MDEV-21278 Assertion `is_unsigned() == attr.unsigned_flag' or Assertion `field.is_sane()' failed

The type handler and unsigned_flag erroneously went out of sync in
Item_func_minus::fix_length_and_dec.

mysql-test/main/func_math.result

@@ -2726,3 +2726,41 @@ DROP TABLE t1,t2;
 #
 # End of 10.4 tests
 #
+#
+# Start of 10.5 tests
+#
+#
+# MDEV-21278 Assertion `is_unsigned() == attr.unsigned_flag' or Assertion `field.is_sane()' failed
+#
+CREATE TABLE t1 (a TIMESTAMP);
+INSERT INTO t1 VALUES (NULL),(NULL);
+SET SESSION SQL_MODE= 'NO_UNSIGNED_SUBTRACTION';
+SELECT DISTINCT UUID_SHORT() - a FROM t1;
+UUID_SHORT() - a
+xxx
+xxx
+CREATE TABLE t2 AS SELECT DISTINCT UUID_SHORT() - a FROM t1;
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `UUID_SHORT() - a` bigint(22) NOT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+DROP TABLE t2, t1;
+SET sql_mode=DEFAULT;
+CREATE  TABLE t1 (a TIMESTAMP);
+INSERT INTO t1 VALUES (NULL),(NULL);
+SET SESSION SQL_MODE= 'NO_UNSIGNED_SUBTRACTION';
+SELECT UUID_SHORT() - a FROM t1;
+UUID_SHORT() - a
+xxx
+xxx
+CREATE TABLE t2 AS SELECT UUID_SHORT() - a FROM t1;
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `UUID_SHORT() - a` bigint(22) NOT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+DROP TABLE t2, t1;
+#
+# End of 10.5 tests
+#

mysql-test/main/func_math.test

@@ -1736,3 +1736,36 @@ DROP TABLE t1,t2;
 --echo #
 --echo # End of 10.4 tests
 --echo #
+
+
+--echo #
+--echo # Start of 10.5 tests
+--echo #
+
+--echo #
+--echo # MDEV-21278 Assertion `is_unsigned() == attr.unsigned_flag' or Assertion `field.is_sane()' failed
+--echo #
+
+CREATE TABLE t1 (a TIMESTAMP);
+INSERT INTO t1 VALUES (NULL),(NULL);
+SET SESSION SQL_MODE= 'NO_UNSIGNED_SUBTRACTION';
+--replace_column 1 xxx
+SELECT DISTINCT UUID_SHORT() - a FROM t1;
+CREATE TABLE t2 AS SELECT DISTINCT UUID_SHORT() - a FROM t1;
+SHOW CREATE TABLE t2;
+DROP TABLE t2, t1;
+SET sql_mode=DEFAULT;
+
+CREATE  TABLE t1 (a TIMESTAMP);
+INSERT INTO t1 VALUES (NULL),(NULL);
+SET SESSION SQL_MODE= 'NO_UNSIGNED_SUBTRACTION';
+--replace_column 1 xxx
+SELECT UUID_SHORT() - a FROM t1;
+CREATE TABLE t2 AS SELECT UUID_SHORT() - a FROM t1;
+SHOW CREATE TABLE t2;
+DROP TABLE t2, t1;
+
+
+--echo #
+--echo # End of 10.5 tests
+--echo #

sql/item_func.cc

@@ -1235,9 +1235,8 @@ bool Item_func_minus::fix_length_and_dec()
   if (Item_func_minus::type_handler()->Item_func_minus_fix_length_and_dec(this))
     DBUG_RETURN(TRUE);
   DBUG_PRINT("info", ("Type: %s", type_handler()->name().ptr()));
-  if ((m_depends_on_sql_mode_no_unsigned_subtraction= unsigned_flag) &&
-      (current_thd->variables.sql_mode & MODE_NO_UNSIGNED_SUBTRACTION))
-    unsigned_flag= false;
+  m_depends_on_sql_mode_no_unsigned_subtraction= unsigned_flag;
+  fix_unsigned_flag();
   DBUG_RETURN(FALSE);
 }