swc-project/swc · error · Error

Expected 'none' value of an ident token

Error message

Expected 'none' value of an ident token

What it means

Fired while parsing an alpha component (e.g. in rgb()/hsl() color functions): the token must be a number, percentage, math function, or the ident 'none', but none matched. The parser cannot interpret the token as an alpha value.

Source

Thrown at crates/swc_css_parser/src/parser/values_and_units/mod.rs:1547

                    values.push(ComponentValue::Delimiter(self.parse()?));

                    self.input.skip_ws();

                    let alpha_value = self.try_parse_variable_function(
                        |parser, has_variable_before| match cur!(parser) {
                            tok!("number") | tok!("percentage") => {
                                Ok(Some(ComponentValue::AlphaValue(parser.parse()?)))
                            }
                            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)
                                }
                            }

View on GitHub (pinned to 5176682b65)

Solutions

1. Use a number (0-1), a percentage, a math function like calc(), or 'none' for the alpha slot
2. Fix typos in the alpha value

When it happens

Trigger: Thrown at crates/swc_css_parser/src/parser/values_and_units/mod.rs:1547 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/dd148e843e68f394. Report an issue: GitHub.