Module compiled with swift 3.0.2 cannot be imported in swift 3.1
You’ll have to build that module in Swift 3.1. As things currently stand all modules in your program (that is, the main app and any frameworks) must be built with the same version of the compiler. It seems that you’re using Swift 3.0.2 to build some part of your app and Swift 3.1 to build another. That’s just not going to work.
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Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware
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If that is the case how can anyone possibly use any 3rd part frameworks or libraries? Its one thing to require that I have the same version or newer, but to say that I can't use any frameworks that were compiled in an older version doesnt make any sense. Not all companies will always have the a version of their framework rebuilt just because Apple updated their version of swift. And this is only dot release, not a major release.
Unfortunately, the only answer to everything you've said is, 'Yep'.
There was an expectation of this kind of stability in Swift 4 but I believe it has been pused out even farther now.
(It has become another joke, like trying out Xcode's "Refactor" option to make sure that the "Can’t refactor Swift code." alert still works.)