Fix Swift snapshot build: don't reference withAUAudioUnit#1039
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…ilds) The Swift main-snapshot build (newer compiler + current stable macOS SDK) fails with "cannot find 'withAUAudioUnit' in scope": `#if compiler(>=6.4)` selects the `withAUAudioUnit` branch, but that symbol only exists in the macOS 27 SDK, and the snapshot toolchain pairs a >=6.4 compiler with the macOS 26 SDK. There's no reliable compile-time SDK / API-presence check in Swift (`canImport(_:_version:)` doesn't distinguish the SDKs), so drop `withAUAudioUnit` and reach `auAudioUnit` — which exists on every SDK — under `if #available(macOS 13.0)`, falling back to `LKObjCHelpers` below macOS 13. `#if compiler(>=6.4)` is kept only so older toolchains use the property directly (no ObjC shim) down to macOS 10.13. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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hiroshihorie
approved these changes
Jun 10, 2026
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Summary
Follow-up to #1038. The nightly Swift Snapshot Build (
.github/workflows/swift-snapshot.yaml) fails onmainafter #1038:Root cause
That workflow runs
swift buildwith the main-snapshot compiler (so#if compiler(>=6.4)is true) but against the runner's current stable SDK (macOS 26 —latestXcode, since 27 is still beta).withAUAudioUnitonly exists in the macOS 27 SDK, so thecompiler(>=6.4)branch compiles the symbol in, but the SDK doesn't have it.The deeper issue:
#if compiler(>=6.4)is a compiler check used as an SDK proxy. That holds for shipping Xcode (compiler and SDK ship together) but not for the snapshot toolchain (new compiler + stable SDK). There's no reliable compile-time SDK/API-presence check in Swift —canImport(AVFAudio, _version:)reports the same version in both SDKs, and keying off a new-in-27 framework would be fragile.Fix
Drop
withAUAudioUnitand reachauAudioUnit— which exists on every SDK (only its Swift availability annotation differs) — underif #available(macOS 13.0), falling back toLKObjCHelpersbelow macOS 13.#if compiler(>=6.4)is kept so older toolchains (Xcode 16.4 / 26.5) use the property directly with no ObjC shim down to macOS 10.13.This compiles on every compiler/SDK combination, including the snapshot's newer-compiler + macOS 26 SDK.
Testing
swift build --build-system nativewith the Xcode 27 compiler + macОS 26 SDK (reproduces the snapshot combo): Build complete ✅ (was:cannot find 'withAUAudioUnit').No user-facing behavior change (the
auAudioUnitaccess is functionally identical), so no changeset.🤖 Generated with Claude Code