Add syntax highlighting for named arguments

[alfredomtx]

Summary

Adds syntax highlighting for PHP 8+ named arguments in function/method calls.

Named arguments like id:, firstName:, lastName: in:

$this->users->map(fn (User $user) => new UserDTO(
    id: $user->id,
    firstName: $user->first_name,
    lastName: $user->last_name,
));

Are now highlighted with the @label token, which themes can style distinctly (e.g., JetBrains IDEs use a muted blue for these).

Implementation

Added a simple tree-sitter query that captures the name field of argument nodes:

(argument
  name: (name) @label)

The tree-sitter-php grammar already exposes the name field on argument nodes for named arguments, so no grammar changes are needed.

Test plan

• Tested locally with zed: install dev extension
• Named arguments now highlight correctly in PHP files

[MrSubidubi]

Thanks for this!

Can you quickly elaborate why this shoud be highlighted as label? From an initial view, this seems unintuitive to me, but I might be lacking context here. Thanks!

[alfredomtx]

Thanks for this!

Can you quickly elaborate why this shoud be highlighted as label? From an initial view, this seems unintuitive to me, but I might be lacking context here. Thanks!

Hello @MrSubidubi, you are welcome! And thanks for questioning this.

The ideal semantic token would be @variable.parameter (which nvim-treesitter uses for Python's keyword arguments), but Zed's theme system doesn't support that capture. Of the supported captures, @label is the closest fit because:

1. Named arguments follow the name: syntax pattern similar to labels
2. It's already used for regex group names in Zed (another form of named reference)
3. Themes like One Dark style labels with a muted color, which matches how JetBrains IDEs(I come from PHPStorm) render named arguments

Alternatively, this could be an argument for Zed to support @variable.parameter as a capture.

Source: https://zed.dev/docs/extensions/languages#syntax-highlighting

The documentation provides a comprehensive list of captures supported by themes, and the only variable-related captures listed are:

• @variable
• @variable.special