Inaccurate return type of plus between bit and int

[yuqi1129]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

Master branch and execute the following sql

2. What did you expect to see? (Required)

MySQL 5.7

mysql> select d_bit + d_smallint, d_bit + d_decimal from all_types;
Field   1:  `d_bit + d_smallint`
Catalog:    `def`
Database:   ``
Table:      ``
Org_table:  ``
Type:       LONGLONG
Collation:  binary (63)
Length:     11
Max_length: 2
Decimals:   0
Flags:      UNSIGNED BINARY NUM

Field   2:  `d_bit + d_decimal`
Catalog:    `def`
Database:   ``
Table:      ``
Org_table:  ``
Type:       NEWDECIMAL
Collation:  binary (63)
Length:     15
Max_length: 5
Decimals:   2
Flags:      BINARY NUM


+--------------------+-------------------+
| d_bit + d_smallint | d_bit + d_decimal |
+--------------------+-------------------+
|                 13 |             22.23 |
+--------------------+-------------------+
1 row in set (0.02 sec)

bit + smallint return LONGLONG and bit + decimal return NEWDECIMAL*

3. What did you see instead (Required)

mysql> select d_bit + d_smallint, d_bit + d_decimal from all_types;
No connection. Trying to reconnect...
Connection id:    3
Current database: test

Field   1:  `d_bit + d_smallint`
Catalog:    `def`
Database:   ``
Table:      ``
Org_table:  ``
Type:       DOUBLE
Collation:  binary (63)
Length:     0
Max_length: 2
Decimals:   31
Flags:      NOT_NULL BINARY NUM

Field   2:  `d_bit + d_decimal`
Catalog:    `def`
Database:   ``
Table:      ``
Org_table:  ``
Type:       DOUBLE
Collation:  binary (63)
Length:     0
Max_length: 5
Decimals:   31
Flags:      NOT_NULL BINARY NUM


+--------------------+-------------------+
| d_bit + d_smallint | d_bit + d_decimal |
+--------------------+-------------------+
|                 13 |             22.23 |
+--------------------+-------------------+
1 row in set (0.00 sec)

bit + smallint return DOUBLE and bit + decimal return DOUBLE

4. What is your TiDB version? (Required)

[ti-srebot]

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