function-local struct def can never be Comparable?

Question

Created Mar ’21

Replies 4

Boosts 0

Participants 2

If i have a struct inside a function, swift keeps telling me is doesn't conform to Comparable, even though the same definition is fine outside of a function -- why is this?

Foo fails Comparable here:

func foo() {
struct Foo : Equatable, Comparable {
let x: Int
let y: Int
static func < (lhs: Foo, rhs: Foo) -> Bool {
return lhs.x+lhs.y < rhs.x+rhs.y
}
}
}

Boost

Answer 1

OOPer OP

Mar ’21

even though the same definition is fine outside of a function

Your code lacks the definition of ==, so it is not fine even in outside of a function.

Code Block func foo() {
    struct Foo : Equatable, Comparable {
        let x: Int
        let y: Int
        
        static func < (lhs: Foo, rhs: Foo) -> Bool {
            return lhs.x+lhs.y < rhs.x+rhs.y
        }
        static func == (lhs: Foo, rhs: Foo) -> Bool {
            return lhs.x+lhs.y == rhs.x+rhs.y
        }
    }
}

I can find Swift compiler shows error even with this code, but the same definition is fine outside of a function would be needed to state that something weird is going on.

I could not find why nor what some notes added to the error message mean, like `Candidate would match if 'Foo' conformed to 'FloatingPoint' and so on.

You should better ask in the forums.swift.org, or send a bug report to bugs.swift.org .

0

Answer 2

remsleep OP

Mar ’21

Thanx -- i've asked on forums.swift.org

0

Answer 3

remsleep OP

Mar ’21

Confirmed - it's a known bug. SR-3092

1

Answer 4

OOPer OP

Mar ’21

Thanks for sharing the info.

0