Langium grammar extension to specify scoping

[goto40]

What do you think of a grammar extension, we introduced in textx two years ago: http://textx.github.io/textX/3.0/rrel/

The feature makes it easier to define custom scoping within the grammar file (without additional coding). The following discussion illustrates the use of the feature: textX/textX#387

I could imagine that this could be relatively straightforward to incorporate into langium (langium grammar extension and extended default scope provider).

I would be happy to discuss this. With a little guidance I could prepare something if we agree on a feature.

[spoenemann]

Hi @goto40, the idea looks nice. It's a pity that we can specify the type of reference target in the grammar, but not how to resolve it. On the other hand, I currently doubt that such an expression syntax would be sufficient for anything more than simple example languages. Scoping implementations for complex expressions tend to be quite involving and often depend on a type system (type inference).

[goto40]

Yepp. This was just an Idea... You are right: in the end, manual scoping implementations for such simple cases are not so complicated...

[Lotes]

I like the idea of having no or low-code for things like scoping or the type system.
We could migrate some Antlr4 grammars and add scoping together with crossreferences. After some usecases we could extract patterns.
I was thinking of Fritzing schemas. They have a view for the PCB, one for a abstract schema and further more views.
So like a additional fileformat... *.langiumscopes.... I am just dreaming haha

[spoenemann]

Idea for experimenting: create an external DSL (separate from the grammar language) to describe scoping / linking rules (possibly even supporting advanced stuff like function / method overloading). This DSL could be used to generate TypeScript code or be interpreted at runtime. All you'd need to do to use it in your language project is register the generated / interpreter ScopeProvider (and maybe other services) in your DI module.

The benefit: this would not complicate the grammar language at all, and would leave lots of room for experimentation.

[goto40]

A good idea. I will have a look, maybe the end of the year.