Did MoonBit add support for some kind of shared memory concurrency like threads? I remember discovering the language, being very excited about it, and then learning it is single-threaded, which makes it a poor replacement for Rust IMHO.
Agreed. There was a period of time roughly 10-15 years ago where symbolic operators in Scala were very en vogue. That fell out of style in a big way and I haven't encountered symbol soup in a very long time.
Most of the conversations I have with folks about Scala issues these days center around implicits, tooling, and its decline/lack of popularity.
Not confident it's quite that straightforward. Here's a presentation from Meta showing a 6-12% increase in diff throughput for above-median users of agentic coding: https://www.youtube.com/watch?v=1OzxYK2-qsI
From my perspective the two biggest challenges of the Scala 3 migration were macros and poor tooling support.
Macros were an experimental Scala 2 feature, but were used all over the Scala ecosystem. Because they were considered experimental a good migration story for them was never developed. That lack of support stopped migration efforts dead in their tracks at our company for a long while. It just wasn't worth contributing simultaneous support for Scala 3 and Scala 2 macros to every third party dependency who used Scala 2 macros. That said, we did it for some and lived on a fork for others.
IDE support for Scala 3 was really rough when it first released. We checked in on it with every IntelliJ release for roughly 3 years before we decided it was far enough along. Prior to that it was rough enough that we froze migration efforts in order to keep the tooling usable enough for engineers to be productive.
Compiler error messages improved significantly with Scala 3. IIRC there was a dedicated effort with Scala 3 to improve error messages and make them more actionable. Scala 2 error messages improved somewhat over time, but can still be obtuse.