Revisiting Union Types in Swift for typed throws

[tera]

@GreatApe

As much as I like the idea in principle, I seem to remember the core team being very explicitly against it.

Yeah, it's in frequently rejected proposals.

@GreatApe

But also, how would you catch the errors?

I guess like so:

do {
	try load()
} catch let error as NetworkError {
    ...
} catch let error as OtherError {
    ...
}

@GreatApe

Would the union of two error enum behave like a bigger enum, with all cases from both enums, meaning you don’t have to un-nest them when catching them?

Union types could be implemented as if they were written:

enum AnonymousUnionType_123 {
    case case1(NetworkError)
    case case2(DecodingError)
}

automatically wrapped / unwrapped by the compiler, so you won't see or use them as enum.