Named function expression causes duplicate scopes in ScopeManager about escope HOT 3 CLOSED

Hmm, I think this may be a false alarm. Comparing [3] and [4]'s scope objects, I noticed that they differ in the functionExpressionScope field

3: Scope
block: Object
directCallToEvalScope: false
dynamic: false
functionExpressionScope: true
left: null
references: Array[0]
set: Map
taints: Map
thisFound: false
through: Array[0]
type: "function"
upper: Scope
variableScope: Scope
variables: Array[1]
__proto__: Scope

4: Scope
block: Object
directCallToEvalScope: false
dynamic: false
functionExpressionScope: false
left: null
references: Array[0]
set: Map
taints: Map
thisFound: false
through: Array[0]
type: "function"
upper: Scope
variableScope: Scope
variables: Array[1]
__proto__: Scope

This means that [4].upper = [3], [4].variables = ['arguments'], [3].variables = ['move']

@Constellation Would you mind explaining why it's necessary to create a hierarchy for named function expressions rather than just having something like [4].variables = ['arguments', 'move']?

from escope.

This is because escope scope hierachy is very precise to ECMA262 5th spec.
According to the ECMA262 5th section 13

The production
FunctionExpression : function Identifier ( FormalParameterListopt ) { FunctionBody }
is evaluated as follows:

1. Let funcEnv be the result of calling NewDeclarativeEnvironment passing the running execution context’s Lexical Environment as the argument
2. Let envRec be funcEnv’s environment record.
3. Call the CreateImmutableBinding concrete method of envRec passing the String value of Identifier as the argument.
4. Let closure be the result of creating a new Function object as specified in 13.2 with parameters specified by FormalParameterListopt and body specified by FunctionBody. Pass in funcEnv as the Scope. Pass in true as the Strict flag if the FunctionExpression is contained in strict code or if its FunctionBody is strict code.
5. Call the InitializeImmutableBinding concrete method of envRec passing the String value of Identifier and closure as the arguments.
6. Return closure.

So escope creates scope for FunctionExpression's name.

from escope.

Thank you, that explains it.

from escope.