Swift 6 Concurrency warnings

Using Swift
1

I'm using Xcode 26.1 and encountering a Swift concurrency warning related to an enum's protocol conformance.

I have the following APIEndpoint protocol and the Endpoint enum that conforms to it:

protocol APIEndpoint {
    var baseURL: URL { get }
    var path: String { get }
    var method: HTTPMethod { get }
    var headers: [String: String]? { get }
    var body: Data? { get }
}

enum Endpoint: APIEndpoint { 
    // ... implementation details ... 
}

I also have a generic URLSessionAPIClient<EndpointType: APIEndpoint> class.

When initializing this client in a unit test class context: apiClient = URLSessionAPIClient<Endpoint>(session: MockURLSession())

I receive the warning: **Main actor-isolated conformance of 'Endpoint' to 'APIEndpoint' cannot be used in nonisolated context; this is an error in the Swift 6 language mode
**
My question is: Why is Endpoint's conformance to APIEndpoint being considered MainActor-isolated, and what is the proper fix? I'd prefer a solution that avoids marking the entire unit test class with @MainActor or adding nonisolated to the Endpoint enum itself, as these seem like workarounds.

1 Like
2

Check your "Default actor isolation" build setting, it's likely set to MainActor, as that's the default for new projects in Xcode 26.

4 Likes
3

Thanks so much for this new info for me.