On Apr 7, 2012, at 1:40 PM, Erik Arvidsson wrote: > This does not work for rest parameter since ... is only allowed inside > array literals. > > var tail = (x, ...xs) => xs; > > This can of course be solved in numerous ways but it is not true that > the Expression is a cover grammar for FormalParameterList. > > Another option is to allow ...expression in an expression which would > have the same semantics as a comma expression where the expression has > been spread:
Or allow it in the grammar and then disallow it in the post-processing. IOW, a cover grammar doesn't have to force us to introduce new syntactic forms, they just force us to put them in the *grammar*. The post-processing, which essentially defines the two sub-grammars for the two separate contexts, can remove the syntactic forms we don't want to provide semantics for. Dave _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
