bug: tree-sitter parses complex declaration as pseudo-class instead of CSS custom property

[kensternberg-authentik]

Did you check existing issues?

• I have read all the tree-sitter docs if it relates to using the parser
• I have searched the existing issues

Tree-Sitter CLI Version, if relevant (output of tree-sitter --version)

tree-sitter 0.24.5

Describe the bug

In the following Sass rule_set.block:

.#{$backdrop} {
  --#{$backdrop}--Position: fixed;
  --#{$backdrop}--ZIndex: var(--#{$pf-global}--ZIndex--lg);
}

tree-sitter-scss correctly parses the first declaration as property name. It ERRORs on the second declaration, and claims its best-fit is as a pseudo_class_selector.

I believe part of the confusion comes from an inappropriate declaration in tree-sitter-css, namely this one:

    _selector: $ => choice(
      $.universal_selector,
      alias($.identifier, $.tag_name),
      $.class_selector,

// ... much later....

    identifier: _ => /(--|-?[a-zA-Z_\xA0-\xFF])[a-zA-Z0-9-_\xA0-\xFF]*/,

To the best of my knowledge, a tag_name cannot start with the -- sequence, yet here it's allowed, creating an ambiguity. Unfortunately, the confusion of tag_name with identifier goes pretty deep and recursive in the definition of _selector, leading to the problem.

Steps To Reproduce/Bad Parse Tree

1. Attempt to parse this file with $ tree-sitter parse file.scss:

.#{$backdrop} {
  --#{$backdrop}--Position: fixed;
  --#{$backdrop}--ZIndex: var(--#{$pf-global}--ZIndex--lg);
}

2. See this message:

      (ERROR [2, 2] - [2, 59]
        (pseudo_class_selector [2, 2] - [2, 58]
          (tag_name [2, 2] - [2, 24]
            (identifier [2, 2] - [2, 4])
            (interpolation [2, 4] - [2, 16]

Expected Behavior/Parse Tree

I would expect the second declaration to be correctly interpreted as a declaration.

Repro

The example is given above.