Use Legacy Swift Language Version - Xcode 8.2

Question

After updating to Xcode 8.2 the compiler throws one error for my App target:

“Use Legacy Swift Language Version” (SWIFT_VERSION) is required to be con

Answer 1

It turns out that Apple decided to reference a version of the swift language that doesn't exist yet within the pbxprojec file. They hard coded 3.0.1, and by manually editing the sudo XML in the pbx file back to 3.0 everything worked again. Apple apparently overlooked some simple QA work before they released 8.2

This could also explain why toggling between legacy in the build settings worked for some people.