[PATCH] rust: alloc: add doc test for `Vec::extend_with` and fix comment

[Hsiu Che Yu]

Add a doc test for `Vec::extend_with` demonstrating basic usage and the
zero-length case.

Also fix an incorrect operator in the SAFETY comment, changing `<` to `<=`,
since `Vec::reserve` guarantees capacity for exactly n additional elements,
so the equal case should be included.

Signed-off-by: Hsiu Che Yu <yu.whisper.personal@xxxxxxxxx>
---
 rust/kernel/alloc/kvec.rs | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/rust/kernel/alloc/kvec.rs b/rust/kernel/alloc/kvec.rs
index ac8d6f763ae8..fc4bf0a7934d 100644
--- a/rust/kernel/alloc/kvec.rs
+++ b/rust/kernel/alloc/kvec.rs
@@ -737,6 +737,24 @@ pub fn retain(&mut self, mut f: impl FnMut(&mut T) -> bool) {
 
 impl<T: Clone, A: Allocator> Vec<T, A> {
     /// Extend the vector by `n` clones of `value`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let mut v = KVec::new();
+    /// v.push(1, GFP_KERNEL)?;
+    ///
+    /// v.extend_with(3, 5, GFP_KERNEL)?;
+    /// assert_eq!(&v, &[1, 5, 5, 5]);
+    ///
+    /// v.extend_with(2, 8, GFP_KERNEL)?;
+    /// assert_eq!(&v, &[1, 5, 5, 5, 8, 8]);
+    ///
+    /// v.extend_with(0, 3, GFP_KERNEL)?;
+    /// assert_eq!(&v, &[1, 5, 5, 5, 8, 8]);
+    ///
+    /// # Ok::<(), Error>(())
+    /// ```
     pub fn extend_with(&mut self, n: usize, value: T, flags: Flags) -> Result<(), AllocError> {
         if n == 0 {
             return Ok(());
@@ -754,7 +772,7 @@ pub fn extend_with(&mut self, n: usize, value: T, flags: Flags) -> Result<(), Al
         spare[n - 1].write(value);
 
         // SAFETY:
-        // - `self.len() + n < self.capacity()` due to the call to reserve above,
+        // - `self.len() + n <= self.capacity()` due to the call to reserve above,
         // - the loop and the line above initialized the next `n` elements.
         unsafe { self.inc_len(n) };
 
-- 
2.43.0