This is what I do:
Module compiled with Swift 3.0 cannot be imported in Swift 2.3
Edit > Convert -> Current Swift Syntax
Use Legacy Swift Language Version
You'll need to change the
Use Legacy Swift Language Version to
NO - this makes sure your project will use swift 3.
If you want to package your project as a POD (for cocoapods) you'll need to add a file named .swift-version (containing 1 single line, "3.0"). This will tell cocoapods to use the swift 3 compiler.
Everything should work after this changes.