interface Script

// Builder to help describe a script.
interface ScriptBuilder {
  fun doSomething()

  // A script can call other scripts, including itself.
  fun callSubscript(script: Script)

  fun doSomethingElse()
}

fun Script(builder: ScriptBuilder.() -> Unit): Script {
  TODO()
}

val firstScript = Script {
  doSomething()
}

val secondScript = Script {
  doSomethingElse()

  // This compiles:
  callSubscript(firstScript)

  // This does not compile because "Variable secondScript must be initialized":
  callSubscript(secondScript)
}

// If a contract allowed the `Script` function to specify that its builder will not be invoked
// before the function returns, then a script could use itself inside its builder lambda because
// the compiler can infer that the variable is initialized (given that its initializing method
// `Script` will have returned, by contract).
fun Script2(builder: ScriptBuilder.() -> Unit): Script {
  contract {
    callsInPlace(builder, InvocationKind.LAZY)
  }
  TODO()
}