I'm not entirely sure what's the best way to deal with the polymorphic problem, but on the other hand as Robert says downthread maybe we shouldn't be solving it at this stage anyway. So let's step back a bit, get a patch that works for the case where the types match on both sides of the FK, then we review that patch; if all is well, we can discuss the other problem as a stretch goal.
+1
Regular FK functionality have type restrictions based on btree opfamilies and implicit casts. Array FK should not necessary have the same type restrictions. Also, we don't necessary need to make those restrictions as soft as possible during this GSoC project.
