Bug#42525: TIMEDIFF function

In 37553 we declared longlong results for
class Item_str_timefunc as per comments/docs,
but didn't add a method for that. And the
default just wasn't good enough for some
cases.

Changeset adds dedicated val_int() to class.

mysql-test/r/func_sapdb.result:
  More tests for casts of TIME() / TIMEDIFF() with negative results.
mysql-test/t/func_sapdb.test:
  More tests for casts of TIME() / TIMEDIFF() with negative results.
sql/item_timefunc.h:
  Since we claim to provide longlong results, we should have
  a suitable function to provide them (the default won't do).
  This one matches the val_real() variant.

mysql-test/r/func_sapdb.result

@@ -268,3 +268,17 @@ timediff('2008-09-29 20:10:10','2008-09-30 20:10:10')<time('00:00:00')
 SELECT CAST(time('-73:42:12') AS DECIMAL);
 CAST(time('-73:42:12') AS DECIMAL)
 -734212
+SELECT TIMEDIFF(TIME('17:00:00'),TIME('17:00:00'))=TIME('00:00:00') AS 1Eq,
+TIMEDIFF(TIME('17:59:00'),TIME('17:00:00'))=TIME('00:00:00') AS 1NEq1,
+TIMEDIFF(TIME('18:00:00'),TIME('17:00:00'))=TIME('00:00:00') AS 1NEq2,
+TIMEDIFF(TIME('17:00:00'),TIME('17:00:00'))=     '00:00:00'  AS 2Eq,
+TIMEDIFF(TIME('17:59:00'),TIME('17:00:00'))=     '00:00:00'  AS 2NEq1,
+TIMEDIFF(TIME('18:00:00'),TIME('17:00:00'))=     '00:00:00'  AS 2NEq2,
+TIMEDIFF(TIME('17:00:00'),TIME('17:00:00'))=TIME(0)          AS 3Eq,
+TIMEDIFF(TIME('17:59:00'),TIME('17:00:00'))=TIME(0)          AS 3NEq1,
+TIMEDIFF(TIME('18:00:00'),TIME('17:00:00'))=TIME(0)          AS 3NEq2,
+TIME(0) AS Time0, TIME('00:00:00') AS Time00, '00:00:00' AS Literal0000,
+TIMEDIFF(TIME('17:59:00'),TIME('17:00:00')),
+TIMEDIFF(TIME('17:00:00'),TIME('17:59:00'));
+1Eq	1NEq1	1NEq2	2Eq	2NEq1	2NEq2	3Eq	3NEq1	3NEq2	Time0	Time00	Literal0000	TIMEDIFF(TIME('17:59:00'),TIME('17:00:00'))	TIMEDIFF(TIME('17:00:00'),TIME('17:59:00'))
+1	0	0	1	0	0	1	0	0	00:00:00	00:00:00	00:00:00	00:59:00	-00:59:00

mysql-test/t/func_sapdb.test

@@ -151,4 +151,22 @@ select timediff('2008-09-29 20:10:10','2008-09-30 20:10:10')<time('00:00:00');
 SELECT CAST(time('-73:42:12') AS DECIMAL);
 
 
+
+#
+# Bug#42525 - TIMEDIFF function
+#
+
+SELECT TIMEDIFF(TIME('17:00:00'),TIME('17:00:00'))=TIME('00:00:00') AS 1Eq,
+       TIMEDIFF(TIME('17:59:00'),TIME('17:00:00'))=TIME('00:00:00') AS 1NEq1,
+       TIMEDIFF(TIME('18:00:00'),TIME('17:00:00'))=TIME('00:00:00') AS 1NEq2,
+       TIMEDIFF(TIME('17:00:00'),TIME('17:00:00'))=     '00:00:00'  AS 2Eq,
+       TIMEDIFF(TIME('17:59:00'),TIME('17:00:00'))=     '00:00:00'  AS 2NEq1,
+       TIMEDIFF(TIME('18:00:00'),TIME('17:00:00'))=     '00:00:00'  AS 2NEq2,
+       TIMEDIFF(TIME('17:00:00'),TIME('17:00:00'))=TIME(0)          AS 3Eq,
+       TIMEDIFF(TIME('17:59:00'),TIME('17:00:00'))=TIME(0)          AS 3NEq1,
+       TIMEDIFF(TIME('18:00:00'),TIME('17:00:00'))=TIME(0)          AS 3NEq2,
+       TIME(0) AS Time0, TIME('00:00:00') AS Time00, '00:00:00' AS Literal0000,
+       TIMEDIFF(TIME('17:59:00'),TIME('17:00:00')),
+       TIMEDIFF(TIME('17:00:00'),TIME('17:59:00'));
+
 # End of 5.0 tests

sql/item_timefunc.h

@@ -398,6 +398,7 @@ public:
   {
     return save_time_in_field(field);
   }
+  longlong val_int() { return val_int_from_decimal(); }
   bool result_as_longlong() { return TRUE; }
 };