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Editorial: Clarify GetIterator #3021

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merged 4 commits into from
Mar 30, 2023
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Editorial: Clarify GetIterator #3021

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956e5af
Editorial: Refactor GetIterator to GetIteratorFromMethod (#3021)
syg Mar 30, 2023
2562811
Editorial: Make GetIterator's hint parameter required (#3021)
syg Mar 30, 2023
ff60140
Editorial: IterableToList -> IteratorToList (#3021)
syg Mar 30, 2023
784fc65
Editorial: Throw on undefined early in GetIterator (#3021)
syg Mar 30, 2023
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96 changes: 52 additions & 44 deletions spec.html
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Original file line number Diff line number Diff line change
Expand Up @@ -6797,26 +6797,16 @@ <h1>Iterator Records</h1>
</emu-table>
</emu-clause>

<emu-clause id="sec-getiterator" type="abstract operation">
<emu-clause id="sec-getiteratorfrommethod" type="abstract operation">
<h1>
GetIterator (
GetIteratorFromMethod (
_obj_: an ECMAScript language value,
optional _hint_: ~sync~ or ~async~,
optional _method_: a function object,
_method_: a function object,
): either a normal completion containing an Iterator Record or a throw completion
</h1>
<dl class="header">
</dl>
<emu-alg>
1. If _hint_ is not present, set _hint_ to ~sync~.
1. If _method_ is not present, then
1. If _hint_ is ~async~, then
1. Set _method_ to ? GetMethod(_obj_, @@asyncIterator).
1. If _method_ is *undefined*, then
1. Let _syncMethod_ be ? GetMethod(_obj_, @@iterator).
1. Let _syncIteratorRecord_ be ? GetIterator(_obj_, ~sync~, _syncMethod_).
1. Return CreateAsyncFromSyncIterator(_syncIteratorRecord_).
1. Otherwise, set _method_ to ? GetMethod(_obj_, @@iterator).
1. Let _iterator_ be ? Call(_method_, _obj_).
1. If _iterator_ is not an Object, throw a *TypeError* exception.
1. Let _nextMethod_ be ? GetV(_iterator_, *"next"*).
Expand All @@ -6825,6 +6815,29 @@ <h1>
</emu-alg>
</emu-clause>

<emu-clause id="sec-getiterator" type="abstract operation">
<h1>
GetIterator (
_obj_: an ECMAScript language value,
_kind_: ~sync~ or ~async~,
): either a normal completion containing an Iterator Record or a throw completion
</h1>
<dl class="header">
</dl>
<emu-alg>
1. If _kind_ is ~async~, then
1. Let _method_ be ? GetMethod(_obj_, @@asyncIterator).
1. If _method_ is *undefined*, then
1. Let _syncMethod_ be ? GetMethod(_obj_, @@iterator).
1. If _syncMethod_ is *undefined*, throw a *TypeError* exception.
1. Let _syncIteratorRecord_ be ? GetIteratorFromMethod(_obj_, _syncMethod_).
1. Return CreateAsyncFromSyncIterator(_syncIteratorRecord_).
1. Otherwise, let _method_ be ? GetMethod(_obj_, @@iterator).
1. If _method_ is *undefined*, throw a *TypeError* exception.
1. Return ? GetIteratorFromMethod(_obj_, _method_).
</emu-alg>
</emu-clause>

<emu-clause id="sec-iteratornext" type="abstract operation">
<h1>
IteratorNext (
Expand Down Expand Up @@ -6997,20 +7010,15 @@ <h1>
</emu-note>
</emu-clause>

