Map u8 iterator with char::from instead of working with `String.i…

…nner`

src/distr/other.rs

@@ -172,10 +172,7 @@ impl Distribution<u8> for Alphabetic {
 #[cfg(feature = "alloc")]
 impl SampleString for Alphanumeric {
     fn append_string<R: Rng + ?Sized>(&self, rng: &mut R, string: &mut String, len: usize) {
-        unsafe {
-            let v = string.as_mut_vec();
-            v.extend(self.sample_iter(rng).take(len));
-        }
+        string.extend(self.sample_iter(rng).take(len).map(char::from));
     }
 }