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[SR-2704] T: Protocol generic constraint doesn't accept protocol existentials #45308

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swift-ci opened this issue Sep 20, 2016 · 0 comments
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@swift-ci swift-ci commented Sep 20, 2016

Previous ID SR-2704
Radar None
Original Reporter chadaustin (JIRA User)
Type Bug
Status Resolved
Resolution Duplicate
Environment

swift 3.0, both in xcode 8 and in the swiftc 3 toolchain.

Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug, TypeChecker
Assignee None
Priority Medium

md5: 2e6e3deb4b4efc9e73cefa9c355867b0

duplicates:

  • SR-55 non-@objc protocol existentials do not conform to their own protocol type

Issue Description:

I would expect the following to compile. The protocol used as an existential type should also conform to the constraint given in the generic function concrete.

However, it gives the error: error: cannot invoke 'concrete' with an argument list of type '(P)'

protocol P {
    func go()
}

extension String: P {
    func go() {
        print("String")
    }
}
extension Int: P {
    func go() {
        print("Int")
    }
}

func concrete<T: P>(_ a: T) {
    a.go()
}

func abstract(a: P) {
    concrete(a)
}
@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
This issue was closed.
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