I think you are correct, and it (as expected) changes the results. I ran owensd code on my machine, in a completely non scientific and error prone setup. For release builds:
Objective-C: 0.0310617s
Safe Swift (incorrect): 0.0641295s (106.5% slower)
Safe Swift (correct): 0.0355441s (14.4% slower)
So the "safe" Swift version is running about 14.4% slower than the Objective-C version. It's not bad at all for a language that is so young! In debug mode, however, I didn't even have the patience to wait for the test run to finish...
Objective-C: 0.0310617s
Safe Swift (incorrect): 0.0641295s (106.5% slower)
Safe Swift (correct): 0.0355441s (14.4% slower)
So the "safe" Swift version is running about 14.4% slower than the Objective-C version. It's not bad at all for a language that is so young! In debug mode, however, I didn't even have the patience to wait for the test run to finish...