On Oct 17, 2008, at 3:47 PM, Brendan Eich wrote: > On Oct 17, 2008, at 3:39 PM, Brendan Eich wrote: > >> On Oct 17, 2008, at 12:25 PM, Waldemar Horwat wrote: >> >>> ... >>> let (a = 1) a ? f : x++(); >>> >>> The grammar states that the last statement must evaluate to "f". >>> Firefox gives a syntax error. This is incorrect because the let >>> expression up to the ++ is a PrimaryExpression so can be used as the >>> left operand of a function call. > > Er, you are right, I should have acknowedged this point. The rest of > my post is about x++() not being a valid sentence, which supports your > argument. > > While we don't have any usability problems, and torturous statements > such as > > let (a = 1) a ? f : x++(); > > are not written by real users (they'd parenthesize to clear up > things), I agree that we don't want the "prove a negative" problem.
This shows a problem with ES4's reliance on top-down parser construction. We never created an LR(1) grammar (ignoring ASI and the other exceptions that don't fit in LR-anything, and solving dangling else as is customary). To avoid the "prove a negative" problem, we need one. IIRC you have one -- can you share it via ecmascript.org? /be _______________________________________________ Es-discuss mailing list Es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss
