SERIAL problems?

Hi,

I just saw these in the TODO list:

o %Disallow changing DEFAULT expression of a SERIAL column?
This should be done only if the existing SERIAL problems cannot be
fixed.
o %Disallow ALTER SEQUENCE changes for SERIAL sequences
because pg_dump does not dump the changes

What are the "existing problems"?

I am asking because I am experimenting to implement
the SQL2003 compliant form for the serial type
to be able specify the underlying sequence
parameters:

SERIAL [ GENERATED [ ALWAYS | BY DEFAULT ]
AS IDENTITY (
[ INCREMENT [ BY ] increment ]
[ MINVALUE minvalue | NO MINVALUE ]
[ MAXVALUE maxvalue | NO MAXVALUE ]
[ START [ WITH ] start ]
[ CACHE cache ]
[ [ NO ] CYCLE ]
) ]

Best regards,
Zoltán Böszörményi