RefUpdateDuringRollback.scala

package foo

import scala.concurrent.stm._

object Test {
  def main(args: Array[String]): Unit = {
    var b = true

    atomic { implicit tx =>
      println("atomic")
      test() {
        println(s"b = $b")
        if (b) {
          b = false
          Txn.retryFor(1000)
        }
      }
    }
    sys.exit()
  }

  val ref = Ref(0)

  def test[A]()(thunk: => A)(implicit tx: InTxn): A = {
    val old = ref.swap(1)
    try {
      thunk
    } finally {
      ref() = old   // seems this is fine even during roll-back
    }
  }
}