swc-project/swc · error · swc_css_parser::Error

Unexpected

Error message

Unexpected 

What it means

parse_at_rule_block hit an ErrorKind::Unexpected(...) arm with no handler for the current block-contents grammar, so the unexpected token text is reported. It means the CSS inside this at-rule block cannot be classified by the active grammar (rule list vs style block).

Source

Thrown at crates/swc_css_parser/src/parser/at_rules/mod.rs:668

                BlockContentsGrammar::StyleBlock => {
                    let style_blocks: Vec<StyleBlock> = self.parse()?;
                    let style_blocks: Vec<ComponentValue> =
                        style_blocks.into_iter().map(ComponentValue::from).collect();

                    style_blocks
                }
                _ => {
                    let rule_list = self.parse_as::<Vec<Rule>>()?;
                    let rule_list: Vec<ComponentValue> =
                        rule_list.into_iter().map(ComponentValue::from).collect();

                    rule_list
                }
            },
            "namespace" => {
                let span = self.input.cur_span();

                return Err(Error::new(span, ErrorKind::Unexpected("")));
            }
            "nest" => {
                let style_blocks: Vec<StyleBlock> = self.parse()?;
                let style_blocks: Vec<ComponentValue> =
                    style_blocks.into_iter().map(ComponentValue::from).collect();

                style_blocks
            }
            "page" => {
                let declaration_list = self
                    .with_ctx(Ctx {
                        in_page_at_rule: true,
                        ..self.ctx
                    })
                    .parse_as::<Vec<DeclarationOrAtRule>>()?;
                let declaration_list: Vec<ComponentValue> = declaration_list
                    .into_iter()
                    .map(ComponentValue::from)

View on GitHub (pinned to 5176682b65)

Solutions

1. Inspect the Unexpected payload to find the offending token
2. Fix the CSS around the at-rule block
3. Extend parse_at_rule_block for the missing grammar combination

When it happens

Trigger: Thrown at crates/swc_css_parser/src/parser/at_rules/mod.rs:668 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/c8f1df95e355b832. Report an issue: GitHub.