Swift 2.0 interop with Objective C not working as expected? - objective-c

Question

I'm porting a Swift 1.2 framework to 2.0. After fixing the 3 million compiler errors courtesy of the new Swift 2.0 error handling scheme, I was finally able to link my test app (written in Objective C) to use the updated framework.
Xcode version 7.0 beta 3 (7A121l)
However, I ran into a problem. Some Swift functions are no longer generated into the automatically generated Objective C header (MyFramework-Swift.h) used by the Objective C test app.
Here is an example of a function that is not exposed: (My actual framework function returned an enum, but I tried to simplify to illustrate the problem more clearly).
public func calculateImportantValueDangerously() throws -> Int
{
return 42
}
Note that other functions like the following actually do get exposed as expected (and can be called):
public func doSomething()
{
}
public func doSomethingDangerous() throws
{
}
public func calculateMeaninglessValue() -> Int
{
return -1
}
Here's the Objective C side:
MyClass *newInstance = [[MyClass alloc] init];
[newInstance doSomething];
NSError *error = nil;
[newInstance doSomethingDangerousAndReturnError:&error];
long meaninglessValue = [newInstance calculateMeaninglessValue];
NSLog(#"%ld", meaninglessValue);
long importantValue = [newInstance calculateImportantValueDangerouslyAndReturnError:&error]; <-COMPILE ERROR
NSLog(#"%ld", importantValue);
From watching this video, I had expected that it should "just work":
https://developer.apple.com/videos/wwdc/2015/?id=401
...but it seems like we can't currently use functions that both throw and return a value.
Is this a bug, or not implemented feature? My apologies if I missed something in the release notes somewhere.
Any advice appreciated.

Answer 1

It is not possible.
If you annotate your method with #objc you will see the problem.
Throwing method cannot be marked #objc because it returns a value of
type 'Int'; return 'Void' or a type that bridges to an Objective-C
class
You can return only objects, primitives are not supported.

Answer 2

Although the selected answer is correct; you can't return an Int for a throwing function, I wanted to note an alternate solution since Apple has this same issue for a function in the CoreData framework:
func countForFetchRequest(request: NSFetchRequest, error: NSErrorPointer) -> Int
Note that in this case Apple is not using the throws pattern and instead reverting to the classic NSError out parameter mechanism.