[Switch expression + Sealed Types] Suspect diagnostic about switch expression being inexhaustive

[srikanth-sankaran]

This program compiles with javac, but ECJ complains about A switch expression should have a default case

public interface X {

  static <T extends Object & AbstractSealedInterface> Integer get(T object) {
    return switch (object) {
      case ClassC ignored -> 42;
    };
  }

  public abstract sealed interface AbstractSealedInterface permits InterfaceB {
  }

  public sealed interface InterfaceB extends AbstractSealedInterface permits ClassC {
  }
  
  final class ClassC implements InterfaceB {}

  public static void main(String[] args) {
   System.out.println(get(new ClassC()));
  }
}

ECJ behavior is suspect - this is a follow up from #2714

[nlisker]

I've just ran into what seems to be the same problem:

sealed interface I {

	enum E implements I {
		A, B, C;
	}
} 

class Test {

	void d(I i) {
		switch (i) { // error: An enhanced switch statement should be exhaustive; a default label expected
			case I.E.A -> {}
			case I.E.B -> {}
			case I.E.C -> {}
		}
	}
}

But there are no other valid cases (I must be an E, which must be A, B or C).

Didn't test with javac.

Version: 2024-06 (4.32)
Build id: I20240601-0610

[srikanth-sankaran]

I've just ran into what seems to be the same problem:

No, this is a different problem with the same symptom - I have raised #2720 with the test case.

[srikanth-sankaran]

More useful test case with some twists that is faultily rejected by ECJ, but accepted by javac:

public interface X {

  static <T extends Object & I1 & I2> Integer get(T object) {
    return switch (object) {
      case AB ignored -> 42;
      case BA ignored -> 420;
    };
  }

  public abstract sealed interface I1 permits A, AB, BA {
  }
  
  public abstract sealed interface I2 permits B, AB, BA {
  }

  
  final class A implements I1 {}
  final class B implements I2 {}
  final class AB implements I1, I2 {}
  final class BA implements I1, I2 {}

  public static void main(String[] args) {
	  System.out.println(get(new AB()));
	  System.out.println(get(new BA()));
  }
}