Documentation Chapter 16: 8.21

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/16/datatype-pseudo.html
Description:

I tryed to implement a safe_cast function with 2 parameters and a return of
type "any" but it failed. I get a syntax error, if I use "any" as a data
type, because it is a sql function (similar to array contains) and not a
data type.

And if there is a data type "any" in postgres too, how should it work as
parameter and wheres the difference to "anyelement"?