anchor.diff:  // does anyone have any ideas?
   testStrongTyping() {
     print("testStrongTyping");
  -  var jsonString = _getStrongTypingJsonString();
  +  String jsonString = _getStrongTypingJsonString();
   
     // Create a new JSON object which looks like our Person
     // A Person Interface extends the JsonObject, so no
     // warning is reported
   
  -  Person person = new JsonObject.fromJsonString(jsonString); // this will fail.
  -
  +  Person person = new Person.fromString(jsonString); // this will not fail
  +  
   
   
     //verify property access
  
positive.code: }
  
  
  _getStrongTypingJsonString() {
  //Create the JSON which looks like our interface structure
    var jsonString = """
        {
  
negative.code: //Define some interfaces
  //that we want our JSON structure to look like
  
  interface Person default _PersonImpl{
     AddressList addresses;
     Person.fromString(String jsonString);
  }
  
  class _PersonImpl extends JsonObject implements Person {
    _PersonImpl();
    factory _PersonImpl.fromString(String jsonString) {
      return new JsonObject.fromJsonString(jsonString, new _PersonImpl());  
    } 
  }
  
  
  