Yep, I'm sorry for the complicated question title but couldn't do better:)

This is a follow-up from my answer to that question:

When doing any kind of computation with a user-defined type, the result seems to lose that user-defined type. (At least sa_describe_query implies so.) That is sometimes inevatible, when the result won't fit in the user-defined domain because the domain range would be to small, e.g. when adding two money values, and the sum requires an additional digit.

In other cases, the result would fit in the domain type, e.g. when limiting a char type to a smaller length with LEFT() or when adding 0 to a numeric type as in

select column_number, domain_name_with_size, user_type_name
from sa_describe_query('select cast(1 as money), cast(1 as money) + 0')

returns

column_number,domain_name_with_size,user_type_name
1,'numeric(19,4)','money'
2,'numeric(20,4)',

(Note: Casting the computed expression back to the user-defined type as in "cast(cast(1 as money) + 0 as money)" works as expected, i.e. then sa_describe_query returns the user-defined type.)

General question:

Is this "losing the user-defined type" in the course of any computation by design? (I realize that a "smarter approach" would be very sophisticated to implement.)