alt Hacker NewsI don't think it's horrible, but I really do wish they would copy TypeScript here.
Let me do this:
const x: String | Int
enum MyEnum {
case string(String)
case int(Int)
}
https://forums.swift.org/t/re-proposal-type-only-unions/7270...
Replies
kibwen • today at 1:38 AM
Note that union types are not the same thing as sum types, even if they're somewhat similar. https://viralinstruction.com/posts/uniontypes/
It's worth pointing out that the two examples that you're writing are actually strictly different, and not just "better syntax for the same thing". (This is assuming `String | Int` works as in Python, and the second example works as in Rust.)
To understand the difference, `String | String` is just `String`. It's a union, not a sum type. There's no tag or identifier, so you cannot distinguish whether it's the first or the second string.
If this sounds pedantic, this has pretty important ramifications, especially once generics get involved.