That's why str::from_utf8 returns Result<&str, FromUtf8Error>. And if you know the string is UTF-8 encoded and don't want to pay the cost, there's `from_utf8_unchecked`, which is marked unsafe.
Ah, I thought you were referring to the benefits of such a system as compared to zig and blithely passing the responsibility of input validation on to the programmer. Rust of course demonstrates the benefit of checking validity at initialization.