protocol ContainerType {
    associatedtype Parent

    var parent: Parent { get }
}

@dynamicMemberLookup
struct Context<Container: ContainerType> {
    let container: Container

    subscript<T>(dynamicMember keyPath: KeyPath<Context<Container.Parent>, T>) -> T {
        Context<Container.Parent>(container: container.parent)[keyPath: keyPath]
    }
}

struct NotContainer {
    let value = 42
}

struct ContainerImpl: ContainerType {
    let parent = NotContainer()
}

// uncomment next line to get a crash with "Illegal instuction: 4" message
// print(Context(container: ContainerImpl()).value)