fix issue with using single child of the file as new root for structure view popup

platform/lang-impl/src/com/intellij/ide/commander/AbstractListBuilder.java

@@ -77,7 +77,7 @@ public abstract class AbstractListBuilder {
     final Object rootElement = myTreeStructure.getRootElement();
     final Object[] rootChildren = myTreeStructure.getChildElements(rootElement);
 
-    if (!showRoot && rootChildren.length == 1) {
+    if (!showRoot && rootChildren.length == 1 && shouldEnterSingleTopLevelElement(rootChildren[0])) {
       myShownRoot = (AbstractTreeNode)rootChildren[0];
     }
     else {
@@ -85,6 +85,8 @@ public abstract class AbstractListBuilder {
     }
   }
 
+  protected abstract boolean shouldEnterSingleTopLevelElement(Object rootChild);
+
   public final void setParentTitle(final JLabel parentTitle) {
     myParentTitle = parentTitle;
   }

platform/lang-impl/src/com/intellij/ide/commander/ProjectListBuilder.java

@@ -74,6 +74,11 @@ public class ProjectListBuilder extends AbstractListBuilder {
     }
   }
 
+  @Override
+  protected boolean shouldEnterSingleTopLevelElement(Object rootChild) {
+    return true;
+  }
+
   protected boolean nodeIsAcceptableForElement(AbstractTreeNode node, Object element) {
     return Comparing.equal(node.getValue(), element);
   }

platform/lang-impl/src/com/intellij/ide/util/FileStructureDialog.java

@@ -183,6 +183,11 @@ public class FileStructureDialog extends DialogWrapper {
     PsiFile psiFile = getPsiFile(myProject);
     boolean showRoot = isShowRoot(psiFile);
     ProjectListBuilder projectListBuilder = new ProjectListBuilder(myProject, myCommanderPanel, myTreeStructure, null, showRoot) {
+      @Override
+      protected boolean shouldEnterSingleTopLevelElement(Object rootChild) {
+        return myBaseTreeModel.shouldEnterElement(((StructureViewTreeElement)((AbstractTreeNode)rootChild).getValue()).getValue());
+      }
+
       protected boolean nodeIsAcceptableForElement(AbstractTreeNode node, Object element) {
         return Comparing.equal(((StructureViewTreeElement)node.getValue()).getValue(), element);
       }