Recognize .ispc extension as CPP

[MarijnS95]

Intel's Implicit SIMD Program Compiler (https://ispc.github.io/) files are "a variant of the C programming language" with support for templates and references.

Unfortunately they also use some custom keywords and constructs that make this language unsuitable for clangd, but the CPP grammar works well enough for most highlighting. There is supposedly a user-made tree-sitter grammar: https://github.com/tree-sitter/tree-sitter/pull 2282

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Creating this as draft as we should probably not use clangd as LSP here, and perhaps switch to https://github.com/fab4100/tree-sitter-ispc for grammar.

[cloudhan]

ISPC has a language server and is pending a release https://togithub.com/ispc/ispc/issues/1605#issuecomment-1771833547

[the-mikedavis]

Let's focus this PR on using tree-sitter-ispc and the ispc language server. For those looking for some basic syntax highlighting for ispc in the mean time, the current change can be added to your custom language config:

# ~/.config/helix/languages.toml
[[language]]
name = "cpp"
file-types = ["cc", "hh", "c++", "cpp", "hpp", "h", "ipp", "tpp", "cxx", "hxx", "ixx", "txx", "ino", "C", "H", "cu", "cuh", "cppm", "h++", "ii", "inl", "ispc", { suffix = ".hpp.in" }, { suffix = ".h.in" }]

[MarijnS95]

Imported the grammar from https://github.com/fab4100/tree-sitter-ispc.

Somewhat strangely some of the queries were removed in tree-sitter-grammars/tree-sitter-ispc@0197076 and have been moved into https://github.com/nvim-treesitter/nvim-treesitter/tree/7da3cb6323d1e1fbfc4d7dc05cac74946458b8a0/queries/ispc. I have imported the latter and should probably update the commit hash to 0197076648b8f31aab85c447015f29dadb53a8b3~, or ask the author what source is supposed to be latest/source-of-truth. At least it provides indent queries.

[the-mikedavis]

The queries will need to be adjusted - neovim queries don't work out of the box for Helix. For example some captures need to be adjusted to match the ones we use (https://docs.helix-editor.com/master/themes.html#syntax-highlighting) like @repeat should be @keyword.control.repeat. #lua-match? will need to be replaced with an equivalent #match?

[fab4100]

The two sets of queries exist because neovim has its own query engine with some extensions as mentioned above. Unfortunately there is no common ground for query syntax at the moment. The queries in the ISPC parser repo are very basic and minimal (based off the C language parser). As mentioned, you will need to adjust and modify for your needs. If you have additions that will work for general queries (without custom engine syntax) I am happy to add them in the ISPC parser repo. Both query sets (in the ISPC parser repo and nvim-treesitter) are currently maintained (the one in nvim-treesitter more actively however).

[MarijnS95]

I'll unfortunately be unavailable for the next month but hope to pick this back up after that and finalize this PR!

[the-mikedavis]

For indents see https://docs.helix-editor.com/master/guides/indent.html

[the-mikedavis]

For locals we follow tree-sitter: https://tree-sitter.github.io/tree-sitter/syntax-highlighting#local-variables

So these should be changed to only use the @local.definition, @local.reference and @local.scope captures

[MarijnS95]

Thanks for these pointers! I've quickly cobbled some changes together that I was able to debug using :treesitter commands and validate visually in the editor, and now understand a lot better how these are supposed to work.

There's still more to do, and I should likely also contribute the C changes separately, which enable parameter highlights for int x[10] and int **x (only int *x was supported).

Since there's no locals.scm for C yet, and this PR adds a bunch of them that apply to C, should I move the base of it to c/locals.scm and have an ; Inherits: c in the ISPC file?

[the-mikedavis]

Yep feel free to add some locals for C and re-use them if possible, that should be a nice improvement to C highlighting

[MarijnS95]

Factored out to a separate file 👍