swc-project/swc · error

auto accessor

Error message

auto accessor

What it means

A catch-all arm in `Babelify for ClassMember` (babelify/class.rs:65). The match maps swc class members to Babel ClassBodyEl variants; the arm labeled 'auto accessor' fires for auto-accessor class members (`accessor x = ...`), a decorator-proposal feature whose Babel ESTree representation is not wired up in this conversion, so any ClassMember of that shape reaching the catch-all aborts the babelify pass.

Source

Thrown at crates/swc_estree_compat/src/babelify/class.rs:65

}

impl Babelify for ClassMember {
    type Output = ClassBodyEl;

    fn babelify(self, ctx: &Context) -> Self::Output {
        match self {
            ClassMember::Constructor(c) => ClassBodyEl::Method(c.babelify(ctx)),
            ClassMember::Method(m) => ClassBodyEl::Method(m.babelify(ctx)),
            ClassMember::PrivateMethod(m) => ClassBodyEl::PrivateMethod(m.babelify(ctx)),
            ClassMember::ClassProp(p) => ClassBodyEl::Prop(p.babelify(ctx)),
            ClassMember::PrivateProp(p) => ClassBodyEl::PrivateProp(p.babelify(ctx)),
            ClassMember::TsIndexSignature(s) => ClassBodyEl::TSIndex(s.babelify(ctx)),
            ClassMember::Empty(_) => panic!(
                "illegal conversion: Cannot convert {:?} to ClassBodyEl",
                &self
            ),
            ClassMember::StaticBlock(s) => ClassBodyEl::StaticBlock(s.babelify(ctx)),
            ClassMember::AutoAccessor(..) => todo!("auto accessor"),
            #[cfg(swc_ast_unknown)]
            _ => panic!("unable to access unknown nodes"),
        }
    }
}

impl Babelify for ClassProp {
    type Output = ClassProperty;

    fn babelify(self, ctx: &Context) -> Self::Output {
        let computed = Some(self.key.is_computed());

        ClassProperty {
            base: ctx.base(self.span),
            key: self.key.babelify(ctx),
            value: self
                .value
                .map(|val| Box::alloc().init(val.babelify(ctx).into())),

View on GitHub (pinned to 5176682b65)

Solutions

1. Lower auto-accessor members to explicit getter/setter backing-field pairs in an earlier pass before babelifying
2. Add a ClassBodyEl mapping for auto accessors if the target ESTree AST supports them
3. Reject inputs using accessor syntax with a clear unsupported-feature error instead of panicking

When it happens

Trigger: Thrown at crates/swc_estree_compat/src/babelify/class.rs:65 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/0cdacc58aaef739a. Report an issue: GitHub.