There is a new blog post titled Swift 5 Exclusivity Enforcement, authored by @Andrew_Trick, that is now available to read. It discusses how the policies for memory exclusivity have further matured in Swift 5.
If you have any questions about the material of that blog post, please feel free to post them here!
Right, the capture list causes a copy from an instantaneous access to happen at the point of closure formation, which would be before the formal inout access to count begins.