swift-concurrency-6-2

Swift 6.2 keeps async functions on the calling actor by default, so most data-race errors disappear once you enable the approachable concurrency build settings. For remaining issues, annotate shared state with @MainActor or offload heavy work explicitly with @concurrent.

Mark the containing type as nonisolated, add @concurrent to the function, ensure it is async, and use await at call sites. This explicitly moves work like image processing to the concurrent thread pool while the rest of your code stays on the calling actor.

An isolated conformance lets a MainActor type conform to a non-isolated protocol by writing extension MyType: @MainActor SomeProtocol. The compiler guarantees the conformance is only used on the main actor, producing an error if accessed from a nonisolated context.

No. Swift 6.2 changed the default so async functions stay on the calling actor instead of being implicitly offloaded to background threads. Background execution now requires an explicit @concurrent annotation.

Enable it through the Swift Compiler Concurrency build settings in Xcode, or use the SwiftSettings API in your Package.swift manifest. The mode is opt-in and recommended for apps, scripts, and other executable targets.

Avoid applying @concurrent to every async function, since most code does not need background execution. Reserve it for CPU-intensive work like image processing or compression, and profile with Instruments first to confirm actual bottlenecks.