2.1.18 [ECMA-262/6] Section 12.4.5.1 Runtime Semantics: Evaluation
V0047: The reference is retrieved twice
The specification states:
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12.4.5.1 Runtime Semantics: Evaluation PostfixExpression : LeftHandSideExpression -- 1. Let lhs be the result of evaluating LeftHandSideExpression. 2. Let oldValue be ToNumber(GetValue(lhs)). 3. ReturnIfAbrupt(oldValue). 4. Let newValue be the result of subtracting the value 1 from oldValue, using the same rules as for the - operator (12.7.5). 5. Let status be PutValue(lhs, newValue). 6. ReturnIfAbrupt(status). 7. Return oldValue.
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Between steps 3 and 4 the following steps are added:
a. If Type(lhs) is a Reference and if IsUnresolvableReference(_lhs_) is false and IsPropertyReference(_lhs_) is false:
1. Assert: lhs is a reference to an Environment Record.
2. Let hs be the result of evaluating an Identifier _id_ whose StringValue is GetReferencedName(lhs) as if _id_ were a LeftHandSideExpression.
3. ReturnIfAbrupt(lhs);
This retrieves the reference twice.