Documentation Checking and Compiler Extensions

[tothambrus11]

Designing the interaction of HyloDoc and the rest of the compiler requires more research into compiler and language server extensions. Documentation checking relies on having an AST in which we can resolve identifiers and check that expressions like document.is_loaded are valid in the documented symbol's scope.

It could make sense to integrate the documentation parsing into Hylo's frontend, as this will be something that's supposedly needed all the time. Why would somebody want to have their parameter list go out of date?

While this would be probably the most performant option, we can realize that documentation is not uniuqe from a tooling perspective. Seamless interoperating with other languages always requires some level of interaction of the compilers/language servers. E.g. imagine writing SQL queries, of which a tool like squirrel generates Hylo functions and glue code to call them with proper static types. When we rename a projected SQL column, the generated Hylo types change, which would need to be reflected on all the use sites in Hylo as well.

In general, a frontend compiler extension may want to do any of the following:

• Generate additional diagnostics - static analysis (both in LSP and when compiling code (or with a flag, so that the check is only turned on needed)).
• Provide additional code actions in LSP
• Handle and issue symbol renaming actions
• Possibly more?

So my questions are:

• Can you think of other interesting use cases of frontend compiler extensions?
• Do you know of any languages/ecosystems where compiler / language server extensions are popular?