Revert "No longer depend on heaps"
Revert "No longer depend on heaps"

This reverts commit fa4e7025c63a8f3befc9746b1a9d517095040f36.

ndmitchell/shake,ndmitchell/shake,ndmitchell/shake,ndmitchell/shake,ndmitchell/shake,ndmitchell/shake