I'm sure that, if you're carrying a torch for Haskell, TypeScript can feel very primitive--though I don't enjoy writing Haskell, in my experience it turns into an exercise in navel-gazing and write-only code compared to TypeScript or F#--but on the other hand normal people can write it and be productive and that's kind of important, yeah? I think the TS folks did a great job in making something that I can bring into engineering shops to make average to average-plus developers significantly better and significantly safer.

I'd really disagree with the notion that discriminated unions/ADTs are useless; the compiler is clever and will constrain the type in an `if` or a `switch` (particularly useful with an enum type, too). I use this regularly and it's really effective; my `nestjs-auth` library makes it more or less a requirement and its users seem to really dig it. And if you do it as an abstract class instead of a key, you can use polymorphism to take care of a lot of what would otherwise be pretty clunky--this is how you can make a solid maybe/option type in the vein of Scala.