*.empty Idea

Mark S. Miller erights at google.com
Thu Apr 30 19:48:35 UTC 2015

On Thu, Apr 30, 2015 at 12:46 PM, C. Scott Ananian <ecmascript at cscott.net>

> I like the idea of snapshot methods, but they can be implemented in user
> code using subclasses in ES6.  I'm particularly interested in the "lock
> down in place" mechanism because it *cannot* be implemented in user code.
> And yes, if we had it all to do over again, it would have been nice if the
> Map prototype chain was:
> Map instance -> Map.prototype -> ReadOnlyMap.prototype -> null
> And clear/set/delete were properties of Map.prototype.
> But that would still have required an explicit test in
> Map.clear/set/delete to ensure that they were operating on an instanceof
> Map and not just on a ReadOnlyMap.

Yes, it does not save a test. Rather it only rationalizes the types of
objects so that the type of an immutable or readOnly collection does not
include useless mutation methods; that's all.

>   --scott

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