Typeerasure for AnyNavigator

AnyNavigator.swift

struct AnyNavigator<Destination_>: Navigator {
   typealias Destination = Destination_
   private let _navigateTo: (Destination_) -> Void
   private let _start: () -> Void

   init<Concrete>(_ concrete: Concrete) where Concrete: Navigator, Concrete.Destination == Destination_ {
       _navigateTo = concrete.navigate
       _start = concrete.start
   }

   // MARK: - Navigator methods
   func navigate(to destination: Destination) {
       _navigateTo(destination)
   }

   func start() {
       _start()
   }
}