Is there any reason that arrows `either` builder has to be called from a suspending context? It seem...

# arrow

[asdf asdf]

Is there any reason that arrows either builder has to be called from a suspending context? It seems to work fine with a non-suspending implementation like this:

fun main() {
    val res = nonSuspendingEither {
        if (Random.nextBoolean()) shift(AuthResult.Success(534))
        else AuthResult.Failure("Invalid")
    }
    println(res)
}

@RestrictsSuspension
interface RestrictedEffectScope<E> : EffectScope<E>

fun <E, A> nonSuspendingEither(closure: suspend RestrictedEffectScope<E>.() -> A): Either<E, A> {
    var result: Either<E, A>? = null
    val scope = object : RestrictedEffectScope<E> {
        override suspend fun <B> shift(r: E): B {
            result = Either.Left(r)
            return suspendCoroutine { /*no-op*/ }
        }
    }
    closure.startCoroutine(scope, Continuation(EmptyCoroutineContext) {
        result = Either.Right(it.getOrThrow())
    })
    return result!!
}

[simon.vergauwen]

Hey @asdf asdf,
This is an implementation detail in 1.1.x, and you can use either.eager to achieve the same as you do here with @RestrictSuspension. In fact the implementation is 99% the same.

However in 1.2.x we've simplified this, and either is simply inline fun there. You can use it in 1.1.6-alpha.59, it's source compatible with 1.1.x given some extra imports 😉

[asdf asdf]

Neat, thanks!