The high-level-variant is a dynamic language with optional typing, which is good for scripting, fast prototyping, fast time-to-market, etc.
The low-level-variant is similar to the high-level-variant (same syntax, same features mostly, same documentation), but it has no garbage collector, typing is mandatory and it runs fast like C/C++/Rust. Compiled packages that are written in the low-level-variant can be used from the high-level-variant with minimal effort or without additional effort at all. The tooling to achieve this comes with the language.
The one major wart with Julia is reliance on GC, I'm interested to hear what workarounds exist. If no common usage patterns rely on the GC, it should be possible to write "recycling" code that doesn't incur GC pauses and hence, unpredictable latency.
I really enjoy using Julia, it's a great balance of concision, expressiveness, and performance.
I think it will also rocket up Julia's popularity and usage not just for ML but as a general purpose language
Is some concept of language support for traits/ interfaces and/or static typing part of this effort?
Also, would there be different levels of leanness for the static compile? I can see some people wanting binaries that use a minimal runtime or GC, but no heavy JIT etc so that a larger set of programs can be distributed but at some tradeoff.
The closest thing to this I can think of is Racket. It's supposedly powerful enough to embed Haskell in it https://lexi-lambda.github.io/hackett/
Racket is special because its designers provide dedicated support of language-oriented programming. But that is about ecosystems, not typesystems.
The substitution macros aren't that much fun either since they lack certain capabilities (like introducing a new variable into the current scope without having to specify the name redundantly).
Without a lot of external libraries, procedural macros are almost impossible to write in my experience.
Neither of them allows one to properly code onto the type system or replace it and neither is properly supported by the IDEs (or RLS).