Swift 4 hasPrefix in switch

hasPrefix.swift

let string = "www."

func hasPrefix(_ prefix: String) -> (String) -> Bool {
    return { value in value.hasPrefix(prefix) }
}

func ~=(block: (String) -> Bool, string: String) -> Bool {
    return block(string)
}

switch string {
case hasPrefix("www"):
    debugPrint("Has www")
default:
    ()
}