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make @@toStringTag and constructor prototype properties funky accessors #287

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merged 4 commits into from
Dec 4, 2023
Merged

make @@toStringTag and constructor prototype properties funky accessors #287

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e298671
make @@toStringTag and constructor prototype properties funky accessors
michaelficarra Sep 18, 2023
f481720
throw instead of silently doing nothing
michaelficarra Oct 12, 2023
7d48c43
throw when this value is Iterator.prototype
michaelficarra Oct 12, 2023
d741076
rewrite funky setter and extract as an AO
michaelficarra Oct 17, 2023
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69 changes: 66 additions & 3 deletions spec.html
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Original file line number Diff line number Diff line change
Expand Up @@ -107,6 +107,30 @@ <h1>Well-Known Intrinsic Objects</h1>
<emu-clause id="sec-abstract-operations">
<h1>Abstract Operations</h1>

<emu-clause id="sec-SetterThatIgnoresPrototypeProperties" type="abstract operation">
<h1>
SetterThatIgnoresPrototypeProperties (
_home_: an Object,
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_p_: a property key,
_v_: an ECMAScript language value,
): either a normal completion containing ~unused~ or a throw completion
</h1>
<dl class="header">
</dl>
<emu-alg>
1. Let _O_ be ? RequireObjectCoercible(*this* value).
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1. If _O_ is _home_, then
1. NOTE: Throwing here emulates assignment to a non-writable data property on the _home_ object in strict mode code.
1. Throw a *TypeError* exception.
1. Let _desc_ be ? _O_.[[GetOwnProperty]](_p_).
1. If _desc_ is *undefined*, then
1. Perform ? CreateDataPropertyOrThrow(_O_, _p_, _v_).
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1. Else,
1. Perform ? Set(_O_, _p_, _v_, *true*).
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1. Return ~unused~.
</emu-alg>
</emu-clause>

<emu-clause id="sec-operations-on-iterator-objects">
<h1>Operations on Iterator Objects</h1>

Expand Down Expand Up @@ -289,7 +313,28 @@ <h1>Iterator.prototype</h1>

<emu-clause id="sec-iteratorprototype.constructor">
<h1>Iterator.prototype.constructor</h1>
<p>The initial value of %Iterator.prototype%.constructor is %Iterator%.</p>
<p>`Iterator.prototype.constructor` is an accessor property with attributes { [[Enumerable]]: *false*, [[Configurable]]: *true* }. The [[Get]] and [[Set]] attributes are defined as follows:</p>

<emu-clause id="sec-get-iteratorprototype-constructor">
<h1>get Iterator.prototype.constructor</h1>
<p>The value of the [[Get]] attribute is a built-in function that requires no arguments. It performs the following steps when called:</p>
<emu-alg>
1. Return %Iterator%.
</emu-alg>
</emu-clause>

<emu-clause id="sec-set-iteratorprototype-constructor">
<h1>set Iterator.prototype.constructor</h1>
<p>The value of the [[Set]] attribute is a built-in function that takes an argument _v_. It performs the following steps when called:</p>
<emu-alg>
1. Perform ? SetterThatIgnoresPrototypeProperties(%Iterator.prototype%, *"constructor"*, _v_).
1. Return *undefined*.
</emu-alg>
</emu-clause>

<emu-note>
<p>Unlike the *"constructor"* property on most built-in prototypes, for web-compatibility reasons this property must be an accessor.</p>
</emu-note>
</emu-clause>

<emu-clause id="sec-iteratorprototype.map">
Expand Down Expand Up @@ -563,9 +608,27 @@ <h1>Iterator.prototype.find ( _predicate_ )</h1>

<emu-clause id="sec-iteratorprototype-@@tostringtag">
<h1>Iterator.prototype [ @@toStringTag ]</h1>
<p>The initial value of the @@toStringTag property is the String value "Iterator".</p>
<p>`Iterator.prototype[@@toStringTag]` is an accessor property with attributes { [[Enumerable]]: *false*, [[Configurable]]: *true* }. The [[Get]] and [[Set]] attributes are defined as follows:</p>

<emu-clause id="sec-get-iteratorprototype-@@tostringtag">
<h1>get Iterator.prototype [ @@toStringTag ]</h1>
<p>The value of the [[Get]] attribute is a built-in function that requires no arguments. It performs the following steps when called:</p>
<emu-alg>
1. Return *"Iterator"*.
</emu-alg>
</emu-clause>

<emu-clause id="sec-set-iteratorprototype-@@tostringtag">
<h1>set Iterator.prototype [ @@toStringTag ]</h1>
<p>The value of the [[Set]] attribute is a built-in function that takes an argument _v_. It performs the following steps when called:</p>
<emu-alg>
1. Perform ? SetterThatIgnoresPrototypeProperties(%Iterator.prototype%, %Symbol.toStringTag%, _v_).
1. Return *undefined*.
</emu-alg>
</emu-clause>

<emu-note>
<p>Unlike the @@toStringTag on most built-in classes, for web-compatibility reasons this property must be writable.</p>
<p>Unlike the @@toStringTag property on most built-in prototypes, for web-compatibility reasons this property must be an accessor.</p>
</emu-note>
</emu-clause>
</emu-clause>
Expand Down