Rollup merge of #134576 - hkBst:patch-4, r=jhpratt

Improve prose around basic examples of Iter and IterMut

library/core/src/slice/iter.rs

@@ -46,13 +46,19 @@ impl<'a, T> IntoIterator for &'a mut [T] {
 /// Basic usage:
 ///
 /// ```
-/// // First, we declare a type which has `iter` method to get the `Iter` struct (`&[usize]` here):
+/// // First, we need a slice to call the `iter` method on:
 /// let slice = &[1, 2, 3];
 ///
-/// // Then, we iterate over it:
+/// // Then we call `iter` on the slice to get the `Iter` struct,
+/// // and iterate over it:
 /// for element in slice.iter() {
 ///     println!("{element}");
 /// }
+///
+/// // This for loop actually already works without calling `iter`:
+/// for element in slice {
+///     println!("{element}");
+/// }
 /// ```
 ///
 /// [`iter`]: slice::iter
@@ -166,11 +172,11 @@ impl<T> AsRef<[T]> for Iter<'_, T> {
 /// Basic usage:
 ///
 /// ```
-/// // First, we declare a type which has `iter_mut` method to get the `IterMut`
+/// // First, we need a slice to call the `iter_mut` method on:
-/// // struct (`&[usize]` here):
+/// let slice = &mut [1, 2, 3];
-/// let mut slice = &mut [1, 2, 3];
 ///
-/// // Then, we iterate over it and increment each element value:
+/// // Then we call `iter_mut` on the slice to get the `IterMut` struct,
+/// // iterate over it and increment each element value:
 /// for element in slice.iter_mut() {
 ///     *element += 1;
 /// }