postgres parser: multiple or trailing underscores should error

[Jefffrey]

We can use underscores in numbers, however if we have more than one in succession 10__00 or trailing 10_00_ this should error according to postgres:

postgres=# select version();
                                                         version
--------------------------------------------------------------------------------------------------------------------------
 PostgreSQL 18.2 (Debian 18.2-1.pgdg13+1) on aarch64-unknown-linux-gnu, compiled by gcc (Debian 14.2.0-19) 14.2.0, 64-bit
(1 row)

postgres=# select 10__00;
ERROR:  trailing junk after numeric literal at or near "10__00"
LINE 1: select 10__00;
               ^
postgres=# select 10_00_;
ERROR:  trailing junk after numeric literal at or near "10_00_"
LINE 1: select 10_00_;
               ^
postgres=# select 10_00;
 ?column?
----------
     1000
(1 row)

This seems to currently be accepted:

// tests/sqlparser_postgres.rs

#[test]
fn parse_incorrect_underscores() {
    let sql = "SELECT 10_00";
    let result = pg().parse_sql_statements(sql);
    assert!(result.is_err());

    let sql = "SELECT 10_00_";
    let result = pg().parse_sql_statements(sql);
    assert!(result.is_err());
}

• test fails since both of the statements parse successfully