Squeal: inserting default values when using subqueries

Using squeal-postgresql, how do I get the columns’ default values when I’m inserting based on a sub-query?

In the schema I have I’d use this SQL to create a row each in processes and products where the latter refers to the former:

with proc as
    (insert into processes (type)
     values ('the-type')
     returning id)
insert into products (proc_id, eid, name)
select id, ($1 :: uuid), ($2 :: text)
  from proc

trying to translate that into squeal I’ve got this so far

sql = with
        (insertInto #processes
            (Values_ (Default `as` #id :*
                      Default `as` #eid :*
                      Default `as` #generation :*
                      Set "the-type" `as` #type :*
                      Default `as` #extras))
            OnConflictDoRaise
            (Returning_ #id) `as` #proc)
    (insertInto_ #products
        (Subquery (select_ (undefined `as` #id :*
                            (param @1) `as` #eid :*
                            (param @2) `as` #name :*
                            #proc ! #id `as` #proc_id :*
                            undefined `as` #alloc)
                    (from (common #proc)))))

AFAIU there’s no way getting around giving values for all columns (right???), and that’s easy for the insert in the with-clause, but what do I use instead of undefined in the lower insert?

Originally asked here.