@swift-ci create

It looks like `A.a` has to have an `Optional` payload to trigger the leak. Making `B` CustomDebugStringConvertible seems to work around the leak.

It also looks like `B` has to specifically be an enum, as opposed to a struct. Slightly reduced repro case:

import Foundation

public enum B: Error { case b }

autoreleasepool {
  print(B.b as Error?)
}

Leak appears to be independent of the `Error` protocol as well. This also reproduces the leak for me:

import Foundation

protocol P {}

public enum B: P { case b }

autoreleasepool {
  print(B.b as P?)
}

Leak seems to be caused somewhere during mirror traversal. This also leaks, using `dump` instead of `print`:

import Foundation

protocol P {}

public enum B: P {
  case b
}

autoreleasepool {
  dump(B.b as P)
}

Comment by James Froggatt (JIRA)

I'm getting something like this bug as well, without Optional:

public enum ANTLRException: Error {
    case parseCancellation(e: RecognitionException)
    case recognition(e: RecognitionException)
}

Here, `RecognitionException` doesn't conform to `Error`. Attempting to catch the `ANTLRException` error (from another module) gives a `_SwiftNativeNSError`, and attempts to cast to `ANTLRException` fail. Attempts to print or get the localizedDescription also result in a crash.

SAJim (JIRA User) Can you file a new bug for that? Looking at the presence of _SwiftNativeNSError itself is probably misleading, since that is the representation for all values of Error type in Swift. It should be an implementation detail.

Comment by James Froggatt (JIRA)

Thanks Joe, it did turn out to be a completely different problem. I'll file a report when I have a moment.

@slavapestov fixed a runtime leak in #13792 that's probably responsible for this.