static async Eff Test()
{
var x = await NonDetEffect.Choose(1, 2, 3);
var y = await NonDetEffect.Choose("one", "two", "three");
var z = await NonDetEffect.Choose(false, true);
Console.WriteLine($"x = {x}, y = {y}, z = {z}");
}
static async Eff <(int, string, bool)> Test()
{
var x = await NonDetEffect.Choose(1, 2, 3);
var y = await NonDetEffect.Choose("one", "two", "three");
var z = await NonDetEffect.Choose(false, true);
return(x, y, z);
}