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Normative: Add "Runtime Errors for Function Call Assignment Targets" to Annex B #3568

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Normative: Add "Runtime Errors for Function Call Assignment Targets" to Annex B #3568

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18d3969
Normative: Add "Late Errors for Function Call Assignment Targets" to …
rkirsling Apr 18, 2025
7e73bf6
Explicitly throw after Evaluation of LHS.
rkirsling Apr 19, 2025
71a8236
Be more fully explicit.
rkirsling Apr 23, 2025
9ea9da8
Address editor feedback.
rkirsling May 15, 2025
cedf79f
Simplify further.
rkirsling May 16, 2025
0863404
Address bakkot's feedback.
rkirsling May 29, 2025
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46 changes: 39 additions & 7 deletions spec.html
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Original file line number Diff line number Diff line change
Expand Up @@ -9980,7 +9980,7 @@ <h1>
</emu-clause>

<emu-clause id="sec-static-semantics-assignmenttargettype" oldids="sec-identifiers-static-semantics-assignmenttargettype,sec-identifiers-static-semantics-isvalidsimpleassignmenttarget,sec-semantics-static-semantics-assignmenttargettype,sec-semantics-static-semantics-isvalidsimpleassignmenttarget,sec-grouping-operator-static-semantics-assignmenttargettype,sec-grouping-operator-static-semantics-isvalidsimpleassignmenttarget,sec-static-semantics-static-semantics-assignmenttargettype,sec-static-semantics-static-semantics-isvalidsimpleassignmenttarget,sec-update-expressions-static-semantics-assignmenttargettype,sec-update-expressions-static-semantics-isvalidsimpleassignmenttarget,sec-unary-operators-static-semantics-assignmenttargettype,sec-unary-operators-static-semantics-isvalidsimpleassignmenttarget,sec-exp-operator-static-semantics-assignmenttargettype,sec-exp-operator-static-semantics-isvalidsimpleassignmenttarget,sec-multiplicative-operators-static-semantics-assignmenttargettype,sec-multiplicative-operators-static-semantics-isvalidsimpleassignmenttarget,sec-additive-operators-static-semantics-assignmenttargettype,sec-additive-operators-static-semantics-isvalidsimpleassignmenttarget,sec-bitwise-shift-operators-static-semantics-assignmenttargettype,sec-bitwise-shift-operators-static-semantics-isvalidsimpleassignmenttarget,sec-relational-operators-static-semantics-assignmenttargettype,sec-relational-operators-static-semantics-isvalidsimpleassignmenttarget,sec-equality-operators-static-semantics-assignmenttargettype,sec-equality-operators-static-semantics-isvalidsimpleassignmenttarget,sec-binary-bitwise-operators-static-semantics-assignmenttargettype,sec-binary-bitwise-operators-static-semantics-isvalidsimpleassignmenttarget,sec-binary-logical-operators-static-semantics-assignmenttargettype,sec-binary-logical-operators-static-semantics-isvalidsimpleassignmenttarget,sec-conditional-operator-static-semantics-assignmenttargettype,sec-conditional-operator-static-semantics-isvalidsimpleassignmenttarget,sec-assignment-operators-static-semantics-assignmenttargettype,sec-assignment-operators-static-semantics-isvalidsimpleassignmenttarget,sec-comma-operator-static-semantics-assignmenttargettype,sec-comma-operator-static-semantics-isvalidsimpleassignmenttarget" type="sdo">
<h1>Static Semantics: AssignmentTargetType ( ): ~simple~ or ~invalid~</h1>
<h1>Static Semantics: AssignmentTargetType ( ): ~simple~, ~web-compat~, or ~invalid~</h1>
<dl class="header">
</dl>
<emu-grammar>IdentifierReference : Identifier</emu-grammar>
Expand Down Expand Up @@ -10015,6 +10015,16 @@ <h1>Static Semantics: AssignmentTargetType ( ): ~simple~ or ~invalid~</h1>
1. Let _expr_ be the |ParenthesizedExpression| that is covered by |CoverParenthesizedExpressionAndArrowParameterList|.
1. Return the AssignmentTargetType of _expr_.
</emu-alg>
<emu-grammar>
CallExpression :
CoverCallExpressionAndAsyncArrowHead
CallExpression Arguments
</emu-grammar>
<emu-alg>
1. [id="step-assignmenttargettype-web-compat", normative-optional] If the host is a web browser or otherwise supports <emu-xref href="#sec-runtime-errors-for-function-call-assignment-targets" title></emu-xref> and IsStrict(this |CallExpression|) is *false*, then
1. Return ~web-compat~.
1. Return ~invalid~.
</emu-alg>
<emu-grammar>
PrimaryExpression :
`this`
Expand All @@ -10030,10 +10040,8 @@ <h1>Static Semantics: AssignmentTargetType ( ): ~simple~ or ~invalid~</h1>
TemplateLiteral

