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Editorial: Add Iterator Record type #2591

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Feb 16, 2022
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Editorial: Add Iterator Record type #2591

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88 changes: 71 additions & 17 deletions spec.html
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Original file line number Diff line number Diff line change
Expand Up @@ -6909,12 +6909,66 @@ <h1>
<h1>Operations on Iterator Objects</h1>
<p>See Common Iteration Interfaces (<emu-xref href="#sec-iteration"></emu-xref>).</p>

<emu-clause id="sec-iterator-records">
<h1>Iterator Records</h1>
<p>An <dfn variants="Iterator Records">Iterator Record</dfn> is a Record value used to encapsulate an Iterator or AsyncIterator along with the `next` method.</p>
<p>Iterator Records have the fields listed in <emu-xref href="#table-iterator-record-fields"></emu-xref>.</p>
<emu-table id="table-iterator-record-fields" caption="Iterator Record Fields">
<table>
<tr>
<th>
Field Name
</th>
<th>
Value
</th>
<th>
Meaning
</th>
</tr>
<tr>
<td>
[[Iterator]]
</td>
<td>
An object
</td>
<td>
An object that conforms to the <i>Iterator</i> or <i>AsyncIterator</i> interface.
</td>
</tr>
<tr>
<td>
[[NextMethod]]
</td>
<td>
A function object
</td>
<td>
The `next` method of the [[Iterator]] object.
</td>
</tr>
<tr>
<td>
[[Done]]
</td>
<td>
Boolean
</td>
<td>
Whether the iterator has been closed.
</td>
</tr>
</table>
</emu-table>
</emu-clause>

<emu-clause id="sec-getiterator" type="abstract operation">
<h1>
GetIterator (
_obj_: unknown,
_obj_: an ECMAScript language value,
optional _hint_: ~sync~ or ~async~,
optional _method_: unknown,
optional _method_: a function object,
)
</h1>
<dl class="header">
Expand All @@ -6932,16 +6986,16 @@ <h1>
1. Let _iterator_ be ? Call(_method_, _obj_).
1. If Type(_iterator_) is not Object, throw a *TypeError* exception.
1. Let _nextMethod_ be ? GetV(_iterator_, *"next"*).
1. Let _iteratorRecord_ be the Record { [[Iterator]]: _iterator_, [[NextMethod]]: _nextMethod_, [[Done]]: *false* }.
1. Let _iteratorRecord_ be the Iterator Record { [[Iterator]]: _iterator_, [[NextMethod]]: _nextMethod_, [[Done]]: *false* }.
1. Return _iteratorRecord_.
</emu-alg>
</emu-clause>

