Rust programs are not 'safe' in the sense that they cannot crash or have security bugs, but they are 'safer' in that the compiler automatically performs a series of safety checks to prevent common errors.
1: Widespread meaning OSes and popular platforms, not custom LOB apps where SQL injection exists on the login page.
It is effectively impossible to have an unsafe memory access error in Rust
Rust just has less of them, because it has a smart compiler. ...but it's not right to suggest that it has none.
Remember:
There is no way of ensuring that a rust program does not result in a segmentation fault or other memory or race condition as a result of unsafe code.
There is no way of ensuring a rust program does not contain any unsafe code.
There's no way to ensure the compiler is perfect, but rust itself is not capable of certain types of errors.
You can always code the wrong algorithm, but that doesn't mean you can segfault or use after free (in the default safe mode you almost never have an excuse to leave).
That's why effectively impossible is an OK statement. Unless you go out of your way, your program will not contain such bugs.
Sure there is. There's a compiler lint available which can disallow "unsafe" code, i.e. code which is able to create null pointer errors (and thus segfaults).
Of course, the standard library will always contain a bunch of unsafe stuff - but at least it's shared between every project, and any bugs can be fixed once, and assuming it's correct any non-unsafe code that depends on it is memory-safe.