IDEA-262337 refactor this: suggest push members down when there are inheritors only

GitOrigin-RevId: b214655cfcb043081116cbb28c47dccc053a5560

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

@@ -27,6 +27,7 @@ import com.intellij.openapi.util.NlsContexts;
 import com.intellij.openapi.util.Ref;
 import com.intellij.psi.*;
 import com.intellij.psi.impl.source.jsp.jspJava.JspClass;
+import com.intellij.psi.search.searches.ClassInheritorsSearch;
 import com.intellij.psi.util.PsiTreeUtil;
 import com.intellij.refactoring.HelpID;
 import com.intellij.refactoring.RefactoringActionHandler;
@@ -54,7 +55,11 @@ public class JavaPushDownHandler implements RefactoringActionHandler, ElementsHa
 
   @Override
   public boolean isAvailableForQuickList(@NotNull Editor editor, @NotNull PsiFile file, @NotNull DataContext dataContext) {
-    return !getElements(editor, file, Ref.create(), true).isEmpty();
+    final List<PsiElement> elements = getElements(editor, file, Ref.create(), true);
+    if (elements.isEmpty()) return false;
+    PsiClass psiClass = PsiTreeUtil.getParentOfType(elements.get(0), PsiClass.class, false);
+    if (psiClass == null) return false;
+    return ClassInheritorsSearch.search(psiClass).iterator().hasNext();
   }
 
   @Override

java/java-tests/testData/refactoring/refactorThis/PushDownFiltered.java

@@ -0,0 +1,7 @@
+class Parent {
+  void test(){}
+}
+
+class Child extends Parent {
+  void foo<caret>(){}
+}

java/java-tests/testData/refactoring/refactorThis/PushDownOnClass.java

@@ -0,0 +1,7 @@
+class Parent<caret> {
+  void test(){}
+}
+
+class Child extends Parent {
+  void foo(){}
+}

java/java-tests/testData/refactoring/refactorThis/PushDownOnMethod.java

@@ -0,0 +1,7 @@
+class Parent {
+  void test<caret>(){}
+}
+
+class Child extends Parent {
+  void foo(){}
+}

java/java-tests/testSrc/com/intellij/java/refactoring/RefactorThisTest.kt

@@ -160,6 +160,18 @@ class RefactorThisTest: LightJavaCodeInsightTestCase() {
     assertFalse(doActionExists<ConvertToInstanceMethodAction>())
   }
 
+  fun testPushDownOnMethod() {
+    assertTrue(doActionExists<PushDownAction>())
+  }
+
+  fun testPushDownOnClass() {
+    assertTrue(doActionExists<PushDownAction>())
+  }
+
+  fun testPushDownFiltered() {
+    assertFalse(doActionExists<PushDownAction>())
+  }
+
   private inline fun <reified A> doActionExists(): Boolean {
     configureByFile("$BASE_PATH/${getTestName(false)}.java")
     val actions = findAvailableActions()