/** Fails to compile on purpose: a pattern switch over a sealed type must cover every permitted subtype. */
public class NonExhaustive {
    sealed interface S permits A, B {}
    record A() implements S {}
    record B() implements S {}
    static String f(S s) { return switch (s) { case A a -> "a"; }; }
    public static void main(String[] args) { }
}