Revert "double deletion bug fix"

This reverts commit f980ae6f5c9a3d6d8d37054759d6a3353f7282bc.
Revert "ScopedExpression now uses abandoned flag, inlined FutureExpression"

This reverts commit 08c8d0bab3a9a2e6ae0fc117afa4b016a1094d81.