Skip to content

Commit

Permalink
Editorial: Model a declarative binding as a Record
Browse files Browse the repository at this point in the history
  • Loading branch information
@jmdyck
jmdyck committed Feb 10, 2023
1 parent cad610c commit e023ad5
Showing 1 changed file with 97 additions and 26 deletions.
123 changes: 97 additions & 26 deletions spec.html
View file
Original file line number Diff line number Diff line change
Expand Up @@ -9968,14 +9968,53 @@ <h1>Declarative Environment Records</h1>
[[Bindings]]
</td>
<td>
a List of bindings
a List of DeclarativeBindings
</td>
<td>
Satisfies the invariant that no two bindings in [[Bindings]] are bindings for the same name.
Satisfies the invariant that no two records in [[Bindings]] have the same [[BoundName]].
</td>
</tr>
</table>
</emu-table>

<p>A <dfn>DeclarativeBinding</dfn> is either a SimpleDeclarativeBinding or an ImportDeclarativeBinding. SimpleDeclarativeBindings can appear in any Declarative Environment Record, but ImportDeclarativeBindings can only appear in a Module Environment Record.</p>

<p>A <dfn>SimpleDeclarativeBinding</dfn> has the following fields:</p>
<emu-table id="table-fields-of-simpledeclarativebindings" caption="SimpleDeclarativeBinding Fields">
<table>
<tr>
<th>Field Name</th>
<th>Value</th>
<th>Meaning</th>
</tr>
<tr>
<td>[[BoundName]]</td>
<td>a String</td>
<td>the name being bound.</td>
</tr>
<tr>
<td>[[BoundValue]]</td>
<td>an ECMAScript language value or ~uninitialized~</td>
<td>the value that the name is bound to.</td>
</tr>
<tr>
<td>[[IsMutable]]</td>
<td>a Boolean</td>
<td>if *true*, indicates that the binding is mutable.</td>
</tr>
<tr>
<td>[[IsDeletable]]</td>
<td>a Boolean</td>
<td>if *true*, indicates that the binding may be deleted by a subsequent DeleteBinding call.</td>
</tr>
<tr>
<td>[[IsStrict]]</td>
<td>a Boolean</td>
<td>if *true*, indicates that the binding is a strict binding.</td>
</tr>
</table>
</emu-table>

<p>The behaviour of the concrete specification methods for Declarative Environment Records is defined by the following algorithms.</p>

