Representing a SRF return column in catalogs

Hi,

I am working on something that requires representing a SRF return column in
pg_proc and being able to retrieve it, retrieve the name of the column and
make a ColumnRef node from it.

The catch here are aliases:

SELECT generate_series(1,100) AS a ORDER BY a;

I need to know that the return column of generate_series is being referred
as a in this query (hence tlist, sortClause will have 'c').

I discussed and think that a way can be to have position of column rather
than the actual name but that raises the question of the functionality
needed for back resolving position to name (to make a ColumnRef node) and
then infer that the column is being referred as an alias in this query.

Any pointers will be really helpful.

Regards,

Atri