Delete a case and read the error

import java.math.BigDecimal;
import java.util.*;

/**
 * WARM-UP — 5 minutes. One concept. Hard to fail.
 *
 * A closed set of three payment types, and a switch with no default.
 *
 * TASKS
 *   1. Run it. Nothing surprising yet.
 *   2. Delete the `case Cash` line. Compile. Read the error out loud.
 *   3. Put it back. Now change describe's parameter from Payment to Object
 *      and compile again. Same error, different reason — work out which.
 *   4. Change it back, and answer in a comment: if this switch had a
 *      `default -> throw new IllegalStateException()`, what would step 2
 *      have produced instead of a compile error?
 */
public class Starter {

    sealed interface Payment permits Card, Upi, Cash {}

    record Card(String network, int lastFour) implements Payment {}

    record Upi(String handle) implements Payment {}

    record Cash(BigDecimal amount) implements Payment {}

    static String describe(Payment payment) {
        return switch (payment) {
            case Card(String network, int last) -> network + " ending " + last;
            case Upi(String handle) -> "UPI " + handle;
            case Cash c -> "cash " + c.amount();
        };
    }

    public static void main(String[] args) {
        List<Payment> payments = List.of(
                new Card("visa", 4242),
                new Upi("ravi@okhdfc"),
                new Cash(new BigDecimal("250.00")));

        for (Payment payment : payments) {
            System.out.println(describe(payment));
        }

        // Bonus: Payment.class.getPermittedSubclasses() is a real runtime
        // call. Print it. Where is that list stored, and who enforces it?
    }
}