[pharmakom]

> Java’s exceptions are pretty much the exact same sum type as in Rust, just with added syntactic sugar.

Except Java doesn’t actually return a result object that can be assigned to a variable by default.

[kaba0]

And in case of exceptions, why would that be useful?

(For other things, I agree that sum types are cool, and fortunately are supported in Java through sealed classes)

[pharmakom]

I don’t think sealed classes offer exhaustive pattern matching. Instead you have an if-else ladder of instanceof checks. This is not the same as most union type implementations.

[kaba0]

They do with switch expressions. It is only type based for now, but deconstructs are coming with full blown pattern matching a la Haskell.