Abort trap 6/nonzero exit code

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1

This code causes abort trap 6 in Xcode 13 and in Xcode 14 beta 6 causes "Command CompileSwift failed with a nonzero exit code"

///
protocol Wrapper {
    associatedtype Wrapped
    var wrapped: Wrapped { get }
}

///
struct SimpleWrapper <Wrapped>: Wrapper {
    var wrapped: Wrapped
}

///
func unwrap <T: Wrapper> (_ wrapper: T) -> T.Wrapped {
    wrapper.wrapped
}

///
extension Wrapper where Self == SimpleWrapper<Wrapped> {
    static func simple (_ value: Wrapped) -> Self {
        SimpleWrapper<Wrapped>(wrapped: value)
    }
}

///
func demo () -> Int {
    unwrap(.simple(0))
}

Even better than giving a more helpful error message would be that this code compiled and worked :pray: I think I see what about it makes it tricky, but I also think I see no logical holes, i.e., in theory, logically speaking, this code could work, not speaking to how much compiler development would remain to be done.

2

On the latest 5.7 nightly build and main I see:

17:19: error: same-type constraint 'Self' == 'SimpleWrapper<Self.Wrapped>' is recursive
extension Wrapper where Self == SimpleWrapper<Wrapped> {
                  ^
5:5: error: type of expression is ambiguous without more context
    unwrap(.simple(0))
    ^~~~~~~~~~~~~~~~~~

On Xcode 14 RC it does result in a crash.

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