MDEV-17634 Regression: TIME(0)=TIME('z') returns NULL vs 1

mysql-test/main/type_time.result

@@ -2094,5 +2094,28 @@ SELECT TIME(99991231235957), TIME(99991231235958), TIME(99991231235959);
 TIME(99991231235957)	TIME(99991231235958)	TIME(99991231235959)
 23:59:57	23:59:58	23:59:59
 #
+# MDEV-17634 Regression: TIME(0)=TIME('z') returns NULL vs 1
+#
+SELECT
+TIMESTAMP(0)=TIMESTAMP('z') AS ts,
+DATE(0)=DATE('z') AS d,
+TIME(0)=TIME('z') AS t;
+ts	d	t
+1	1	1
+Warnings:
+Warning	1292	Incorrect datetime value: 'z'
+Warning	1292	Incorrect datetime value: 'z'
+Warning	1292	Truncated incorrect time value: 'z'
+SELECT
+TIMESTAMP(0)=TIMESTAMP('') AS ts,
+DATE(0)=DATE('') AS d,
+TIME(0)=TIME('') AS t;
+ts	d	t
+1	1	1
+Warnings:
+Warning	1292	Incorrect datetime value: ''
+Warning	1292	Incorrect datetime value: ''
+Warning	1292	Truncated incorrect time value: ''
+#
 # End of 10.4 tests
 #

mysql-test/main/type_time.test

@@ -1366,6 +1366,18 @@ SET optimizer_use_condition_selectivity=DEFAULT;
 --echo #
 SELECT TIME(99991231235957), TIME(99991231235958), TIME(99991231235959);
 
+--echo #
+--echo # MDEV-17634 Regression: TIME(0)=TIME('z') returns NULL vs 1
+--echo #
+SELECT
+  TIMESTAMP(0)=TIMESTAMP('z') AS ts,
+  DATE(0)=DATE('z') AS d,
+  TIME(0)=TIME('z') AS t;
+
+SELECT
+  TIMESTAMP(0)=TIMESTAMP('') AS ts,
+  DATE(0)=DATE('') AS d,
+  TIME(0)=TIME('') AS t;
 
 --echo #
 --echo # End of 10.4 tests

sql/item_timefunc.cc

@@ -2416,9 +2416,9 @@ void Item_char_typecast::fix_length_and_dec_internal(CHARSET_INFO *from_cs)
 }
 
 
-bool Item_time_typecast::get_date(THD *thd, MYSQL_TIME *ltime, date_mode_t fuzzydate)
+bool Item_time_typecast::get_date(THD *thd, MYSQL_TIME *to, date_mode_t mode)
 {
-  Time *tm= new(ltime) Time(thd, args[0], Time::Options_for_cast(),
+  Time *tm= new(to) Time(thd, args[0], Time::Options_for_cast(mode),
                          MY_MIN(decimals, TIME_SECOND_PART_DIGITS));
   return (null_value= !tm->is_valid_time());
 }

sql/sql_type.h

@@ -790,6 +790,10 @@ class Time: public Temporal
     Options_for_cast()
      :Options(flags_for_get_date(), DATETIME_TO_TIME_YYYYMMDD_TRUNCATE)
     { }
+    Options_for_cast(date_mode_t mode)
+     :Options(flags_for_get_date() | (mode & TIME_FUZZY_DATES),
+              DATETIME_TO_TIME_YYYYMMDD_TRUNCATE)
+    { }
   };
 private:
   bool is_valid_value_slow() const