Wow, thanks for the reference to clause 16 (c16). I'm having a blast
getting further into the spec and it really helps to have these
conversations about it!
I believe its safe to say then that operating on c16 alone, FF handles
the spec appropriately and Chrome probably gave too much heed to this:
"An early error is an error that can be detected and reported prior to
the evaluation of any construct in the <i>Program</i> containing the
error" - c16
This must account for why the following doesn't throw an early error in
Chrome:
function passes(){alert(++++someVar);}
In either case, it appears that Annex A is slightly out of sync with
c16, and may benefit from being updated.
On Thu, 2012-09-06 at 16:35 -0700, Brendan Eich wrote:
> Allen Wirfs-Brock wrote:
> > On Sep 6, 2012, at 12:17 PM, Joseph Spencer wrote:
> >
> >> My apologies on that one. I meant to type the following:
> >>
> >> PostfixExpression:
> >> LeftHandSideExpression [no LineTerminator here] ++
> >> LeftHandSideExpression [no LineTerminator here] --
> >>
> >> PrefixExpression:
> >> ++ [no LineTerminator here] LeftHandSideExpression
> >> -- [no LineTerminator here] LeftHandSideExpression
> >>
> >> It appears to me that as currently written the following is considered
> >> valid sytax:
> >>
> >> ++++someVar;
> >>
> >> I hadn't thought about es3 compatability though, so I could see the
> >> reasoning in keeping it as is.
> >> As a noobie (and most likely someone in dire need of correction ;)
> >> approaching this , it seems to
> >> me that there are a few loose ends in the grammar. For instance, the
> >> following statements seem
> >> allowable by the grammar as currently written:
> >>
> >>
> >> ++typeof someVar;
> >> ++new Date();
> >> ++null;
> >>
> >> My knowledge is lacking on this though, so I am probably missing
> >> something. I was surprised
> >> to find that the following is valid syntax and a perfectly legal
> >> FunctionDeclaration, but throws a
> >> ReferenceError when executed:
> >>
> >> function failPlease(){
> >> alert(++++a);
> >> }
> >
> > According to the specification, those all should produce runtime
> > ReferenceError exceptions. However, at least Firefox, reports them as
> > early syntax errors. Technically, that is out of conformance with the spec.
>
> Really? Clause 16 says:
>
> "An implementation must treat any instance of the following kinds of
> errors as an early error:
>
> * ...
> * Attempts to call PutValue on any value for which an early
> determination can be made that the value is
> not a Reference (for example, executing the assignment statement 3=4)."
>
> How are we not conforming?
>
> > Based upon that evidence, it would appear that FF implements a grammar that
> > is closer to you are suggesting rather than what is in the spec.
>
> No. We implement a recursive descent parser that follows the grammar but
> does early error checking based on parse tree inspection.
>
> /be
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