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Normative: Add Logical Assignment Operators #2030

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Jul 21, 2020
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Normative: Add Logical Assignment Operators #2030

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68 changes: 64 additions & 4 deletions spec.html
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Original file line number Diff line number Diff line change
Expand Up @@ -11145,6 +11145,7 @@ <h2>Syntax</h2>
`&amp;&amp;` `||` `??`
`?` `:`
`=` `+=` `-=` `*=` `%=` `**=` `&lt;&lt;=` `&gt;&gt;=` `&gt;&gt;&gt;=` `&amp;=` `|=` `^=`
`&amp;&amp;=` `||=` `??=`
`=&gt;`

DivPunctuator ::
Expand Down Expand Up @@ -15332,6 +15333,9 @@ <h2>Syntax</h2>
AsyncArrowFunction[?In, ?Yield, ?Await]
LeftHandSideExpression[?Yield, ?Await] `=` AssignmentExpression[?In, ?Yield, ?Await] #assignment
LeftHandSideExpression[?Yield, ?Await] AssignmentOperator AssignmentExpression[?In, ?Yield, ?Await]
LeftHandSideExpression[?Yield, ?Await] `&amp;&amp;=` AssignmentExpression[?In, ?Yield, ?Await]
LeftHandSideExpression[?Yield, ?Await] `||=` AssignmentExpression[?In, ?Yield, ?Await]
LeftHandSideExpression[?Yield, ?Await] `??=` AssignmentExpression[?In, ?Yield, ?Await]

