swift-concurrency-expert

# Swift Concurrency Expert ## Overview Review and fix Swift Concurrency issues in Swift 6.2+ codebases by applying actor isolation, Sendable safety, and modern concurrency patterns with minimal behavior changes. ## When to Use - When the user asks to review Swift concurrency usage or fix compiler diagnostics. - When you need guidance on actor isolation, `Sendable`, `@MainActor`, or async migration. ## Workflow ### 1. Triage the issue - Capture the exact compiler diagnostics and the offending symbol(s). - Check project concurrency settings: Swift language version (6.2+), strict concurrency level, and whether approachable concurrency (default actor isolation / main-actor-by-default) is enabled. - Identify the current actor context (`@MainActor`, `actor`, `nonisolated`) and whether a default actor isolation mode is enabled. - Confirm whether the code is UI-bound or intended to run off the main actor. ### 2. Apply the smallest safe fix Prefer edits that preserve existing behavior while satisfying data-race safety. Common fixes: - **UI-bound types**: annotate the type or relevant members with `@MainActor`. - **Protocol conformance on main actor types**: make the conformance isolated (e.g., `extension Foo: @MainActor SomeProtocol`). - **Global/static state**: protect with `@MainActor` or move into an actor. - **Background work**: move expensive work into a `@concurrent` async function on a `nonisolated` type or use an `actor` to guard mutable state. - **Sendable errors**:...