layer-error.scala

package test

import zio._
import zio.console._

type FakeExchange = Has[FakeExchange.Service]

object FakeExchange:
   trait Service:
      def blah(): UIO[Unit]
   def blah(): ZIO[FakeExchange, Nothing, Unit] = ZIO.accessM(_.get.blah())
val fakeExchangeLayer: ZLayer[Any, Nothing, FakeExchange] = 
   ZLayer.succeed(new FakeExchange.Service {
      override def blah() = UIO.unit
   })
     
     
// main program
object Main extends zio.App:
   def run(args: List[String]) =
      val infra = ZLayer.requires[zio.console.Console] ++ ZLayer.requires[zio.clock.Clock] ++
         ZLayer.requires[zio.blocking.Blocking] ++ ZLayer.requires[zio.random.Random]    
      type TargetEnv = zio.console.Console & zio.clock.Clock & zio.blocking.Blocking
               & FakeExchange & zio.random.Random
      val finalLayer: ZLayer[zio.random.Random & zio.console.Console & zio.clock.Clock & zio.blocking.Blocking, Nothing, TargetEnv] = 
         infra >+> fakeExchangeLayer
      val program2: ZIO[TargetEnv, Nothing, Int] = ZIO.succeed(0)
      (putStrLn("running...") *> program2).provideCustomLayer(finalLayer).exitCode