[Sealed types] Broken program crashes the compiler

[srikanth-sankaran]

While experimenting I found the following program to crash ECJ:

public interface X {

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

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

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

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

Notice that I2's declaration is syntactically flawed. Nevertheless the compiler should not crash.

[stephan-herrmann]

@srikanth-sankaran during your work on sealed types, you may want to check if the following has any impact for ecj: https://bugs.openjdk.org/browse/JDK-8338981

Thanks, and sorry for hijacking this issue :)

[srikanth-sankaran]

Thanks for the pointer. I'll follow up.

[srikanth-sankaran]

Smaller test case:

public interface X {

  static <T extends Object & I2> Integer get(T object) {
    return switch (object) {
      case A ignored -> 42;
      default -> 42;
    };
  }

  public abstract sealed interface I2 permits , AB {
  }


  final class AB implements I2 {}

}

Stack trace:

java.lang.NullPointerException: Cannot invoke "org.eclipse.jdt.internal.compiler.lookup.ModuleBinding.isUnnamed()" because "sourceModuleBinding" is null
	at org.eclipse.jdt.internal.compiler.lookup.SourceTypeBinding.checkPermitsInType(SourceTypeBinding.java:1153)
	at org.eclipse.jdt.internal.compiler.lookup.SourceTypeBinding.faultInTypesForFieldsAndMethods(SourceTypeBinding.java:1117)
	at org.eclipse.jdt.internal.compiler.lookup.ClassScope.buildLocalTypeBinding(ClassScope.java:394)
	at org.eclipse.jdt.internal.compiler.lookup.BlockScope.addLocalType(BlockScope.java:129)
	at org.eclipse.jdt.internal.compiler.ast.TypeDeclaration.resolve(TypeDeclaration.java:1633)
	at org.eclipse.jdt.internal.compiler.ast.Statement.resolveWithBindings(Statement.java:496)
	at org.eclipse.jdt.internal.compiler.ast.ASTNode.resolveStatements(ASTNode.java:725)
	at org.eclipse.jdt.internal.compiler.ast.AbstractMethodDeclaration.resolveStatements(AbstractMethodDeclaration.java:713)
	at org.eclipse.jdt.internal.compiler.ast.MethodDeclaration.resolveStatements(MethodDeclaration.java:409)
	at org.eclipse.jdt.internal.compiler.ast.AbstractMethodDeclaration.resolve(AbstractMethodDeclaration.java:611)
	at org.eclipse.jdt.internal.compiler.ast.TypeDeclaration.resolve(TypeDeclaration.java:1537)
	at org.eclipse.jdt.internal.compiler.ast.TypeDeclaration.resolve(TypeDeclaration.java:1666)
	at org.eclipse.jdt.internal.compiler.ast.CompilationUnitDeclaration.resolve(CompilationUnitDeclaration.java:670)
	at org.eclipse.jdt.core.dom.CompilationUnitResolver.resolve(CompilationUnitResolver.java:1372)

[srikanth-sankaran]

The relevant code has completely overhauled and this program doesn't crash anymore - I will add a regression test and close this.

[srikanth-sankaran]

@srikanth-sankaran during your work on sealed types, you may want to check if the following has any impact for ecj: https://bugs.openjdk.org/browse/JDK-8338981

Thanks, and sorry for hijacking this issue :)

We compile the program fine!

This slightly modified program draws one error from ECJ: The type X.C is not visible

public sealed class X permits X.C {
    private final static class C extends X implements I {}
}

sealed interface I permits X.C {}

while javac complains:

X.java:5: error: C has private access in X
sealed interface I permits X.C {}
                            ^
X.java:1: error: C has private access in X
public sealed class X permits X.C {
                               ^
X.java:2: error: class is not allowed to extend sealed class: X (as it is not listed in its 'permits' clause)
    private final static class C extends X implements I {}
                         ^
3 errors

[srikanth-sankaran]

public record X(I i) {
	private class I {}
}

This one compiles too - so we seem not to have a problem with * Access occurs in the record component list of the top level record class that encloses the declaration of the member. clause.