MDEV-20517 Assertion `!is_expensive()' failed in Item::value_depends_on_sql_mode_const_item

mysql-test/r/func_misc.result

@@ -1557,5 +1557,14 @@ numgtfmt
 DROP VIEW v1;
 DROP TABLE t1;
 #
+# MDEV-20517 Assertion `!is_expensive()' failed in Item::value_depends_on_sql_mode_const_item
+#
+SELECT ( 1 LIKE GET_LOCK( 'foo', 0 ) ) - 2;
+( 1 LIKE GET_LOCK( 'foo', 0 ) ) - 2
+-1
+SELECT RELEASE_LOCK('foo');
+RELEASE_LOCK('foo')
+1
+#
 # End of 10.2 tests
 #

mysql-test/t/func_misc.test

@@ -1192,6 +1192,12 @@ SELECT * FROM v1 WHERE numgtfmt =  NAME_CONST('wnumgtfmt',_utf8'QEDITIONS' COLLA
 DROP VIEW v1;
 DROP TABLE t1;
 
+--echo #
+--echo # MDEV-20517 Assertion `!is_expensive()' failed in Item::value_depends_on_sql_mode_const_item
+--echo #
+
+SELECT ( 1 LIKE GET_LOCK( 'foo', 0 ) ) - 2;
+SELECT RELEASE_LOCK('foo');
 
 --echo #
 --echo # End of 10.2 tests

sql/item_func.cc

@@ -1423,17 +1423,22 @@ bool Item_func_minus::fix_length_and_dec()
 {
   if (Item_num_op::fix_length_and_dec())
     return TRUE;
-  m_sql_mode_dependency= Item_func::value_depends_on_sql_mode();
-  if (unsigned_flag)
-  {
-    m_sql_mode_dependency|= Sql_mode_dependency(0,MODE_NO_UNSIGNED_SUBTRACTION);
-    if (current_thd->variables.sql_mode & MODE_NO_UNSIGNED_SUBTRACTION)
-      unsigned_flag= false;
-  }
+  if ((m_depends_on_sql_mode_no_unsigned_subtraction= unsigned_flag) &&
+      (current_thd->variables.sql_mode & MODE_NO_UNSIGNED_SUBTRACTION))
+    unsigned_flag= false;
   return FALSE;
 }
 
 
+Sql_mode_dependency Item_func_minus::value_depends_on_sql_mode() const
+{
+  Sql_mode_dependency dep= Item_func_additive_op::value_depends_on_sql_mode();
+  if (m_depends_on_sql_mode_no_unsigned_subtraction)
+    dep|= Sql_mode_dependency(0, MODE_NO_UNSIGNED_SUBTRACTION);
+  return dep;
+}
+
+
 double Item_func_minus::real_op()
 {
   double value= args[0]->val_real() - args[1]->val_real();

sql/item_func.h

@@ -773,16 +773,15 @@ class Item_func_plus :public Item_func_additive_op
 
 class Item_func_minus :public Item_func_additive_op
 {
-  Sql_mode_dependency m_sql_mode_dependency;
+  bool m_depends_on_sql_mode_no_unsigned_subtraction;
 public:
   Item_func_minus(THD *thd, Item *a, Item *b):
-    Item_func_additive_op(thd, a, b) {}
+    Item_func_additive_op(thd, a, b),
+    m_depends_on_sql_mode_no_unsigned_subtraction(false)
+  { }
   const char *func_name() const { return "-"; }
   enum precedence precedence() const { return ADD_PRECEDENCE; }
-  Sql_mode_dependency value_depends_on_sql_mode() const
-  {
-    return m_sql_mode_dependency;
-  }
+  Sql_mode_dependency value_depends_on_sql_mode() const;
   longlong int_op();
   double real_op();
   my_decimal *decimal_op(my_decimal *);