@Override
 public IQuickAssistAssistant getQuickAssistAssistant(ISourceViewer sourceViewer) {
   ITextEditor editor = getEditor();
   if (editor != null) {
     DartCorrectionAssistant assistant = new DartCorrectionAssistant(editor);
     assistant.setRestoreCompletionProposalSize(
         getSettings("quick_assist_proposal_size")); // $NON-NLS-1$
     return assistant;
   }
   return null;
 }