anchor.diff:    return retVal;
   }
   
  -@After(SomeService_sayHello, retValNull: true)
  +someService_sayHello_retValNull(component, Invocation inv, retVal) =>
  +    retVal == null && SomeService_sayHello(component, inv);
  +
  +@After(someService_sayHello_retValNull)
   noIncreaseAfterCounter(retVal) {
     //this should not happens
     afterCounter++;
  
positive.code: 
  var afterCounter2 = 0;
  
  @After(SomeService_sayHello, retVal: "hello impl")
  increaseAfterCounter2(retVal) {
    afterCounter2++;
    print("after sayHello 2 $afterCounter2");
  
negative.code: 
  var afterCounter = 0;
  
  someService_sayHello_noRetVal(component, Invocation inv, retVal) =>
      SomeService_sayHello(component, inv);
  
  @After(someService_sayHello_noRetVal)
  increaseAfterCounter(retVal) {
    afterCounter++;
    print("after sayHello $afterCounter");
  