Bug 38496 sort members: should be disabled on types with no members [code manipulation]
20030604 currently what you get is a no-op. not even an info dialog
org.eclipse.jdt.ui/ui/org/eclipse/jdt/ui/actions/SortMembersAction.java
IEditorPart editor= EditorUtility.openInEditor(cu);
			if (editor != null) {
				run(shell, JavaModelUtil.toWorkingCopy(cu), editor);
			}
		} catch (CoreException e) {
			ExceptionHandler.handle(e, shell, getDialogTitle(), null); 
		}			
	}
	
	
	/* (non-Javadoc)
	 * Method declared on SelectionDispatchAction
	 */
	public void selectionChanged(ITextSelection selection) {
	}
	
	/* (non-Javadoc)
	 * Method declared on SelectionDispatchAction
	 */
	public void run(ITextSelection selection) {
		Shell shell= getShell();
		IJavaElement input= SelectionConverter.getInput(fEditor);
		if (input instanceof ICompilationUnit) {
			if (ElementValidator.check(input, getShell(), getDialogTitle(), true)) {
				run(shell, (ICompilationUnit) input, fEditor);
			}
		} else {
			MessageDialog.openInformation(shell, getDialogTitle(), ActionMessages.getString("SortMembersAction.not_applicable")); 
		}