anchor.diff:  import 'inferrer/type_graph_inferrer.dart' as type_graph_inferrer;
   import 'io/code_output.dart' as io;
   import 'js/js.dart' as js;
  +import 'js_backend/js_backend.dart' as js_backend;
   import 'js_emitter/js_emitter.dart' as js_emitter;
   import 'source_file_provider.dart' as source_file_provider;
   import 'ssa/ssa.dart' as ssa;
  
positive.code:   node.asVariableUse();
  }
  
  useConcreteTypesInferrer(concrete_types_inferrer.ConcreteTypesInferrer c) {
    c.debug();
  }
  
negative.code:   useJs(new js.Blob(null));
    useJs(new js.NamedFunction(null, null));
    useJs(new js.ArrayHole());
    useJsBackend(null);
    useConcreteTypesInferrer(null);
    useColor();
    useFilenames();
  