anchor.diff:    useSsa(null);
     useCodeBuffer(null);
     usedByTests();
  -  useElements(null, null, null);
  +  useElements(null, null, null, null, null);
     useIr(null, null, null);
     useCompiler(null);
     useTypes();
  
positive.code: 
  void useUtil(util.Link link) {
    link.reversePrependAll(link);
    util.longestCommonPrefixLength(null, null);
    new util.Pair(null, null);
  }
  
negative.code: import 'universe/universe.dart' as universe;
  import 'util/util.dart' as util;
  
  import 'scanner/scannerlib.dart' show
      PartialClassElement,
      PartialFunctionElement;
  
  class ElementVisitor extends elements_visitor.ElementVisitor {
    visitElement(e) {}
  }
  