Fix TR regression and use abstraction recipe

A function like (lambda (x) (lambda (y) y)) would cause TR
to fail in an internal metafunction. The fault was triggered
when the object y is abstracted to (0 0) and then the outer
lambda tries to abstract (0 0) and fails.

The problem was triggered by the new path index changes in
v6.0 because TR did not previously try to abstract objects
that occurs in the target type (now necessary for scope
lifting of path indices), which may contain non-identifier
objects.

This error didn't occur in another nearly identical (except
for one crucial identifier? check) code path, so this commit
also eliminates the duplication by abstracting.