swc-project/swc · error · Error

ident token

Error message

ident token

What it means

Thrown by swc_css_parser inside color(...) when the first parameter is not an identifier. That parameter must be a predefined color space ident (srgb, display-p3, a98-rgb, prophoto-rgb, rec2020, xyz, xyz-d50, xyz-d65 — unknown idents are deliberately tolerated because browsers fall back) or a dashed custom ident starting with '--'. Unlike the component slots, this arm errors unconditionally — the closure ignores has_variable_before (mod.rs:1318-1346).

Source

Thrown at crates/swc_css_parser/src/parser/values_and_units/mod.rs:1340

                                is_custom_params = true;

                                Ok(Some(ComponentValue::DashedIdent(parser.parse()?)))
                            } else {
                                if matches_eq_ignore_ascii_case!(value, "xyz", "xyz-d50", "xyz-d65")
                                {
                                    is_xyz = true
                                } else {
                                    // There are predefined-rgb-params , but
                                    // For unknown, we don't return an error
                                    // to
                                    // continue to support invalid color,
                                    // because they fallback in browser
                                }

                                Ok(Some(ComponentValue::Ident(parser.parse()?)))
                            }
                        }
                        _ => Err(Error::new(
                            parser.input.cur_span(),
                            ErrorKind::Expected("ident token"),
                        )),
                    },
                    &mut has_variable,
                )?;

                if let Some(ident) = ident {
                    values.push(ident);
                }

                self.input.skip_ws();

                let number_or_percentage_or_none = self.try_parse_variable_function(
                    |parser, has_variable_before| match cur!(parser) {
                        tok!("number") => Ok(Some(ComponentValue::Number(parser.parse()?))),
                        tok!("percentage") if !is_xyz => {
                            Ok(Some(ComponentValue::Percentage(parser.parse()?)))

View on GitHub (pinned to 5176682b65)

Solutions

  1. Write the color space as a bare, unquoted identifier: color(srgb 0 0 0).
  2. For ICC profiles use a dashed ident: color(--my-profile 0.5 0.2 0.2).
  3. If the space comes from a variable, use var(): color(var(--space) 0 0 0).
  4. Remove any nested function or literal that occupies the first parameter position.

Example fix

/* before */
color: color("srgb" 0 0 0);

/* after */
color: color(srgb 0 0 0);
Defensive patterns

Strategy: validation

Validate before calling

fn color_space_ok(tok: &str) -> bool {
    let t = tok.trim();
    t.starts_with("--") || t.chars().all(|c| c.is_ascii_alphanumeric() || c == '-')
    // must be a bare ident (predefined space or --custom), not number/string/hash/function
}

Type guard

fn is_color_space_ident(tok: &str) -> bool {
    let t = tok.trim();
    !t.is_empty()
        && !t.starts_with('"')
        && !t.starts_with('#')
        && t.parse::<f64>().is_err()
        && !t.ends_with(')')
}

Try / catch

Err(e) if matches!(e.kind(), swc_css_parser::error::ErrorKind::Expected(m) if m == "ident token") => {
    let (span, _) = e.into_inner();
    // color() first parameter at span must be a color space ident or --custom ident
}

Prevention

When it happens

Trigger: `color(123 0 0 0)` — number as color space; `color("srgb" 0 0 0)` — quoted color space; `color(#fff 0 0 0)`; `color(rgb(0 0 0))` — a nested function where the space ident should be. `color(var(--space) 0 0 0)` is fine because var() is intercepted first.

Common situations: New color() syntax where authors quote the color space or forget it entirely; generated CSS that interpolates the space from a typed (non-ident) variable; copy-paste from examples that wrap the space in quotes.

Related errors

AI-assisted analysis of swc-project/swc@5176682b65 (2026-08-17). Data as JSON: /api/errors/62ff3d4f449657a2. Report an issue: GitHub.