java sealed types: ensure sealed class inheritors are sealed/non-sealed/final (IDEA-243536)

GitOrigin-RevId: 768635cd8a1b237893429ac1882296de8477536d

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

@@ -947,6 +947,21 @@ public class HighlightClassUtil {
     }
     return null;
   }
+  
+  public static HighlightInfo checkWellFormedSealedInheritor(PsiClass psiClass) {
+    if (!psiClass.hasModifierProperty(PsiModifier.SEALED) &&
+        !psiClass.hasModifierProperty(PsiModifier.NON_SEALED) &&
+        !psiClass.hasModifierProperty(PsiModifier.FINAL)) {
+      PsiIdentifier nameIdentifier = psiClass.getNameIdentifier();
+      if (nameIdentifier == null) return null;
+      if (Arrays.stream(psiClass.getSuperTypes()).map(superType -> superType.resolve())
+        .anyMatch(superClass -> superClass != null && superClass.hasModifierProperty(PsiModifier.SEALED))) {
+        return HighlightInfo.newHighlightInfo(HighlightInfoType.ERROR).range(nameIdentifier)
+          .descriptionAndTooltip(JavaErrorBundle.message("sealed.type.inheritor.expected.modifiers", PsiModifier.SEALED, PsiModifier.NON_SEALED, PsiModifier.FINAL)).create();
+      }
+    }
+    return null;
+  }
 
   public static HighlightInfo checkIllegalInstanceMemberInRecord(PsiMember member) {
     if (!member.hasModifierProperty(PsiModifier.STATIC)) {

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

@@ -472,6 +472,7 @@ public class HighlightVisitorImpl extends JavaElementVisitor implements Highligh
     if (!myHolder.hasErrorResults()) myHolder.add(HighlightClassUtil.checkClassAndPackageConflict(aClass));
     if (!myHolder.hasErrorResults()) myHolder.add(HighlightClassUtil.checkPublicClassInRightFile(aClass));
     if (!myHolder.hasErrorResults()) myHolder.add(HighlightClassUtil.checkWellFormedRecord(aClass));
+    if (!myHolder.hasErrorResults()) myHolder.add(HighlightClassUtil.checkWellFormedSealedInheritor(aClass));
     if (!myHolder.hasErrorResults()) myHolder.add(GenericsHighlightUtil.checkTypeParameterOverrideEquivalentMethods(aClass, myLanguageLevel));
   }
 

java/java-psi-impl/src/messages/JavaErrorBundle.properties

@@ -465,3 +465,4 @@ bad.type.in.switch.expression=Bad type in switch expression: {0} cannot be conve
 switch.expression.cannot.be.void=Target type for switch expression cannot be void
 annotation.on.static.member.qualifying.type.family.name=Move type annotation
 functional.interface.must.not.be.sealed.error.description=Functional interface can''t be declared as ''{0}''
+sealed.type.inheritor.expected.modifiers={0}, {1} or {2} modifiers expected

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

@@ -3,7 +3,7 @@ sealed class A permits B {}
 sealed class B extends A permits C, D {}
 final class C extends B {}
 non-sealed class D extends B {}
-class E extends A {}
+class <error descr="sealed, non-sealed or final modifiers expected">E</error> extends A {}
 <error descr="Illegal combination of modifiers: 'sealed' and 'sealed'">sealed</error> <error descr="Illegal combination of modifiers: 'sealed' and 'sealed'">sealed</error> class SealedSealed {}
 <error descr="Illegal combination of modifiers: 'sealed' and 'non-sealed'">sealed</error> <error descr="Illegal combination of modifiers: 'non-sealed' and 'sealed'">non-sealed</error> class SealedNonSealed {}
 <error descr="Illegal combination of modifiers: 'sealed' and 'final'">sealed</error> <error descr="Illegal combination of modifiers: 'final' and 'sealed'">final</error> class SealedFinal {}
@@ -12,7 +12,7 @@ class E extends A {}
 sealed interface IA permits IB, IC {}
 final class IB implements IA {}
 sealed interface IC extends IA {}
-class ICSameFile implements IC {}
+class <error descr="sealed, non-sealed or final modifiers expected">ICSameFile</error> implements IC {}
 
 sealed interface ID0 {}
 non-sealed interface ID1 extends ID0 {}