Thanks for your clarification! I filed this issue to bugs.ecmascript.org https://bugs.ecmascript.org/show_bug.cgi?id=414
Regards, Yusuke Suzuki On Sun, Jun 24, 2012 at 11:50 PM, Allen Wirfs-Brock <[email protected]>wrote: > Yes, please file a bug report at bugs.ecmascript.org > > As you suggest, the straight forward way to specify this is probably to > use a normal array for the actual argument values for Binding > Initialisation of the formals rather than trying to use the arguments > object for that purpose. Of course, that doesn't mean that the additional > array actually has to be created at runtme, it will just be a specification > device. > > Allen > > > On Jun 24, 2012, at 5:11 AM, Yusuke Suzuki wrote: > > Hello everyone, > > I'm now implementing ES.next engine in ES5.1 and I may find issue on > current draft. > > In June 15 draft, to realize destructuring assignment in FormalParameters, > we perform Binding Initialisation for formals with Arguments object. > > In section 10.5.3, step 8-d, > > d. Let formalStatus be the result of performing Binding Initialisation > for formals with ao and undefined as arguments. > > But, ao.[[Get]], ao.[[GetOwnProperty]] have been already overriden to > mapped arguments special internal methods in non-strict function. > > For example, > > function test(a) { } > test(10); > > In this script, we perform Indexed Binding Initialisation and finally, we > perform ao.[[Get]]('a'). > But, in this phase, 'a' entry of environmental record is initialized to > undefined in 10.5.3-5-c-ii-1, so ao's getter defined in > CreateMappedArgumentsObject step 7-c-ii-2, > > function () { return a; } > > always returns undefined. > As the result, ao.[[Get]] result is always undefined, and we cannot > initialize argument by correct value. > > I think it is issue of current draft, is it right? > > To fix this, I suggest creating JS Array from argumentsList and performing > Binding Initialisation with it, or delaying internal method override phase > of ao. > > Regards, > Yusuke Suzuki > > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss > > >
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