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Normative: Make Async-from-Sync iterator object inaccessible to ECMAScript code #1474

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Jun 19, 2019
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Normative: Make Async-from-Sync iterator object inaccessible to ECMAScript code #1474

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33 changes: 10 additions & 23 deletions spec.html
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Original file line number Diff line number Diff line change
Expand Up @@ -3369,7 +3369,7 @@ <h1>CompletePropertyDescriptor ( _Desc_ )</h1>
<p>When the abstract operation CompletePropertyDescriptor is called with Property Descriptor _Desc_, the following steps are taken:</p>
<emu-alg>
1. Assert: _Desc_ is a Property Descriptor.
1. Let _like_ be Record { [[Value]]: *undefined*, [[Writable]]: *false*, [[Get]]: *undefined*, [[Set]]: *undefined*, [[Enumerable]]: *false*, [[Configurable]]: *false* }.
1. Let _like_ be the Record { [[Value]]: *undefined*, [[Writable]]: *false*, [[Get]]: *undefined*, [[Set]]: *undefined*, [[Enumerable]]: *false*, [[Configurable]]: *false* }.
1. If IsGenericDescriptor(_Desc_) is *true* or IsDataDescriptor(_Desc_) is *true*, then
1. If _Desc_ does not have a [[Value]] field, set _Desc_.[[Value]] to _like_.[[Value]].
1. If _Desc_ does not have a [[Writable]] field, set _Desc_.[[Writable]] to _like_.[[Writable]].
Expand Down Expand Up @@ -4888,7 +4888,7 @@ <h1>GetIterator ( _obj_ [ , _hint_ [ , _method_ ] ] )</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 Record { [[Iterator]]: _iterator_, [[NextMethod]]: _nextMethod_, [[Done]]: *false* }.
1. Let _iteratorRecord_ be the Record { [[Iterator]]: _iterator_, [[NextMethod]]: _nextMethod_, [[Done]]: *false* }.
1. Return _iteratorRecord_.
</emu-alg>
</emu-clause>
Expand Down Expand Up @@ -37021,7 +37021,9 @@ <h1>CreateAsyncFromSyncIterator ( _syncIteratorRecord_ )</h1>
<emu-alg>
1. Let _asyncIterator_ be ! ObjectCreate(%AsyncFromSyncIteratorPrototype%, &laquo; [[SyncIteratorRecord]] &raquo;).
1. Set _asyncIterator_.[[SyncIteratorRecord]] to _syncIteratorRecord_.
1. Return ? GetIterator(_asyncIterator_, ~async~).
1. Let _nextMethod_ be ! Get(_asyncIterator_, `"next"`).
1. Let _iteratorRecord_ be the Record { [[Iterator]]: _asyncIterator_, [[NextMethod]]: _nextMethod_, [[Done]]: *false* }.
1. Return _iteratorRecord_.
</emu-alg>
</emu-clause>

Expand All @@ -37039,11 +37041,8 @@ <h1>The %AsyncFromSyncIteratorPrototype% Object</h1>
<h1>%AsyncFromSyncIteratorPrototype%.next ( _value_ )</h1>
<emu-alg>
1. Let _O_ be the *this* value.
1. Assert: Type(_O_) is Object and _O_ has a [[SyncIteratorRecord]] internal slot.
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1. Let _promiseCapability_ be ! NewPromiseCapability(%Promise%).
1. If Type(_O_) is not Object, or if _O_ does not have a [[SyncIteratorRecord]] internal slot, then
1. Let _invalidIteratorError_ be a newly created *TypeError* object.
1. Perform ! Call(_promiseCapability_.[[Reject]], *undefined*, &laquo; _invalidIteratorError_ &raquo;).
1. Return _promiseCapability_.[[Promise]].
1. Let _syncIteratorRecord_ be _O_.[[SyncIteratorRecord]].
1. Let _result_ be IteratorNext(_syncIteratorRecord_, _value_).
1. IfAbruptRejectPromise(_result_, _promiseCapability_).
Expand All @@ -37056,11 +37055,8 @@ <h1>%AsyncFromSyncIteratorPrototype%.return ( _value_ )</h1>

