push down: show conflict on attempt to push implements to anonymous

EA-118269 - NPE: JavaPushDownDelegate.pushDownToClass

java/java-impl/src/com/intellij/refactoring/memberPushDown/JavaPushDownDelegate.java

@@ -102,6 +102,10 @@ public class JavaPushDownDelegate extends PushDownDelegate<MemberInfo, PsiMember
         context = (PsiElement)newClassContext;
       }
     }
+    if (targetClass instanceof PsiAnonymousClass && 
+        toMove.stream().map(MemberInfoBase::getOverrides).anyMatch(Objects::nonNull)) {
+      conflicts.putValue(targetClass, "Unable to push implements to anonymous class");
+    }
     new PushDownConflicts((PsiClass)pushDownData.getSourceClass(), toMove.toArray(new MemberInfo[0]), conflicts)
       .checkTargetClassConflicts(targetClass, context);
   }
@@ -304,10 +308,11 @@ public class JavaPushDownDelegate extends PushDownDelegate<MemberInfo, PsiMember
               }
             }
             PsiJavaCodeReferenceElement classRef = classType != null ? factory.createReferenceElementByType(classType) : factory.createClassReferenceElement(psiClass);
-            if (psiClass.isInterface() && !targetClass.isInterface()) {
-              targetClass.getImplementsList().add(classRef);
-            } else {
-              targetClass.getExtendsList().add(classRef);
+            PsiReferenceList extendsImplementsList = psiClass.isInterface() && !targetClass.isInterface() 
+                                                     ? targetClass.getImplementsList() 
+                                                     : targetClass.getExtendsList();
+            if (extendsImplementsList != null) {
+              extendsImplementsList.add(classRef);
             }
           }
         }

java/java-tests/testData/refactoring/pushDown/PassingImplementsToAnonymous.java

@@ -0,0 +1,7 @@
+interface I {}
+class Test implements I {}
+class C {
+  {
+    Test a = new Test() {};
+  }
+}

java/java-tests/testData/refactoring/pushDown/PassingImplementsToAnonymous_after.java

@@ -0,0 +1,7 @@
+interface I {}
+class Test {}
+class C {
+  {
+    Test a = new Test() {};
+  }
+}

java/java-tests/testSrc/com/intellij/java/refactoring/PushDownTest.java

@@ -108,6 +108,10 @@ public class PushDownTest extends LightRefactoringTestCase {
     doTestImplements(true, true);
   }
 
+  public void testPassingImplementsToAnonymous() {
+    doTestImplements(false, true);
+  }
+
   public void testInterfaceVisibilityInClass() {
     doTest();
   }