[4.2 EARLY] Hack: Force UIEdgeInsets.zero to always come from the SDK #17149
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…17122) ...instead of relying on the one in the overlay in pre-4.2 versions of Swift. This caused crashes in deserialization, which (deliberately) doesn't respect availability. There are three changes here: - Remove UIEdgeInsets.zero and UIOffset.zero from the UIKit overlay. - Always use the 4.2 name for UIEdgeInsetsZero and UIOffsetZero from the underlying UIKit framework. (This is the nested name.) - Ignore the unavailability messages for those two constants in pre-4.2 Swift, since we're now relying on them being present. The latter two, the compiler changes, can go away once UIKit's API notes no longer specify different pre-4.2 behavior, but meanwhile we need to keep compatibility with the SDKs released in Xcode 10b1. https://bugs.swift.org/browse/SR-7879 (cherry picked from commit a6ae2d7)
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@swift-ci Please test |
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@swift-ci Please test source compatibility |
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@swift-ci Please nominate |
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The source compat failures are the 20 projects that are XFAILed on master. Merging. |
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Explanation: The UIKit overlay has long had convenience properties
UIEdgeInsets.zeroandUIOffset.zero, as Swiftier versions of constants in the UIKit framework UIEdgeInsetsZero and UIOffsetZero. In the iOS 12 SDK, we (Apple) tried to switch over to using the real C constants, since there's no need to duplicate the logic in Swift. However, trying to keep both declarations around but with different availability led to a crash in deserialization, which (deliberately) doesn't respect availability. Instead, let's go all the way to using the framework declarations…even though that means hacking the importer a little to pretend that UIKit's already updated their API notes.Scope: Affects UIEdgeInsetsZero and UIOffsetZero only.
Issue: SR-7879 / rdar://problem/40735990
Risk: Low. This is a targeted hack with very little chance of affecting anything else, and it should not make things worse either.
Testing: Added compiler regression tests.
Reviewed by: @moiseev