On 5 January 2012 20:10, Brendan Eich <bren...@mozilla.com> wrote: > On Jan 5, 2012, at 6:31 AM, Andreas Rossberg wrote: >> Sorry, I still think that a growing set of subtle implicit rules for >> activating subtle semantic changes > > Not changes, new semantics for new syntax.
I was referring to strict vs classic mode. The way I understood the discussion so far, certain syntax would implicitly opt into extended mode, and thereby also into strict mode -- locally, and from classic. That implies semantic changes for existing features. [The discussion seems to have changed direction again with Allen's "state machine" idea. That probably makes some of my comments obsolete. Sorry for lagging behind.] >> on a fine-grained level is far more >> confusing (and error-prone!) than helpful. In all sorts of ways. > > Our experience was that adding new features to the default version where > there was no backward incompatibility was not confusing. We've been doing > this since 2006. Not to say all the particulars are right, or that we > anticipated all the combinations of ES5-strict and Harmony, of course! But I > think you protest too much without evidence. Yes, but these didn't imply semantic changes to existing features, like with implicit strict mode opt-in. >> I'm also concerned about the 3 and a half language modes that might >> result. With Dave's original proposal at least, the only opt-in was on >> module level. > > Dave mentioned generators, IIRC. We were thinking of classes too (talked > about it privately). > > >> That precluded a number of highly undesirable >> combinations, e.g. extended mode nested into a "with" statement. > > You can "use strict"; in a with statement's body block. But see below, I > agree the opt in has to be "chunky", and is in the (not perfectly clear, > complete, etc.) proposal for "ES6 doesn't need [version] opt-in". We had been discussing opting in a function if it's using destructuring on its parameters, for example. I would count that as a case that is not "chunky" enough, because it can be local to "evil" classic features and e.g. screw up lexical scoping. Likewise generators. I really think we should avoid these cases. [Now the idea seems to be that any ES6 feature would always opt-in the whole program. A like that much better, but it is not what Dave originally proposed, and what we had been discussing before, as far as I can tell.] /Andreas _______________________________________________ es-discuss mailing list es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss
