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Editorial: Model a binding as a Record
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‎spec.html‎

Lines changed: 149 additions & 26 deletions
Original file line numberDiff line numberDiff line change
@@ -10139,14 +10139,98 @@ <h1>Declarative Environment Records</h1>
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[[Bindings]]
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</td>
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<td>
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List of bindings
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List of DeclarativeBindingRecord
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</td>
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<td>
10145-
Satisfies the invariant that no two bindings in [[Bindings]] are bindings for the same name.
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Satisfies the invariant that no two records in [[Bindings]] have the same [[BoundName]].
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</td>
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</tr>
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</table>
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</emu-table>
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<p>A <dfn>DeclarativeBindingRecord</dfn> has the following fields:</p>
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<emu-table id="table-fields-of-declarative-binding-records" caption="DeclarativeBindingRecord Fields">
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<table>
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<tr>
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<th>
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Field Name
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</th>
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<th>
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Value
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</th>
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<th>
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Meaning
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</th>
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</tr>
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<tr>
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<td>
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[[BoundName]]
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</td>
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<td>
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a String
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</td>
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<td>
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the name being bound.
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</td>
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</tr>
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<tr>
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<td>
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[[IsInitialized]]
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</td>
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<td>
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a Boolean
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</td>
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<td>
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indicates whether the binding is initialized.
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</td>
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</tr>
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<tr>
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<td>
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[[BoundValue]]
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</td>
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<td>
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an ECMAScript language value
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</td>
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<td>
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the value that the name is bound to.
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</td>
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</tr>
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<tr>
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<td>
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[[IsMutable]]
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</td>
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<td>
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a Boolean
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</td>
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<td>
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if *true*, indicates that the binding is mutable.
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</td>
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</tr>
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<tr>
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<td>
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[[IsDeletable]]
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</td>
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<td>
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a Boolean
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</td>
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<td>
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if *true*, indicates that the binding may be deleted by a subsequent DeleteBinding call.
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</td>
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</tr>
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<tr>
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<td>
10222+
[[IsStrict]]
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</td>
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<td>
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a Boolean
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</td>
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<td>
10228+
if *true*, indicates that the binding is a strict binding.
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</td>
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</tr>
10231+
</table>
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</emu-table>
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1015010234
<p>The behaviour of the concrete specification methods for declarative Environment Records is defined by the following algorithms.</p>
1015110235

