Pragmas

[Peter Hall]

Also, there is a minor bug [1] with the pragma syntax:

Pragma :
	UsePragma  SemicolonFull
	ImportPragma  SemicolonFull
	
UsePragma :
	use  PragmaItems  SemicolonFull


resulting in two semicolons being required after a "use" pragma.


Peter


[1] http://wiki.ecmascript.org/doku.php?id=proposals:syntax_for_pragmas





On 11/12/07, Peter Hall <peter.hall at memorphic.com> wrote:
> What is the scope of a pragma such as that? Is it just the current
> lexical scope, like a "use namespace" statement, or does it change the
> behaviour for the entire program? If it's the latter, isn't there a
> compatibility problem between libraries? If it's the former, do you
> anticipate that es4 programs will be littered with "use strict"
> pragmas? Think Fortran and "implicit none"....
>
> I assume this has been previously discussed, but I couldn't find it,
> so apologies if that is the case.
>
> Peter
>
>
> On 11/12/07, Brendan Eich <brendan at mozilla.org> wrote:
> > On Nov 12, 2007, at 9:00 AM, Jonathan Watt wrote:
> >
> > > Hi,
> > >
> > > As I understand it the reason assignment to ReadOnly properties
> > > fails silently
> > > is that there was no try-catch prior to ECMAScript 3.
> >
> > Right. Netscape 2 reported a fatal error, but during ES1
> > standardization we agreed to go with silence is (golden|deadly).
> >
> > > Could/will edition 4 require an exception to be thrown in strict mode?
> >
> > Overtly incompatible, also highly desirable. So opt-in versioning
> > could enable this, but it's one more migration headache (see recent
> > exchange between Mark Miller and myself). An alternative would be a
> > pragma of some sort:
> >
> >    use readonly error
> >
> > or perhaps
> >
> >    use readonly throw
> >
> > We try to make pragmas more readable, sometimes with an extra word;
> > not sure this is the best way to phrase it still, but the idea would
> > be to enable throwing of a ReadOnlyError on assignment to a ReadOnly
> > property. Comments?
> >
> > /be
> >
> > _______________________________________________
> > Es4-discuss mailing list
> > Es4-discuss at mozilla.org
> > https://mail.mozilla.org/listinfo/es4-discuss
> >
>