Functions can be polymorphic in their effectfulness, so the coloring problem isn't. Functions only become incompatible where you've made them incompatible on pu

Functions can be polymorphic in their effectfulness, so the coloring problem isn't. Functions only become incompatible where you've made them incompatible on purpose - the whole point of annotating functions' effectfulness is to statically know you're not accidentally invoking particular effects where you promised you wouldn't.