1015210236
<emu-clause id="sec-declarative-environment-records-hasbinding-n" type="concrete method">
@@ -10163,7 +10247,7 @@ <h1>
1016310247
<dd>It determines if the argument identifier is one of the identifiers bound by the record.</dd>
1016410248
</dl>
1016510249
<emu-alg>
10166-
1. If _envRec_.[[Bindings]] contains a binding for the name that is the value of _N_, return *true*.
10250+
1. If _envRec_.[[Bindings]] contains a DeclarativeBindingRecord whose [[BoundName]] field is equal to the value of _N_, return *true*.
1016710251
1. Return *false*.
1016810252
</emu-alg>
1016910253
</emu-clause>
@@ -10184,7 +10268,7 @@ <h1>
1018410268
</dl>
1018510269
<emu-alg>
1018610270
1. Assert: _envRec_.HasBinding(_N_) is *false*.
10187-
1. Let _binding_ be a mutable binding for _N_ and record that it is uninitialized. If _D_ is *true*, record that the newly created binding may be deleted by a subsequent DeleteBinding call.
10271+
1. Let _binding_ be DeclarativeBindingRecord { [[BoundName]]: _N_, [[IsInitialized]]: *false*, [[BoundValue]]: *undefined*, [[IsMutable]]: *true*, [[IsDeletable]]: _D_, [[IsStrict]]: *false* }.
1018810272
1. Append _binding_ to _envRec_.[[Bindings]].
1018910273
1. Return NormalCompletion(~empty~).
1019010274
</emu-alg>
@@ -10206,7 +10290,7 @@ <h1>
1020610290
</dl>
1020710291
<emu-alg>
1020810292
1. Assert: _envRec_.HasBinding(_N_) is *false*.
10209-
1. Let _binding_ be an immutable binding for _N_ and record that it is uninitialized. If _S_ is *true*, record that the newly created binding is a strict binding.
10293+
1. Let _binding_ be DeclarativeBindingRecord { [[BoundName]]: _N_, [[IsInitialized]]: *false*, [[BoundValue]]: *undefined*, [[IsMutable]]: *false*, [[IsDeletable]]: *false*, [[IsStrict]]: _S_ }.
1021010294
1. Append _binding_ to _envRec_.[[Bindings]].
1021110295
1. Return NormalCompletion(~empty~).
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</emu-alg>
@@ -10228,10 +10312,10 @@ <h1>
1022810312
</dl>
1022910313
<emu-alg>
1023010314
1. Assert: _envRec_.HasBinding(_N_) is *true*.
10231-
1. Let _binding_ be the binding for _N_ in _envRec_.[[Bindings]].
10232-
1. Assert: _binding_ is uninitialized.
10233-
1. Set the bound value of _binding_ to _V_.
10234-
1. <emu-not-ref>Record</emu-not-ref> that _binding_ has been initialized.
10315+
1. Let _binding_ be the DeclarativeBindingRecord in _envRec_.[[Bindings]] whose [[BoundName]] field equals _N_.
10316+
1. Assert: _binding_.[[IsInitialized]] is *false*.
10317+
1. Set _binding_.[[BoundValue]] to _V_.
10318+
1. Set _binding_.[[IsInitialized]] to *true*.
1023510319
1. Return NormalCompletion(~empty~).
1023610320
</emu-alg>
1023710321
</emu-clause>
@@ -10257,10 +10341,10 @@ <h1>
1025710341
1. Perform _envRec_.CreateMutableBinding(_N_, *true*).
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1. Perform _envRec_.InitializeBinding(_N_, _V_).
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1. Return NormalCompletion(~empty~).
10260-
1. Let _binding_ be the binding for _N_ in _envRec_.[[Bindings]].
10261-
1. If _binding_ is a strict binding, set _S_ to *true*.
10262-
1. If _binding_ has not yet been initialized, throw a *ReferenceError* exception.
10263-
1. Else if _binding_ is a mutable binding, change its bound value to _V_.
10344+
1. Let _binding_ be the DeclarativeBindingRecord in _envRec_.[[Bindings]] whose [[BoundName]] field equals _N_.
10345+
1. If _binding_.[[IsStrict]] is *true*, set _S_ to *true*.
10346+
1. If _binding_.[[IsInitialized]] is *false*, throw a *ReferenceError* exception.
10347+
1. Else if _binding_.[[IsMutable]] is *true*, change its bound value to _V_.
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1. Else,
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1. Assert: This is an attempt to change the value of an immutable binding.
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1. If _S_ is *true*, throw a *TypeError* exception.
@@ -10288,9 +10372,9 @@ <h1>
1028810372
</dl>
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<emu-alg>
1029010374
1. Assert: _envRec_.HasBinding(_N_) is *true*.
10291-
1. Let _binding_ be the binding for _N_ in _envRec_.[[Bindings]].
10292-
1. If _binding_ is an uninitialized binding, throw a *ReferenceError* exception.
10293-
1. Return the value currently bound in _binding_.
10375+
1. Let _binding_ be the DeclarativeBindingRecord in _envRec_.[[Bindings]] whose [[BoundName]] field equals _N_.
10376+
1. If _binding_.[[IsInitialized]] is *false*, throw a *ReferenceError* exception.
10377+
1. Return _binding_.[[BoundValue]].
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</emu-alg>
1029510379
</emu-clause>
1029610380

@@ -10309,8 +10393,8 @@ <h1>
1030910393
</dl>
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<emu-alg>
1031110395
1. Assert: _envRec_.HasBinding(_N_) is *true*.
10312-
1. Let _binding_ be the binding for _N_ in _envRec_.[[Bindings]].
10313-
1. If _binding_ cannot be deleted, return *false*.
10396+
1. Let _binding_ be the DeclarativeBindingRecord in _envRec_.[[Bindings]] whose [[BoundName]] field equals _N_.
10397+
1. If _binding_.[[IsDeletable]] is *false*, return *false*.
1031410398
1. Remove _binding_ from _envRec_.[[Bindings]].
1031510399
1. Return *true*.
1031610400
</emu-alg>
@@ -11319,6 +11403,44 @@ <h1>Module Environment Records</h1>
1131911403
</tr>
1132011404
</table>
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</emu-table>
11406+
<p>The [[Bindings]] of a Module Environment Record can include ImportDeclarativeBindingRecords. These have all the fields of DeclarativeBindingRecords, plus the additional state fields listed in the following table.</p>
11407+
<emu-table id="table-additional-fields-of-importdeclarativebindingrecords" caption="Additional Fields of ImportDeclarativeBindingRecords">
11408+
<table>
11409+
<tr>
11410+
<th>
11411+
Field Name
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</th>
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<th>
11414+
Value
11415+
</th>
11416+
<th>
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Meaning
11418+
</th>
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</tr>
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<tr>
11421+
<td>
11422+
[[TargetModuleRec]]
11423+
</td>
11424+
<td>
11425+
a Module Record
11426+
</td>
11427+
<td>
11428+
?
11429+
</td>
11430+
</tr>
11431+
<tr>
11432+
<td>
11433+
[[TargetName]]
11434+
</td>
11435+
<td>
11436+
a String
11437+
</td>
11438+
<td>
11439+
the name of a binding that exists in [[TargetModuleRec]]'s module Environment Record.
11440+
</td>
11441+
</tr>
11442+
</table>
11443+
</emu-table>
1132211444
<p>The behaviour of the additional concrete specification methods for module Environment Records are defined by the following algorithms:</p>
1132311445

