ECMAScript spec assertion fails when binding is deleted?
Jim Blandy
jimb at mozilla.com
Mon Mar 21 11:44:42 PDT 2011
This is a bug in the spec, and has been previously discussed here:
https://mail.mozilla.org/pipermail/es5-discuss/2010-November/003839.html
(Thanks, Jeff!)
On 03/20/2011 11:22 PM, Jim Blandy wrote:
> When executing this code:
>
> (function () {
> eval("var x=delete(x)")
> })()
>
> I think the assertion in the ECMAScript description of the declarative
> environment record's SetMutableBinding algorithm, 10.2.1.1.3 step 2,
> fails.
>
> * On entry to the function, we create a lexical environment with a
> declarative environment record (10.4.3).
> * When we enter the eval code, we create the binding for 'x' in
> that environment record (10.5, step 8.c.1). This is a deletable
> binding, as per 10.5 step 2.
> * When we evaluate the declaration, we produce a reference with
> that environment record as its base, delete the binding, and
> then call PutValue (12.2, VariableDeclaration : Identifier
> Initialiser semantics).
> * PutValue calls the environment record's SetMutableBinding
> concrete method (8.7.2 step 5.a).
> * SetMutableBinding's assertion fails, because 'x' is no longer
> bound in that environment record (10.2.1.1.3 step 2).
>
> Have I missed something?
>
>
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