🌸[NFC] [PrintAsClang] Add tiebreaking rule to sort #74643
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beccadax
commented
Jun 22, 2024
beccadax
commented
- Explanation: Adds additional sort rules to PrintAsClang to eliminate nondeterministic behavior in generated headers.
- Scope: Affects projects using generated headers (-Swift.h headers) in both ObjC and C++ modes. Should only cause different behavior in edge cases where two declarations would previously have been printed in an arbitrary order.
- Issue: rdar://129485103
- Original PR: [NFC] [PrintAsClang] Add tiebreaking rule to sort #74597
- Risk: Low. The new rules mean that the compiler will now process declarations in a consistent order when it would otherwise have processed them in an arbitrary order. The logic that ensures types are declared before they're used has not been changed, so this should make no semantic difference—it just helps ensure consistency.
- Testing: Includes new unit tests.
- Reviewer: @tshortli and @nkcsgexi
Because the underlying API for fetching top-level decls returns them in an unspecified order, PrintAsClang sorts the decls before printing them to make the output order more stable. However, the rules currently implemented have at least one known defect (they compare only the unqualified name of a nested class, so two nested classes with the same Swift name sort in an arbitrary order), and there are likely many more. Add a fallback rule which sorts declarations by their mangled name; this should at least distinguish all non-colliding ValueDecls from each other, albeit according to fairly opaque criteria. Additionally add a rule to help distinguish extensions with very similar content, and tweak other logic so that the comparison function is less likely to give up early rather than continuing to look for a usable difference. Fixes rdar://129485103.
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@swift-ci please test |
nkcsgexi
approved these changes
Jun 24, 2024
beccadax
changed the title
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