Parse a statement, get parameter types and return types

Given a statement, eg:

select foo from bar where col = $1

I'd really like to get the types deduced by the PostgreSQL parser for
the input variables ($1, etc.) and the result column(s). eg. it might
be $1 :: int4 and foo :: text, or whatever.

It seems from reading about PQprepare that getting the input types
isn't yet possible, but might be in future:

http://www.postgresql.org/docs/current/static/libpq-exec.html#AEN23157

I have no idea where to start getting the result types.

Is this possible in some way? Is the data perhaps hidden in one of
the pg_* system tables?

Note that I don't want to actually execute the statement, just parse
it.

Rich.

--
Richard Jones, CTO Merjis Ltd.
Merjis - web marketing and technology - http://merjis.com
Team Notepad - intranets and extranets for business - http://team-notepad.com