Why does the actionscript3.0 class heirachy fail (sometimes)?

Question

All Objects in actionscript3.0 inherit from the Object class, but the actionscript3.0 compiler seems not to be smart enough to understand this.

take a look at the following code:

package{
   public class TestOne{
      public function TestOne(){
        var t2: TestTwo = new TestTwo();
        trace(t2.toString()); // COMPILE TIME ERROR
        trace((t2 as Object).toString(); // [object TestTwo]

        var t22 : * = new TestTwo();
        trace(t22.toString()); // [object TestTwo]
        trace((t22 as Object).toString(); // [object TestTwo]
      }
   }
}
class TestTwo{}

t2.toString() gives a compile time error because the data type t2 does not include toString(). However, t2 does include toString() because it is an object as (t2 as Object).toString() shows. If we do not give the variable a datatype, like t22, then the problem is never encountered. Why cant the actionscript3.0 compiler relize that t2 is both TestTwo and Object?

Answer 1

This is because

Methods of the Object class are dynamically created on Object's prototype. To redefine this method in a subclass of Object, do not use the override keyword. For example, a subclass of Object implements function toString():String instead of using an override of the base class.

So if you cast TestTwo to an Object, the compiler knows those methods will be implemented. If you don't cast it, TestTwo does not inherit those methods and so they have not been implemented and will error.

It's a bit of a weird one!