new instantiation design alternatives

Allen Wirfs-Brock allen at
Thu Sep 11 09:35:56 PDT 2014

At the last TC39 meeting ( and ) we agreed to a general direction to try for a new object instantiation design to replace @@create. 

Since then I have gotten feedback and had design discussions with a number of individuals. This has lead to a number of refinements of the core design and one remaining point where there are strong contrary positions. The point of contention is about whether or not a subclass construction ever implicitly calls its superclass constructor.  summaries the  main syntactic changes since the meeting and provides rationales them. These features are common  to both alternates.  this is a good place to start, after reading the meeting notes. 

I have prepared two longer Gists that outline the two alternatives designs, presents design rationales,  and provides usage examples for a number of likely use cases. Note that  there is more commonalities then differences among the two alternatives.  the syntactic choices and semantics of [[Construct]] are the same for both. 

These two Gist have parallel construction for easy comparison. I suggest approaching this is by first readying through one of the Gists and then doing a side by side read through of the alternative to see the differences in the designs and usage. with implicit super construct if no local allocation explicit super construct required if no local allocation

I appreciate it if major constructive feedback on any of these documents were made via Gist comments. 

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