“Use Legacy Swift Language Version” (SWIFT_VERSION) is required to be configured correctly for targets which use Swift. Use the [Edit > Convert > To Current Swift Syntax…] menu to choose a Swift version or use the Build Settings editor to configure the build setting directly.
What's going on?
This relates to an imported framework, in this situation it is HanekeSwift, and it would appear there is a version dependency difference that doesn't quite match up.
That said, the app has been updated to Swift 3.0 and it would appear that the app is only compatible with 2.3.
As always, it is best to look at whether others have addressed the issue and in this situation it looks like someone has created a branch that is updated to the most recent 3.0
But, nothing is ever that simple. Just copying-&-pasting the update into the terminal doesn't seem to work.
[computername:ProjectFolderName chriscantley$ pod update"HanekeSwift", :git => 'https://github.com/Haneke/HanekeSwift.git', :branch => 'feature/swift-3'
-bash: https://github.com/Haneke/HanekeSwift.git,: No such file or directory
And now off to StackExchange to figure out what is going on. There I found a suggestion to update Cocoa Pods.
sudo gem update cocoapods
So I downloaded the Branch and performed a compare using BeyondCompare and everything was different in the primary directory. So I just moved everything over from the 3.0 branch to my copy.
Other errors came up, however on removing the derived data (remove or rename the folder for your project at /Users/chriscantley/Library/Developer/Xcode/DerivedData), cleaning the project, executing it to build, cleaning again and then building... a Whole new set of errors came up.
But this one is resolved.