Re: BUG #18422: Assert in expandTupleDesc() fails on row mismatch with additional SRF

Wilco.  Another thing I was considering, but didn't pull the trigger
on in the draft patch, was to introduce a funcapi.c function on the
order of
        get_expr_result_rtfunc(RangeTblFunction *rtfunc, ...)
which would encapsulate applying either BuildDescFromLists or
get_expr_result_type.  I didn't do it because I found that the
only places that would want to use it are the two that are correct
already; the places we still need to fix have short-cuts they can
take rather than building an intermediate tupdesc.  (The present
bug could be summarized as "the short-cuts still need to pay
attention to the coldeflist".)  But the advantage of doing this
anyway is that its header comment would be a natural place to
document this issue and policy.  Thoughts?