really search for private class inheritors outside the current file (IDEA-167877)

java/java-tests/testSrc/com/intellij/navigation/GotoImplementationHandlerTest.java

@@ -282,6 +282,18 @@ public class GotoImplementationHandlerTest extends JavaCodeInsightFixtureTestCas
     assertEquals(1, impls.length);
   }
 
+  public void testPrivateClassInheritors() {
+    PsiFile file = myFixture.addFileToProject("Foo.java",
+                                                          "class C {\n" +
+                                                          "  private static class Pr<caret>ivate {}\n" +
+                                                          "  public static class Public extends Private {}" +
+                                                          "}");
+    myFixture.addClass("class Inheritor extends C.Public {}");
+    myFixture.configureFromExistingVirtualFile(file.getVirtualFile());
+
+    assertSize(2, getTargets(file));
+  }
+
   private PsiElement[] getTargets(PsiFile file) {
     GotoTargetHandler.GotoData gotoData = CodeInsightTestUtil.gotoImplementation(myFixture.getEditor(), file);
     assertNotNull(gotoData);

platform/indexing-api/src/com/intellij/psi/search/searches/DefinitionsScopedSearch.java

@@ -17,9 +17,11 @@
 package com.intellij.psi.search.searches;
 
 import com.intellij.openapi.application.ApplicationManager;
+import com.intellij.openapi.application.ReadAction;
 import com.intellij.openapi.extensions.ExtensionPointName;
 import com.intellij.openapi.util.Computable;
 import com.intellij.psi.PsiElement;
+import com.intellij.psi.PsiFile;
 import com.intellij.psi.search.PsiSearchHelper;
 import com.intellij.psi.search.SearchScope;
 import com.intellij.util.Processor;
@@ -98,11 +100,10 @@ public class DefinitionsScopedSearch extends ExtensibleQueryFactory<PsiElement,
 
     @NotNull
     public SearchScope getScope() {
-      return ApplicationManager.getApplication().runReadAction(new Computable<SearchScope>() {
-        @Override
-        public SearchScope compute() {
-          return myScope.intersectWith(PsiSearchHelper.SERVICE.getInstance(myElement.getProject()).getUseScope(myElement));
-        }
+      return ReadAction.compute(() -> {
+        PsiFile file = myElement.getContainingFile();
+        return myScope.intersectWith(
+          PsiSearchHelper.SERVICE.getInstance(myElement.getProject()).getUseScope(file != null ? file : myElement));
       });
     }
   }

platform/lang-impl/src/com/intellij/codeInsight/TargetElementEvaluatorEx2.java

@@ -88,6 +88,10 @@ public abstract class TargetElementEvaluatorEx2 implements TargetElementEvaluato
     return true;  
   }
 
+  /**
+   * @return a scope where element's implementations (Goto/Show Implementations) should be searched.
+   * If null is returned, default (module-with-dependents) scope will be used.
+   */
   @Nullable
   public SearchScope getSearchScope(Editor editor, @NotNull PsiElement element) {
     return null;

platform/lang-impl/src/com/intellij/codeInsight/TargetElementUtil.java

@@ -457,7 +457,10 @@ public class TargetElementUtil extends TargetElementUtilBase {
   public SearchScope getSearchScope(Editor editor, @NotNull PsiElement element) {
     TargetElementEvaluatorEx2 evaluator = getElementEvaluatorsEx2(element.getLanguage());
     SearchScope result = evaluator != null ? evaluator.getSearchScope(editor, element) : null;
-    return result != null ? result : PsiSearchHelper.SERVICE.getInstance(element.getProject()).getUseScope(element);
+    if (result != null) return result;
+
+    PsiFile file = element.getContainingFile();
+    return PsiSearchHelper.SERVICE.getInstance(element.getProject()).getUseScope(file != null ? file : element);
   }
 
   protected final LanguageExtension<TargetElementEvaluator> targetElementEvaluator =

platform/lang-impl/src/com/intellij/codeInsight/TargetElementUtilBase.java

@@ -96,6 +96,9 @@ public abstract class TargetElementUtilBase {
 
   public abstract boolean acceptImplementationForReference(@Nullable PsiReference reference, @Nullable PsiElement element);
 
+  /**
+   * @return a scope where element's implementations (Goto/Show Implementations) should be searched
+   */
   @NotNull
   public abstract SearchScope getSearchScope(Editor editor, @NotNull PsiElement element);
 }