has_many :through a polymorphic has_many - Broken Again

Hey guys.

Having a has_many :through a polymorphic has_many relationship just wasn't possible prior to Changeset 8776.

It was great having it fixed, but now it is broken again.

9231 (Vague because 9230 just consumed lots of resource trying to do it, and never gave a me a definitive result).

I'm not familiar enough with the Rails core to say why this happening, but hopefully the changeset numbers will help those more familiar to find the problem.