Avoiding "Simultaneous accesses to ..., but modification requires exclusive access." - automate action after modification of a property in a property observer

[lukasa (Cory Benfield)]

There has been spotty enforcement of this in some cases in the past: Exclusive access duration relative to didSet. I'd recommend filing a bug on GitHub with a complete description of your environment (Xcode version, Swift version, macOS version, hardware version) and your project or compiler command line and test environment. That will let the Swift team nail it down.