// check: VerificationError
// check: MoveLocUnavailableError

main() {
    let x: u64;
    let y: u64;
    let b: bool;
    x = 0;
    b = true;
    while (true) {
        if (copy(b)) {
            y = move(x);
        } else {
            x = move(y);
        }
        b = false;
    }
    return;
}