Bug 32664 Package Explorer: hierarchical layout and back-linking don't work allways together.
The following triggers it: - initially 'flat layout' is used, 'link with editor' is on or off - open a java file - use 'collapse all' in the package explorer - select 'hierarchical layout' - switch 'link with editor' on or off&on -> no back-linking
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/packageview/PackageExplorerContentProvider.java
private boolean isOnClassPath(ICompilationUnit element) throws JavaModelException {
		IJavaProject project= element.getJavaProject();
		if (project == null || !project.exists())
			return false;
		return project.isOnClasspath(element);
	}
	/**
	 * Updates the selection. It finds newly added elements
	 * and selects them.
	 */
	private void updateSelection(IJavaElementDelta delta) {
		final IJavaElement addedElement= findAddedElement(delta);
		if (addedElement != null) {
			final StructuredSelection selection= new StructuredSelection(addedElement);
			postRunnable(new Runnable() {
				public void run() {
					Control ctrl= fViewer.getControl();
					if (ctrl != null && !ctrl.isDisposed()) {
						
						
						if (fViewer.testFindItem(addedElement) != null)
							fViewer.setSelection(selection);
					}
				}
			});	
		}	
	}
	private IJavaElement findAddedElement(IJavaElementDelta delta) {
		if (delta.getKind() == IJavaElementDelta.ADDED)  
			return delta.getElement();