result of "return" method in IteratorClose

[GeorgNeis]

7.4.6 IteratorClose enforces that the result of the return method is an object:

8. If Type(innerResult.[[value]]) is not Object, throw a TypeError exception.
9. Return Completion(completion).

This seems strange as the result is not used. What's the reason for this check?

[ljharb]

It's defined by user code, so it might return a primitive - and given that it's an iterator result, its return value must conform with the contract. See step 3 in http://tc39.github.io/ecma262/#sec-iteratornext and step 1 in http://tc39.github.io/ecma262/#sec-iteratorcomplete and http://tc39.github.io/ecma262/#sec-iteratorvalue.

[ljharb]

It's defined by user code, so it might return a primitive - and given that it's an iterator result, its return value must conform with the contract. See step 3 in http://tc39.github.io/ecma262/#sec-iteratornext and step 1 in http://tc39.github.io/ecma262/#sec-iteratorcomplete and http://tc39.github.io/ecma262/#sec-iteratorvalue.