How can I get the list of index(or other objects) which depends on a function

I want to get all the dependencies of a table, I know how to get the index
list using sql, but I don't know how to get the list of objects who using a
function, for example:

CREATE OR REPLACE FUNCTION reverse_last_64(TEXT) RETURNS TEXT AS $$
SELECT
array_to_string(
ARRAY
( SELECT substring($1, s.i,1) FROM generate_series(length($1),
greatest(length($1) - 64 + 1, 1), -1) AS s(i) ),
'');
$$ LANGUAGE SQL IMMUTABLE"

CREATE TABLE Test2(id BIGSERIAL PRIMARY KEY, name varchar(100))
CREATE INDEX idx_test2_name ON test2(reverse_last_64(name)
varchar_pattern_ops)

drop function reverse_last_64(TEXT) ;

will show
ERROR: cannot drop function reverse_last_64(text) because other objects
depend on it
DETAIL: index idx_test2_name depends on function reverse_last_64(text)
HINT: Use DROP ... CASCADE to drop the dependent objects too.

what I want to get is the list of index(or maybe other function) which using
the function using sql.

anyone can help me? thanks

--
Xu Wei

Email: eagleinfly(at)gmail(dot)com