Re: Error-safe user functions

Here are some proposed patches for converting range_in and multirange_in.

0001 tackles the straightforward part, which is trapping syntax errors
and called-input-function errors. The only thing that I think might
be controversial here is that I chose to change the signatures of
the exposed functions range_serialize and make_range rather than
inventing xxx_safe variants. I think this is all right, because
AFAIK the only likely reason for extensions to call either of those
is that custom types' canonical functions would need to call
range_serialize --- and those will need to be touched anyway,
see 0002.

What 0001 does not cover is trapping errors occurring in range
canonicalize functions. I'd first thought maybe doing that wasn't
worth the trouble, but it's not really very hard to fix the built-in
canonicalize functions, as shown in 0002. Probably extensions would
not find it much harder, and in any case they're not really required
to make their errors soft.

Any objections?

regards, tom lane