You're not wrong that Rust is "trusting" the developer. But in most situations this is the same as any developer claiming that they've written a thread safe typ

You're not wrong that Rust is "trusting" the developer. But in most situations this is the same as any developer claiming that they've written a thread safe type. Rust's type system just guarantees that you have declared these things to be true, which at a high level gives you a lot of confidence. Thanks for the details, much appreciated!