swc-project/swc · error · Error

Expected percentage, number, function (math functions) or id

Error message

Expected percentage, number, function (math functions) or ident (with 'none' value) token

What it means

Fired while parsing a color function component: expected a percentage, number, math function, or the ident 'none', but the current token is none of these (except that within device-cmyk the ident case is excluded). The component cannot be parsed into any accepted form.

Source

Thrown at crates/swc_css_parser/src/parser/values_and_units/mod.rs:1555

                            }
                            Token::Function { value, .. } if is_math_function(value) => {
                                Ok(Some(ComponentValue::Function(parser.parse()?)))
                            }
                            tok!("ident") if !matches!(&*lower_fname, "device-cmyk") => {
                                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 {
                                    Err(Error::new(
                                        parser.input.cur_span(),
                                        ErrorKind::Expected(
                                            "percentage, number, function (math functions) or \
                                             ident (with 'none' value) token",
                                        ),
                                    ))
                                } else {
                                    Ok(None)
                                }
                            }
                        },
                        &mut has_variable,
                    )?;

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

View on GitHub (pinned to 5176682b65)

Solutions

1. Use a percentage or number for the channel value
2. Use a math function (calc, min, max, ...) or 'none' where allowed
3. Remove invalid identifiers from the component slot

When it happens

Trigger: Thrown at crates/swc_css_parser/src/parser/values_and_units/mod.rs:1555 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of swc-project/swc@5176682b65 (2026-08-17). Data as JSON: /api/errors/222047329d1bc7ba. Report an issue: GitHub.