<emu-clause id="sec-declarative-environment-records-hasbinding-n" type="concrete method">
Expand All @@ -9992,7 +10031,7 @@ <h1>
<dd>It determines if the argument identifier is one of the identifiers bound by the record.</dd>
</dl>
<emu-alg>
1. If _envRec_.[[Bindings]] contains a binding for _N_, return *true*.
1. If _envRec_.[[Bindings]] contains a DeclarativeBinding whose [[BoundName]] field equals _N_, return *true*.
1. Return *false*.
</emu-alg>
</emu-clause>
Expand All @@ -10013,7 +10052,7 @@ <h1>
</dl>
<emu-alg>
1. Assert: _envRec_.HasBinding(_N_) is *false*.
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.
1. Let _binding_ be SimpleDeclarativeBinding { [[BoundName]]: _N_, [[BoundValue]]: ~uninitialized~, [[IsMutable]]: *true*, [[IsDeletable]]: _D_, [[IsStrict]]: *false* }.
1. Append _binding_ to _envRec_.[[Bindings]].
1. Return ~unused~.
</emu-alg>
Expand All @@ -10035,7 +10074,7 @@ <h1>
</dl>
<emu-alg>
1. Assert: _envRec_.HasBinding(_N_) is *false*.
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.
1. Let _binding_ be SimpleDeclarativeBinding { [[BoundName]]: _N_, [[BoundValue]]: ~uninitialized~, [[IsMutable]]: *false*, [[IsDeletable]]: *false*, [[IsStrict]]: _S_ }.
1. Append _binding_ to _envRec_.[[Bindings]].
1. Return ~unused~.
</emu-alg>
Expand All @@ -10057,10 +10096,10 @@ <h1>
</dl>
<emu-alg>
1. Assert: _envRec_.HasBinding(_N_) is *true*.
1. Let _binding_ be the binding for _N_ in _envRec_.[[Bindings]].
1. Assert: _binding_ is uninitialized.
1. Set the bound value of _binding_ to _V_.
1. <emu-not-ref>Record</emu-not-ref> that _binding_ has been initialized.
1. Let _binding_ be the DeclarativeBinding in _envRec_.[[Bindings]] whose [[BoundName]] field equals _N_.
1. Assert: _binding_ is a SimpleDeclarativeBinding.
1. Assert: _binding_.[[BoundValue]] is ~uninitialized~.
1. Set _binding_.[[BoundValue]] to _V_.
1. Return ~unused~.
</emu-alg>
</emu-clause>
Expand All @@ -10086,10 +10125,12 @@ <h1>
1. Perform ! _envRec_.CreateMutableBinding(_N_, *true*).
1. Perform ! _envRec_.InitializeBinding(_N_, _V_).
1. Return ~unused~.
1. Let _binding_ be the binding for _N_ in _envRec_.[[Bindings]].
1. If _binding_ is a strict binding, set _S_ to *true*.
1. If _binding_ has not yet been initialized, throw a *ReferenceError* exception.
1. Else if _binding_ is a mutable binding, change its bound value to _V_.
1. Let _binding_ be the DeclarativeBinding in _envRec_.[[Bindings]] whose [[BoundName]] field equals _N_.
1. If _binding_ is an ImportDeclarativeBinding, throw a *TypeError* exception.
1. Assert: _binding_ is a SimpleDeclarativeBinding.
1. If _binding_.[[IsStrict]] is *true*, set _S_ to *true*.
1. If _binding_.[[BoundValue]] is ~uninitialized~, throw a *ReferenceError* exception.
1. Else if _binding_.[[IsMutable]] is *true*, change its bound value to _V_.
1. Else,
1. Assert: This is an attempt to change the value of an immutable binding.
1. If _S_ is *true*, throw a *TypeError* exception.
Expand Down Expand Up @@ -10117,9 +10158,10 @@ <h1>
</dl>
<emu-alg>
1. Assert: _envRec_.HasBinding(_N_) is *true*.
1. Let _binding_ be the binding for _N_ in _envRec_.[[Bindings]].
1. If _binding_ is an uninitialized binding, throw a *ReferenceError* exception.
1. Return the value currently bound in _binding_.
1. Let _binding_ be the DeclarativeBinding in _envRec_.[[Bindings]] whose [[BoundName]] field equals _N_.
1. Assert: _binding_ is a SimpleDeclarativeBinding.
1. If _binding_.[[BoundValue]] is ~uninitialized~, throw a *ReferenceError* exception.
1. Return _binding_.[[BoundValue]].
</emu-alg>
</emu-clause>

Expand All @@ -10138,8 +10180,9 @@ <h1>
</dl>
<emu-alg>
1. Assert: _envRec_.HasBinding(_N_) is *true*.
1. Let _binding_ be the binding for _N_ in _envRec_.[[Bindings]].
1. If _binding_ cannot be deleted, return *false*.
1. Let _binding_ be the DeclarativeBinding in _envRec_.[[Bindings]] whose [[BoundName]] field equals _N_.
1. Assert: _binding_ is a SimpleDeclarativeBinding.
1. If _binding_.[[IsDeletable]] is *false*, return *false*.
1. Remove _binding_ from _envRec_.[[Bindings]].
1. Return *true*.
</emu-alg>
Expand Down Expand Up @@ -11151,6 +11194,31 @@ <h1>Module Environment Records</h1>
</tr>
</table>
</emu-table>
<p>The [[Bindings]] of a Module Environment Record can include both SimpleDeclarativeBindings and ImportDeclarativeBindings. An <dfn>ImportDeclarativeBinding</dfn> has the following fields:</p>
<emu-table id="table-fields-of-importdeclarativebindings" caption="ImportDeclarativeBinding Fields">
<table>
<tr>
<th>Field Name</th>
<th>Value</th>
<th>Meaning</th>
</tr>
<tr>
<td>[[BoundName]]</td>
<td>a String</td>
<td>the name being bound.</td>
</tr>
<tr>
<td>[[TargetModuleRec]]</td>
<td>a Module Record</td>
<td>the imported module that provides the binding.</td>
</tr>
<tr>
<td>[[TargetName]]</td>
<td>a String</td>
<td>the name of a binding that exists in the target module.</td>
</tr>
</table>
</emu-table>
<p>The behaviour of the additional concrete specification methods for Module Environment Records are defined by the following algorithms:</p>

