simple case syntax oddity in 8.0.0

Vlad <marchenko@gmail.com> writes:

Postgresql 8.0.0, FreeBSD 5.3

test=> select case 0 when 0 then null else 1/0 end as test;
ERROR: division by zero

Hmm ... unexpected side effect of the change to avoid evaluating the
test-expression multiple times. This used to be transformed into
this at parse time:

select case when 0=0 then null else 1/0 end as test;

and then constant-folding would do the right thing.
But now it's transformed into something sort of like

select (let x = 0 in case when x=0 then ...)

and the when-clause therefore appears not to be constant. I think
I can fix this for 8.0.2, though.

regards, tom lane