False Positive : Non-fall-through switch branches are still reported

[Carlson-JLQ]

False Positive : Non-fall-through switch branches are still reported

Affects errorprone Version:

2.48.0

Checker:

FallThrough

Description:

According to the official FallThrough documentation, a warning is only appropriate when one switch statement group can continue into the next without terminating abruptly and without an intentional fall-through comment. The following samples all terminate the earlier branch with break, return, or throw, so no fall-through is possible.

Code Sample demonstrating the issue:

// NegCase1
switch (x) {
    case 1:
        System.out.println("Case 1");
        break;
    case 2:
        System.out.println("Case 2");
        break;
}

// PMD NegCase3
switch (x) {
    case 1:
        System.out.println("Case 1");
        return;
    case 2:
        System.out.println("Case 2");
        break;
    default:
        break;
}

// PMD NegCase1
switch (x) {
    case 1:
        System.out.println("Case 1");
        break;
    case 2:
        System.out.println("Case 2");
        return;
    case 3:
        System.out.println("Case 3");
        throw new RuntimeException();
    case 4:
        throw new RuntimeException();
    default:
        System.out.println("Default");
}

Each branch above already terminates abruptly, so execution cannot reach the next statement group. Reporting these cases as missing fall-through comments would contradict the checker's own documented condition.

Expected outcome:

Error Prone should not report a FallThrough warning for these switch branches, but it does. This is a false-positive.