anchor.diff:        this.printProcedure,
         this.completerConstructor,
         this.syncIterableConstructor,
  +      this.streamIteratorConstructor,
         this.futureMicrotaskConstructor,
         this.streamControllerConstructor,
         this.asyncThenWrapper,
  
positive.code:   Statement buildCatchBody(Statement exceptionVariable,
                             Statement stackTraceVariable);
  
    defaultExpression(TreeNode node) {
      return expressionRewriter.rewrite(node);
    }
  
negative.code:         findProcedure(coreLibrary, 'print'),
          findFactoryConstructor(completerClass, 'sync'),
          findConstructor(syncIterableClass, ''),
          findConstructor(streamIteratorClass , ''),
          findFactoryConstructor(futureClass, 'microtask'),
          findConstructor(streamControllerClass, ''),
          findProcedure(asyncLibrary, '_asyncThenWrapperHelper'),
  