Convert text to user defined datatype

Hi,
I have a user defined data type as below.

postgres=# \d t2;
Composite type "public.t2"
Column | Type | Collation | Nullable | Default
--------+-------------------------+-----------+----------+---------
t2 | character varying(30)[] | | |

I need to cast values to the above type. Getting error below.

postgres=# CREATE CAST (text as t2) without function;
ERROR: source and target data types are not physically compatible

If I have to create a CAST with function. Could you please suggest how to
write this function?

Regards,
Aditya.