Allen Wirfs-Brock (2014-09-10T15:56:53.000Z)
domenic at domenicdenicola.com (2014-09-17T22:00:45.231Z)
We agree at our June meeting to add the "return" method to generators and to conditionally call "return" (if it is present) when a for-of loop terminates before it exhausts its generator. See https://github.com/rwaldron/tc39-notes/blob/master/es6/2014-06/jun-5.md#conclusionresolution-2 . IteratorClose is part of the implementation of this features and was added in Rev 27 of the spec. I believe that #1 is implicit in that decision as it has always been an ES6 goal that most library methods should be self-hostable in ES. That means that for-of like iteration in those methods should be specified in a manner that matches the observable semantics of for-of.