{"ast_node_type":"variable","tokens":[{"end":47,"kind":"keyword","start":0,"text":"let"}]}
    let root = db.parse_or_expand(ast.file_id);
fn proc_macro_span(db: &dyn ExpandDatabase, ast: AstId<ast::Fn>) -> Span {
    let ast_id_map = &db.ast_id_map(ast.file_id);