{"ast_node_type":"variable","tokens":[{"end":58,"kind":"keyword","start":0,"text":"let"}]}
        let ast_id = self.source_ast_id_map.ast_id(block);
    fn lower_extern_block(&mut self, block: &ast::ExternBlock) -> ItemTreeAstId<ExternBlock> {
        let children: Box<[_]> = block.extern_item_list().map_or(Box::new([]), |list| {