zio-deadlock.scala

import zio._
import zio.syntax._

// ZIO version 2.12-1.0.0-RC9.4

object Deadlock {

  val runtime = new DefaultRuntime {}

  trait Logger {
    def log(s: AnyRef): Unit = println(s)
  }

  // changing either lazy val to def remove the deadlock.

  trait Log {
    // this one
    lazy val logEffect = new Logger(){}
    // here, this does not block: ... = IO.effect(logEffect.log(msg)).ignore
    // but this blocks: ... = IO.yieldNow *> IO.effect(logEffect.log(msg)).ignore
    final def info (msg: => AnyRef) =  zio.blocking.effectBlocking(logEffect.log(msg)).ignore
  }

  class Blocking extends Log {
    def test = info("in test") *> "oups".succeed
    // or this one
    lazy val block = {
      runtime.unsafeRun(test.either) match {
        case Right(value) => "yes"
        case Left(value)  => "no"
      }
    }
  }
  def main(args: Array[String]): Unit = {
    println("start")
    val blockling = new Blocking()
    println("blocking created")
    println(blockling.block)
    println("never reaches end")
  }
}