CallExpression :
CoverCallExpressionAndAsyncArrowHead
SuperCall
ImportCall
CallExpression Arguments
CallExpression TemplateLiteral

NewExpression :
Expand Down Expand Up @@ -19990,7 +19998,7 @@ <h1>Static Semantics: Early Errors</h1>
</emu-grammar>
<ul>
<li>
It is an early Syntax Error if the AssignmentTargetType of |LeftHandSideExpression| is not ~simple~.
It is an early Syntax Error if the AssignmentTargetType of |LeftHandSideExpression| is ~invalid~.
</li>
</ul>

Expand All @@ -20001,7 +20009,7 @@ <h1>Static Semantics: Early Errors</h1>
</emu-grammar>
<ul>
<li>
It is an early Syntax Error if the AssignmentTargetType of |UnaryExpression| is not ~simple~.
It is an early Syntax Error if the AssignmentTargetType of |UnaryExpression| is ~invalid~.
</li>
</ul>
</emu-clause>
Expand All @@ -20014,6 +20022,7 @@ <h1>Runtime Semantics: Evaluation</h1>
<emu-grammar>UpdateExpression : LeftHandSideExpression `++`</emu-grammar>
<emu-alg>
1. Let _lhs_ be ? Evaluation of |LeftHandSideExpression|.
1. If the AssignmentTargetType of |LeftHandSideExpression| is ~web-compat~, throw a *ReferenceError* exception.
1. Let _oldValue_ be ? ToNumeric(? GetValue(_lhs_)).
1. If _oldValue_ is a Number, then
1. Let _newValue_ be Number::add(_oldValue_, *1*<sub>𝔽</sub>).
Expand All @@ -20034,6 +20043,7 @@ <h1>Runtime Semantics: Evaluation</h1>
<emu-grammar>UpdateExpression : LeftHandSideExpression `--`</emu-grammar>
<emu-alg>
1. Let _lhs_ be ? Evaluation of |LeftHandSideExpression|.
1. If the AssignmentTargetType of |LeftHandSideExpression| is ~web-compat~, throw a *ReferenceError* exception.
1. Let _oldValue_ be ? ToNumeric(? GetValue(_lhs_)).
1. If _oldValue_ is a Number, then
1. Let _newValue_ be Number::subtract(_oldValue_, *1*<sub>𝔽</sub>).
Expand All @@ -20054,6 +20064,7 @@ <h1>Runtime Semantics: Evaluation</h1>
<emu-grammar>UpdateExpression : `++` UnaryExpression</emu-grammar>
<emu-alg>
1. Let _expr_ be ? Evaluation of |UnaryExpression|.
1. If the AssignmentTargetType of |UnaryExpression| is ~web-compat~, throw a *ReferenceError* exception.
1. Let _oldValue_ be ? ToNumeric(? GetValue(_expr_)).
1. If _oldValue_ is a Number, then
1. Let _newValue_ be Number::add(_oldValue_, *1*<sub>𝔽</sub>).
Expand All @@ -20074,6 +20085,7 @@ <h1>Runtime Semantics: Evaluation</h1>
<emu-grammar>UpdateExpression : `--` UnaryExpression</emu-grammar>
<emu-alg>
1. Let _expr_ be ? Evaluation of |UnaryExpression|.
1. If the AssignmentTargetType of |UnaryExpression| is ~web-compat~, throw a *ReferenceError* exception.
1. Let _oldValue_ be ? ToNumeric(? GetValue(_expr_)).
1. If _oldValue_ is a Number, then
1. Let _newValue_ be Number::subtract(_oldValue_, *1*<sub>𝔽</sub>).
Expand Down Expand Up @@ -20776,12 +20788,20 @@ <h1>Static Semantics: Early Errors</h1>
If |LeftHandSideExpression| is either an |ObjectLiteral| or an |ArrayLiteral|, |LeftHandSideExpression| must cover an |AssignmentPattern|.
</li>
<li>
If |LeftHandSideExpression| is neither an |ObjectLiteral| nor an |ArrayLiteral|, it is a Syntax Error if the AssignmentTargetType of |LeftHandSideExpression| is not ~simple~.
If |LeftHandSideExpression| is neither an |ObjectLiteral| nor an |ArrayLiteral|, it is a Syntax Error if the AssignmentTargetType of |LeftHandSideExpression| is ~invalid~.
</li>
</ul>
<emu-grammar>
AssignmentExpression :
LeftHandSideExpression AssignmentOperator AssignmentExpression
</emu-grammar>
<ul>
<li>
It is a Syntax Error if the AssignmentTargetType of |LeftHandSideExpression| is ~invalid~.
</li>
</ul>
<emu-grammar>
AssignmentExpression :
LeftHandSideExpression `&amp;&amp;=` AssignmentExpression
LeftHandSideExpression `||=` AssignmentExpression
