Weird Inference – narrowed down a bit

WeirdInferenceNarrowed.swift

infix operator |> {
    associativity left
}

func |><A,B>(a: A, f: A->B) -> B {
    return f(a)
}

// this ought to be enough...
func reverse<D: CollectionType where D.Index : BidirectionalIndexType>(source: LazyRandomAccessCollection<D>) -> LazyBidirectionalCollection<RandomAccessReverseView<D>> {
    return source.reverse()
}

func double(i: Int) -> Int { return i*2 }

// x is of type LazyBidirectionalCollection
let x = reverse(LazyRandomAccessCollection(1...10)) |> { $0.map(double) }

// y is of type [Int]
let y = reverse(lazy(1...10)) |> { $0.map(double) }