SQLcl

the codescan rule G-1050 should not apply to check constraints.

create table t (
    c char(1) default on null 'Y' not null,
    constraint t_c_chk check (c in ('Y', 'N'))
);

results in

Warning (3,37): G-1050: Avoid using literals in your code

Check constraints only accept literals, sql-functions (not PL/SQL) and references to columns in same row.
see section "Restrictions on Check Constraints".

In the example above one can't avoid the literals in the check constraint.

I already opened an issue with plsql-and-sql-coding-guidelines.
We are still arguing about changing the rule but already agreed on that this should be fixed in SQLcl's implementation.