we require that all stored types are available at runtime, that is, not any newer than the intersection of the current deployment target and the availability context of their type.
This means that stored properties and enum elements with associated values must have the same availability checking behavior as each other, and also that both existing behaviors were wrong.
The new rule is that
@availableis only allowed on either kind of declaration if the OS version is not any newer than the enclosing availability context.