<emu-clause id="sec-iterabletolist" type="abstract operation">
<emu-clause id="sec-iteratortolist" oldids="sec-iterabletolist" type="abstract operation">
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<h1>
IterableToList (
_items_: an ECMAScript language value,
optional _method_: a function object,
IteratorToList (
_iteratorRecord_: an Iterator Record,
): either a normal completion containing a List of ECMAScript language values or a throw completion
</h1>
<dl class="header">
</dl>
<emu-alg>
1. If _method_ is present, then
1. Let _iteratorRecord_ be ? GetIterator(_items_, ~sync~, _method_).
1. Else,
1. Let _iteratorRecord_ be ? GetIterator(_items_, ~sync~).
1. Let _values_ be a new empty List.
1. Let _next_ be *true*.
1. Repeat, while _next_ is not *false*,
Expand Down Expand Up @@ -9351,7 +9359,7 @@ <h1>
</emu-alg>
<emu-grammar>BindingPattern : ArrayBindingPattern</emu-grammar>
<emu-alg>
1. Let _iteratorRecord_ be ? GetIterator(_value_).
1. Let _iteratorRecord_ be ? GetIterator(_value_, ~sync~).
1. Let _result_ be Completion(IteratorBindingInitialization of |ArrayBindingPattern| with arguments _iteratorRecord_ and _environment_).
1. If _iteratorRecord_.[[Done]] is *false*, return ? IteratorClose(_iteratorRecord_, _result_).
1. Return ? _result_.
Expand Down Expand Up @@ -18046,7 +18054,7 @@ <h1>
<emu-alg>
1. Let _spreadRef_ be ? Evaluation of |AssignmentExpression|.
1. Let _spreadObj_ be ? GetValue(_spreadRef_).
1. Let _iteratorRecord_ be ? GetIterator(_spreadObj_).
1. Let _iteratorRecord_ be ? GetIterator(_spreadObj_, ~sync~).
1. Repeat,
1. Let _next_ be ? IteratorStep(_iteratorRecord_).
1. If _next_ is *false*, return _nextIndex_.
Expand Down Expand Up @@ -19087,7 +19095,7 @@ <h1>Runtime Semantics: ArgumentListEvaluation ( ): either a normal completion co
1. Let _list_ be a new empty List.
1. Let _spreadRef_ be ? Evaluation of |AssignmentExpression|.
1. Let _spreadObj_ be ? GetValue(_spreadRef_).
1. Let _iteratorRecord_ be ? GetIterator(_spreadObj_).
1. Let _iteratorRecord_ be ? GetIterator(_spreadObj_, ~sync~).
1. Repeat,
1. Let _next_ be ? IteratorStep(_iteratorRecord_).
1. If _next_ is *false*, return _list_.
Expand All @@ -19105,7 +19113,7 @@ <h1>Runtime Semantics: ArgumentListEvaluation ( ): either a normal completion co
<emu-alg>
1. Let _precedingArgs_ be ? ArgumentListEvaluation of |ArgumentList|.
1. Let _spreadRef_ be ? Evaluation of |AssignmentExpression|.
1. Let _iteratorRecord_ be ? GetIterator(? GetValue(_spreadRef_)).
1. Let _iteratorRecord_ be ? GetIterator(? GetValue(_spreadRef_), ~sync~).
1. Repeat,
1. Let _next_ be ? IteratorStep(_iteratorRecord_).
1. If _next_ is *false*, return _precedingArgs_.
Expand Down Expand Up @@ -20529,19 +20537,19 @@ <h1>
</emu-alg>
<emu-grammar>ArrayAssignmentPattern : `[` `]`</emu-grammar>
<emu-alg>
1. Let _iteratorRecord_ be ? GetIterator(_value_).
1. Let _iteratorRecord_ be ? GetIterator(_value_, ~sync~).
1. Return ? IteratorClose(_iteratorRecord_, NormalCompletion(~unused~)).
</emu-alg>
<emu-grammar>ArrayAssignmentPattern : `[` Elision `]`</emu-grammar>
<emu-alg>
1. Let _iteratorRecord_ be ? GetIterator(_value_).
1. Let _iteratorRecord_ be ? GetIterator(_value_, ~sync~).
1. Let _result_ be Completion(IteratorDestructuringAssignmentEvaluation of |Elision| with argument _iteratorRecord_).
1. If _iteratorRecord_.[[Done]] is *false*, return ? IteratorClose(_iteratorRecord_, _result_).
1. Return _result_.
</emu-alg>
<emu-grammar>ArrayAssignmentPattern : `[` Elision? AssignmentRestElement `]`</emu-grammar>
<emu-alg>
1. Let _iteratorRecord_ be ? GetIterator(_value_).
1. Let _iteratorRecord_ be ? GetIterator(_value_, ~sync~).
1. If |Elision| is present, then
1. Let _status_ be Completion(IteratorDestructuringAssignmentEvaluation of |Elision| with argument _iteratorRecord_).
1. If _status_ is an abrupt completion, then
Expand All @@ -20553,14 +20561,14 @@ <h1>
</emu-alg>
<emu-grammar>ArrayAssignmentPattern : `[` AssignmentElementList `]`</emu-grammar>
<emu-alg>
1. Let _iteratorRecord_ be ? GetIterator(_value_).
1. Let _iteratorRecord_ be ? GetIterator(_value_, ~sync~).
1. Let _result_ be Completion(IteratorDestructuringAssignmentEvaluation of |AssignmentElementList| with argument _iteratorRecord_).
1. If _iteratorRecord_.[[Done]] is *false*, return ? IteratorClose(_iteratorRecord_, _result_).
1. Return _result_.
</emu-alg>
<emu-grammar>ArrayAssignmentPattern : `[` AssignmentElementList `,` Elision? AssignmentRestElement? `]`</emu-grammar>
<emu-alg>
1. Let _iteratorRecord_ be ? GetIterator(_value_).
1. Let _iteratorRecord_ be ? GetIterator(_value_, ~sync~).
1. Let _status_ be Completion(IteratorDestructuringAssignmentEvaluation of |AssignmentElementList| with argument _iteratorRecord_).
1. If _status_ is an abrupt completion, then
1. If _iteratorRecord_.[[Done]] is *false*, return ? IteratorClose(_iteratorRecord_, _status_).
Expand Down Expand Up @@ -21891,9 +21899,9 @@ <h1>
1. Return the Iterator Record { [[Iterator]]: _iterator_, [[NextMethod]]: _nextMethod_, [[Done]]: *false* }.
1. Else,
1. Assert: _iterationKind_ is either ~iterate~ or ~async-iterate~.
1. If _iterationKind_ is ~async-iterate~, let _iteratorHint_ be ~async~.
1. Else, let _iteratorHint_ be ~sync~.
1. Return ? GetIterator(_exprValue_, _iteratorHint_).
1. If _iterationKind_ is ~async-iterate~, let _iteratorKind_ be ~async~.
1. Else, let _iteratorKind_ be ~sync~.
1. Return ? GetIterator(_exprValue_, _iteratorKind_).
</emu-alg>
</emu-clause>

