fn integer_number_parser(input: &mut &str) -> PResult<i64> {

    fn integer_number_parser(input: &mut &str) -> PResult<(i64, u32)> {

                Ok::<_, ParseIntError>(base * 10i64.pow(exponent))

                Ok::<_, ParseIntError>((base, exponent))

    fn parse_integer(lexer: &mut Lexer<Token>) -> Result<i64, LexError> {

    fn parse_integer(lexer: &mut Lexer<Token>) -> Result<(i64, u32), LexError> {

        Integer(i64),

        Integer((i64, u32)),

            assert!(lexer.next() == Some(Ok(Token::Integer(3))));

            assert!(lexer.next() == Some(Ok(Token::Integer((3, 0)))));