@MainActor 
struct Bar {
  init() { 
    print("bar init is main", Thread.isMainThread) 
  } 
  func barCall() { 
    print("bar call is main", Thread.isMainThread) 
  } 
} 

@MainActor 
struct Foo { 
  @MainActor 
  static let global = Foo() 

  init() { 
    print("foo init is main", Thread.isMainThread) 
    let b = Bar() 
    b.barCall() 
  } 

  func fooCall() { 
    print("foo call is main", Thread.isMainThread) 
  } 

} 

Task.detached { 
  await Foo.global.fooCall() 
} 
// prints: 
// foo init is main false 
// bar init is main false 
// bar call is main false 
// foo call is main true