MDEV-9862 Illegal mix of collation, when comparing column with CASE expression

mysql-test/r/ctype_cp850.result

+#
+# Start of 5.5 tests
+#
+#
+# MDEV-9862 Illegal mix of collation, when comparing column with CASE expression
+#
+SET NAMES cp850;
+CREATE TABLE t1 (a CHAR(1) CHARACTER SET latin1);
+SELECT a FROM t1 WHERE CASE a WHEN 'aaaa' THEN 'Y' WHEN 'aaaa' THEN 'Y' ELSE NULL END <> a;
+a
+DROP TABLE t1;
+#
+# End of 5.5 tests
+#

mysql-test/t/ctype_cp850.test

+--echo #
+--echo # Start of 5.5 tests
+--echo #
+
+--echo #
+--echo # MDEV-9862 Illegal mix of collation, when comparing column with CASE expression
+--echo #
+SET NAMES cp850;
+CREATE TABLE t1 (a CHAR(1) CHARACTER SET latin1);
+SELECT a FROM t1 WHERE CASE a WHEN 'aaaa' THEN 'Y' WHEN 'aaaa' THEN 'Y' ELSE NULL END <> a;
+DROP TABLE t1;
+
+
+--echo #
+--echo # End of 5.5 tests
+--echo #

sql/item.h

@@ -2175,7 +2175,7 @@ public:
     max_length= 0;
     name= name_par ? name_par : (char*) "NULL";
     fixed= 1;
-    collation.set(&my_charset_bin, DERIVATION_IGNORABLE);
+    collation.set(&my_charset_bin, DERIVATION_IGNORABLE, MY_REPERTOIRE_ASCII);
   }
   enum Type type() const { return NULL_ITEM; }
   bool eq(const Item *item, bool binary_cmp) const;