The following bug has been logged online:

Bug reference: 1441
Logged by: Koei Kim
Email address: koeikim (AT) gmail (DOT) com
PostgreSQL version: 7.4.6, 8.0
Operating system: Linux
Description: casting problem when lower limit, ERROR out of range
Details:

when casting numeric types with lower limit value, postgresql report ERROR
out of range.

koei~# select -32768::int2 ;
ERROR: integer out of range

koei~# select -2147483648::int4;
ERROR: integer out of range

test=# SELECT -9223372036854775808::int8;
ERROR: integer out of range

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