“Use Legacy Swift Language Version” (SWIFT_VERSION) is required to be configured correctly for targets which use Swift."

Question

Ever since I've updated to Xcode 8.2 (GM seed, from the App Store), I have been stuck at the following error:

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.

So I went to my target's Build Settings, and searched for SWIFT_VERSION to see where I was erring. However, I was surprised to find that it was already set to No!

How do I fix this?

Solution 1

Xcode 8 seems to be wrongfully displaying a nonexistent ("phantom", if you will) No. There's a trivial fix for this:

1. Click the tiny arrow next to SWIFT_VERSION to toggle the drop-down list.
2. Set the values for Debug and Release to Yes.
3. Set the values for Debug and Release back to No.

The image below was taken just after setting Debug to No. Xcode shows that both Debug and Release are set to No, however SWIFT_VERSION reads <Multiple Values>:

From this, I can only conclude that it is a bug; and that some value (or more probably a null value) is being misrepresented as No.

Solution 2

Please select the target in pod alamofire, search 'SWIFT_VERSION', select swift3.

Solution 3

Xcode 8.3.2 go to :

Build Settings > Swift Compiler - Viersion > change Swift Version

....works

Solution 4

Just in case anyone else runs into the same issue I just had.

I had an app that was ready to launch onto the app store but i was waiting, meanwhile i updated to Xcode 9 beta and was messing around, changed a few things in my app. I went to upload it to the app store and it said you could not use beta versions to upload so i went back to Xcode 8 but it started giving me the “Swift Language Version” (SWIFT_VERSION)..." error.

My fix

Under your project Build Settings > Swift Compiler Version > I had to change this from Swift 4(currently not supported) to Swift 3.

Problem Solved :)

Solution 5

The phantom No answer will work. The real reason XCode is broken is because Apples XCode "use legacy setting" is really a Swift Version number. In XCode 8.1 'No' translated to 3.0.1, in XCode 8.2 'No' translates to 3.0. So you need to switch the version to Swift 3.0 . Which makes sense. Was a bug in XCode 8.1 I guess.

My git diff:

--- a/ios/myapp.xcodeproj/project.pbxproj
+++ b/ios/myapp.xcodeproj/project.pbxproj
@@ -1757,7 +1757,7 @@
                                SDKROOT = iphoneos;
                                SKIP_INSTALL = YES;
                                SWIFT_OPTIMIZATION_LEVEL = "-Onone";
-                               SWIFT_VERSION = 3.0.1;
+                               SWIFT_VERSION = 3.0;
                                TARGETED_DEVICE_FAMILY = "1,2";
                        };
                        name = Debug;

I see a comment above that has the same answer just think it needs to stand out more.

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