BUG #7797: datetime + '1 month'::interval is going outside of a month's bounds

The following bug has been logged on the website:

Bug reference: 7797
Logged by: Jared Thompson
Email address: afonit(at)gmail(dot)com
PostgreSQL version: 9.2.2
Operating system: Ubuntu 12.04
Description:

This query:

select
'2012-01-31'::date + '1 month'::interval

Produces this result:
"2012-02-29 00:00:00"

2012-02-29 is not a valid date. February only goes to 28 days.

I am not sure what the expected behavior should be, but what I was expecting
is (in the above instance):
Adding one month to 2012-01-31 would yield the last day of February
2012-01-28

and if we added one month to 2012-01-25 we do get 2012-02-25.

It appears that the +'1 month'::interval is making it the next month and
same date - but if there aren't the same number of days in the months it
seems to be breaking as noted in the first example.

Again, not sure what the expected behavior is but I would think that 'last
day of a month' + '1 month'::interval would give 'last day of next month'.

I realize on January 29-30th I am not sure what the expected behavior should
be.