Semantic token localScope/globalScope/fileScope/classScope modifiers #2152

I would like to have the standard support scope modifiers for tokens. We're considering possibly implementing these at static-ls at work, but the lack of standardization makes it so that we probably will implement "is exported" as a code lens instead initially as most engineers won't have editors that display them.

It seems like this is a pretty broadly applicable concern: whether something is exported public API or internal API. Go considers this so important as to reserve first-character casing for communicating this information, but LSP currently doesn't have a standard way to offer it on other languages.

Prior art: https://clangd.llvm.org/features#modifiers

Clangd uses these like so:

• fileScope: static void foo(void) has call and definition sites of foo annotated as fileScope
• globalScope: write(2, "meow", 4) has write as globalScope and defaultLibrary. Similarly for a void bar(void); in the same file since it is exported.
• classScope: idk, probably member variables. This functionality is really important since this is a confusing part of C++.
• functionScope: variables which are just inside one function, e.g. int j;

I will note that in my role as a Haskell programmer classScope is not useful to us as we don't have objects with scope that behaves like C++/Java classes, but many languages have an idea of classes and it would be useful for those. I also don't know how e.g. OCaml modules should handle module-local variables. Should "is in scope because of the current module" be a modifier? Should those be "global scope" regardless?

What about nested Python functions?

IMO the most important of these to get standardized is whether something is an export (globalScope) or file-scope only, though.