[karl-police]

I made a tree-sitter https://github.com/karl-police/tree-sitter-luau-new/blob/main/out.html

Well, actually I took the lua ones and the luau ones, read it a little bit to learn about tree-sitter. Then made some fixes until the highlights looked okay.

I even added comments in some places :)

I also added const and yup.
Just the highlight support, not the internal node naming. 🤔

Since the first thing someone tried was to see if const was added too, and then they realized it wasn't. :(

And now this thing is not lua dependent anymore, its in its own file, which makes editing it less complicated and it's easier to install and run and test.

What is missing in both still are Function Attributes, I think.

Also the ? for optional types, maybe.

This also adds the Experimental class syntax, which is just a copy paste of the stat_do rule, the do ... end syntax. It can easily be disabled and removed. Given that it's also removed from the queries folder.

Their RFC for classes is merged anyways, so.
Except the inheritance one. Syntax wom't be visible unless used. And if someone that doesn't know about the class syntax yet, it might invite them to the Luau RFC discussion, so why not.

Now, there can't be complains about const missing nor open class. 😁

const

GitHub has it already.

For instance:

• class A end RFC approved
• open class A extends Base end not RFC approved yet but the syntax highlighting supports it anyways

What might also not work yet could be type function

Now to support the highlight for it, change would be really really easy, but the node name would interally be treated as a regular function so... would need extra lines here.

It might also not support something even more new which is "if local".

Which is

if local test then end

[appellation]

Note: this review was written by Claude (an AI assistant) at the maintainer's request, not by the maintainer personally. The findings below were checked by building this branch with the repo's own ./scripts/arborium-rt build wasm grammar group-hazel luau pipeline, parsing ~80 Luau snippets with both this branch and main, and running a sample file through the wasm highlighter.

Thanks for working on this. const declarations and a basic class statement now parse and highlight, which is a real improvement. But as it stands the PR breaks several common Luau constructs that work on main, and it drops required license notices, so it needs changes before it can merge.

Attribution / licensing (blocking)

About 54% of the grammar's lines come from tree-sitter-lua (Munif Tanjim, MIT), about 19% from tree-sitter-luau (Amaan Qureshi, MIT), and about 90% of scanner.c is tree-sitter-lua's scanner. The rest looks like your own work, and the PR description already says this is where the code came from. All of that is fine under MIT, but MIT requires keeping the original copyright notices.

arborium.yaml now points at karl-police/tree-sitter-luau-new, and our THIRD_PARTY_NOTICES step clones that repo at the pinned commit and ships its LICENSE. That LICENSE says only Copyright (c) 2026 karl-police, so the Munif Tanjim and Amaan Qureshi notices would be dropped from what we ship (they're listed as authors in that repo's tree-sitter.json, but that isn't a license notice). Please add both original copyright lines to the upstream repo's LICENSE, for example:

Copyright (c) 2021 Munif Tanjim
Copyright (c) 2023 Amaan Qureshi
Copyright (c) 2026 karl-police

and bump commit: here once that's done.

Regressions compared with main

Problem	Example	Cause
Interpolated strings starting with a letter misparse	`Hello {name}` is parsed as a call to an identifier named `Hello with a table argument	The identifier regex allows `
Optional types are lexed as one identifier	local x: string? = nil, type B = Foo?	The identifier regex allows ?
Typed generic for loops error	for k: string, v in pairs(t) do end	for_generic_clause is defined twice and the untyped one wins
Ordinary identifiers break at the start of a statement	open("f"), class.isinstance(p, Point), class = 1, const = 1	open / extends / class / const became hard keywords
Parser is about 5x larger	585 → 2852 parse states; luau wasm 100 KB → 424 KB raw, 16.7 KB → 48.8 KB after brotli

Details are in the inline comments.

Luau correctness

• The const RFC says const is a contextual keyword and "fully backwards compatible with existing code", so local const = 5; const = 1 must keep working.
• The merged classes RFC uses public x: number fields in class bodies and allows export class X. The RFC's own Point example doesn't parse with this grammar, and neither does export class X end. class is also contextual there (it's a library name too: class.isinstance). open and extends aren't in any accepted RFC, so I'd suggest leaving them out rather than reserving them.
• The grammar still carries Lua 5.4/5.5-only syntax that isn't Luau: global declarations, <attrib> (local x <const>), and the bitwise operators | & ~ << >>. These grow the parse table for no benefit.
• Still unsupported (same as main, so not a regression, just noting): @native / @[...] function attributes, type function, generic defaults (<T = string>), leading | / & in unions, read / write properties, ; separators in table types, typeof(...) inside annotations, typed numeric for, and ...: T....

