java sealed types: forbid non-sealed classes without sealed supers (IDEA-243536)

GitOrigin-RevId: ce7b48fc5df80edf0a4efc987a23850aff993f6c

java/java-analysis-impl/src/com/intellij/codeInsight/daemon/impl/analysis/HighlightUtil.java

@@ -988,6 +988,11 @@ public class HighlightUtil {
           isAllowed &= !privateOrProtected;
         }
       }
+      if (PsiModifier.NON_SEALED.equals(modifier) && !aClass.hasModifierProperty(PsiModifier.SEALED)) {
+        isAllowed = Arrays.stream(aClass.getSuperTypes())
+          .map(PsiClassType::resolve)
+          .anyMatch(superClass -> superClass != null && superClass.hasModifierProperty(PsiModifier.SEALED));
+      }
     }
     else if (modifierOwner instanceof PsiMethod) {
       PsiMethod method = (PsiMethod)modifierOwner;

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/advHighlightingSealedTypes/SealedTypesBasics.java

@@ -13,3 +13,7 @@ sealed interface IA permits IB, IC {}
 final class IB implements IA {}
 sealed interface IC extends IA {}
 class ICSameFile implements IC {}
+
+sealed interface ID0 {}
+non-sealed interface ID1 extends ID0 {}
+<error descr="Modifier 'non-sealed' not allowed here">non-sealed</error> interface ID extends ID1 {}