No? I think you're confusing ADT with a Typescript-like type system. Adding language support for ADT is not really a warrant for an "enough DOF to become scary

No? I think you're confusing ADT with a Typescript-like type system. Adding language support for ADT is not really a warrant for an "enough DOF to become scary" sticker. I find modern Java surprisingly pretty good at capturing the essence of ADT without introducing way too much fancy stuff. Modern Java supports ADT via `sealed` classes (sum types) and `record` (product types). For working with ADT classes, modern Java provides exhaustive `switch` expression and `record` destructuring. That's enough for minimal "language ADT support". You still can't do Typescript's wacky operations like conditional / mapped types or type parameter recursion in Java. You can't do fancy Haskell's typeclasses here either. And it is certainly not turning Java's type system into a Turing-complete type system at all.