valderman/haste-compiler — pull request #279 by klarh (2014-12-26 02:53:32+00:00)
Title: Add mkWeak#, mkWeakNoFinalizer#, derefWeak#, and finalizeWeak# primops

These are needed for elerea, at least (see #210 ). Based on the GHC documentation these shouldn't be an issue in JS as far as correctness goes, I think.