Rust's type system for thread safety is actually remarkably simple. Types declare whether they add or remove thread safety (e.g. Mutex adds safety, non-atomic Rc removes). Structs automatically become non-thread-safe if they have non-thread-safe fields. Then all the functions that spawn threads or send data over channels require thread-safe types.

The fearless concurrency is real. It reliably prevents data races, use-after-free, and moving of thread-specific data to another thread. It works across arbitrarily large and complex call graphs, including 3rd party dependencies and dynamic callbacks. Plus immutability is strongly enforced, and global mutable state without synchronization is not allowed.

It doesn't prevent deadlocks, but compared to data corruption heisenbugs, these are pretty easy — attach a debugger and you can see exactly what deadlocked where.