https://stackoverflow.com/a/79019679/1271826

TypedErrorBug.swift

enum MyError: Error {
    case one
    case two
}

struct MyTest {
    private func funcWithTypedThrow() async throws(MyError) {…}

    // example where typed-throw incorrectly concludes catch is not exhaustive
    
    func foo() async {
        do {
            try await funcWithTypedThrow() // Swift 6.0 compiler incorrectly produces error: “Errors thrown from here are not handled because the enclosing catch is not exhaustive”
        } catch .one {
            print("one")
        } catch .two {
            print("two")
        }
    }

    // example where we add extra `catch`, but compiler now recognizes that is unnecessary
    
    func bar() async {
        do {
            try await funcWithTypedThrow()
        } catch .one {
            print("one")
        } catch .two {
            print("two")
        } catch {  // Swift 6.0 compiler correctly produces warning: “Case will never be executed”
            print("this is required to silence 'non-exhaustive' warning")
        }
    }
}

If you used typed-throwing, Swift 6.0 (in Xcode 16.0) will understand that the error is MyError, but incorrectly concludes that the catch blocks are not exhaustive (see foo). However, if you add a catch block to silence that incorrect error (in bar), it now correctly recognizes that this extra catch is unnecessary and “will never be executed.”