Xcode 8 (Swift 3) Command failed due to signal: Killed: 9

Question

After upgrading to Xcode 8 and converting all my code to Swift 3, I have troubles compiling swift resources. It takes a very long time, and my computer gets super laggy and

Answer 1

In my case, I was writing a class that implemented Equatable and also had generic members. My issue was rooted in comparing the generic members with ==, when the generic class didn't have a == operator implemented.

For example (using Variable from RxSwift):

class Foo: Equatable {

  var fieldOne: Variable = Variable("fieldOne")
  var fieldTwo: Variable = Variable(nil)

  public static func ==(lhs: Foo, rhs: Foo) -> Bool {
    //should be marked as a compiler error, since Variable doesn't have == 
    return lhs.fieldOne == rhs.fieldOne && lhs.fieldTwo == rhs.fieldTwo 
  }

}

I should have seen a compiler error for this since no definition of == exists for Variable, but the compiler would crash (as well as the static analysis) before being able to show it. I was seeing memory usage of 60GB+ before the crash. Yikes.

It seems swift still has some lingering bugs when it comes to generics.