Mysterious "Will never be executed" warning

I'm trying to understand "Will never be executed" warning here:

protocol FatalErrorReporterInterface {

    func fail(_ message: String) -> Never

}

final class FatalErrorReporter: FatalErrorReporterInterface {

    // This line emits "Will never be executed" warning
    func fail(_ message: String) -> Never {
        fatalError(message)
    }

}

Yet another compiler bug?