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SKILL.md
npx skills add dimillian/skills --skill swift-concurrency-expert
Swift Concurrency review and remediation for Swift 6.2+. Use when asked to review Swift Concurrency usage, improve concurrency compliance, or fix Swift concurrency compiler errors in a feature or file. Concrete actions include adding Sendable conformance, applying @MainActor annotations, resolving actor isolation warnings, fixing data race diagnostics, and migrating completion handlers to async/await.
npx skills add dimillian/skills --skill swift-concurrency-expert
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.
@MainActor, actor, nonisolated) and whether a default actor isolation mode is enabled.Prefer edits that preserve existing behavior while satisfying data-race safety.
Common fixes:
@MainActor.extension Foo: @MainActor SomeProtocol).@MainActor or move into an actor.@concurrent async function on a nonisolated type or use an actor to guard mutable state.Sendable conformance only when correct; avoid @unchecked Sendable unless you can prove thread safety.UI-bound type — adding @MainActor
Protocol conformance isolation
Background work with @concurrent
references/swift-6-2-concurrency.md for Swift 6.2 changes, patterns, and examples.references/approachable-concurrency.md when the project is opted into approachable concurrency mode.references/swiftui-concurrency-tour-wwdc.md for SwiftUI-specific concurrency guidance.// Before: compiler error — SomeProtocol method is nonisolated but the
// conforming type is @MainActor
@MainActor
class Foo: SomeProtocol {
func protocolMethod() { /* accesses main-actor state */ }
}
// After: scope the conformance to @MainActor so the requirement is
// satisfied inside the correct isolation context
@MainActor
extension Foo: SomeProtocol {
func protocolMethod() { /* safely accesses main-actor state */ }
}// Before: expensive computation blocks the main actor
@MainActor
func processData(_ input: [Int]) -> [Int] {
input.map { heavyTransform($0) } // runs on main thread
}
// After: hop off the main actor for the heavy work, then return the result
// The caller awaits the result and stays on its own actor
nonisolated func processData(_ input: [Int]) async -> [Int] {
await Task.detached(priority: .userInitiated) {
input.map { heavyTransform($0) }
}.value
}
// Or, using a @concurrent async function (Swift 6.2+):
@concurrent
func processData(_ input: [Int]) async -> [Int] {
input.map { heavyTransform($0) }
}