langium capabilities QA

[deadlocklogic]

I am interested in using langium to create a custom language which can transpile to different targets (similar to haxe but very minimal).
Can langium handle these features (not necessarily but via custom extensions/providers):

• type inference (var and return type)
• generics, constraints?
• cross references across files

If so, where should I look for more examples as I couldn't find information about my use case.
Thanks.

[msujew]

Hey @deadlocklogic,

As for type inference, generics and constraints, these are part of a type system, that will have to be implemented in "user land" so to speak. See our Lox example which does this and our (still in beta) Typir library which enables adopters to build type systems. Langium

cross references across files

Works out of the box in Langium, though you might need to adjust the linking/indexing logic of your language depending on your use case. We have a few guides for that on our website.

[deadlocklogic]

Really nice and remarkable. The only thing which is still missing is extensive docs/examples, maybe because the project is still in early phase.
I will try tinkering around and see where I get stuck.
Thanks.

[msujew]

I wouldn't say the project is still in its early phase, the first official release was 4 years ago :)

We do have a few examples, see our readme, and have quite a bit of documentation and guides over at our website. Feel free to open a feature request if you're missing specific info/guides over at the website repo.

[deadlocklogic]

Just an idea (might be worth it thought), would be somehow kind of next gen to create a showcase of a language which supports all know object oriented language idioms (classes/inheritance/inference/generics/constraints etc..., Lox on steroids maybe), and such features can be enabled/disabled as options.
Imagine someone wants to create his own language, it will be a matter or syntax choice/taste everything else is already implemented for him, even vscode integration. So his efforts can be focused on a compiler/transpiler/VM/analyzers etc....
Same pattern can be added to different language paradigms/styles etc...
This really sounds like the Holy Grail of language design.

[msujew]

Unfortunately, I don't think this is easily possible. Syntax has a rather large influence on the shape of the AST and depending on that how the type inference and type system as a whole works. So even if we were to give adopters something like this, it would be trivial to break the systems within using a simple grammar change.

As someone who has done a few projects designing and implementing languages, I can rather confidently say that there is no silver bullet for this problem. No two languages are alike and even relatively similar languages from the outside often times use vastly different implementations for a lot of their internals.

[deadlocklogic]

Yes you are right here, I was maybe overambitious there.