Quick fix for S6877 "Replace if with pattern match guard" produces uncompilable code on constant cas

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And a thorough description of the problem / question:

Reproducer:

enum Type { DATE, TEXT }

record Match(Object value) {}

public class Example {
    void process(Type type, Match match) {
        switch (type) {
            case DATE -> { if (match.value() instanceof String s) System.out.println(s); }
            case TEXT -> {}
        }
    }
}

What happens:

S6877 suggests replacing the if with a pattern match guard. Applying the quick fix produces:

case DATE when match.value() instanceof String s -> { System.out.println(s); }

This does not compile. The when guard is only valid after a pattern case label (JEP 441), not after a constant case label like an enum value. The Java grammar:

case Pattern [Guard] ->    // âś… guard allowed
case CaseConstant ->       // ❌ no guard allowed

Expected: Rule should not trigger (or quick fix should not be offered) when the case label is a constant rather than a pattern.

4

Hello, thanks for the report, I created a ticket to fix the bug :slight_smile: