swc-project/swc · error

Expected percentage token

Error message

Expected percentage token

What it means

Fired while parsing a Percentage: the current token was not a Percentage token (e.g. 50%), which is required to build a Percentage node. This `if !is!(self, Percentage)` check is a validation guard; input at fault is a percentage-required context receiving a plain number or other token.

Source

Thrown at crates/swc_css_parser/src/parser/values_and_units/mod.rs:2542

                Ok(CmykComponent::Function(self.parse()?))
            }
            _ => {
                unreachable!()
            }
        }
    }
}

impl<I> Parse<Percentage> for Parser<I>
where
    I: ParserInput,
{
    fn parse(&mut self) -> PResult<Percentage> {
        let span = self.input.cur_span();

        if !is!(self, Percentage) {
            return Err(Error::new(span, ErrorKind::Expected("percentage token")));
        }

        match bump!(self) {
            Token::Percentage { value, raw } => {
                let value = Number {
                    span: Span::new(span.lo, span.hi - BytePos(1)),
                    value,
                    raw: Some(raw),
                };

                Ok(Percentage { span, value })
            }
            _ => {
                unreachable!()
            }
        }
    }
}

View on GitHub (pinned to 5176682b65)

Solutions

1. Add the '%' suffix to the number
2. Use a Number or Dimension parser if a different value type was intended

When it happens

Trigger: Thrown at crates/swc_css_parser/src/parser/values_and_units/mod.rs:2542 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/ea0651e422b06a63. Report an issue: GitHub.