type exp = | Js_function of {arity: int,arrow: bool,
}| Js_literal of {
}| Js_exp_unknown
;type raw_kind = | Raw_re| Raw_exp| Raw_program
;type stmt = | Js_stmt_unknown
;type code_info = | Exp(exp)| Stmt(stmt)
;type t = {code: string,code_info: code_info,
};