Module compiled with swift 4.0 cannot be imported in swift 3.1 — Carthage

Question

I wanted to test my app using Xcode 9 beta. Now I am back to Xcode 8 and I have the following error:

Module compiled with swift 4.0 cannot be imported in swift 3.1

To solve this error I refresh all Carthage build and made some cleaning:

removed all Carthage build and checkout
removed Derived Data directory
cleaned the project
run carthage update

But the error still here.

Carthage

The command used is: 'carthage update --platform iOS'

As the problem lie on always the same framework, DeviceKit I then manage to remove it from Cartfile.

Project build then show errors as DeviceKit is not found. I then re-add it to Cartfile and run carthage update DeviceKit --platform iOS --no-use-binaries

And the error re-appear.

This related question bring answer but for Cocoapods: Module compiled with swift 4.0 cannot be imported in swift 3.1

Specifically what command did you use for `Carthage` to update? — l'L'l, Aug 02 '17 at 03:24
Maybe try `carthage update NameOfTheLibrary --platform iOS --no-use-binaries`. Also make sure you've switched the command-line tools back to the Xcode 8 version : `sudo xcode-select --switch /Applications/Xcode.app/Contents/Developer` — l'L'l, Aug 02 '17 at 03:26
My only other immediate suggestions would be to use `TOOLCHAINS=com.apple.dt.toolchain.Swift_3_1 carthage bootstrap`, and perhaps remove/recreate `Cartfile.resolved` if that doesn't work. — l'L'l, Aug 02 '17 at 03:35
Did you upgrade to Swift 4.0 when you opened up Xcode 9? Do you have a backup? Otherwise, while I feel for you - I think your options are very limited. — , Aug 02 '17 at 03:38
@dfd No, I did not update to Swift ' on Xcode 9. And yes I have a backup. — Dominique Vial, Aug 02 '17 at 03:41
@Domsware: It allows you to choose which toolchain version of swift to use for `carthage bootstrap`. — l'L'l, Aug 02 '17 at 03:46
@l'L'l Problem not solved after using the TOOLCHAINS... command... — Dominique Vial, Aug 02 '17 at 04:05
Problem solved by cleaning Carthage' derived data. See my answer below. — Dominique Vial, Aug 02 '17 at 04:23

Dominique Vial · Answer 1 · 2017-08-02T04:23:15.520

4

Solved by the following steps:

delete some Derived Data for Carthage: rm -rf ~/Library/Caches/org.carthage.CarthageKit/DerivedData
delete the Carthage folder for your project
Update Carthage: carthage update --platform iOS

I found the answer on the dedicated Carthage' page on GitHub: https://github.com/Carthage/Carthage/issues/2062

edited Aug 02 '17 at 04:23

answered Aug 02 '17 at 04:16

Dominique Vial

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Module compiled with swift 4.0 cannot be imported in swift 3.1 — Carthage

Carthage

And the error re-appear.

1 Answers1