Suggested changes

1. Restore the previous Luau identifier regex (excludes ` and ?, uses the /u flag).
2. Delete the duplicate for_generic_clause and the unused rules (binding_list, _vararg_parameter, special_self).
3. Make const and class contextual, and drop open / extends.
4. Support public fields (and export class) in class bodies.
5. Remove the Lua 5.4/5.5-only syntax.
6. Fix the upstream LICENSE as described above.

🤖 Generated with Claude Code

[karl-police]

I think I should have covered most things now except func<<>>() both didn't support it anyways yet. And Luau needs to update the grammar for it as well. https://luau.org/grammar/

New output:
https://github.com/karl-police/tree-sitter-luau-new/blob/main/out.html

[karl-police]

I have to remove the "global" stuff another time. I actually added that in my comments somewhere.

[karl-police]

Parser is about 5x larger

well yup that prob Claude funny comment, it is not wrong though

simce this grammar.js does not require lua anymore it is larger

but I want to remove all of the non-Luau things

today I replaced a lot of functions, I think it even got rid of most of the previous luau tree-sitter...

I primarly used Luau grammar for guidance, so the structure is similar to how they define it.

Fun fact is that they haven't updated it in a while and are missing a few things 🙃

[karl-police]

ugh I put scanner back to something and it may be missing tree_sitter_luau_external_scanner_create now and complains?

[karl-police]

epic it is green https://github.com/karl-police/arborium-rt/actions/runs/43370335596

that's good it means this time the files are in a good state

[karl-police]

and bump commit: here once that's done.

What is it trying to say? I don't use git CLI often.

[karl-police]

Okay yeah gotta add public function and export to class

but that also future update theory 🤔

before there was no class at all, so

I was actually (for some reason) worrying about the names of the nodes.

Not only, but they're important for the .scm files.

as_exp being my biggest enemy, until I solved it... well extra node for .scm, otherwise it's based on Luau so it should be better.

So const has its own declaration now. Uh... although this is not a code parser and compiler, it wohldn't need it. But 🤷

The unused functions and comments... yes... they came from my repository so. I gotta remove them manually, unless commenting them out is fine.

I keep them there for reference until they can go.

The name list function from Lua is interesting.
It made me think on why it is not a rule.

I had to create a function by myself, because when I added "binding" rule to classes. Everything exploded, but not if I added the function, which returns a cloned copy of the rule, I think.

So probably Lua had the same issue.

Solving grammar.js errors are simple. Solving the .scm issues... That one, that one is a big issue if the error is unclear.

For instance, grammar.js alone can make the most random errors appear in .scm.

If I replace binding_func with binding .scm explodes, for instance.

Ah yes, now it also supports [read | write] all automatically 😊
That wasn't the case before

Their grammar defines structure and where to set the "loops" at. A few features they have are missing in their grammar, so they're not included here. Except classes though.
The missing one which the previous didn't have is type instantiation.

It may had the highlights, but that's due to the bitwise operators. Which is funny to Luau because when it was being developed, they talked about how it would kill << support. And mistakenly they are currently included through the current tree-sitter, lol 🙃

Also self is a keyword highlight now. That's on purpose.

Similar to this. Although some implementation can detect whether it is left hand or right hand to determine when to highlight it, but yeah... that's like future update tech.

Point is, it has its highlight.

I don't know if @boolean highlight is a real thing.

[appellation]

Note: this follow-up review was written by Claude (an AI assistant) at the maintainer's request, not by the maintainer personally. I generated the parser from 2c72a68 and parsed the same snippets with this branch and with main.

Thanks for the updates. const, contextual class/public, export class, attributes, type function, typeof in types and read/write all parse now, and the Lua 5.4 syntax is gone.

One blocker remains: a < b comparisons no longer parse (see the inline comment on function_call). There are also a few smaller regressions compared with main, and the pinned commit: in arborium.yaml is still out of date (see my reply on that thread). Note that CI only builds the grammar; it doesn't parse any Luau, so it can't catch these.

🤖 Generated with Claude Code

[karl-police]

May I note that it allows

function f(): (number, string, ...string) return; return; end

hmmm, if I fix it the highlighting doesn't break, so lemme apply the fix

[karl-police]

May I note that it allows

function f(): (number, string, ...string) return; return; end

hmmm, if I fix it the highlighting doesn't break, so lemme apply the fix

now is fix