full outer join bug?

Here is a report from a user in Japan. I confirmed it happens in
current.

DROP TABLE t1;
CREATE TABLE t1 ( name TEXT, n INTEGER);
DROP TABLE t2;
CREATE TABLE t2 ( name TEXT, n INTEGER);
DROP TABLE t3;
CREATE TABLE t3 ( name TEXT, n INTEGER);

INSERT INTO t1 VALUES ( 'aa', 11 );
INSERT INTO t2 VALUES ( 'aa', 12 );
INSERT INTO t2 VALUES ( 'bb', 22 );
INSERT INTO t3 VALUES ( 'aa', 13 );
INSERT INTO t3 VALUES ( 'cc', 33 );

SELECT * FROM t1 FULL JOIN t2 USING (name) FULL JOIN t3 USING (name); -- NG
ERROR: FULL JOIN is only supported with mergejoinable join conditions
--
Tatsuo Ishii