ES6 classes: deferring the creation step

new_construct.md

F.[[Call]](thisArgument, argumentsList, thisConstructor) :

0. ...
1. If thisArgument is empty, then let calledAsConstructor be true; else let calledAsConstructor be false.
2. Let result be the result of EvaluateBody...
3. ReturnIfAbrupt(result).
4. If calledAsConstructor is true and Type(result) is not Object, then
5. TODO: Interaction with Tail-Call semantics?
6. Let thisValue be GetThisBinding().
7. NOTE: 'thisValue' may be empty, callers need to handle this case!
8. Let result be NormalCompletion(thisValue).
9. Return result.

---

F.[[Construct]](receiver, argumentsList):

1. If F.[[NeedsSuper]] is false, then
2. Let obj be the result of OrdinaryCreateFromConstructor(receiver.prototype, "%ObjectPrototype%").
3. ReturnIfAbrupt(obj).
4. Else,
5. Let obj be empty.
6. Let result be the result of F.[[Call]](obj, argumentsList, receiver).
7. ReturnIfAbrupt(result).
8. If result is empty, then throw a (Reference|Type)Error exception.
9. If Type(result) is Object, return result.
10. Assert: obj is not empty.
11. Return obj.

---

Semantics of a super-method call:

1. Let F be the method referenced by super.method. (!!!)
2. Let thisValue be GetThisBinding().
3. If thisValue is not empty,
   1. Let result be the result of F.[[Call]](thisValue, args).
4. Else,
   1. If IsConstructor(F) is false, then throw a TypeError exception.
   2. Let receiver be GetThisConstructor().
   3. Let result be the result of F.[[Construct]](receiver, args).
   4. ReturnIfAbrupt(result).
   5. Assert: Type(result) is Object.
   6. If GetThisBinding() is empty, then InitializeThisBinding(result).
5. Return result.