BUG #5400: Columns count mismatch in RULE with subquery

The following bug has been logged online:

Bug reference:      5400
Logged by:          Teodor Buchner
Email address:      t.buchner@autoguard.pl
PostgreSQL version: 8.4.1
Operating system:   Linux
Description:        Columns count mismatch in RULE with subquery
Details:

When SELECT INSERT syntax is used to pump data in a rule, an error appears
during creation of this rule if only SELECT has more than one argument.
ERROR: INSERT has more target columns than expressions
Stan SQL:42601
Znak:137

CREATE OR REPLACE RULE move_iteration_1 AS ON INSERT TO a.iteration  DO ALSO

INSERT INTO b.iteration(id,date_period_begin)
    SELECT (NEW.id,NEW.date_period_begin) FROM a.iteration;

The example is dummy as INSERT VALUES can be used here but it is impossible
to build any complex subquery instead. Reduction to a single variable
(removing date_period_begin from INSERT/SELECT) removes this error.
Rgds
TB