Yes, it does crash if two threads write to a property at the same time. The worst thing about this kind of bug is the inconsistency - often being discovered fir

Yes, it does crash if two threads write to a property at the same time. The worst thing about this kind of bug is the inconsistency - often being discovered first by real users. There are also a plethora of shared state bugs that should be reduced with clearer concurrency semantics. All-around big step forward towards Swift's goal of being a "safe" language.