This is an interesting example because it demonstrates a way to confuse programmers that wasn't previously possible. Thanks for sharing it; it was a gem on an a

This is an interesting example because it demonstrates a way to confuse programmers that wasn't previously possible. Thanks for sharing it; it was a gem on an article otherwise full of confused comments. After sharing it at work, someone pointed out that it isn't technically a race condition. The problem isn't caused by operations happening in an unpredictable order. It's unlikely that any of the promises are already resolved, so the lhs is always evaluated first. It's just that the programmer is surprised by the order of operations. The takeaway is unsurprising: that `await` should be a signal to make one think carefully about state change; having `await` right after `+=` should be a big signal. But the fact that an unwary programmer can actually be tripped up is interesting, despite some other comments on this article claiming such trip-ups are inevitable.