swc-project/swc · error · Error

number, dimension, functions (math functions) or ident (with

Error message

number, dimension, functions (math functions) or ident (with 'none' value) token

What it means

Thrown by swc_css_parser when the hue (third) component of lch()/oklch() starts with a token that is not a number, dimension, math function, or ident. This catch-all arm is the only one in the group that uses `return Err(...)` (mod.rs:1186-1193); the span is the current token. Suppressed when a var() precedes it in the same color function.

Source

Thrown at crates/swc_css_parser/src/parser/values_and_units/mod.rs:1187

                                        Ok(Some(ComponentValue::Function(parser.parse()?)))
                                    }
                                    tok!("ident") => {
                                        let ident: Box<Ident> = parser.parse()?;

                                        if ident.value.eq_ignore_ascii_case("none") {
                                            Ok(Some(ComponentValue::Ident(ident)))
                                        } else {
                                            Err(Error::new(
                                                ident.span,
                                                ErrorKind::Expected(
                                                    "'none' value of an ident token",
                                                ),
                                            ))
                                        }
                                    }
                                    _ => {
                                        if !has_variable_before {
                                            return Err(Error::new(
                                                parser.input.cur_span(),
                                                ErrorKind::Expected(
                                                    "number, dimension, functions (math \
                                                     functions) or ident (with 'none' value) token",
                                                ),
                                            ));
                                        } else {
                                            Ok(None)
                                        }
                                    }
                                },
                                &mut has_variable,
                            )?;

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

View on GitHub (pinned to 5176682b65)

Solutions

Provide hue as number/angle or via a math function: oklch(70% 0.1 120) or oklch(70% 0.1 calc(120deg * 2)).
Remove commas: lch(50% 10 30).
Unquote interpolated numeric values.
Wrap dynamic hue in var().

Example fix

/* before */
color: oklch(70% 0.1 "120");

/* after */
color: oklch(70% 0.1 120);

Defensive patterns

Strategy: try-catch

Validate before calling

fn lch_hue_token_ok(tok: &str) -> bool {
    let t = tok.trim();
    t.eq_ignore_ascii_case("none")
        || t.parse::<f64>().is_ok()
        || is_angle_or_number(t)
        || is_math_fn(t)
}

Type guard

fn hue_is_unquoted(t: &str) -> bool {
    !t.trim().starts_with('"') && !t.trim().starts_with('\'')
}

Try / catch

if let Err(e) = swc_css_parser::parse_file::<swc_css_ast::Stylesheet>(&fm, None, config, &mut errs) {
    if let swc_css_parser::error::ErrorKind::Expected(m) = e.kind() {
        if m.starts_with("number, dimension, functions") {
            // bad hue token in lch/oklch at e span; recover and report
        }
    }
}

Prevention

Never quote hue values produced by templating.
Strip commas when converting legacy color syntax.
Reject nested non-math functions in the hue slot during lint.
Feed dynamic hue through var().

When it happens

Trigger: `oklch(70% 0.1 "120")` — hue given as a string; `lch(50% 10, 30)` — legacy comma reaching the hue slot; `lch(50% 10 #fff)`; `oklch(70% 0.1 rgb(0 0 0))` — a non-math function in the hue slot.

Common situations: Mechanical conversion from comma-separated syntax; string interpolation of hue values; nesting a color function where a hue is expected.

Related errors

AI-assisted analysis of swc-project/swc@5176682b65 (2026-08-17). Data as JSON: /api/errors/3b6983b656ac1d89. Report an issue: GitHub.