idea: allow AS label inside ROW constructor

Hi

with new functions row_to_json(b), there is more often usage of ROW
constructor. Using names in fields is relative difficult. Because ROW has
special clause in parser, I am thinking so we can enable labeling inside
ROW constructor

so instead currently supported:

select row_to_json(r) from (select 10 as a, 20 as b) r;

users can to write:

select row_to_json(row(10 as a,20 as b));

labeling will be enabled "only" inside ROW constructor. I don't propose
enable it everywhere.

What do you think about it?

Regards

Pavel

Currently supported syntax is natural for long time PostgreSQL user, but it
is relative strange for usual user.