The criteria of success for me is simplicity and generality. The part of OOP I am interested in is first-class modules, being able to package up types and functions acting on those types into records. Dotty is not the core of the current version of Scala. It does look interesting, but personally I would prefer an approach that does not use subtyping. My point is only that Scala does not represent the last word in FP+OOP.

I didn't say Scala represents the last word, I said it's a "successful marriage" of "ML-style functional languages with class-based OO". I implicitly assumed that subtyping is part of of class-based OO.

I expect Scala to gravitate more towards DOT in the future, as early mistakes in Scala's design will be ironed out.

It might be interesting to see how the form of OOP that you are interested in can be expressed in DOT, for example by removing subtyping form D_{<:}. Have a go at it!

I didn't mean to imply you had said it was the last word. The form of OOP that I would be interested in would probably use row polymorphism instead of subtyping. It might indeed be possible to encode this in DOT.

I think understanding the expressivity of the DOT approach vis-a-vis the more conventional 1ML approach should be interesting.

1ML is based on F-omega, which has higher kinds but not dependent sums or products, while D_{<:} has path-dependent products but no apparent higher kinds, if I understand the paper correctly.

I think they model higher kinds as a special case of path-dependent types.

Record and row types are already under consideration for Dotty.

Interestingly though, Scala's model is basically Javascript, with a sound type system. As much as classes have been discredited as the fundamental structure of a system's architecture, they still prove their usefulness in Java and all the dynamic languages, and now a new crop of languages, like Swift, Rust, and Kotlin. So, I'd suggest that the Scala route may well be the path forward, especially post-DOT.

Huh? Scala has nothing remotely resembling Javascript's weird prototype thing.

True, there's nothing in Scala that's like the dynamic inheritance/delegation of JS. But I'd say that in practice, people use Javascript's prototype functionality to implement static class- or mixin-based OOP.

Well sure, but I'd say Scala's model is more similar to any of Java, Python, Ruby or C++ than it is to Javascript. So I don't see that it's a "Javascript model".

The "path forward" is purely a socioeconomic one and quite unrelated to any technical argument.

Not true. The rise of Scala itself is probably the clearest counterexample; there is no socioeconomic case for it, it's succeeded purely on its technical merits.

Quite a bit of Scala's design was influenced by the goal of Java/JVM compatibility. This was clearly a purely "socioeconomic" decision. Without this compromise, Scala would never have taken off.

I disagree. There are any number of failed JVM languages, and no non-JVM equivalent of Scala that I'm aware of. The biggest effect of the JVM on Scala was a "free" high-quality (and high-performance), multithreaded, garbage-collecting runtime (contrast with OCaml) which is an engineering-driven decision.

Scala's success has technical and socio-economical causes. Here are some more non-technical factors.

- The existence of a reasonably well-funded organisation (Typesafe/Lightbend) stewarding Scala was well-received.

- Typesafe/Lightbend's independence also helped, in the sense that I cannot see a Scala-like language succeeded if it had come from e.g. Oracle.

- Scala's open-sourcing of everything helped.

- The well-executed and well-timed Scala-MOOC also helped a great deal.

- Odersky's fame and track-record helped too.

None of those might have driven your Scala adoption (or mine), but they might have helped others to shift their dev towards Scala.

You realize that all of that (except the last point) happened after Scala got traction?

That depends on what you mean by tracking. Typesafe was founded in 2011. Scala really took off around 2013 in my entirely unscientific observation.