do not generate protected constructors for enums (IDEA-53086)

java/java-impl/src/com/intellij/codeInsight/generation/GenerateConstructorHandler.java

@@ -259,7 +259,7 @@ public class GenerateConstructorHandler extends GenerateMembersHandlerBase {
   private static String getConstructorModifier(final PsiClass aClass) {
     @Modifier String modifier = PsiModifier.PUBLIC;
 
-    if (aClass.hasModifierProperty(PsiModifier.ABSTRACT)) {
+    if (aClass.hasModifierProperty(PsiModifier.ABSTRACT) && !aClass.isEnum()) {
       modifier =  PsiModifier.PROTECTED;
     }
     else if (aClass.hasModifierProperty(PsiModifier.PACKAGE_LOCAL)) {

java/java-tests/testData/codeInsight/generateConstructor/afterEnumWithAbstractMethod.java

@@ -0,0 +1,12 @@
+public enum Operation {
+    PLUS {
+        int eval(int x, int y) {
+            return x + y;
+        }
+    };
+
+    abstract int eval(int x, int y);
+
+    Operation() {
+    }
+}

java/java-tests/testData/codeInsight/generateConstructor/beforeEnumWithAbstractMethod.java

@@ -0,0 +1,10 @@
+public enum Operation {
+    PLUS {
+        int eval(int x, int y) {
+            return x + y;
+        }
+    };
+
+    abstract int eval(int x, int y);
+    <caret>
+}

java/java-tests/testSrc/com/intellij/codeInsight/GenerateConstructorTest.java

@@ -16,6 +16,7 @@ public class GenerateConstructorTest extends LightCodeInsightTestCase {
   public void testPrivateClass() throws Exception { doTest(); }
   public void testBoundComments() throws Exception { doTest(); }
   public void testSameNamedFields() throws Exception { doTest(); }
+  public void testEnumWithAbstractMethod() throws Exception { doTest(); }
 
   public void testImmediatelyAfterRBrace() throws Exception {    // IDEADEV-28811
     final CodeStyleSettings settings = CodeStyleSettingsManager.getInstance(getProject()).getCurrentSettings();