Okay, I looked at the patch, and apart from a refleak in one of the compiler methods I couldn't find anything wrong.
I then manually applied the rest of my set comprehension patch. The result is attached.

Grammar, AST and compilation for comprehensions are now really unified.

It passes the tests for listcomps, genexps and setcomps.

I couldn't check properly for refleaks since e.g. test_genexps leaks in the branch head, as well as some other tests. I'm currently searching for the offending revision(s)...
File Added: new-set-comps.diff