@Override
 public void scanFile(JavaFileScannerContext context) {
   this.context = context;
   if (context.getSemanticModel() != null) {
     scan(context.getTree());
   }
 }
 @Override
 public void scanFile(JavaFileScannerContext context) {
   this.context = context;
   validUsagesStack = new ArrayDeque<>();
   exceptions = Splitter.on(",").trimResults().split(exceptionsCommaSeparated);
   exceptionIdentifiers = Lists.newArrayList();
   for (String exception : exceptions) {
     exceptionIdentifiers.add(exception.substring(exception.lastIndexOf(".") + 1));
   }
   semanticModel = (SemanticModel) context.getSemanticModel();
   if (semanticModel != null) {
     scan(context.getTree());
   }
 }