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

Unexpected at-rules are not allowed here

Error message

Unexpected at-rules are not allowed here

What it means

An at-rule appeared in a context where its block is not allowed (e.g. @import or @charset inside another rule's block); the parser rejects it at its span because those at-rules are only valid at the top level.

Source

Thrown at crates/swc_css_parser/src/parser/at_rules/mod.rs:582

            }
            "import" => {
                let span = self.input.cur_span();

                return Err(Error::new(span, ErrorKind::Unexpected("'{' token")));
            }
            "keyframes" | "-webkit-keyframes" | "-moz-keyframes" | "-o-keyframes"
            | "-ms-keyframes" => {
                let ctx = Ctx {
                    block_contents_grammar: BlockContentsGrammar::RuleList,
                    in_keyframes_at_rule: true,
                    ..self.ctx
                };
                let rule_list = self.with_ctx(ctx).parse_as::<Vec<Rule>>()?;
                let rule_list: Vec<ComponentValue> = rule_list
                    .into_iter()
                    .map(|rule| match rule {
                        Rule::AtRule(at_rule) => {
                            self.errors.push(Error::new(
                                at_rule.span,
                                ErrorKind::Unexpected("at-rules are not allowed here"),
                            ));

                            ComponentValue::AtRule(at_rule)
                        }
                        Rule::QualifiedRule(qualified_rule) => {
                            let locv = match qualified_rule.prelude {
                                QualifiedRulePrelude::ListOfComponentValues(locv) => locv,
                                _ => {
                                    unreachable!();
                                }
                            };

                            let res = self.parse_according_to_grammar(&locv, |parser| {
                                parser.input.skip_ws();

                                let child = parser.parse()?;

View on GitHub (pinned to 5176682b65)

Solutions

1. Move the at-rule to the stylesheet's top level
2. Collect and report the error
3. Drop the disallowed at-rule during recovery

When it happens

Trigger: Thrown at crates/swc_css_parser/src/parser/at_rules/mod.rs:582 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/52571fcf27a1a694. Report an issue: GitHub.