refactor(catppuccin)!: reimplement basic hl groups

[Jint-lzxy]

WIP but mostly completed. Ref: #627.

TODO:

• Fully support LSP semantic tokens (should be linked to basic hl)
• Support all miscellaneous highlights (e.g., gitcommit*)

[nullchilly]

Could you port this PR to upstream if you have time? With better highlights decisions and specific language highlights (C/C++) are really well tested, I feel like it would be a waste to remain in a config repo.

Also our semantic tokens highlights reputation are under fire right now (Everything is just blue 😅) and the current treesitter highlights aren't much better, for example ["@method"] = { link = "Function" } makes much more sense

[Jint-lzxy]

@nullchilly Sure! In fact, I plan to open a PR upstream after this PR is merged. The plan is to adjust those treesitter highlights according to the color palette document & existing color presets and attempt to reduce maintenance pressure by linking as many hl groups as possible. But this PR may take more time than expected, as I'm trying to disentangle this "intertwined puzzle" - IMHO upstream support for treesitter is a bit chaotic. Since catppuccin/nvim@f079dda, it has gone through a lot of repairs, which makes the current integration look like a compromise btw old and new palettes¹ (e.g., @field was changed to C.teal in catppuccin/nvim@8a3b892, intended to "<make> current syntactic rules better"², but it got reverted to the previous color in a subsequent commit³), leading to a sense of disharmony between hl groups (which also makes it challenging to support semantic tokens).

This PR will try to make the hl groups self-explanatory, but we definitely need to receive more feedback and make several changeovers before merging this upstream 😄

Footnotes

1. catppuccin/nvim#134 ↩

2. catppuccin/nvim#134 (comment) ↩

3. catppuccin/nvim@b17cfa0 ↩

[Jint-lzxy]

I'm placing the "what's changed" table here to help me better store & track the changes I've made. Perhaps it can also help facilitate some discussions 👍 Sometimes builtin constants are not just constants literally, so it was given another color for differentiation.

---

• LNK(group): Links to group
• NEW(col): [For undefined highlight groups] New color col
• IFP(parent, child): Inherited from the parent class. child, classified under parent, should have a similar color to the parent class.
• R(before, after): Replace before with after
• [+/-] B/I/U: Bold, Italics, Underline
• FNC: Follow Naming Convention
• NS: Not Sure

NS	hl group	operation	reason
	Search	bg: R(darkened sky, surface1) fg: R(text, pink) style: +B	Selected a color similar to CurSearch to avoid confusion (things could get worse when using many highlights with different responsibilities). Added B for differentiation.
	IncSearch	bg: R(darkened sky, pink) fg: R(mantle, surface1)	Invert of Search
	Identifier	fg: R(flamingo, text)	Following @variable. It is widely used, so should have a trivial color.
	@variable	LNK(Identifier)	FNC: Any variable name
	Label	fg: R(sapphire, rosewater)	IFP(Statement, Label) (The reason for not using the same color as the parent class is b/c they still have subtle semantic differences)
●	Keyword	fg: R(mauve, red?)	Classified as any other keyword, so it should have a different color than the parent class. I haven't figured out whether to use red or maroon yet. (Should avoid having the same color as @variable.builtin)
	Exception	fg: NEW(peach)	Inherited from @exception
	@exception	LNK(Exception)	FNC: try, catch, throw
	Include	fg: R(mauve, teal)	To have a similar color to Included (which links to String).
	Float	LNK(Number)	A floating point constant is a number constant
●	Macro	LNK(Constant?)	Although both vim/nvim link it to Define by default, macros are still constants, aren't they?
●	StorageClass	LNK(Keyword?)	Although it is classified under Type, AFAIK many syntax highlighters tend to label that as Keyword (also by definition): C++ Standard - §5.11 [lex.key]
●	Structure	LNK(Keyword?)	ditto. Structure itself is not a valid type.
	Tag	fg: NEW(lavender) style: +B	Inherited from @text.reference
	@text.reference	LNK(Tag)	FNC
	Delimiter	fg: NEW(teal)	The definition for hl-group Delimiter has changed: "delimiters (e.g. ; / . / ,)". Therefore, a suitable color was chosen for it.
	@punctuation.delimiter	LNK(Delimiter)	FNC: delimiters (e.g. ; / . / ,)
	@punctuation.special	LNK(Special)	FNC: special punctuation that does not fall in the categories before (e.g. {} in string interpolation)
	@string.special	LNK(Special)	FNC: other special strings (e.g. dates)
	@float	LNK(Float)	Here, @float should be linked to Float to prevent situations where the user changes the underlying highlight group (Float) but Treesitter highlight doesn't reflect this change.
	@function.call	LNK(Function)	Should be linked to the underlying highlight group, not @function.
●	@function.macro	LNK(Constant?)	I tend to link it to Constant for the same reason as Macro. But I'm not sure if it looks good in every language.
●	@method	LNK(Function?)	IMHO there's no need to set a separate color for @method b/c methods are also functions.
	@method.call	LNK(Function)	ditto.
	@parameter	fg: R(maroon, rosewater)	rosewater is more suitable for the elements under this classification.
	@keyword.operator	LNK(Operator)	FNC: new keyword operator
	@keyword.return	fg: R(maroon, pink)	N/A
	@variable.builtin	style: +styles.properties	Add styles.properties to indicate builtin types (same hereinafter)
	@constant	LNK(Constant)	FNC: constants
●	@constant.builtin	fg: R(peach, lavender?)	Sometimes builtin constants are not just constants literally, so it was given another color for differentiation. For example, in C++ nullptr is a prvalue of type std::nullptr_t.
	@parameter	fg: R(maroon, pink)	Replaced by a softer color.
●	@type.qualifier	LNK(Constant?)	FNC: Type qualifiers should be keywords.
	@field @property	fg: R(lavender, rosewater)	Same as Identifier. Assigned a trivial color.
●	@class @struct @enum @enumMember @event @interface @modifier @regexp @typeParameter @decorator	DELETED?	The comment said those groups are related to LSP Semantic Tokens, but I cannot find any documentation about that. Can someone point out to me where those groups are documented?
●	Diagnostics···Hint	fg: R(teal, rosewater)	IMO "Hints" shouldn't be that eye-catching. It almost matches the color of DiagnosticsInfo.

[Jint-lzxy]

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