The most important feature of an effect typing system is that it's a pain in the ass. More technically, the complexity of effects is (usually) infectious so a t

The most important feature of an effect typing system is that it's a pain in the ass. More technically, the complexity of effects is (usually) infectious so a type system either lies to you about effects or is really obnoxious. The upshot of either thing is that you're heavily encouraged to shatter code into the purest composable fragments you can discover.