MainActor-isolated property not called on the Main Actor

[okla]

Description

Reproduction code works on both iOS and MacOS. Since SwiftUI.App.body is MainActor-isolated, nonIsolatedSyncProperty also called on the Main Actor because it's sync, but its task is non-isolated and called not on the Main Actor, but then it calls MainActor-isolated isolatedGlobalSyncProperty and it crashes because it's called not on the Main Actor for some reason.

Reproduction

import SwiftUI

@MainActor var isolatedGlobalSyncProperty: Void {
  MainActor.assertIsolated("Isolated global sync property called not on the Main Actor")
}

@main
struct SwiftConcurrencyApp: App {
  var nonIsolatedSyncProperty: some View {
    Text("Hello")
      .task {
        await isolatedGlobalSyncProperty
      }
  }

  var body: some Scene {
    WindowGroup {
      nonIsolatedSyncProperty
    }
  }
}

Expected behavior

isolatedGlobalSyncProperty called on the Main Actor.

Environment

swift-driver version: 1.90.11.1 Apple Swift version 5.10 (swiftlang-5.10.0.13 clang-1500.3.9.4)
Target: x86_64-apple-macosx14.0

Additional information

Reproduction code results in a crash with output: SwiftConcurrencyMac/SwiftConcurrencyMacApp.swift:11: Fatal error: Incorrect actor executor assumption; Expected 'UnownedSerialExecutor(executor: (Opaque Value))' executor. Isolated global sync property called not on the Main Actor