Question about "Unrecognized SPI code" ...

I just found an interesting issue in recent PostgreSQL releases:

CREATE VIEW view_nonsense AS SELECT 1 AS a, 2 AS b;

CREATE RULE myrule AS ON INSERT TO view_nonsense        DO INSTEAD NOTHING;

CREATE OR REPLACE FUNCTION debug() RETURNS boolean AS '        DECLARE
        BEGIN                INSERT INTO view_nonsense VALUES (10, 20);                RETURN true;        END;
' LANGUAGE 'plpgsql';

SELECT debug();

The INSERT statement is not doing something useful here


[hs@athlon tmp]$ psql test < view.sql
CREATE VIEW
CREATE RULE
CREATE FUNCTION
ERROR:  SPI_execute_plan failed executing query "INSERT INTO 
view_nonsense VALUES (10, 20)": Unrecognized SPI code 0
CONTEXT:  PL/pgSQL function "debug" line 4 at SQL statement


SPI_result_code_string(int code) and PL/pgSQL don't seem to be aware of 
DO NOTHING rules.
Is it desired behaviour?
Best regards,
    Hans

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