{"ast_node_type":"variable","tokens":[{"end":89,"kind":"keyword","start":0,"text":"let"}]}
        let elements = ctx.arena.alloc_from_iter(fmt.template.iter().filter_map(|piece| {
        //     &[format_spec_0, format_spec_1, format_spec_2]
            let FormatArgsPiece::Placeholder(placeholder) = piece else { return None };