Identify the error in the following PHP code that tries to resolve trait method conflicts:

Identify the error in the following PHP code that tries to resolve trait method conflicts:

trait X {
    public function test() {
        return "X";
    }
}
trait Y {
    public function test() {
        return "Y";
    }
}
class Demo {
    use X, Y {
        test insteadof X, Y;
    }
}