allow override in interfaces (IDEA-109506)

java/java-psi-impl/src/com/intellij/codeInsight/generation/OverrideImplementExploreUtil.java

@@ -30,7 +30,7 @@ public class OverrideImplementExploreUtil {
 
   @NotNull
   public static Collection<MethodSignature> getMethodSignaturesToOverride(@NotNull PsiClass aClass) {
-    if (aClass.isInterface()) return Collections.emptySet();
+    if (aClass.isAnnotationType()) return Collections.emptySet();
     return getMapToOverrideImplement(aClass, false).keySet();
   }
 

java/java-tests/testData/codeInsight/overrideImplement/afterOverrideInInterface.java

@@ -0,0 +1,8 @@
+interface A {
+  void foo();
+}
+
+interface B extends A {
+    @Override
+    void foo();
+}

java/java-tests/testData/codeInsight/overrideImplement/beforeOverrideInInterface.java

@@ -0,0 +1,7 @@
+interface A {
+  void foo();
+}
+
+interface B extends A {
+  <caret>
+}

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

@@ -71,6 +71,9 @@ public class OverrideImplementTest extends LightCodeInsightTestCase {
   public void testOverrideExtensionMethods() { doTest8(false, false); }
   public void testDoNotImplementExtensionMethods() { doTest8(false, true); }
 
+
+  public void testOverrideInInterface() { doTest8(false, false); }
+
   public void testLongFinalParameterList() {
     CodeStyleSettings codeStyleSettings = CodeStyleSettingsManager.getSettings(getProject()).clone();
     try {