When implementing a parameterized Dynamic, you will get the same behavior as with a non-parameterized Dynamic except that the fields that are not declared in the class will be of the type given as a parameter.

Let's take almost the same example but with a parameterized Dynamic:

class User implements Dynamic<String>
{
   public var name : String;
   public var age : Int;
   //...
}

//...
var u = new User(); //u is of type User
u.name = "Benjamin"; //String
u.age = 22; //Int
u.functionrole = "Author"; //String because of the type parameter