Double dot, potential issue?

[Czajnikowski]

Hey guys,

I encountered a (strange?) behavior while working with that nice package.

Take a look at this code:

enum A {
    case b(B)
    case void
}

enum B {
    case void
    case some(C)
}

enum C {}

func x() {
    let cp1 = /A.void       // correct: CasePath<A, Void>
    let cp2 = /A.b..B.some  // correct: CasePath<A, C>
    let cp3 = /A.b..B.void  // build failed: Binary operator '..' cannot be applied to operands of type 'CasePath<A, B>' and 'B'
}

Shouldn't cp3 be a valid CasePath<A, Void> as well 🤔?

[Czajnikowski]

I just figured out that I can work around it by wrapping the B.void in a closure (let cp3 = /A.b..{ B.void })

[stephencelis]

Glad you worked it out!

One thing to note is that while we have embraced the / prefix operator, the other operators in the library have been exercised far less and we didn't think it was good to overload them more than they already are for the permutations we support.

For now we recommend using .appending(path:) for building up case paths. It's a little more verbose, but fights the language and compiler less:

(/A.b).appending(path: /B.void)

[Czajnikowski]

Alright, thanks for the hint!