loop: while true {
    let cbl = onlyCallback()
    switch (cbl.firstCallback, cbl.furtherCallbacks) {
    case (.none, _):
        break loop
    case (.some(let ocb), .none):
        onlyCallback = ocb
        continue loop
    case (.some(_), .some(_)):
        var pending = cbl._allCallbacks()
        while let f = pending.popFirst() {
            let next = f()
            next.appendAllCallbacks(&pending)
        }
        break loop
    }
}

swift-nio/Sources/NIO/EventLoopFuture.swift:88:13: warning: will never be executed
            loop: while true {
            ^
swift-nio/Sources/NIO/EventLoopFuture.swift:88:25: note: condition always evaluates to true
            loop: while true {
                        ^