> -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Mike Shaver > Sent: 7. mars 2008 03:34 > To: es4-discuss Discuss > Subject: Re: ES4 draft: Error classes > > 2008/3/7 Ash Berlin <[EMAIL PROTECTED]>: > > I forget all the problems, but from memory the main one is that: > > > > MyError = function() {}; > > MyError.prototype = Error.prototype; > > > > Doesn't do what you'd expect. And doing > > > > MyError.prototype = new Error(); > > > > Is no good since then the filename and linenumber will be of that > > line, not where you create the MyError instance. > > Right, and the idea of mutating an object when it's thrown in > order to reset its stack information seems bogus. > > What about Error.prototype.throw, which would throw |this|, > and act as a hook for the stack/location setting > implementation behaviour? We might want to permit an > implementation to elide the Error.prototype.throw frame > itself in whatever stack reflection is provided (though if > E.p.throw has an internal error of some kind, it should > probably be visible in the trace).
Not really endorsing any of these ideas as of yet, would like to see a concrete proposal with details fleshed out. The chances that the spec will *require* a useful backtrace (quasi-fixed format and requirements about which frames may or may not be in it, say) or source location information to be created for E.p.throw are probably quite low. Realistically what we could hope for is a statement of intent and well-defined hooks for implementations who want to support something, like the case is for the ControlInspector proposal (which is optional). Adding file/line info to errors thrown by the language implementation looks easier to do across diverse runtimes, but I don't know for sure. --lars > > (We could also put it on Object.prototype, which would make > |e.throw()| work for almost all values of e rather than just Errors, > but that might be a bit beyond the pale.) > > Mike > _______________________________________________ > Es4-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es4-discuss > _______________________________________________ Es4-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es4-discuss
