MultiTypeDictionary.swift

struct MultiTypeDictionary<Root> {
    private var dict: [PartialKeyPath<Root>: Any] = [:]

    // Called for non-optional properties
    subscript<Value>(keyPath: KeyPath<Root, Value>) -> Value? {
        get { dict[keyPath] as? Value }
        set { dict[keyPath] = newValue }
    }

    // Called for optional properties
    subscript<Value>(keyPath: KeyPath<Root, Value?>) -> Value? {
        get { dict[keyPath] as? Value }
        set { dict[keyPath] = newValue }
    }
}