> Yes. Roslyn, Mono and some Mono-like thing from Unity to compile it into C++. Roslyn is more like the next gen compiler and will be included in Mono once it’

> Yes. Roslyn, Mono and some Mono-like thing from Unity to compile it into C++. Roslyn is more like the next gen compiler and will be included in Mono once it’s ready to replace msc. I view it as closer to polonius because it’s an evolutionary step to upgrade the previous compiler into a new implementation. It’s still a single reference implementation. > Mono is still a thing I think you misunderstood my point. It had started as a fork but then Microsoft adopted it by buying Xamarin. It’s not totally clear to me if it’s actually a fork at this point or if it’s merged and shares a lot of code with .NET core. I could be mistaken but Mono and .Net core these days also share quite a bit of code. > rebuild can build typescript code Yes, there are plenty of transpilers because the language is easy to desugar into JavaScript (intentionally so - TS stopped accepting any language syntax extensions and follows ES 1:1 now and all the development is in the typing layer). That’s very different from a forked implementation of the type checker which is the real meat of the TS language compiler. > The second most popular TS compiler probably It’s a transpiler and not a compiler. If TS had substantial language extensions on top of JS that it was regularly adding, all these forks would be dead in the water. > That’s not true. There are multiple JDKs and even more JVMs I meant to say they’re the only ones with any meaningful adoption. All the other JDKs and JVMs are much more niche and often benefit from living in a niche that is often behind on the adoption curve (i.e. still running Java 8 or something or are willing to stay on older Java versions because there’s some key benefit in the other version that is operationally critical). > Good thing Java has specs with multiple versions, so that you can target a version… Good for people implementing forks, less good for people living within the ecosystem in terms of having to worry about which version of the compiler to support with their library. For what it’s worth Rust also has language versions but it’s more like an LTS version of the language whereas Java versions come out more frequently & each implementation is on whatever year they wanted to snapshot against.