Expand Down Expand Up @@ -30778,7 +30786,7 @@ <h1>AggregateError ( _errors_, _message_ [ , _options_ ] )</h1>
1. Let _msg_ be ? ToString(_message_).
1. Perform CreateNonEnumerableDataPropertyOrThrow(_O_, *"message"*, _msg_).
1. Perform ? InstallErrorCause(_O_, _options_).
1. Let _errorsList_ be ? IterableToList(_errors_).
1. Let _errorsList_ be ? IteratorToList(? GetIterator(_errors_, ~sync~)).
1. Perform ! DefinePropertyOrThrow(_O_, *"errors"*, PropertyDescriptor { [[Configurable]]: *true*, [[Enumerable]]: *false*, [[Writable]]: *true*, [[Value]]: CreateArrayFromList(_errorsList_) }).
1. Return _O_.
</emu-alg>
Expand Down Expand Up @@ -37258,7 +37266,7 @@ <h1>Array.from ( _items_ [ , _mapfn_ [ , _thisArg_ ] ] )</h1>
1. Let _A_ be ? Construct(_C_).
1. Else,
1. Let _A_ be ! ArrayCreate(0).
1. Let _iteratorRecord_ be ? GetIterator(_items_, ~sync~, _usingIterator_).
1. Let _iteratorRecord_ be ? GetIteratorFromMethod(_items_, _usingIterator_).
1. Let _k_ be 0.
1. Repeat,
1. If _k_ ≥ 2<sup>53</sup> - 1, then
Expand Down Expand Up @@ -39011,7 +39019,7 @@ <h1>%TypedArray%.from ( _source_ [ , _mapfn_ [ , _thisArg_ ] ] )</h1>
1. Let _mapping_ be *true*.
1. Let _usingIterator_ be ? GetMethod(_source_, @@iterator).
1. If _usingIterator_ is not *undefined*, then
1. Let _values_ be ? IterableToList(_source_, _usingIterator_).
1. Let _values_ be ? IteratorToList(? GetIteratorFromMethod(_source_, _usingIterator_)).
1. Let _len_ be the number of elements in _values_.
1. Let _targetObj_ be ? TypedArrayCreate(_C_, « 𝔽(_len_) »).
1. Let _k_ be 0.
Expand Down Expand Up @@ -40102,7 +40110,7 @@ <h1>_TypedArray_ ( ..._args_ )</h1>
1. Assert: _firstArgument_ is an Object and _firstArgument_ does not have either a [[TypedArrayName]] or an [[ArrayBufferData]] internal slot.
1. Let _usingIterator_ be ? GetMethod(_firstArgument_, @@iterator).
1. If _usingIterator_ is not *undefined*, then
1. Let _values_ be ? IterableToList(_firstArgument_, _usingIterator_).
1. Let _values_ be ? IteratorToList(? GetIteratorFromMethod(_firstArgument_, _usingIterator_)).
1. Perform ? InitializeTypedArrayFromList(_O_, _values_).
1. Else,
1. NOTE: _firstArgument_ is not an Iterable so assume it is already an array-like object.
Expand Down Expand Up @@ -40390,7 +40398,7 @@ <h1>
<dd>_adder_ will be invoked, with _target_ as the receiver.</dd>
</dl>
<emu-alg>
1. Let _iteratorRecord_ be ? GetIterator(_iterable_).
1. Let _iteratorRecord_ be ? GetIterator(_iterable_, ~sync~).
1. Repeat,
1. Let _next_ be ? IteratorStep(_iteratorRecord_).
1. If _next_ is *false*, return _target_.
Expand Down Expand Up @@ -40702,7 +40710,7 @@ <h1>Set ( [ _iterable_ ] )</h1>
1. If _iterable_ is either *undefined* or *null*, return _set_.
1. Let _adder_ be ? Get(_set_, *"add"*).
1. If IsCallable(_adder_) is *false*, throw a *TypeError* exception.
1. Let _iteratorRecord_ be ? GetIterator(_iterable_).
1. Let _iteratorRecord_ be ? GetIterator(_iterable_, ~sync~).
1. Repeat,
1. Let _next_ be ? IteratorStep(_iteratorRecord_).
1. If _next_ is *false*, return _set_.
