Assertion `index.fields[i].col->same_format( *oindex.fields[i].col)' failed in dict_table_t::prepare_instant

--source include/have_innodb.inc

CREATE TABLE t1 (f1 VARCHAR(1), f2 VARCHAR(1)) ENGINE=InnoDB;

ALTER TABLE t1 MODIFY f2 VARCHAR (8) FIRST;

# Cleanup

DROP TABLE t1;

mysqld: /data/src/bb-10.4-MDEV-17520/storage/innobase/handler/handler0alter.cc:304: void dict_table_t::prepare_instant(const dict_table_t&, const ulint*, unsigned int&): Assertion `index.fields[i].col->same_format( *oindex.fields[i].col)' failed.

181207  0:15:49 [ERROR] mysqld got signal 6 ;

#7  0x00007fa3375ddee2 in __assert_fail () from /lib/x86_64-linux-gnu/libc.so.6

#8  0x0000559a7fd971c5 in dict_table_t::prepare_instant (this=0x7fa2e80a6178, old=..., col_map=0x7fa2e80a5b88, first_alter_pos=@0x7fa2e80164e8: 1) at /data/src/bb-10.4-MDEV-17520/storage/innobase/handler/handler0alter.cc:303

#9  0x0000559a7fd9c2db in ha_innobase_inplace_ctx::prepare_instant (this=0x7fa2e8016378) at /data/src/bb-10.4-MDEV-17520/storage/innobase/handler/handler0alter.cc:1059

#10 0x0000559a7fd87227 in prepare_inplace_alter_table_dict (ha_alter_info=0x7fa330920bb0, altered_table=0x7fa2e8132f00, old_table=0x7fa2e8095f70, table_name=0x7fa2e81304cd "t1", flags=33, flags2=80, fts_doc_id_col=18446744073709551615, add_fts_doc_id=false, add_fts_doc_id_idx=false) at /data/src/bb-10.4-MDEV-17520/storage/innobase/handler/handler0alter.cc:6517

#11 0x0000559a7fd8c124 in ha_innobase::prepare_inplace_alter_table (this=0x7fa2e8096ba8, altered_table=0x7fa2e8132f00, ha_alter_info=0x7fa330920bb0) at /data/src/bb-10.4-MDEV-17520/storage/innobase/handler/handler0alter.cc:8064

#12 0x0000559a7fa27cbb in handler::ha_prepare_inplace_alter_table (this=0x7fa2e8096ba8, altered_table=0x7fa2e8132f00, ha_alter_info=0x7fa330920bb0) at /data/src/bb-10.4-MDEV-17520/sql/handler.cc:4437

#13 0x0000559a7f7ecd5c in mysql_inplace_alter_table (thd=0x7fa2e8000b00, table_list=0x7fa2e8014eb0, table=0x7fa2e8095f70, altered_table=0x7fa2e8132f00, ha_alter_info=0x7fa330920bb0, inplace_supported=HA_ALTER_INPLACE_INSTANT, target_mdl_request=0x7fa330920ce0, alter_ctx=0x7fa3309218d0) at /data/src/bb-10.4-MDEV-17520/sql/sql_table.cc:7515

#14 0x0000559a7f7f2f79 in mysql_alter_table (thd=0x7fa2e8000b00, new_db=0x7fa2e80051b8, new_name=0x7fa2e8005588, create_info=0x7fa3309224c0, table_list=0x7fa2e8014eb0, alter_info=0x7fa330922400, order_num=0, order=0x0, ignore=false) at /data/src/bb-10.4-MDEV-17520/sql/sql_table.cc:9691

#15 0x0000559a7f87d121 in Sql_cmd_alter_table::execute (this=0x7fa2e8015610, thd=0x7fa2e8000b00) at /data/src/bb-10.4-MDEV-17520/sql/sql_alter.cc:497

#16 0x0000559a7f71ae4a in mysql_execute_command (thd=0x7fa2e8000b00) at /data/src/bb-10.4-MDEV-17520/sql/sql_parse.cc:6290

#17 0x0000559a7f71fd6e in mysql_parse (thd=0x7fa2e8000b00, rawbuf=0x7fa2e8014da8 "ALTER TABLE t1 MODIFY f2 VARCHAR (8) FIRST", length=42, parser_state=0x7fa330923600, is_com_multi=false, is_next_command=false) at /data/src/bb-10.4-MDEV-17520/sql/sql_parse.cc:8092

#18 0x0000559a7f70d05c in dispatch_command (command=COM_QUERY, thd=0x7fa2e8000b00, packet=0x7fa2e800b411 "ALTER TABLE t1 MODIFY f2 VARCHAR (8) FIRST", packet_length=42, is_com_multi=false, is_next_command=false) at /data/src/bb-10.4-MDEV-17520/sql/sql_parse.cc:1851

#19 0x0000559a7f70ba80 in do_command (thd=0x7fa2e8000b00) at /data/src/bb-10.4-MDEV-17520/sql/sql_parse.cc:1396

#20 0x0000559a7f877168 in do_handle_one_connection (connect=0x559a82ad3810) at /data/src/bb-10.4-MDEV-17520/sql/sql_connect.cc:1402

#21 0x0000559a7f876eec in handle_one_connection (arg=0x559a82ad3810) at /data/src/bb-10.4-MDEV-17520/sql/sql_connect.cc:1308

#22 0x0000559a7fd2b3e2 in pfs_spawn_thread (arg=0x559a82b58b90) at /data/src/bb-10.4-MDEV-17520/storage/perfschema/pfs.cc:1862

#23 0x00007fa339099494 in start_thread (arg=0x7fa330924700) at pthread_create.c:333

#24 0x00007fa33769a93f in clone () from /lib/x86_64-linux-gnu/libc.so.6