push down: don't remove body when it's possible to keep it (IDEA-114041)

add intention with suggestion to push down

java/java-analysis-api/src/com/intellij/codeInsight/intention/QuickFixFactory.java

@@ -321,4 +321,7 @@ public abstract class QuickFixFactory {
 
   @Nullable
   public abstract IntentionAction createCreateClassInPackageInModuleFix(@NotNull Module module, @Nullable String packageName);
+  
+  public abstract IntentionAction createPushDownMethodFix();
+  
 }

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

@@ -1306,6 +1306,7 @@ public class HighlightMethodUtil {
     HighlightInfo info = HighlightInfo.newHighlightInfo(HighlightInfoType.ERROR).range(textRange).descriptionAndTooltip(description).create();
     if (!hasNoBody) {
       QuickFixAction.registerQuickFixAction(info, QUICK_FIX_FACTORY.createDeleteMethodBodyFix(method));
+      QuickFixAction.registerQuickFixAction(info, QUICK_FIX_FACTORY.createPushDownMethodFix());
     }
     if (method.hasModifierProperty(PsiModifier.ABSTRACT) && !isInterface) {
       QuickFixAction.registerQuickFixAction(info, QUICK_FIX_FACTORY.createModifierListFix(method, PsiModifier.ABSTRACT, false, false));

java/java-analysis-impl/src/com/intellij/codeInsight/intention/EmptyQuickFixFactory.java

@@ -717,4 +717,9 @@ public class EmptyQuickFixFactory extends QuickFixFactory {
   public IntentionAction createCreateClassInPackageInModuleFix(@NotNull Module module, @Nullable String packageName) {
     return QuickFixes.EMPTY_FIX;
   }
+
+  @Override
+  public IntentionAction createPushDownMethodFix() {
+    return QuickFixes.EMPTY_FIX;
+  }
 }

java/java-impl/src/com/intellij/codeInsight/intention/impl/config/QuickFixFactoryImpl.java

@@ -18,6 +18,7 @@ import com.intellij.codeInsight.intention.IntentionManager;
 import com.intellij.codeInsight.intention.QuickFixFactory;
 import com.intellij.codeInsight.intention.impl.CreateClassInPackageInModuleFix;
 import com.intellij.codeInsight.intention.impl.ReplaceAssignmentWithComparisonFix;
+import com.intellij.codeInsight.intention.impl.RunRefactoringAction;
 import com.intellij.codeInspection.*;
 import com.intellij.codeInspection.deadCode.UnusedDeclarationInspectionBase;
 import com.intellij.codeInspection.ex.EntryPointsManagerBase;
@@ -45,6 +46,7 @@ import com.intellij.psi.tree.IElementType;
 import com.intellij.psi.util.ClassKind;
 import com.intellij.psi.util.InheritanceUtil;
 import com.intellij.psi.util.PropertyMemberType;
+import com.intellij.refactoring.memberPushDown.JavaPushDownHandler;
 import com.intellij.util.DocumentUtil;
 import com.intellij.util.IncorrectOperationException;
 import org.jetbrains.annotations.Nls;
@@ -918,4 +920,15 @@ public class QuickFixFactoryImpl extends QuickFixFactory {
   public IntentionAction createCreateClassInPackageInModuleFix(@NotNull Module module, @Nullable String packageName) {
     return CreateClassInPackageInModuleFix.createFix(module, packageName);
   }
+
+  @Override
+  public IntentionAction createPushDownMethodFix() {
+    return new RunRefactoringAction(new JavaPushDownHandler(), "Push method down...") {
+      @NotNull
+      @Override
+      public Priority getPriority() {
+        return Priority.NORMAL;
+      }
+    };
+  }
 }

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

@@ -256,7 +256,9 @@ public class JavaPushDownDelegate extends PushDownDelegate<MemberInfo, PsiMember
           if (sourceClass.isInterface() && !targetClass.isInterface()) {
             PsiUtil.setModifierProperty(newMember, PsiModifier.PUBLIC, true);
             if (oldMethod.hasModifierProperty(PsiModifier.ABSTRACT)) {
-              RefactoringUtil.makeMethodAbstract(targetClass, (PsiMethod)newMember);
+              if (oldMethod.getBody() == null) {
+                RefactoringUtil.makeMethodAbstract(targetClass, (PsiMethod)newMember);
+              }
             }
             else {
               PsiUtil.setModifierProperty(newMember, PsiModifier.DEFAULT, false);

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

@@ -0,0 +1,7 @@
+interface I {
+  void m<caret>() {
+    System.out.println();
+  }
+}
+
+class Test implements I {}

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

@@ -0,0 +1,8 @@
+interface I {
+}
+
+class Test implements I {
+    public void m() {
+      System.out.println();
+    }
+}

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

@@ -82,6 +82,7 @@ public class PushDownTest extends LightRefactoringTestCase {
   public void testThisSuperExpressions() {doTest();}
   public void testMethodsInheritedFromSuper() {doTest();}
   public void testCopyAnnotationsFromSuper() {doTest();}
+  public void testKeepBodyFromInterfaceMethod() {doTest();}
 
   public void testInterfaceMethodToClass() { doTest();}