given:

public class X1 {
    sealed interface I permits C1 {}
    non-sealed class C1 implements I {}
    class C2 extends C1 {}
    class C3 {}
    I m2(int s, C3 c3) {
        return switch (s) {
            case 0 -> (I) c3;
            default -> null;
        };
    }
}

javac is failing to determine that C3 and I are disjoint and thus C3 is not castable to I

reported by Stephan Herrmann:
https://mail.openjdk.org/pipermail/compiler-dev/2024-October/028344.html