Author here. I hear your feedback about unsafe blocks. Similar sentiment is shared by other delegates of the JS standards committee.
The main reason it is there today is to satisfy some delegates' requirement that we build in guardrails so as to naturally discourage authors from creating thread-unsafe public APIs and libraries by default. We're exploring other ideas to try to satisfy that requirement without unsafe blocks.
There's already a precedent of ownership on transferred objects. Why not have an `.unsafe(cb)` method on the structs? Error if you don't have ownership, then use the callback to temporarily acquire ownership. At least to me, it's more intuitive and seems idiomatic.
bike-shedding but you should consider renaming them from "unsafe" to "volatile" or some other word that expresses that they are not unsafe to the user/browser/os. They are only changeable by other threads.
The word "unsafe" will be picked up as meaning "can infect your computer" which we can already see examples of these messages.
The main reason it is there today is to satisfy some delegates' requirement that we build in guardrails so as to naturally discourage authors from creating thread-unsafe public APIs and libraries by default. We're exploring other ideas to try to satisfy that requirement without unsafe blocks.