import Foundation

final class BlockRunner {
  var block: () -> ()
  init(_ b: @escaping () -> ()) { block = b }
  func run() { block() }
  deinit { print("Deinit: \(self)") }
}

final class BlockExperiment {
  func f() { 
    let queue = DispatchQueue(label: "Queue")
    let runner = BlockRunner { print("hello", self, "world") }
    queue.asyncAfter(deadline: .now() + 1) { runner.run() }
  }
  deinit { print("Deinit: \(self)") }
}

do {
  let e = BlockExperiment()
  e.f()
  RunLoop.current.run(until: Date() + 1 + 0.000000000000001)
}