A test for the resolution of the `@MainActor` wrapper in Swift

main.swift

import Foundation

protocol AProtocol {
    func printIsMainThread()
}

struct AStruct: AProtocol {
    @MainActor
    func printIsMainThread() {
        print("(struct) isMainThread=\(Thread.isMainThread)")
    }
}

class AClass: AProtocol {
    @MainActor
    func printIsMainThread() {
        print("(class) isMainThread=\(Thread.isMainThread)")
    }
}

actor AnActor {
    // by uncommenting the protocol type, the method will not be called on the main thread.
    let aStructInstance/*: AProtocol*/ = AStruct()
    let aClassInstance/*: AProtocol*/ = AClass()
    
    func run() async {
        await aStructInstance.printIsMainThread()
        await aClassInstance.printIsMainThread()
    }
}

@main
struct App {
    static let anActorInstance = AnActor()
    
    static func main() async {
        await anActorInstance.run()
    }
}