Can I use Swiftify to convert Swift 1/2/3/4 code to Swift 5.10?

Swiftify does not include a converter between different Swift versions because such a converter exists in Xcode.

To migrate to a newer version from Xcode, choose Edit -> Convert -> To Current Swift Syntax from the Xcode menu.

Depending on your source code's Swift version, you might need a different Xcode version for the conversion. To get an earlier version of Xcode, you can use your Apple Developer Account to download it from the Apple Developer Portal:

• Swift 1 -> 2, Xcode 7
• Swift 2 -> 3, Xcode 8
• Swift 3 -> 4, Xcode 9
• Swift 3 or 4 -> 4.2, Xcode 10
• Swift 4 or 4.2 -> 5, Xcode 10.2.1
• Swift 4 or 4.2 -> 5.1, Xcode 11.1
• Swift 4 or 4.2 -> 5.2, Xcode 11.4
• Swift 4 or 4.2 -> 5.3, Xcode 12
• Swift 4 or 4.2 -> 5.4, Xcode 12.5
• Swift 4 or 4.2 -> 5.5, Xcode 13
• Swift 4 or 4.2 -> 5.6.1, Xcode 13.4
• Swift 4 or 4.2 -> 5.7.1, Xcode 14.1
• Swift 4 or 4.2 -> 5.8.1, Xcode 14.3.1
• Swift 4 or 4.2 -> 5.9, Xcode 15
• Swift 4 or 4.2 -> 5.10, Xcode 15.3

For more information on migrating to Swift 5, check Swift’s official blog, where you can also find migration guides for earlier versions of Swift.

Note: Xcode 15.3 converts your Swift code to Swift 5.10, even though the Swift Language Version dropdown under Build Settings shows Swift 5 (learn more). 

Since Swift 5.0 achieved ABI Stability, all new changes to the language are additive. As there are no changes to the existing format, there isn't a syntax converter for converting between Swift 5.x versions in Xcode.