swift 4 is not supported

[vadimkononov]

hi, steps to reproduce:

1. create a new project in xcode9
2. add podfile with pod 'MetalScope' in it
3. build

AR: build failed (screenshots attached)

[ElizaSapir]

Hey @junpluse we have customers with swift4 already, looks like you did some xcode9 fixes do we miss somthing?

Thanks!

[toemat]

I'm not sure this is a Swift 4 issue. I got the same thing with Swift 3.2. It looks like maybe the Metal API changed some things to optionals?

Either way, going through and doing the Xcode fix for each error got it working for me.