BUG #18878: PostgreSQL triggers Assertion Failure in Debug build

PG Bug reporting form <noreply@postgresql.org> writes:

In the debug build of PostgreSQL 17.4, compiled with `configure
--enable-debug --prefix=$(pwd) --exec-prefix=$(pwd) --enable-cassert`,
triggered Assertion Failure when executing the following statement:

```sql
WITH RECURSIVE ta01 AS NOT MATERIALIZED ( WITH RECURSIVE any_cte_name AS
MATERIALIZED ( TABLE ta01 ) DELETE FROM v00 RETURNING *, CASE WHEN FALSE
THEN TRUE WHEN FALSE THEN TRUE ELSE TRUE END IDENT ) SELECT FROM JSON_ARRAY
( TABLE v00 ORDER BY CASE WHEN FALSE THEN TRUE END NULLS FIRST FOR READ
ONLY) GROUP BY ROLLUP ( CASE WHEN FALSE NOT BETWEEN ASYMMETRIC CASE WHEN
FALSE THEN TRUE END AND FALSE <> CASE WHEN EXISTS ( SELECT GROUP BY ALL ( )
FOR READ ONLY ) > CASE WHEN FALSE THEN TRUE END THEN FALSE END IS NULL THEN
ARRAY ( ( TABLE ta01 ) ) ELSE CASE WHEN TRUE BETWEEN EXISTS ( SELECT GROUP
BY ALL ( ) FOR READ ONLY ) AND TRUE IS NOT FALSE > EXISTS ( SELECT ALL GROUP
BY ( ) FOR READ ONLY ) THEN TRUE END > CASE WHEN FALSE THEN TRUE END END )
FOR READ ONLY;
```

This can be reduced to

WITH RECURSIVE ta01 AS (
WITH any_cte_name AS ( TABLE ta01 )
DELETE FROM v00 RETURNING * )
TABLE ta01;

That should be rejected, because ta01 has a self-reference and is not
in the allowed form "base-case UNION query-with-self-reference".
However, we managed to miss the appearance of the self-reference
because the code in charge of detecting it hadn't been taught that
WITH is now allowed in INSERT/UPDATE/DELETE. (Which is a bit
disheartening, but there you have it.)

Fixed, thanks for the report!

regards, tom lane