IPP: recognize enum constants correctly (IDEA-196541)

in "Create Enum Switch Branches" intention

plugins/IntentionPowerPak/src/com/siyeh/ipp/enumswitch/EnumSwitchPredicate.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2003-2013 Dave Griffith, Bas Leijdekkers
+ * Copyright 2003-2018 Dave Griffith, Bas Leijdekkers
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -57,15 +57,11 @@ class EnumSwitchPredicate implements PsiElementPredicate {
     }
     final Set<String> enumElements = new HashSet<>(fields.length);
     for (final PsiField field : fields) {
-      final PsiType fieldType = field.getType();
-      if (!fieldType.equals(type)) {
-        continue;
+      if (field instanceof PsiEnumConstant) {
+        enumElements.add(field.getName());
       }
-      final String fieldName = field.getName();
-      enumElements.add(fieldName);
     }
-    final PsiStatement[] statements = body.getStatements();
-    for (PsiStatement statement : statements) {
+    for (PsiStatement statement : body.getStatements()) {
       if (!(statement instanceof PsiSwitchLabelStatement)) {
         continue;
       }

plugins/IntentionPowerPak/test/com/siyeh/ipp/enumswitch/NotAvailable.java

@@ -0,0 +1,13 @@
+enum E {
+  foo, bar;
+
+  private E e;
+
+  int foo() {
+    switch (this) {
+      case foo: return 1;
+      case bar: return 2;
+      <caret>default: return 3;
+    }
+  }
+}

plugins/IntentionPowerPak/testSrc/com/siyeh/ipp/enumswitch/EnumSwitchBranchesIntentionTest.java

@@ -1,18 +1,4 @@
-/*
- * Copyright 2000-2016 JetBrains s.r.o.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
+// Copyright 2000-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
 package com.siyeh.ipp.enumswitch;
 
 import com.siyeh.IntentionPowerPackBundle;
@@ -28,6 +14,7 @@ public class EnumSwitchBranchesIntentionTest extends IPPTestCase {
   public void testBeforeFallthrough() { doTest(); }
   public void testMultiple() { doTest(); }
   public void testNoActionAfterBraces() { assertIntentionNotAvailable(); }
+  public void testNotAvailable() { assertIntentionNotAvailable(); }
 
   @Override
   protected String getIntentionName() {