make sure that cast(... as date) returns a valid date, as specified by the caller.

make Item::send() request a date according to the current SQL mode limitations.

mysql-test/r/cast.result

@@ -733,3 +733,8 @@ select cast(f1 as unsigned), cast(f2 as unsigned), cast(f3 as unsigned) from t1;
 cast(f1 as unsigned)	cast(f2 as unsigned)	cast(f3 as unsigned)
 112233	20111213	20111213112233
 drop table t1;
+SELECT CAST(TIME('10:20:30') AS DATE) + INTERVAL 1 DAY;
+CAST(TIME('10:20:30') AS DATE) + INTERVAL 1 DAY
+NULL
+Warnings:
+Warning	1292	Truncated incorrect date value: '0000-00-00'

mysql-test/t/cast.test

@@ -407,3 +407,8 @@ insert into t1 values ('11:22:33','2011-12-13','2011-12-13 11:22:33');
 select cast(f1 as unsigned), cast(f2 as unsigned), cast(f3 as unsigned) from t1;
 drop table t1;
 
+#
+# CAST(... AS DATE) and invalid dates
+#
+SELECT CAST(TIME('10:20:30') AS DATE) + INTERVAL 1 DAY;
+

sql/item.cc

@@ -5982,7 +5982,7 @@ bool Item::send(Protocol *protocol, String *buffer)
   case MYSQL_TYPE_TIMESTAMP:
   {
     MYSQL_TIME tm;
-    get_date(&tm, TIME_FUZZY_DATE);
+    get_date(&tm, TIME_FUZZY_DATE | sql_mode_for_dates());
     if (!null_value)
     {
       if (f_type == MYSQL_TYPE_DATE)

sql/item_timefunc.cc

@@ -2304,7 +2304,17 @@ bool Item_date_typecast::get_date(MYSQL_TIME *ltime, uint fuzzy_date)
     return 1;
   ltime->hour= ltime->minute= ltime->second= ltime->second_part= 0;
   ltime->time_type= MYSQL_TIMESTAMP_DATE;
-  return 0;
+
+  int unused;
+  if (check_date(ltime, ltime->year || ltime->month || ltime->day,
+                 fuzzy_date, &unused))
+  {
+    Lazy_string_time str(ltime);
+    make_truncated_value_warning(current_thd, MYSQL_ERROR::WARN_LEVEL_WARN,
+                                 &str, MYSQL_TIMESTAMP_DATE, 0);
+    return (null_value= 1);
+  }
+  return (null_value= 0);
 }