Highlight variable definitions

[yuyichao]

Ref JuliaLang/julia#8723

We should highlight variables introduced with let, global, local or const. We'll need to be careful here to ensure that we handle commas correctly.

[tpapp]

Can someone post a screenshot or an example of how this works in some other mode?

Incidentally, I use https://github.com/nschum/highlight-symbol.el/ for visual tracing, eg

with some hotkeys setup for navigation and toggling highlights. There are other Emacs packages with similar functionality.

[tpapp]

@Wilfred, since you opened the original issue JuliaLang/julia#8723, can you please clarify the desired behavior here? Eg in

let x = "foo, bar", y = foo(1, 2)
    x + y
end

would you want to highlight the first x and y, or all occurrences within the let?

[non-Jedi]

Per the emacs manual, it would be traditional to highlight the first x and y but not subsequent occurrences with font-lock-variable-name-face: https://www.gnu.org/software/emacs/manual/html_node/elisp/Faces-for-Font-Lock.html

[non-Jedi]

I started working on this. Ran into trouble. The problem is that assignment can occur in a lot of contexts in julia, and = means something else entirely in other contexts. For example, how do tell whether (a = ...) is an assignment to a or a named tuple without parsing the whole expression? Any ideas would be helpful.

non-Jedi@0c802f9

[tpapp]

I have thought about this and for every regex-based approach I can think of there is some corner case.

I am not sure this functionality is worth implementing what amounts to a subset of the Julia parser. I would be inclined to close it as wontfix, but I can leave it open too.

[non-Jedi]

I'd leave it open for discoverability if it was me. Having just skimmed the indentation code, we already actually implement a surprisingly large subset of the julia parser; if someone wanted to do the work, I don't think it would be a bad thing to have.