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[Bug 15986] Specify exactly how and when ECMAScript arguments are evaluated

From: <bugzilla@jessica.w3.org>
Date: Tue, 13 Mar 2012 16:57:38 +0000
To: public-script-coord@w3.org
Message-Id: <E1S7V2Y-00047z-H9@jessica.w3.org>

--- Comment #20 from Aryeh Gregor <ayg@aryeh.name> 2012-03-13 16:57:32 UTC ---
(In reply to comment #19)
> What are the concrete bad things about the current overload resolution
> algorithm?

I think the major bad thing is that arguments are evaluated an unpredictable
number of times.  If I call a WebIDL operation on an object with valueOf, I
expect it to be called either zero times or once, and predictably so.  The
simplest thing would be to evaluate all arguments in advance, but I guess we
can't do that because it would require knowing in advance which arguments we
need to convert to primitives and which we want to leave as-is.

But frankly this is a relatively marginal concern.  At this point I think we've
spent about as much effort on it as it deserves, if not more.  If the current
spec is unambiguous and makes enough sense in common cases, I don't have a
problem with leaving it alone.  The problem is a lot hairier than I had
initially assumed, because I hadn't thought about the fact that identifying the
type of an object can have side-effects in JS.

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Received on Tuesday, 13 March 2012 16:57:45 UTC

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