swc-project/swc · error

failed to parse args of #[ast_node]

Error message

failed to parse args of #[ast_node]

What it means

On the non-enum arm of #[ast_node] (structs/unions), the attribute arguments failed to parse into ast_node_macro::Args. This fires when the payload after the node tag uses an unknown or malformed option — the expected forms are a quoted tag like #[ast_node("Ident")] plus recognized flags such as no_partial_eq; anything else fails at compile time.

Source

Thrown at crates/ast_node/src/lib.rs:260

                )]
                #clone
                #non_exhaustive
                #[cfg_attr(
                    feature = "serde-impl",
                    serde(untagged)
                )]
                #[cfg_attr(
                    feature = "encoding-impl",
                    derive(::swc_common::Encode, ::swc_common::Decode)
                )]
                #input
            ));
        }
        _ => {
            let args: Option<ast_node_macro::Args> = if args.is_empty() {
                None
            } else {
                Some(parse(args).expect("failed to parse args of #[ast_node]"))
            };

            let serde_tag = match input.data {
                Data::Struct(DataStruct {
                    fields: Fields::Named(..),
                    ..
                }) => {
                    if args.is_some() {
                        Some(quote!(#[cfg_attr(
                            feature = "serde-impl",
                            serde(tag = "type")
                        )]))
                    } else {
                        None
                    }
                }
                _ => None,
            };

View on GitHub (pinned to 5176682b65)

Solutions

1. Verify the arguments match the documented grammar, e.g. #[ast_node("Tag", no_partial_eq)]
2. Remove unsupported options and check crate docs for the accepted flag list
3. For enums, drop arguments entirely — the enum arm rejects them with its own message

When it happens

Trigger: Thrown at crates/ast_node/src/lib.rs:260 when the library encounters an invalid state.

Common situations: See trigger scenarios.

Understand the failure class

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

AI-assisted analysis of swc-project/swc@5176682b65 (2026-08-17). Data as JSON: /api/errors/a112be28e2fabd79. Report an issue: GitHub.