show error for enums without constants but with abstract methods

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

@@ -1190,6 +1190,23 @@ public class GenericsHighlightUtil {
     return null;
   }
 
+  public static HighlightInfo checkEnumWithoutConstantsCantHaveAbstractMethods(final PsiClass aClass) {
+    if (!aClass.isEnum()) return null;
+    for (PsiField field : aClass.getFields()) {
+      if (field instanceof PsiEnumConstant) {
+        return null;
+      }
+    }
+    for (PsiMethod method : aClass.getMethods()) {
+      if (method.hasModifierProperty(PsiModifier.ABSTRACT)) {
+        final String description = "Enum declaration without enum constants cannot have abstract methods";
+        final TextRange textRange = HighlightNamesUtil.getClassDeclarationTextRange(aClass);
+        return HighlightInfo.newHighlightInfo(HighlightInfoType.ERROR).range(textRange).descriptionAndTooltip(description).create();
+      }
+    }
+    return null;
+  }
+
   public static HighlightInfo checkSelectStaticClassFromParameterizedType(final PsiElement resolved, final PsiJavaCodeReferenceElement ref) {
     if (resolved instanceof PsiClass && ((PsiClass)resolved).hasModifierProperty(PsiModifier.STATIC)) {
       final PsiElement qualifier = ref.getQualifier();

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

@@ -384,6 +384,7 @@ public class HighlightVisitorImpl extends JavaElementVisitor implements Highligh
     if (!myHolder.hasErrorResults()) myHolder.add(GenericsHighlightUtil.areSupersAccessible(aClass));
     if (!myHolder.hasErrorResults()) myHolder.add(HighlightClassUtil.checkDuplicateTopLevelClass(aClass));
     if (!myHolder.hasErrorResults()) myHolder.add(GenericsHighlightUtil.checkEnumMustNotBeLocal(aClass));
+    if (!myHolder.hasErrorResults()) myHolder.add(GenericsHighlightUtil.checkEnumWithoutConstantsCantHaveAbstractMethods(aClass));
     if (!myHolder.hasErrorResults()) myHolder.add(HighlightUtil.checkImplicitThisReferenceBeforeSuper(aClass, myJavaSdkVersion));
     if (!myHolder.hasErrorResults()) myHolder.add(HighlightClassUtil.checkClassAndPackageConflict(aClass));
     if (!myHolder.hasErrorResults()) myHolder.add(HighlightClassUtil.checkPublicClassInRightFile(aClass));

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/advHighlighting6/EnumWithoutConstants.java

@@ -0,0 +1,4 @@
+<error descr="Enum declaration without enum constants cannot have abstract methods">enum MyEnumTest</error> {
+  ;
+  public abstract void m();
+}

java/java-tests/testSrc/com/intellij/codeInsight/daemon/LightAdvHighlightingJdk6Test.java

@@ -68,6 +68,7 @@ public class LightAdvHighlightingJdk6Test extends LightDaemonAnalyzerTestCase {
   public void testUnsupportedFeatures7() { doTest(false, false); }
   public void testEnumInitializers() { doTest(false, false); }
   public void testEnumSynthetics() { doTest(false, false); }
+  public void testEnumWithoutConstants() { doTest(false, false); }
   public void testIDEA79251() { doTest(false, false); }
   public void testIDEA65473() { doTest(false, false); }
   public void testIDEA61415() { doTest(false, false); }