Reviewing feedback on patterns in switch

[Brian Goetz]

We’ve previewed patterns in switch for two rounds, and have received some feedback.  Overall, things work quite well, but there were a few items which received some nontrivial feedback, and I’m prepared to suggest some changes based on them.  I’ll summarize them here and create a new thread for each with a more detailed description.  

I’ll make a call for additional items a little later; for now, let’s focus on these items before adding new things (or reopening old ones.)  

1.  Treatment of total patterns in switch / instanceof

2.  Positioning of guards

3.  Type refinements for GADTs

4.  Diamond for type patterns (and record patterns)