BUG #5924: bug or feature?

The following bug has been logged online:

Bug reference:      5924
Logged by:          Ferenc Lutischan
Email address:      yoursoft@freemail.hu
PostgreSQL version: 8.3.14 - 9.0.3
Operating system:   Linux
Description:        bug or feature?
Details:

Dear Developers,

Inconsecutive view handling?:

CREATE TABLE ifck.test_tipus
(
  tipus character varying(2) NOT NULL,
  tipus_kod character varying(2) NOT NULL,
  CONSTRAINT pk_test_kod PRIMARY KEY (tipus)
)
WITH (
  OIDS=TRUE
);

insert into ifck.test_tipus values ('GX', 'GG');
insert into ifck.test_tipus values ('GY', 'GG');
insert into ifck.test_tipus values ('EX', 'EE');

CREATE TABLE ifck.test
(
  tipus character varying(2) NOT NULL,
  status boolean NOT NULL,
  id character varying(20) NOT NULL,
  datum character varying(8) NOT NULL,
  CONSTRAINT fk_test_tipus FOREIGN KEY (tipus)
      REFERENCES ifck.test_tipus (tipus) MATCH SIMPLE
      ON UPDATE NO ACTION ON DELETE NO ACTION
)
WITH (
  OIDS=TRUE
);

insert into ifck.test values ('EX', true, '123456', '');

insert into ifck.test values ('GX', true, '123456', '20000101');

insert into ifck.test values ('GY', true, '123456', '20000101');

insert into ifck.test values ('GX', true, '123454', '19991231');

insert into ifck.test values ('GY', false, '123454', '');

insert into ifck.test values ('GY', true, '123454', '19991231');

CREATE OR REPLACE VIEW ifck.v_test AS
 SELECT t.*, tt.tipus_kod from ifck.test t
  JOIN ifck.test_tipus tt ON t.tipus::text = tt.tipus::text and status;

CREATE OR REPLACE VIEW ifck.v_test2 AS
 SELECT * from ifck.v_test
  where tipus_kod='GG' ;

CREATE OR REPLACE VIEW ifck.v_test3 AS
 SELECT * from ifck.v_test
  where tipus like 'G%'  and status;

/*
select * from ifck.v_test2 where id='123456';

result:
"GX";t;"123456";"20000101";"GG"
"GY";t;"123456";"20000101";"GG"
*/

/*
select * from ifck.v_test3 where id='123456';

result:
"GX";t;"123456";"20000101";"GG"
"GY";t;"123456";"20000101";"GG"
*/

/*
select * from ifck.v_test2 where id='123454';
result:
"GX";t;"123454";"19991231";"GG"
"GY";t;"123454";"19991231";"GG"
*/

/*
select * from ifck.v_test3 where id='123454';

result:
"GX";t;"123454";"19991231";"GG"
"GY";t;"123454";"19991231";"GG"
*/

/*
select * from ifck.v_test2 where datum::date=datum::date and id='123456';

result:
ERROR:  invalid input syntax for type date: ""
********** Error **********
ERROR: invalid input syntax for type date: ""
SQL state: 22007
*/

/*
select * from ifck.v_test2 where datum::date=datum::date and id='123454';

result:
"GX";t;"123454";"19991231";"GG"
"GY";t;"123454";"19991231";"GG"
*/

/*
select * from ifck.v_test3 where datum::date=datum::date and id='123454';

result:
"GX";t;"123454";"19991231";"GG"
"GY";t;"123454";"19991231";"GG"
*/

Regards,
     Ferenc Lutischan