LeftHandSideExpression `??=` AssignmentExpression
Expand All @@ -20799,6 +20819,7 @@ <h1>Runtime Semantics: Evaluation</h1>
<emu-alg>
1. If |LeftHandSideExpression| is neither an |ObjectLiteral| nor an |ArrayLiteral|, then
1. Let _lRef_ be ? Evaluation of |LeftHandSideExpression|.
1. If the AssignmentTargetType of |LeftHandSideExpression| is ~web-compat~, throw a *ReferenceError* exception.
1. If IsAnonymousFunctionDefinition(|AssignmentExpression|) is *true* and IsIdentifierRef of |LeftHandSideExpression| is *true*, then
1. Let _lhs_ be the StringValue of |LeftHandSideExpression|.
1. Let _rVal_ be ? NamedEvaluation of |AssignmentExpression| with argument _lhs_.
Expand All @@ -20816,6 +20837,7 @@ <h1>Runtime Semantics: Evaluation</h1>
<emu-grammar>AssignmentExpression : LeftHandSideExpression AssignmentOperator AssignmentExpression</emu-grammar>
<emu-alg>
1. Let _lRef_ be ? Evaluation of |LeftHandSideExpression|.
1. If the AssignmentTargetType of |LeftHandSideExpression| is ~web-compat~, throw a *ReferenceError* exception.
1. [id="step-assignmentexpression-evaluation-compound-getvalue"] Let _lVal_ be ? GetValue(_lRef_).
1. Let _rRef_ be ? Evaluation of |AssignmentExpression|.
1. Let _rVal_ be ? GetValue(_rRef_).
Expand Down Expand Up @@ -22254,7 +22276,7 @@ <h1>Static Semantics: Early Errors</h1>
If |LeftHandSideExpression| is either an |ObjectLiteral| or an |ArrayLiteral|, |LeftHandSideExpression| must cover an |AssignmentPattern|.
</li>
<li>
If |LeftHandSideExpression| is neither an |ObjectLiteral| nor an |ArrayLiteral|, it is a Syntax Error if the AssignmentTargetType of |LeftHandSideExpression| is not ~simple~.
If |LeftHandSideExpression| is neither an |ObjectLiteral| nor an |ArrayLiteral|, it is a Syntax Error if the AssignmentTargetType of |LeftHandSideExpression| is ~invalid~.
</li>
</ul>
<emu-grammar>
Expand Down Expand Up @@ -22498,6 +22520,7 @@ <h1>
1. Let _status_ be Completion(BindingInitialization of _lhs_ with arguments _nextValue_ and *undefined*).
1. Else,
1. Let _lhsRef_ be Completion(Evaluation of _lhs_). (It may be evaluated repeatedly.)
1. If _lhsKind_ is ~assignment~ and the AssignmentTargetType of _lhs_ is ~web-compat~, throw a *ReferenceError* exception.
1. If _lhsRef_ is an abrupt completion, then
1. Let _status_ be _lhsRef_.
1. Else,
Expand Down Expand Up @@ -52991,6 +53014,15 @@ <h1>Non-default behaviour in HostMakeJobCallback</h1>
<h1>Non-default behaviour in HostEnsureCanAddPrivateElement</h1>
<p>The HostEnsureCanAddPrivateElement abstract operation allows hosts which are web browsers to specify non-default behaviour.</p>
</emu-annex>

<emu-annex id="sec-runtime-errors-for-function-call-assignment-targets">
<h1>Runtime Errors for Function Call Assignment Targets</h1>
<p>When a function call (<emu-xref href="#sec-function-calls"></emu-xref>) is used as an assignment target in non-strict code, instead of producing an early error, a *ReferenceError* exception is thrown during evaluation of the assignment.</p>
<emu-note>
<p>When the assignment target is the |LeftHandSideExpression| of an |AssignmentExpression|, the assignment operator must be `=` or an |AssignmentOperator|; in particular, the allowance here does not apply to the logical assignment operators (`??=`, `&&=`, `||=`).</p>
</emu-note>
<p>See step <emu-xref href="#step-assignmenttargettype-web-compat"></emu-xref> of AssignmentTargetType for <emu-grammar>CallExpression : CoverCallExpressionAndAsyncArrowHead</emu-grammar> and <emu-grammar>CallExpression : CallExpression Arguments</emu-grammar>.</p>
</emu-annex>
</emu-annex>
</emu-annex>

Expand Down