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.
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