Thanks. I'll give this a thorough read - I think it deserves more than the cursory read I can afford to give it right now - and appreciate the time investment this no doubt represents.
The first is that the linked post answers a lot of points, but not the ones I made. It makes Dotty sounds really exciting, which it is. It makes it sound as if everybody working on Dotty believes it to be the future of Scala, and I believe that to be true, too. What it does not do (that I could see) is give reassurance that Dotty and Scala will not drift appart and become two similar but incompatible languages. I felt it'd be rude to point this out, since there really is no way to provide such guarantees (just like there really is no way for me to back up my worries with anything concrete).
The second part is, I'm not casting doubts, but expressing worries. I'm not saying it will happen, I fear it might. I'm sorry if this offends - I really am, my goal is not to insult anyone or demean anyone's work. I have no hidden agenda, and I'm not trying to be one of these anti-Scala trolls that sometime crop up. I love Scala. Look at my github profile, most of my public work is in Scala, and some of my libraries represent a lot of work (which obviously does not mean they're actually any good). I really, really hope everything works out the way people mean it to - as I said, Dotty sounds really exciting. I've seen too many "let's rewrite this from scratch and then make it backward compatible, it'll be amazing" projects to be able to believe it blindly, though.
We share your concern. As I said in my comment above -- the Scala and Dotty teams actively work together (we have our roots in the same research group at EPFL) to make sure Scala 2.x evolves towards Dotty and Dotty evolves towards Scala 2.x. Scala 2.12 and 2.13 will have language flags that unlock features being incubated in Dotty that we can already implement, and the Dotty compiler already has a Scala 2 compatibility mode.
We take continuity very seriously. No one wants a Python 3-style transition. In addition to the desire to avoid this, we also have a type system and a community build (think Google Blaze for Scala) that builds > 1MLoC OSS Scala code.
Thanks for taking the time to share this. I was aware of the community build - I believe it was discussed in some depths on Scalawags a while ago? - and find it to be an amazing initiative. Can't think of a better way to minimise the issues that Dotty might cause, and I'm in awe of the amount of work it must represent.
What I fear in that moment down the line where one feature goes over the arbitrary threshold you set yourself for community breakage, but is just too great to pass up on. Since the threshold is arbitrary anyway, it's fine to adjust it a bit... and a bit more later...
Not saying it will happen, and it would be dishonest of me not to say that I don't think you could possibly do more than you're already doing to prevent this kind of issue.
