Conflicting conformances

EmptyContainer.swift

import Cocoa

struct EmptyContainer<T> {
}

typealias IntContainer = EmptyContainer<Int>

extension IntContainer: Sequence {
    struct Iterator: IteratorProtocol {
        func next() -> Int? {
            return nil
        }
    }

    func makeIterator() -> Iterator {
        Iterator()
    }
}

typealias DoubleContainer = EmptyContainer<Double>

extension DoubleContainer: Sequence {
}