<emu-clause id="sec-iteratornext" type="abstract operation">
<h1>
IteratorNext (
_iteratorRecord_: unknown,
optional _value_: unknown,
_iteratorRecord_: an Iterator Record,
optional _value_: an ECMAScript language value,
)
</h1>
<dl class="header">
Expand Down Expand Up @@ -6985,7 +7039,7 @@ <h1>
<emu-clause id="sec-iteratorstep" type="abstract operation">
<h1>
IteratorStep (
_iteratorRecord_: unknown,
_iteratorRecord_: an Iterator Record,
)
</h1>
<dl class="header">
Expand All @@ -7003,7 +7057,7 @@ <h1>
<emu-clause id="sec-iteratorclose" type="abstract operation">
<h1>
IteratorClose (
_iteratorRecord_: unknown,
_iteratorRecord_: an Iterator Record,
_completion_: a Completion Record,
)
</h1>
Expand Down Expand Up @@ -7042,7 +7096,7 @@ <h1>IfAbruptCloseIterator ( _value_, _iteratorRecord_ )</h1>
<emu-clause id="sec-asynciteratorclose" type="abstract operation">
<h1>
AsyncIteratorClose (
_iteratorRecord_: unknown,
_iteratorRecord_: an Iterator Record,
_completion_: a Completion Record,
)
</h1>
Expand All @@ -7069,7 +7123,7 @@ <h1>
<emu-clause id="sec-createiterresultobject" type="abstract operation">
<h1>
CreateIterResultObject (
_value_: unknown,
_value_: an ECMAScript language value,
_done_: a Boolean,
)
</h1>
Expand All @@ -7088,7 +7142,7 @@ <h1>
<emu-clause id="sec-createlistiteratorRecord" type="abstract operation" oldids="sec-createlistiterator,sec-listiteratornext-functions,sec-listiterator-next">
<h1>
CreateListIteratorRecord (
_list_: unknown,
_list_: a List,
)
</h1>
<dl class="header">
Expand All @@ -7101,7 +7155,7 @@ <h1>
1. Perform ? GeneratorYield(! CreateIterResultObject(_E_, *false*)).
1. Return *undefined*.
1. Let _iterator_ be ! CreateIteratorFromClosure(_closure_, ~empty~, %IteratorPrototype%).
1. Return Record { [[Iterator]]: _iterator_, [[NextMethod]]: %GeneratorFunction.prototype.prototype.next%, [[Done]]: *false* }.
1. Return the Iterator Record { [[Iterator]]: _iterator_, [[NextMethod]]: %GeneratorFunction.prototype.prototype.next%, [[Done]]: *false* }.
</emu-alg>
<emu-note>
<p>The list iterator object is never directly accessible to ECMAScript code.</p>
Expand All @@ -7111,8 +7165,8 @@ <h1>
<emu-clause id="sec-iterabletolist" type="abstract operation">
<h1>
IterableToList (
_items_: unknown,
optional _method_: unknown,
_items_: an ECMAScript language value,
optional _method_: a function object,
)
</h1>
<dl class="header">
Expand Down Expand Up @@ -21958,7 +22012,7 @@ <h1>
1. Let _obj_ be ! ToObject(_exprValue_).
1. Let _iterator_ be ? EnumerateObjectProperties(_obj_).
1. Let _nextMethod_ be ! GetV(_iterator_, *"next"*).
1. Return the Record { [[Iterator]]: _iterator_, [[NextMethod]]: _nextMethod_, [[Done]]: *false* }.
1. Return the Iterator Record { [[Iterator]]: _iterator_, [[NextMethod]]: _nextMethod_, [[Done]]: *false* }.
1. Else,
1. Assert: _iterationKind_ is ~iterate~ or ~async-iterate~.
1. If _iterationKind_ is ~async-iterate~, let _iteratorHint_ be ~async~.
Expand Down Expand Up @@ -42876,13 +42930,13 @@ <h1>
</h1>
<dl class="header">
<dt>description</dt>
<dd>It is used to create an async iterator Record from a synchronous iterator Record.</dd>
<dd>It is used to create an async Iterator Record from a synchronous Iterator Record.</dd>
</dl>
<emu-alg>
1. Let _asyncIterator_ be ! OrdinaryObjectCreate(%AsyncFromSyncIteratorPrototype%, &laquo; [[SyncIteratorRecord]] &raquo;).
1. Set _asyncIterator_.[[SyncIteratorRecord]] to _syncIteratorRecord_.
1. Let _nextMethod_ be ! Get(_asyncIterator_, *"next"*).
1. Let _iteratorRecord_ be the Record { [[Iterator]]: _asyncIterator_, [[NextMethod]]: _nextMethod_, [[Done]]: *false* }.
1. Let _iteratorRecord_ be the Iterator Record { [[Iterator]]: _asyncIterator_, [[NextMethod]]: _nextMethod_, [[Done]]: *false* }.
1. Return _iteratorRecord_.
</emu-alg>
</emu-clause>
Expand Down Expand Up @@ -42986,7 +43040,7 @@ <h1>Properties of Async-from-Sync Iterator Instances</h1>
[[SyncIteratorRecord]]
</td>
<td>
A Record, of the type returned by GetIterator, representing the original synchronous iterator which is being adapted.
An Iterator Record representing the original synchronous iterator which is being adapted.
</td>
</tr>
</table>
Expand Down