Summary
We ship a binary XCFramework that bundles OpenAPIURLSession (used internally for REST API calls), and that XCFramework is distributed to React Native developers who integrate it into their apps.
Because those developers build against our prebuilt binary with their own (often older) Xcode/Swift toolchains, we need module stability — i.e. BUILD_LIBRARY_FOR_DISTRIBUTION=YES — so the framework keeps working across compiler versions. That's exactly the configuration that propagates library evolution to OpenAPIURLSession and trips the errors above.
Building OpenAPIURLSession with library evolution enabled (-enable-library-evolution / BUILD_LIBRARY_FOR_DISTRIBUTION=YES) fails to compile on Xcode 26.5 / Swift 6.3. This happens when the package is a (transitive) dependency of a framework that is archived for binary distribution as an XCFramework. The same configuration compiled on earlier toolchains, so this is a regression triggered by the newer compiler's stricter enforcement.
Environment
- Xcode 26.5 (build 17F42)
- Apple Swift 6.3.2 (swiftlang-6.3.2.1.108, clang-2100.1.1.101)
swift-openapi-urlsession main (the constructs below are present in all 1.0.0–1.3.0 releases)
Errors
Sources/OpenAPIURLSession/BufferedStream/Lock.swift:190:5: error: deinitializer can only be '@inlinable' if the class is '@_fixed_layout'
Sources/OpenAPIURLSession/BufferedStream/Lock.swift:244:14: error: 'let' property '_storage' may not be initialized directly; use "self.init(...)" or "self = ..." instead
Sources/OpenAPIURLSession/BufferedStream/Lock.swift:322:14: error: 'let' property '_storage' may not be initialized directly; use "self.init(...)" or "self = ..." instead
Reproduction
swift build -Xswiftc -enable-library-evolution
Cause
In Sources/OpenAPIURLSession/BufferedStream/Lock.swift:
LockStorage (a final class) declares an @inlinable deinit.Lock and LockedValueBox (structs) declare @inlinable initializers that directly initialize their stored let _storage property.
Under library evolution, types have resilient (non-fixed) layout, so the compiler requires @_fixed_layout (class) / @frozen (struct) before allowing an @inlinable deinit or an @inlinable initializer that directly assigns a stored property.
Possible fixes
- Mark
LockStorage @_fixed_layout and Lock / LockedValueBox @frozen — keeps the @inlinable optimizations and requires no opt-in from consumers.
- Drop
@inlinable from those three members (negligible perf impact — a lock's deinit/init are not hot paths).
A PR follows with option (2) gated behind a compilation condition so the default build is byte-for-byte unchanged, but maintainers may prefer option (1).
Summary
We ship a binary XCFramework that bundles
OpenAPIURLSession(used internally for REST API calls), and that XCFramework is distributed to React Native developers who integrate it into their apps.Because those developers build against our prebuilt binary with their own (often older) Xcode/Swift toolchains, we need module stability — i.e.
BUILD_LIBRARY_FOR_DISTRIBUTION=YES— so the framework keeps working across compiler versions. That's exactly the configuration that propagates library evolution toOpenAPIURLSessionand trips the errors above.Building
OpenAPIURLSessionwith library evolution enabled (-enable-library-evolution/BUILD_LIBRARY_FOR_DISTRIBUTION=YES) fails to compile on Xcode 26.5 / Swift 6.3. This happens when the package is a (transitive) dependency of a framework that is archived for binary distribution as an XCFramework. The same configuration compiled on earlier toolchains, so this is a regression triggered by the newer compiler's stricter enforcement.Environment
swift-openapi-urlsessionmain(the constructs below are present in all 1.0.0–1.3.0 releases)Errors
Reproduction
Cause
In
Sources/OpenAPIURLSession/BufferedStream/Lock.swift:LockStorage(afinal class) declares an@inlinable deinit.LockandLockedValueBox(structs) declare@inlinableinitializers that directly initialize their storedlet _storageproperty.Under library evolution, types have resilient (non-fixed) layout, so the compiler requires
@_fixed_layout(class) /@frozen(struct) before allowing an@inlinabledeinit or an@inlinableinitializer that directly assigns a stored property.Possible fixes
LockStorage@_fixed_layoutandLock/LockedValueBox@frozen— keeps the@inlinableoptimizations and requires no opt-in from consumers.@inlinablefrom those three members (negligible perf impact — a lock's deinit/init are not hot paths).A PR follows with option (2) gated behind a compilation condition so the default build is byte-for-byte unchanged, but maintainers may prefer option (1).