Simplify code

Author: vks

rand_core/src/impls.rs

@@ -60,19 +60,13 @@ macro_rules! fill_via_chunks {
         let chunk_size = (chunk_size_u8 + SIZE - 1) / SIZE;
 
         let mut iter_src = $src.iter();
-        let mut iter_chunks = $dst.chunks_exact_mut(SIZE);
-        let mut n;
-        loop {
-            n = iter_src.next();
-            if let (Some(n_), Some(chunk)) = (n, iter_chunks.next()) {
-                chunk.copy_from_slice(&n_.to_le_bytes());
-            } else {
-                break;
-            }
+        let mut chunks = $dst.chunks_exact_mut(SIZE);
+        for (chunk, n) in (&mut chunks).zip(&mut iter_src) {
+            chunk.copy_from_slice(&n.to_le_bytes());
         }
-        let rem = iter_chunks.into_remainder();
-        if let Some(n_) = n {
-            rem.copy_from_slice(&n_.to_le_bytes()[..rem.len()]);
+        let rem = chunks.into_remainder();
+        if let Some(n) = iter_src.next() {
+            rem.copy_from_slice(&n.to_le_bytes()[..rem.len()]);
         }
 
         (chunk_size, chunk_size_u8)