= ANY (SELECT ..) and type casts, what's going on here?

Hi,

Is anybody able to explain the following behaviour?

Server is 8.4.7  RHEL5 build.  Also happens on 8.4.8 Ubuntu x64 package.

mr-russ=# SELECT 'BU'::varchar = ANY ((select '{BU,CI}'::varchar[]));
ERROR:  operator does not exist: character varying = character varying[]
LINE 1: SELECT 'BU'::varchar = ANY ((select '{BU,CI}'::varchar[]));
                             ^
HINT:  No operator matches the given name and argument type(s). You might need to add explicit type casts.
mr-russ=# SELECT 'BU'::varchar = ANY ((select '{BU,CI}'::varchar[])::varchar[]);
 ?column?
----------
 t
(1 row)

mr-russ=#


What I don't understand is what happens to the single SELECT's type, is it because select returns a row?  The error
doesn'tseem to match what I would expect? 

Thanks

Russell