> On Oct 1, 2014, at 9:05 AM, Mark S. Miller <[email protected]> wrote:
>
> Good point. If we can require all such assignments to be rejected statically,
> why is a runtime assignment to a const variable even possible? Can't we just
> assert that this cannot occur?
You mean duplicate assignment? IIRC the problem is code that does
const x;
x=blah;
or
if (foo)
const x = bar
else
const x = wiffle
etc
Whether this is actually still something that exists - I recall in JSC many
years ago we had to allow:
for (......) {
const x = ...
...
}
Even though that is technically duplicate assignment.
But i guess that last case is less relevant as const is now always block scoped
isn't it?
--Oliver
>
>
> On Wed, Oct 1, 2014 at 8:59 AM, Allen Wirfs-Brock <[email protected]
> <mailto:[email protected]>> wrote:
>
> On Oct 1, 2014, at 8:39 AM, Mark S. Miller wrote:
>
> ...
>
> I was with you until you got to the following point
>
> >
> > If there is an intervening "with" or sloppy direct eval, then there is not
> > a statically apparent assignment to a const variable. Since this can only
> > occur in sloppy code anyway, it seems more consistent with the rest of
> > sloppy mode for this failed assignment to be silent, rather than
> > dynamically throwing an error.
> >
>
> const is a new kind of declaration unlike any declaration form that previous
> existed in ES, so Ii don't think its handling introduces any legacy
> consistency issues. If somebody is using const, regard less of mode, they
> pretty clearly expect assignments to any const bindings to be illegal. And,
> I don't think any body wants new silent failure errors, even in sloppy mode.
> The most consistent thing is for runtime detected assignments to const
> bindings to always be noisy errors. Early where possible, at runtime in the
> rest of the cases.
>
> Allen
>
>
>
>
> --
> Cheers,
> --MarkM
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