1132411446
<emu-clause id="sec-module-environment-records-getbindingvalue-n-s" type="concrete method">
@@ -11338,14 +11460,15 @@ <h1>
1133811460
<emu-alg>
1133911461
1. Assert: _S_ is *true*.
1134011462
1. Assert: _envRec_.HasBinding(_N_) is *true*.
11341-
1. Let _binding_ be the binding for _N_ in _envRec_.[[Bindings]].
11342-
1. If _binding_ is an indirect binding, then
11343-
1. Let _M_ and _N2_ be the indirection values provided when this binding for _N_ was created.
11463+
1. Let _binding_ be the DeclarativeBindingRecord in _envRec_.[[Bindings]] whose [[BoundName]] field equals _N_.
11464+
1. If _binding_ is an ImportDeclarativeBindingRecord, then
11465+
1. Let _M_ be _binding_.[[TargetModuleRec]].
11466+
1. Let _N2_ be _binding_.[[TargetName]].
1134411467
1. Let _targetEnv_ be _M_.[[Environment]].
1134511468
1. If _targetEnv_ is ~empty~, throw a *ReferenceError* exception.
1134611469
1. Return ? _targetEnv_.GetBindingValue(_N2_, *true*).
11347-
1. If _binding_ is an uninitialized binding, throw a *ReferenceError* exception.
11348-
1. Return the value currently bound in _binding_.
11470+
1. If _binding_.[[IsInitialized]] is *false*, throw a *ReferenceError* exception.
11471+
1. Return _binding_.[[BoundValue]].
1134911472
</emu-alg>
1135011473
<emu-note>
1135111474
<p>_S_ will always be *true* because a |Module| is always strict mode code.</p>
@@ -11403,7 +11526,7 @@ <h1>
1140311526
<emu-alg>
1140411527
1. Assert: _envRec_.HasBinding(_N_) is *false*.
1140511528
1. Assert: When _M_.[[Environment]] is instantiated it will have a direct binding for _N2_.
11406-
1. Let _binding_ be an immutable indirect binding for _N_ that references _M_ and _N2_ as its target binding and record that the binding is initialized.
11529+
1. Let _binding_ be ImportDeclarativeBindingRecord { [[BoundName]]: _N_, [[IsInitialized]]: *true*, [[BoundValue]]: *undefined*, [[IsMutable]]: *false*, [[IsDeletable]]: *false*, [[IsStrict]]: *false*, [[TargetModuleRec]]: _M_, [[TargetName]]: _N2_ }.
1140711530
1. Append _binding_ to _envRec_.[[Bindings]].
1140811531
1. Return NormalCompletion(~empty~).
1140911532
</emu-alg>
@@ -47560,8 +47683,8 @@ <h1>Changes to BlockDeclarationInstantiation</h1>
4756047683
</emu-alg>
4756147684
<p>During BlockDeclarationInstantiation the following steps are performed in place of step <emu-xref href="#step-blockdeclarationinstantiation-initializebinding"></emu-xref>:</p>
4756247685
<emu-alg replaces-step="step-blockdeclarationinstantiation-initializebinding">
47563-
1. Let _binding_ be the binding for _fn_ in _env_.[[Bindings]].
47564-
1. If _binding_ is an uninitialized binding, then
47686+
1. Let _binding_ be the DeclarativeBindingRecord in _env_.[[Bindings]] whose [[BoundName]] field equals _fn_.
47687+
1. If _binding_.[[IsInitialized]] is *false*, then
4756547688
1. Perform _env_.InitializeBinding(_fn_, _fo_).
4756647689
1. Else,
4756747690
1. Assert: _d_ is a |FunctionDeclaration|.

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