struct TestData {
}

struct Test {
    let v : Int
    var value : Int {
         return v
    }
}

extension Test: Hashable {
    public static func == (lhs: Test, rhs: Test) -> Bool {
        return lhs.value == rhs.value
    }

    public func hash(into hasher: inout Hasher) {
        hasher.combine(self)
    }
}

var _data : [Test: TestData] = [:]

func main() -> Void {
    _data[Test(v:10)] = TestData()
    //_data.updateValue(TestData(), forKey:Test(v:10))
}

main()