Some errors are related to just CORRESPONDING without any columns. So using expr doesn't help here. So parse node CORRESPONDING can solve both issues.
In current implementation pointing to a node means pointing to a node’s first element so I don’t think we can be able to point to CORRESPONDING without any columns
I find out that there is already a node prepare for the case called A_Const.
The attached patch use that node
It looks better
I fixed format of comments and some too long lines.
all regress tests passed
I have not any objection - I'll mark this patch as ready for commiter
