StashToolkit
When StashToolkit.State is not a persistent data structure, it might still provide a way to remember the current state (as if push on the stack) and return to it later (as if pop off the stack). StashToolkit is a Toolkit that supports such operations on Toolkit.State.
trait BranchingToolkit
trait FreeBranchingToolkit
object PropBranch.type
class PropBranchCost[C]
trait PropBranchToolkit
trait PropBranchCostToolkit[C]
trait FreeStashToolkit