[Enhanced Switch][Record Patterns] ECJ compiles non-exhaustive switch resulting in MatchException being thrown at runtime

[srikanth-sankaran]

Found by code inspection & white box testing:

The following program is rejected by javac JDK23 (error: the switch statement does not cover all possible input values) but ECJ faultily compiles the program resulting in MatchException being thrown at runtime.

public sealed interface X {

	record R(X x) {}
	
	final  class C1 implements X {}
	final class C2 implements X {}
	
	public static void main(String[] args) {
        bar(new R(new C1()));
	}
	public static void bar(R r) {
		switch (r) {
		case R(C1 c1) when c1 == null  -> System.out.println();
		case R(C2 c1) -> System.out.println();
		}
	}
}

Problem dates back to atleast 4.32. 4.31 rejects the program but not sure if it doing correct thing correctly or is doing the correct thing incorrectly ;-)

[srikanth-sankaran]

Behavior change seems to have originated from commit cb6774f made for #2011