@override
  visitPartOfDirective(PartOfDirective node) {
    Element element = node.element;
    if(element is LibraryElement) {
      CompilationUnitElement compilationUnitElement = element.definingCompilationUnit;
      if(compilationUnitElement.source != null) {
        if(node.uri != null) {
          recordUriReference(compilationUnitElement, node.uri);
        }
      }
    }
    super.visitPartOfDirective(node);
  }