[cies]

> underappreciated

widely used though. not sure if that count for appreciation, but i think it's one of the highest forms.

it's not bad, not not great either. i miss proper sum types, and it really lament the fact that static things are nearly impossible to be mocked which prompts everyone to use DI for everything instead of static.

[za3faran]

Java has sum types now with sealed interfaces and pattern matching. Records have detructoring out of the box, and I believe supporting it for general classes is in the works.

[cies]

I think sealed interfaces it not quite the same as "tagged unions"-style enum's with payloads.

Also, it does not matter much anymore, the whole std-lib is full of exceptions-to-implement-multiple-return-values.

[za3faran]

    sealed interface Shape {}
    record Square(int x) implements Shape {}
    record Rectangle(int l, int w) implements Shape {}
    record Circle(int r) implements Shape {}
    
    double getArea(Shape s) {
        // Exhaustively checks for all alternatives.
        return switch (s) {
            case Square(var x) -> x * x;
            case Rectangle(var l, var w) -> l * w;
            case Circle(var r) -> Math.PI * r * r;
        }
    }

This is a good article: https://mccue.dev/pages/11-1-21-smuggling-checked-exceptions

[cies]

Loved the article. Thanks for sharing. Maybe I (coming from Haskell and Elm) should not be bothered too much with the verbosity of Java/Kotlin "sum types" :)