It does do something similar... and more. IIUC, when unwinding on panic Rust does unlock the mutex, but it also "poisons" it so that a subsequent attempt to loc

It does do something similar... and more. IIUC, when unwinding on panic Rust does unlock the mutex, but it also "poisons" it so that a subsequent attempt to lock will return an error. This is because on panic all the code protected by the mutex didn't get to run to completion, possibly leaving an inconsistent state. A poisoned mutex can be reset, though.