Re: Allowing extensions to supply operator-/function-specific info

So I am getting much closer to a working implementation in PostGIS,
but have just run into an issue which I am assuming is my
misunderstanding something...

https://github.com/pramsey/postgis/blob/92268c94f3aa1fc63a2941f2b451be15b28662cf/postgis/gserialized_supportfn.c#L287

I had what seemed to be working code except for a couple rare cases,
but when I fixed those cases it turned out that I had a major problem:
building a <var> OP <const> expression works fine, but building a
<const> OP <var> expression returns me an error.

create table f as select st_makepoint(200*random() - 100, 200*random()
- 100) as g from generate_series(0, 100000);
create index f_g_x on f using gist (g);
explain select * from baz where st_coveredby('POINT(5 0)', geom);
explain select * from f where st_coveredby(g, 'POINT(5 0)');

                                    QUERY PLAN
-----------------------------------------------------------------------------------
 Bitmap Heap Scan on f  (cost=13.36..314.58 rows=33334 width=32)
   Filter: st_coveredby(g,
'010100000000000000000014400000000000000000'::geometry)
   ->  Bitmap Index Scan on f_g_x  (cost=0.00..5.03 rows=100 width=0)
         Index Cond: (g @
'010100000000000000000014400000000000000000'::geometry)

postgis=# explain select * from f where st_coveredby('POINT(5 0)', g);

ERROR:  index key does not match expected index column

Any thoughts?

P