Bug #79204 INSERT INTO table from SELECT accepts to insert into generated columns

Description:
With the following table definition:

CREATE TABLE t1 (
  i1 INTEGER NOT NULL,
  i2 INTEGER GENERATED ALWAYS AS (i1 + i1) VIRTUAL NOT NULL
);

the following INSERT statement succeeds:

INSERT INTO t1 (i1, i2) SELECT 5, 6;

It should have failed (or at least given a warning?) that it is not allowed to insert a value into a generated column.

How to repeat:
CREATE TABLE t1 (
  i1 INTEGER NOT NULL,
  i2 INTEGER GENERATED ALWAYS AS (i1 + i1) VIRTUAL NOT NULL
);

INSERT INTO t1 (i1, i2) SELECT 5, 6;

SELECT * FROM t1;

DROP TABLE t1;

Posted by developer:
 
The similar INSERT statement using VALUES to specify what to insert:

  INSERT INTO t1 (i1, i2) VALUES (5,6);

returns an error:

  ERROR 3105 (HY000): The value specified for generated column 'i2' in table 't1' is not allowed.

Noted in 5.7.11, 5.8.0 changelogs.

INSERT INTO ... SELECT statements could insert values other than
DEFAULT into generated columns.