[Enhanced Switch] Bogus duplicate case error from ECJ

[srikanth-sankaran]

Found by code inspection & white box testing:

The program below when compiled with javac and run produces the output:

E1.ONE
E1.TWO
E2.ONE
E2.TWO
E1.TWO
E2.ONE
E2.TWO
E2.ONE
E2.TWO
E2.TWO

but is rejected by ECJ with three errors of: Duplicate case

public sealed interface X {
	public static void main(String[] args) {
        bar(E1.ONE);
        bar(E1.TWO);
        bar(E2.ONE);
        bar(E2.TWO);
	}
	public static void bar(X x) {
		switch (x) {
		case E1.ONE: 
			System.out.println("E1.ONE");
		case E1.TWO: 
			System.out.println("E1.TWO");
		case E2.ONE:
			System.out.println("E2.ONE");
		case E2.TWO:
			System.out.println("E2.TWO");
		}
	}
}
enum E1 implements X { ONE, TWO}
enum E2 implements X { ONE, TWO}

[srikanth-sankaran]

This regression appears to brought on by the commit 37b9382 made for #2866

However at 4.33 we reject the program with a different bogus error about enhanced switch requiring a default. The switch is exhaustive and doesn't require a default