Update for IteratorStep return values

[gibson042]

IteratorStep returns "either an Object or DONE, or a throw completion".

[bakkot]

This works but better is to use IteratorStepValue

[gibson042]

Is that compatible with the Yield in the middle?

[bakkot]

There isn't a Yield in the middle, is there? The Yield is after the IteratorValue.

[gibson042]

IteratorStepValue does

1. Let _result_ be ? IteratorStep(_iteratorRecord_).
1. If _result_ is ~done~, then
  1. Return ~done~.
1. Let _value_ be Completion(IteratorValue(_result_)).

while this operation does

1. Let _innerNext_ be ? IteratorStep(_iteratorRecord_).
1. If _innerNext_ is ~done~, then
  1. Set _innerAlive_ to *false*.
1. Else,
  1. Let _innerValue_ be ? IteratorValue(_innerNext_).
  1. Let _completion_ be Completion(Yield(_innerValue_)).

i.e., IteratorStepValue looks at Completion(IteratorValue($resultFromIteratorStep)) while this operation looks at Completion(Yield(IteratorValue($resultFromIteratorStep))). But it's definitely possible that I'm missing something; I haven't familiarized myself with this part of the spec since introduction of those helper ops.

[michaelficarra]

Fixed using IteratorStepValue in 5e6e3c3. Thanks for the report.