Rethinking Async

[dabrahams (Dave Abrahams)]

@dabrahams

I'd just like to throw in a note of concern for the way closures quietly confer reference semantics on the values they capture.

Cross-reference to an example of a user being bitten by this problem

Understanding Swift's value type thread safety

This really helps crystallize the mechanics of these scenarios. It's unfortunate how easy it is to (silently) lose the safety that value types provide when handing them off to an escaping closure. It makes sense that it behaves this way but the lack of explicit signalling required is a potential footgun. shared/__block would help but I wonder if something at the point of use/capture would be even better (similar to explicit self in a closure). Is a mutation in an escaping closure required to …