inconsistent behave of boolean based domains in XML functions

Hello

On Czech pg mailing list was reported issue about problems with
boolean based domains and XML functions.

There are maybe more issues, but probably there is little bit strange
and unexpected result

postgres=# CREATE DOMAIN booldomain as bool;
CREATE DOMAIN

-- fully expected behave
postgres=# select true, true::booldomain;
bool | booldomain
------+------------
t | t
(1 row)

postgres=# select true::text, true::booldomain::text;
text | text
------+------
true | true
(1 row)

-- unexpected behave
postgres=# select xmlforest(true as bool, true::booldomain as booldomain);
xmlforest
---------------------------------------------
<bool>true</bool><booldomain>t</booldomain>
(1 row)

Best regards

Pavel Stehule