AssignmentOperator : one of
`*=` `/=` `%=` `+=` `-=` `&lt;&lt;=` `&gt;&gt;=` `&gt;&gt;&gt;=` `&amp;=` `^=` `|=` `**=`
Expand All @@ -15355,7 +15359,13 @@ <h1>Static Semantics: Early Errors</h1>
It is a Syntax Error if AssignmentTargetType of |LeftHandSideExpression| is not ~simple~.
</li>
</ul>
<emu-grammar>AssignmentExpression : LeftHandSideExpression AssignmentOperator AssignmentExpression</emu-grammar>
<emu-grammar>
AssignmentExpression :
LeftHandSideExpression AssignmentOperator AssignmentExpression
LeftHandSideExpression `&amp;&amp;=` AssignmentExpression
LeftHandSideExpression `||=` AssignmentExpression
LeftHandSideExpression `??=` AssignmentExpression
</emu-grammar>
<ul>
<li>
It is a Syntax Error if AssignmentTargetType of |LeftHandSideExpression| is not ~simple~.
Expand All @@ -15379,6 +15389,9 @@ <h1>Static Semantics: IsFunctionDefinition</h1>
YieldExpression
LeftHandSideExpression `=` AssignmentExpression
LeftHandSideExpression AssignmentOperator AssignmentExpression
LeftHandSideExpression `&amp;&amp;=` AssignmentExpression
LeftHandSideExpression `||=` AssignmentExpression
LeftHandSideExpression `??=` AssignmentExpression
</emu-grammar>
<emu-alg>
1. Return *false*.
Expand All @@ -15395,6 +15408,9 @@ <h1>Static Semantics: AssignmentTargetType</h1>
AsyncArrowFunction
LeftHandSideExpression `=` AssignmentExpression
LeftHandSideExpression AssignmentOperator AssignmentExpression
LeftHandSideExpression `&amp;&amp;=` AssignmentExpression
LeftHandSideExpression `||=` AssignmentExpression
LeftHandSideExpression `??=` AssignmentExpression
</emu-grammar>
<emu-alg>
1. Return ~invalid~.
Expand Down Expand Up @@ -15424,7 +15440,7 @@ <h1>Runtime Semantics: Evaluation</h1>
<emu-grammar>AssignmentExpression : LeftHandSideExpression AssignmentOperator AssignmentExpression</emu-grammar>
<emu-alg>
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1. Let _lref_ be the result of evaluating |LeftHandSideExpression|.
1. Let _lval_ be ? GetValue(_lref_).
1. [id="step-assignmentexpression-evaluation-compound-getvalue"] Let _lval_ be ? GetValue(_lref_).
1. Let _rref_ be the result of evaluating |AssignmentExpression|.
1. Let _rval_ be ? GetValue(_rref_).
1. Let _assignmentOpText_ be the source text matched by |AssignmentOperator|.
Expand Down Expand Up @@ -15452,8 +15468,49 @@ <h1>Runtime Semantics: Evaluation</h1>
1. [id="step-assignmentexpression-evaluation-compound-putvalue"] Perform ? PutValue(_lref_, _r_).
1. Return _r_.
</emu-alg>
<emu-grammar>AssignmentExpression : LeftHandSideExpression `&amp;&amp;=` AssignmentExpression</emu-grammar>
<emu-alg>
1. Let _lref_ be the result of evaluating |LeftHandSideExpression|.
1. [id="step-assignmentexpression-evaluation-lgcl-and-getvalue"] Let _lval_ be ? GetValue(_lref_).
1. Let _lbool_ be ! ToBoolean(_lval_).
1. If _lbool_ is *false*, return _lval_.
1. If IsAnonymousFunctionDefinition(|AssignmentExpression|) is *true* and IsIdentifierRef of |LeftHandSideExpression| is *true*, then
1. Let _rval_ be NamedEvaluation of |AssignmentExpression| with argument GetReferencedName(_lref_).
1. Else,
1. Let _rref_ be the result of evaluating |AssignmentExpression|.
1. Let _rval_ be ? GetValue(_rref_).
1. [id="step-assignmentexpression-evaluation-lgcl-and-putvalue"] Perform ? PutValue(_lref_, _rval_).
1. Return _rval_.
</emu-alg>
<emu-grammar>AssignmentExpression : LeftHandSideExpression `||=` AssignmentExpression</emu-grammar>
<emu-alg>
1. Let _lref_ be the result of evaluating |LeftHandSideExpression|.
1. [id="step-assignmentexpression-evaluation-lgcl-or-getvalue"] Let _lval_ be ? GetValue(_lref_).
1. Let _lbool_ be ! ToBoolean(_lval_).
1. If _lbool_ is *true*, return _lval_.
1. If IsAnonymousFunctionDefinition(|AssignmentExpression|) is *true* and IsIdentifierRef of |LeftHandSideExpression| is *true*, then
1. Let _rval_ be NamedEvaluation of |AssignmentExpression| with argument GetReferencedName(_lref_).
1. Else,
1. Let _rref_ be the result of evaluating |AssignmentExpression|.
1. Let _rval_ be ? GetValue(_rref_).
1. [id="step-assignmentexpression-evaluation-lgcl-or-putvalue"] Perform ? PutValue(_lref_, _rval_).
1. Return _rval_.
</emu-alg>
<emu-grammar>AssignmentExpression : LeftHandSideExpression `??=` AssignmentExpression</emu-grammar>
<emu-alg>
1. Let _lref_ be the result of evaluating |LeftHandSideExpression|.
1. [id="step-assignmentexpression-evaluation-lgcl-nullish-getvalue"] Let _lval_ be ? GetValue(_lref_).
1. If _lval_ is neither *undefined* nor *null*, return _lval_.
1. If IsAnonymousFunctionDefinition(|AssignmentExpression|) is *true* and IsIdentifierRef of |LeftHandSideExpression| is *true*, then
1. Let _rval_ be NamedEvaluation of |AssignmentExpression| with argument GetReferencedName(_lref_).
1. Else,
1. Let _rref_ be the result of evaluating |AssignmentExpression|.
1. Let _rval_ be ? GetValue(_rref_).
1. [id="step-assignmentexpression-evaluation-lgcl-nullish-putvalue"] Perform ? PutValue(_lref_, _rval_).
1. Return _rval_.
</emu-alg>
<emu-note>
<p>When an assignment occurs within strict mode code, it is a runtime error if _lref_ in step <emu-xref href="#step-assignmentexpression-evaluation-simple-putvalue"></emu-xref> of the first algorithm or step <emu-xref href="#step-assignmentexpression-evaluation-compound-putvalue"></emu-xref> of the second algorithm is an unresolvable reference. If it is, a *ReferenceError* exception is thrown. The |LeftHandSideExpression| also may not be a reference to a data property with the attribute value { [[Writable]]: *false* }, to an accessor property with the attribute value { [[Set]]: *undefined* }, nor to a non-existent property of an object for which the IsExtensible predicate returns the value *false*. In these cases a *TypeError* exception is thrown.</p>
<p>When this expression occurs within strict mode code, it is a runtime error if _lref_ in step <emu-xref href="#step-assignmentexpression-evaluation-simple-putvalue"></emu-xref>, <emu-xref href="#step-assignmentexpression-evaluation-compound-getvalue"></emu-xref>, <emu-xref href="#step-assignmentexpression-evaluation-lgcl-and-getvalue"></emu-xref>, <emu-xref href="#step-assignmentexpression-evaluation-lgcl-or-getvalue"></emu-xref>, <emu-xref href="#step-assignmentexpression-evaluation-lgcl-nullish-getvalue"></emu-xref> is an unresolvable reference. If it is, a *ReferenceError* exception is thrown. Additionally, it is a runtime error if the _lref_ in step <emu-xref href="#step-assignmentexpression-evaluation-compound-putvalue"></emu-xref>, <emu-xref href="#step-assignmentexpression-evaluation-lgcl-and-putvalue"></emu-xref>, <emu-xref href="#step-assignmentexpression-evaluation-lgcl-or-putvalue"></emu-xref>, <emu-xref href="#step-assignmentexpression-evaluation-lgcl-nullish-putvalue"></emu-xref> is a reference to a data property with the attribute value { [[Writable]]: *false* }, to an accessor property with the attribute value { [[Set]]: *undefined* }, or to a non-existent property of an object for which the IsExtensible predicate returns the value *false*. In these cases a *TypeError* exception is thrown.</p>
</emu-note>
</emu-clause>

Expand Down Expand Up @@ -15790,7 +15847,7 @@ <h1>Runtime Semantics: IteratorDestructuringAssignmentEvaluation</h1>
1. ReturnIfAbrupt(_value_).
1. If _iteratorRecord_.[[Done]] is *true*, let _value_ be *undefined*.
1. If |Initializer| is present and _value_ is *undefined*, then
1. If IsAnonymousFunctionDefinition(|Initializer|) and IsIdentifierRef of |DestructuringAssignmentTarget| are both *true*, then
1. If IsAnonymousFunctionDefinition(|AssignmentExpression|) is *true* and IsIdentifierRef of |LeftHandSideExpression| is *true*, then
1. Let _v_ be NamedEvaluation of |Initializer| with argument GetReferencedName(_lref_).
1. Else,
1. Let _defaultValue_ be the result of evaluating |Initializer|.
Expand Down Expand Up @@ -22182,6 +22239,9 @@ <h1>Expression Rules</h1>
AsyncArrowFunction
LeftHandSideExpression `=` AssignmentExpression
LeftHandSideExpression AssignmentOperator AssignmentExpression
LeftHandSideExpression `&amp;&amp;=` AssignmentExpression
LeftHandSideExpression `||=` AssignmentExpression
LeftHandSideExpression `??=` AssignmentExpression

BitwiseANDExpression : BitwiseANDExpression `&amp;` EqualityExpression

Expand Down