lets_build_a_coroutine__coroutine.kt

abstract class Coroutine {
    var isFinished: Boolean = false
        private set

    protected val state: State by lazy { State() }

    protected fun resumeWith(result: Any) {
        state.label++
        state.result = result
    }

    protected fun <T> restore(): T {
        return state.result as T
    }

    protected fun finish() {
        state.label++
        isFinished = true
    }

    protected class State(
        var label: Int = 0,
        var result: Any? = null
    )
}