If you know of a case where rust code violates memory safety without the use of an unsafe block, file a bug and it will probably be fixed within a release or two.
"Fearless concurrency" is more subjective, but rust code (again with the caveat that there isn't unsafe code, or unsafe cose upholds all unvariants) dows eliminate certain classes of concurrency bugs. Although, dreadlocks are definitely possible, and certain kinds of race conditions could potentially exist. But I don't know of any claims that concurrency bugs are impossible in rust.
"Fearless concurrency" is more subjective, but rust code (again with the caveat that there isn't unsafe code, or unsafe cose upholds all unvariants) dows eliminate certain classes of concurrency bugs. Although, dreadlocks are definitely possible, and certain kinds of race conditions could potentially exist. But I don't know of any claims that concurrency bugs are impossible in rust.