swc-project/swc · error

Expected dimension, number or '?' delim token

Error message

Expected dimension, number or '?' delim token

What it means

Fired while parsing a UnicodeRange: after the leading `u`, the parser expected a dimension token (hex digits with `+` unit) or a number, or a `?` delim for wildcard forms, and found none of them. Input at fault is a malformed @unicode-range value such as `U+` with nothing following, or other tokens that do not fit any Unicode range production.

Source

Thrown at crates/swc_css_parser/src/parser/values_and_units/mod.rs:2879

                unicode_range.push_str(&raw.1);

                loop {
                    if !is!(self, "?") {
                        break;
                    }

                    let question = match bump!(self) {
                        Token::Delim { value } => value,
                        _ => {
                            unreachable!();
                        }
                    };

                    unicode_range.push(question);
                }
            }
            _ => {
                return Err(Error::new(
                    span,
                    ErrorKind::Expected("dimension, number or '?' delim token"),
                ));
            }
        }

        let mut chars = unicode_range.chars();

        // 1. Skipping the first u token, concatenate the representations of all the
        // tokens in the production together. Let this be text.
        chars.next();

        // 2. If the first character of text is U+002B PLUS SIGN, consume it. Otherwise,
        // this is an invalid <urange>, and this algorithm must exit.
        let mut next = chars.next();

        if next != Some('+') {
            return Err(Error::new(

View on GitHub (pinned to 5176682b65)

Solutions

1. Follow 'U' with '+', hex digits, or '?' wildcards: 'U+4??'
2. Remove invalid tokens after the leading U

When it happens

Trigger: Thrown at crates/swc_css_parser/src/parser/values_and_units/mod.rs:2879 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/c434a7a0bee58fa9. Report an issue: GitHub.