<emu-alg>
1. Let _O_ be the *this* value.
1. Assert: Type(_O_) is Object and _O_ has a [[SyncIteratorRecord]] internal slot.
1. Let _promiseCapability_ be ! NewPromiseCapability(%Promise%).
1. If Type(_O_) is not Object, or if _O_ does not have a [[SyncIteratorRecord]] internal slot, then
1. Let _invalidIteratorError_ be a newly created *TypeError* object.
1. Perform ! Call(_promiseCapability_.[[Reject]], *undefined*, &laquo; _invalidIteratorError_ &raquo;).
1. Return _promiseCapability_.[[Promise]].
1. Let _syncIterator_ be _O_.[[SyncIteratorRecord]].[[Iterator]].
1. Let _return_ be GetMethod(_syncIterator_, `"return"`).
1. IfAbruptRejectPromise(_return_, _promiseCapability_).
Expand All @@ -37082,11 +37078,8 @@ <h1>%AsyncFromSyncIteratorPrototype%.throw ( _value_ )</h1>

<emu-alg>
1. Let _O_ be the *this* value.
1. Assert: Type(_O_) is Object and _O_ has a [[SyncIteratorRecord]] internal slot.
1. Let _promiseCapability_ be ! NewPromiseCapability(%Promise%).
1. If Type(_O_) is not Object, or if _O_ does not have a [[SyncIteratorRecord]] internal slot, then
1. Let _invalidIteratorError_ be a newly created *TypeError* object.
1. Perform ! Call(_promiseCapability_.[[Reject]], *undefined*, &laquo; _invalidIteratorError_ &raquo;).
1. Return _promiseCapability_.[[Promise]].
1. Let _syncIterator_ be _O_.[[SyncIteratorRecord]].[[Iterator]].
1. Let _throw_ be GetMethod(_syncIterator_, `"throw"`).
1. IfAbruptRejectPromise(_throw_, _promiseCapability_).
Expand All @@ -37102,16 +37095,10 @@ <h1>%AsyncFromSyncIteratorPrototype%.throw ( _value_ )</h1>
</emu-alg>
</emu-clause>

<emu-clause id="sec-%asyncfromsynciteratorprototype%-@@tostringtag">
<h1>%AsyncFromSyncIteratorPrototype% [ @@toStringTag ]</h1>
<p>The initial value of the @@toStringTag property is the String value `"Async-from-Sync Iterator"`.</p>
<p>This property has the attributes { [[Writable]]: *false*, [[Enumerable]]: *false*, [[Configurable]]: *true* }.</p>
</emu-clause>

<emu-clause id="sec-async-from-sync-iterator-value-unwrap-functions">
<h1>Async-from-Sync Iterator Value Unwrap Functions</h1>

<p>An async-from-sync iterator value unwrap function is an anonymous built-in function that is used by methods of %AsyncFromSyncIteratorPrototype% when processing the `value` field of an <i>IteratorResult</i> object, in order to wait for its value if it is a promise and re-package the result in a new "unwrapped" <i>IteratorResult</i> object. Each async iterator value unwrap function has a [[Done]] internal slot.</p>
<p>An async-from-sync iterator value unwrap function is an anonymous built-in function that is used by AsyncFromSyncIteratorContinuation when processing the `value` property of an <i>IteratorResult</i> object, in order to wait for its value if it is a promise and re-package the result in a new "unwrapped" <i>IteratorResult</i> object. Each async-from-sync iterator value unwrap function has a [[Done]] internal slot.</p>

<p>When an async-from-sync iterator value unwrap function is called with argument _value_, the following steps are taken:</p>

Expand All @@ -37124,7 +37111,7 @@ <h1>Async-from-Sync Iterator Value Unwrap Functions</h1>

<emu-clause id="sec-properties-of-async-from-sync-iterator-instances">
<h1>Properties of Async-from-Sync Iterator Instances</h1>
<p>Async-from-Sync Iterator instances are ordinary objects that inherit properties from the %AsyncFromSyncIteratorPrototype% intrinsic object. Async-from-Sync Iterator instances are initially created with the internal slots listed in <emu-xref href="#table-async-from-sync-iterator-internal-slots"></emu-xref>.</p>
<p>Async-from-Sync Iterator instances are ordinary objects that inherit properties from the %AsyncFromSyncIteratorPrototype% intrinsic object. Async-from-Sync Iterator instances are initially created with the internal slots listed in <emu-xref href="#table-async-from-sync-iterator-internal-slots"></emu-xref>. Async-from-Sync Iterator instances are not directly observable from ECMAScript code.</p>
<emu-table id="table-async-from-sync-iterator-internal-slots" caption="Internal Slots of Async-from-Sync Iterator Instances">
<table>
<thead>
Expand Down