Why MySQL substr returns value in data type Text when length is over 512?

[Sanjaya Balasuriya]

I've noticed that MySQL substr() returns value in data type text when the length is over 512.

Please check the example below;

Data table:

create table temp10( c0 int primary key auto_increment, c1 varchar(2500));
insert into temp10(c1) values ('abcd');
Secondary table using temp10 as source;

create table temp11 as
select c1,
substr(c1, 1, 10) as c2,
substr(c1, 1, 100) as c3,
substr(c1, 1, 512) as c4,
substr(c1, 1, 513) as c5,
substr(c1, 1, 2500) as c6
from temp10;
Structure of the table created is;

Table: temp11 Columns:

c1 varchar(2500)
c2 varchar(10)
c3 varchar(100)
c4 varchar(512)
c5 text
c6 text
Is this an expected/ documented behavior?

This same behavior has been noticed for scalar subqueries within select clause too.