MDEV-19449 Got error 168 for valid TRUNCATE (temporary) TABLE

Add the test case.

The parent commit, which cherry-picked the MDEV-17167 fix from 10.3
(commit bad2f156)
fixed the bug.

mysql-test/r/temp_table.result

@@ -572,3 +572,15 @@ LOCK TABLES t2 WRITE;
 TRUNCATE TABLE t1;
 UNLOCK TABLES;
 DROP TABLE t1, t2;
+#
+# MDEV-19449 1030: Got error 168 "Unknown (generic) error from engine"
+# for valid TRUNCATE (temporary) TABLE
+#
+CREATE TEMPORARY TABLE t1 (col1 BIGINT) ENGINE = InnoDB;
+INSERT INTO t1 (no_such_col) SELECT * FROM t1;
+ERROR 42S22: Unknown column 'no_such_col' in 'field list'
+TRUNCATE TABLE t1;
+ALTER TABLE t1 CHANGE no_such_col1 col1 BIGINT NULL;
+ERROR 42S22: Unknown column 'no_such_col1' in 't1'
+TRUNCATE TABLE t1;
+DROP TEMPORARY TABLE t1;

mysql-test/t/temp_table.test

@@ -623,3 +623,19 @@ TRUNCATE TABLE t1;
 UNLOCK TABLES;
 
 DROP TABLE t1, t2;
+
+--echo #
+--echo # MDEV-19449 1030: Got error 168 "Unknown (generic) error from engine"
+--echo # for valid TRUNCATE (temporary) TABLE
+--echo #
+
+CREATE TEMPORARY TABLE t1 (col1 BIGINT) ENGINE = InnoDB;
+--error ER_BAD_FIELD_ERROR
+INSERT INTO t1 (no_such_col) SELECT * FROM t1;
+TRUNCATE TABLE t1;
+--error ER_BAD_FIELD_ERROR
+ALTER TABLE t1 CHANGE no_such_col1 col1 BIGINT NULL;
+# This would wrongly try to re-truncate the old copy of the table that
+# was not dropped during the first TRUNCATE due to extra table handles.
+TRUNCATE TABLE t1;
+DROP TEMPORARY TABLE t1;