Bug#21811 Odd casting with date + INTERVAL arithmetic

- Type casting was not consequent, thus when adding a DATE type with
  a WEEK interval the result type was DATETIME and not DATE as is the
  norm.
- By changing the order of the date internal enumerations the deviant
  type casting is resolved (Item_date_add_interval::fix_length_and_dec()
  which determines result type for this operation assumes that addition
  of any interval with value <= INTERVAL_DAY to date value will result
  in date). There are two independant places to change:
  interval_names[] and interval_type.


mysql-test/r/func_date_add.result:
  Updated result file for type casting test
mysql-test/r/func_time.result:
  Updated result file for type casting test
mysql-test/t/func_date_add.test:
  Added test for type casting when adding intervals to date.
sql/item_timefunc.cc:
  Changed order of "week" key word to match the date interval enumeration.
sql/item_timefunc.h:
  Changed the order of the enumeration to better follow interval sizes.

1 files changed, 14 insertions, 0 deletions

diff --git a/mysql-test/r/func_date_add.result b/mysql-test/r/func_date_add.result
index 841d13a6ea6..ac5709260fd 100644
--- a/mysql-test/r/func_date_add.result
+++ b/mysql-test/r/func_date_add.result
@@ -71,3 +71,17 @@ NULL
 NULL
 NULL
 drop table t1;
+End of 4.1 tests
+SELECT CAST('2006-09-26' AS DATE) + INTERVAL 1 DAY;
+CAST('2006-09-26' AS DATE) + INTERVAL 1 DAY
+2006-09-27
+SELECT CAST('2006-09-26' AS DATE) + INTERVAL 1 MONTH;
+CAST('2006-09-26' AS DATE) + INTERVAL 1 MONTH
+2006-10-26
+SELECT CAST('2006-09-26' AS DATE) + INTERVAL 1 YEAR;
+CAST('2006-09-26' AS DATE) + INTERVAL 1 YEAR
+2007-09-26
+SELECT CAST('2006-09-26' AS DATE) + INTERVAL 1 WEEK;
+CAST('2006-09-26' AS DATE) + INTERVAL 1 WEEK
+2006-10-03
+End of 5.0 tests