-- these should give overflow errors:
SELECT '127.0.0.1'::inet + 10000000000;
-ERROR: result out of range
+ERROR: result is out of range
SELECT '127.0.0.1'::inet - 10000000000;
-ERROR: result out of range
+ERROR: result is out of range
SELECT '126::1'::inet - '127::2'::inet;
-ERROR: result out of range
+ERROR: result is out of range
SELECT '127::1'::inet - '126::2'::inet;
-ERROR: result out of range
+ERROR: result is out of range
-- but not these
SELECT '127::1'::inet + 10000000000;
?column?