func id(_ arg: UnsafeMutablePointer<Int32>?) -> UnsafeMutableBufferPointer<Int32>? { 
    return .init(start: arg, count: 1) 
}

func id(_ arg: UnsafePointer<Int32>?) -> UnsafeBufferPointer<Int32>? { 
    return .init(start: arg, count: 1) 
}

func ohSwift(_ arg: UnsafePointer<Int32>?) -> UnsafeBufferPointer<Int32>? { 
    return .init(start: arg, count: 1) 
}

let ptr: UnsafeMutablePointer<Int32> = .allocate(capacity: 1)
 _ = ohSwift(ptr)    // This shows that we can pass a UMP to a UP
 var other = id(ptr) // Here it'll _PREFER_ the UP? version over the UMP?
                     // version despite the fact we're passing an UMP
 other!.baseAddress!.pointee = 3 // Which is why this fails.