Ergonomic store scoping

StoreScope.swift

struct StoreScope<State, Action, ChildState, ChildAction> {
    typealias Scope<_State, _Action> = StoreScope<State, Action, _State, _Action>
    typealias ScopeOf<R: ReducerProtocol> = StoreScope<State, Action, R.State, R.Action>
    typealias PresentationScope<_State, _Action> = StoreScope<State, Action, PresentationState<_State>, PresentationAction<_Action>>
    typealias PresentationScopeOf<R: ReducerProtocol> = StoreScope<State, Action, PresentationState<R.State>, PresentationAction<R.Action>>

    var toChildState: (State) -> ChildState
    var fromChildAction: (ChildAction) -> Action
}

extension Store {
    func scope<ChildState, ChildAction>(
        to storeScope: StoreScope<State, Action, ChildState, ChildAction>
    ) -> Store<ChildState, ChildAction> {
        self.scope(state: storeScope.toChildState, action: storeScope.fromChildAction)
    }
}