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:   sourceFileProvider.readStringFromUri(null);
  }
  
  useElements(elements.ClassElement e, elements.Name n, modelx.FieldElementX f) {
    e.lookupClassMember(null);
    e.lookupInterfaceMember(null);
    n.isAccessibleFrom(null);
    f.reuseElement();
  }
  
  useIr(cps_ir_nodes_sexpr.SExpressionStringifier stringifier,
  
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) {}
  }
  