Swift 4 — converging "phase 2" discussions

Hi everyone,

In mid-February we kicked of "stage 2" for the discussion of evolution proposals for Swift 4:

  [swift-evolution] Swift 4, stage 2 starts now

The timetable set forth was to have discussions for "stage 2" go through April 1. The intent of that timetable was to (a) timebox discussions on proposals to help *focus* them within the theme/focus areas of the release and to (b) provide time after discussion to *implement* approved proposals for Swift 4.

While the April 1 date for the end of stage 2 has passed, it is clear that by looking at where we are in the development of Swift 4 and what remains to be done that there are still important discussions happening on swift-evolution concerning changes possibly impacting Swift 4. Those discussions should continue and given the opportunity to converge. That said, we have reached to point where we need to be increasingly circumspect on what topics remain in scope for Swift 4.

At this point, discussions about changes impacting Swift 4 should generally focus in the following areas:
Anything fitting in the "stage 1" phase for the release, such as (among others) the `String` re-evaluation and the memory ownership model remain priority topics to discuss.

*Existing* topics we have already covered during "stage 2" also remain relevant to discuss for the release, although the scope of actual change we will consider for Swift 4 is rapidly diminishing.
The distinction of what is "out-of-scope" may not always be clear to everyone, and the Core Team will try and provide clear guidance as discussions happen on swift-evolution where appropriate to indicate whether or not something is in scope for Swift 4.

Looking beyond Swift 4, serious discussion about Swift 5 will likely start up in July as the themes and focus areas of that release are identified.

Thank you to everyone who has contributed to the discussions so far to help shape Swift 4!