Expand Down Expand Up @@ -41141,7 +41149,7 @@ <h1>WeakSet ( [ _iterable_ ] )</h1>
1. If _iterable_ is either *undefined* or *null*, return _set_.
1. Let _adder_ be ? Get(_set_, *"add"*).
1. If IsCallable(_adder_) is *false*, throw a *TypeError* exception.
1. Let _iteratorRecord_ be ? GetIterator(_iterable_).
1. Let _iteratorRecord_ be ? GetIterator(_iterable_, ~sync~).
1. Repeat,
1. Let _next_ be ? IteratorStep(_iteratorRecord_).
1. If _next_ is *false*, return _set_.
Expand Down Expand Up @@ -44493,7 +44501,7 @@ <h1>Promise.all ( _iterable_ )</h1>
1. Let _promiseCapability_ be ? NewPromiseCapability(_C_).
1. Let _promiseResolve_ be Completion(GetPromiseResolve(_C_)).
1. IfAbruptRejectPromise(_promiseResolve_, _promiseCapability_).
1. Let _iteratorRecord_ be Completion(GetIterator(_iterable_)).
1. Let _iteratorRecord_ be Completion(GetIterator(_iterable_, ~sync~)).
1. IfAbruptRejectPromise(_iteratorRecord_, _promiseCapability_).
1. Let _result_ be Completion(PerformPromiseAll(_iteratorRecord_, _C_, _promiseCapability_, _promiseResolve_)).
1. If _result_ is an abrupt completion, then
Expand Down Expand Up @@ -44596,7 +44604,7 @@ <h1>Promise.allSettled ( _iterable_ )</h1>
1. Let _promiseCapability_ be ? NewPromiseCapability(_C_).
1. Let _promiseResolve_ be Completion(GetPromiseResolve(_C_)).
1. IfAbruptRejectPromise(_promiseResolve_, _promiseCapability_).
1. Let _iteratorRecord_ be Completion(GetIterator(_iterable_)).
1. Let _iteratorRecord_ be Completion(GetIterator(_iterable_, ~sync~)).
1. IfAbruptRejectPromise(_iteratorRecord_, _promiseCapability_).
1. Let _result_ be Completion(PerformPromiseAllSettled(_iteratorRecord_, _C_, _promiseCapability_, _promiseResolve_)).
1. If _result_ is an abrupt completion, then
Expand Down Expand Up @@ -44723,7 +44731,7 @@ <h1>Promise.any ( _iterable_ )</h1>
1. Let _promiseCapability_ be ? NewPromiseCapability(_C_).
1. Let _promiseResolve_ be Completion(GetPromiseResolve(_C_)).
1. IfAbruptRejectPromise(_promiseResolve_, _promiseCapability_).
1. Let _iteratorRecord_ be Completion(GetIterator(_iterable_)).
1. Let _iteratorRecord_ be Completion(GetIterator(_iterable_, ~sync~)).
1. IfAbruptRejectPromise(_iteratorRecord_, _promiseCapability_).
1. Let _result_ be Completion(PerformPromiseAny(_iteratorRecord_, _C_, _promiseCapability_, _promiseResolve_)).
1. If _result_ is an abrupt completion, then
Expand Down Expand Up @@ -44819,7 +44827,7 @@ <h1>Promise.race ( _iterable_ )</h1>
1. Let _promiseCapability_ be ? NewPromiseCapability(_C_).
1. Let _promiseResolve_ be Completion(GetPromiseResolve(_C_)).
1. IfAbruptRejectPromise(_promiseResolve_, _promiseCapability_).
1. Let _iteratorRecord_ be Completion(GetIterator(_iterable_)).
1. Let _iteratorRecord_ be Completion(GetIterator(_iterable_, ~sync~)).
1. IfAbruptRejectPromise(_iteratorRecord_, _promiseCapability_).
1. Let _result_ be Completion(PerformPromiseRace(_iteratorRecord_, _C_, _promiseCapability_, _promiseResolve_)).
1. If _result_ is an abrupt completion, then
Expand Down