<emu-clause id="sec-module-environment-records-getbindingvalue-n-s" type="concrete method">
Expand All @@ -11170,14 +11238,16 @@ <h1>
<emu-alg>
1. Assert: _S_ is *true*.
1. Assert: _envRec_.HasBinding(_N_) is *true*.
1. Let _binding_ be the binding for _N_ in _envRec_.[[Bindings]].
1. If _binding_ is an indirect binding, then
1. Let _M_ and _N2_ be the indirection values provided when this binding for _N_ was created.
1. Let _binding_ be the DeclarativeBinding in _envRec_.[[Bindings]] whose [[BoundName]] field equals _N_.
1. If _binding_ is an ImportDeclarativeBinding, then
1. Let _M_ be _binding_.[[TargetModuleRec]].
1. Let _N2_ be _binding_.[[TargetName]].
1. Let _targetEnv_ be _M_.[[Environment]].
1. If _targetEnv_ is ~empty~, throw a *ReferenceError* exception.
1. Return ? <emu-meta effects="user-code">_targetEnv_.GetBindingValue</emu-meta>(_N2_, *true*).
1. If _binding_ is an uninitialized binding, throw a *ReferenceError* exception.
1. Return the value currently bound in _binding_.
1. Assert: _binding_ is a SimpleDeclarativeBinding.
1. If _binding_.[[BoundValue]] is ~uninitialized~, throw a *ReferenceError* exception.
1. Return _binding_.[[BoundValue]].
</emu-alg>
<emu-note>
<p>_S_ will always be *true* because a |Module| is always strict mode code.</p>
Expand Down Expand Up @@ -11235,7 +11305,7 @@ <h1>
<emu-alg>
1. Assert: _envRec_.HasBinding(_N_) is *false*.
1. Assert: When _M_.[[Environment]] is instantiated, it will have a direct binding for _N2_.
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.
1. Let _binding_ be ImportDeclarativeBinding { [[BoundName]]: _N_, [[TargetModuleRec]]: _M_, [[TargetName]]: _N2_ }.
1. Append _binding_ to _envRec_.[[Bindings]].
1. Return ~unused~.
</emu-alg>
Expand Down Expand Up @@ -48285,8 +48355,9 @@ <h1>Changes to BlockDeclarationInstantiation</h1>
<p>During BlockDeclarationInstantiation the following steps are performed in place of step <emu-xref href="#step-blockdeclarationinstantiation-initializebinding"></emu-xref>:</p>
<emu-alg replaces-step="step-blockdeclarationinstantiation-initializebinding">
1. Perform the following steps:
1. Let _binding_ be the binding for _fn_ in _env_.[[Bindings]].
1. If _binding_ is an uninitialized binding, then
1. Let _binding_ be the DeclarativeBinding in _env_.[[Bindings]] whose [[BoundName]] field equals _fn_.
1. Assert: _binding_ is a SimpleDeclarativeBinding.
1. If _binding_.[[BoundValue]] is ~uninitialized~, then
1. Perform ! _env_.InitializeBinding(_fn_, _fo_).
1. Else,
1. Assert: _d_ is a |FunctionDeclaration|.
Expand Down

0 comments on commit e023ad5

Please sign in to comment.