2.1.11 [ECMA-262/7] Section 12.15.4 Runtime Semantics: Evaluation

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V0194: After an assignment, the name of the function is the empty string

The specification states:

 12.15.4 Runtime Semantics: Evaluation
  
     AssignmentExpression : LeftHandSideExpression = AssignmentExpression 
  
         1.  If LeftHandSideExpression is neither an ObjectLiteral nor an ArrayLiteral, 
             then
             a. Let lref be the result of evaluating LeftHandSideExpression.
             b. ReturnIfAbrupt(lref).
             c. Let rref be the result of evaluating AssignmentExpression.
             d. Let rval be ? GetValue(rref).
             e. If IsAnonymousFunctionDefinition(AssignmentExpression) and
                IsIdentifierRef of LeftHandSideExpression are both true, then
                i.   Let hasNameProperty be ? HasOwnProperty(rval, "name").
                ii.  If hasNameProperty is false, perform SetFunctionName(rval, 
                GetReferencedName(lref)).

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After the following assignment:

    var f = function () {}

the name of the function held in f is the empty string.

V0195: The reference is retrieved twice

The specification states:

 12.15.4 Runtime Semantics: Evaluation
  
     AssignmentExpression : LeftHandSideExpression = AssignmentExpression
  
         1.  If LeftHandSideExpression is neither an ObjectLiteral nor an ArrayLiteral, 
             then
             a. Let lref be the result of evaluating LeftHandSideExpression.
             b. ReturnIfAbrupt(lref).
             c. Let rref be the result of evaluating AssignmentExpression.
             d. Let rval be ? GetValue(rref).
             e. If IsAnonymousFunctionDefinition(AssignmentExpression) and
                IsIdentifierRef of LeftHandSideExpression are both true, then
                i.   Let hasNameProperty be ? HasOwnProperty(rval, "name").
                ii.  If hasNameProperty is false, perform SetFunctionName(rval, 
                GetReferencedName(lref)).
             f. Perform ? PutValue(lref, rval).
             g. Return rval.
         ...
  
     AssignmentExpression : LeftHandSideExpression AssignmentOperator AssignmentExpression
  
         1.  Let lref be the result of evaluating LeftHandSideExpression.
         2.  Let lval be ? GetValue(lref).
         3.  Let rref be the result of evaluating AssignmentExpression.
         4.  Let rval be ? GetValue(rref).
         5.  Let op be the @ where AssignmentOperator is @=
         6.  Let r be the result of applying op to lval and rval as if evaluating the 
             expression lval op rval.
         7.  Perform ? PutValue(lref, r).
         8.  Return r.

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In the algorithm for

    AssignmentExpression : LeftHandSideExpression = AssignmentExpression

the following steps are added before step 1f:

    i.   Type(lref) is Reference and if IsUnresolvableReference(_lref_) is false and IsPropertyReference(_lref_) is false then

        1.  Assert: lref is a reference to an Environment Record.

        2.  Let lref be the result of evaluating an Identifier _id_ whose StringValue is GetReferencedName(lref) as if _id_ were a LeftHandSidelrefession.

        3.  ReturnIfAbrupt(lref);

As a result, the reference is retrieved twice.

In the algorithm for

    Assignmentlrefession : LeftHandSidelrefession AssignmentOperator Assignmentlrefession

the following steps are added between steps 4 and 5:

    a. Type(lref) is Reference and if IsUnresolvableReference(_lref_) is false and IsPropertyReference(_lref_) is false then

        i.   Assert: lref is a reference to an Environment Record.

        ii.  Let lref be the result of evaluating an Identifier _id_ whose StringValue is GetReferencedName(lref) as if _id_ were a LeftHandSidelrefession.

        iii. ReturnIfAbrupt(lref);

As a result, the reference is retrieved twice.