[5.0] Extend transitive availability checking to initial value expressions #22516
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Because initial value expressions aren't actually considered /within/ the VarDecl or PatternBindingDecl they're initializing, the existing logic to search for availability attributes wasn't kicking in, leading to errors when a conditionally-unavailable value was used in an initial value expression for a conditionally-unavailable binding. Fix this by walking the enclosing type or extension to find the appropriate PatternBindingDecl. https://bugs.swift.org/browse/SR-9867 (cherry picked from commit 722cb83)
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@swift-ci Please test |
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@swift-ci Please test source compatibility |
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@swift-ci nominate |
AnnaZaks
approved these changes
Feb 12, 2019
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Explanation: A declaration marked unavailable on one platform is allowed to use other declarations marked unavailable on the same platform in its definition. This is especially important for the "application extension" platforms, which expose a subset of the API available on the base platform. However, changes to property initial value type-checking in Swift 5 made them fall outside of this rule. This commit (the important, non-refactoring part of Extend transitive availability checking to initial value expressions (better version) #22460) changes the availability checking logic to look for the associated property decl in an enclosing scope, which makes the code in SR-9867 work again.
Scope: Affects properties marked with
@availablethat use other declarations marked with@available.Issue: SR-9867 / rdar://problem/47852718
Risk: Low. This relaxes restrictions rather than adding them. It does search more of the AST, but only in a simple way based on source ranges.
Testing: Added compiler regression tests, passed source compatibility suite.
Reviewed by: @brentdax, @slavapestov