Add #[must_use] to as_type conversions

6 files changed, 11 insertions, 0 deletions

diff --git a/library/alloc/src/collections/binary_heap.rs b/library/alloc/src/collections/binary_heap.rs
index 75720a970a3..9bc9c6ef162 100644
--- a/library/alloc/src/collections/binary_heap.rs
+++ b/library/alloc/src/collections/binary_heap.rs
@@ -1007,6 +1007,7 @@ impl<T> BinaryHeap<T> {
     ///
     /// io::sink().write(heap.as_slice()).unwrap();
     /// ```
+    #[must_use]
     #[unstable(feature = "binary_heap_as_slice", issue = "83659")]
     pub fn as_slice(&self) -> &[T] {
         self.data.as_slice()
diff --git a/library/alloc/src/collections/linked_list.rs b/library/alloc/src/collections/linked_list.rs
index a769c558b4f..82e866c9504 100644
--- a/library/alloc/src/collections/linked_list.rs
+++ b/library/alloc/src/collections/linked_list.rs
@@ -1384,6 +1384,7 @@ impl<'a, T> CursorMut<'a, T> {
     /// The lifetime of the returned `Cursor` is bound to that of the
     /// `CursorMut`, which means it cannot outlive the `CursorMut` and that the
     /// `CursorMut` is frozen for the lifetime of the `Cursor`.
+    #[must_use]
     #[unstable(feature = "linked_list_cursors", issue = "58533")]
     pub fn as_cursor(&self) -> Cursor<'_, T> {
         Cursor { list: self.list, current: self.current, index: self.index }
diff --git a/library/alloc/src/rc.rs b/library/alloc/src/rc.rs
index c6573597b1e..c337b7c5a59 100644
--- a/library/alloc/src/rc.rs
+++ b/library/alloc/src/rc.rs
@@ -2087,6 +2087,7 @@ impl<T: ?Sized> Weak<T> {
     /// ```
     ///
     /// [`null`]: ptr::null
+    #[must_use]
     #[stable(feature = "rc_as_ptr", since = "1.45.0")]
     pub fn as_ptr(&self) -> *const T {
         let ptr: *mut RcBox<T> = NonNull::as_ptr(self.ptr);
diff --git a/library/alloc/src/string.rs b/library/alloc/src/string.rs
index d00792b9c3e..4be8dddeda8 100644
--- a/library/alloc/src/string.rs
+++ b/library/alloc/src/string.rs
@@ -800,6 +800,7 @@ impl String {
     /// assert_eq!("foo", s.as_str());
     /// ```
     #[inline]
+    #[must_use]
     #[stable(feature = "string_as_str", since = "1.7.0")]
     pub fn as_str(&self) -> &str {
         self
@@ -820,6 +821,7 @@ impl String {
     /// assert_eq!("FOOBAR", s_mut_str);
     /// ```
     #[inline]
+    #[must_use]
     #[stable(feature = "string_as_str", since = "1.7.0")]
     pub fn as_mut_str(&mut self) -> &mut str {
         self
@@ -1160,6 +1162,7 @@ impl String {
     /// assert_eq!(&[104, 101, 108, 108, 111], s.as_bytes());
     /// ```
     #[inline]
+    #[must_use]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn as_bytes(&self) -> &[u8] {
         &self.vec
@@ -1763,6 +1766,7 @@ impl FromUtf8Error {
     ///
     /// assert_eq!(&[0, 159], value.unwrap_err().as_bytes());
     /// ```
+    #[must_use]
     #[stable(feature = "from_utf8_error_as_bytes", since = "1.26.0")]
     pub fn as_bytes(&self) -> &[u8] {
         &self.bytes[..]
@@ -2779,6 +2783,7 @@ impl<'a> Drain<'a> {
     /// let _ = drain.next().unwrap();
     /// assert_eq!(drain.as_str(), "bc");
     /// ```
+    #[must_use]
     #[stable(feature = "string_drain_as_str", since = "1.55.0")]
     pub fn as_str(&self) -> &str {
         self.iter.as_str()
diff --git a/library/alloc/src/sync.rs b/library/alloc/src/sync.rs
index 7dd1bc51560..d0bbab51466 100644
--- a/library/alloc/src/sync.rs
+++ b/library/alloc/src/sync.rs
@@ -822,6 +822,7 @@ impl<T: ?Sized> Arc<T> {
     /// assert_eq!(x_ptr, Arc::as_ptr(&y));
     /// assert_eq!(unsafe { &*x_ptr }, "hello");
     /// ```
+    #[must_use]
     #[stable(feature = "rc_as_ptr", since = "1.45.0")]
     pub fn as_ptr(this: &Self) -> *const T {
         let ptr: *mut ArcInner<T> = NonNull::as_ptr(this.ptr);
@@ -1718,6 +1719,7 @@ impl<T: ?Sized> Weak<T> {
     /// ```
     ///
     /// [`null`]: core::ptr::null "ptr::null"
+    #[must_use]
     #[stable(feature = "weak_into_raw", since = "1.45.0")]
     pub fn as_ptr(&self) -> *const T {
         let ptr: *mut ArcInner<T> = NonNull::as_ptr(self.ptr);
diff --git a/library/alloc/src/vec/drain.rs b/library/alloc/src/vec/drain.rs
index fb32d144f87..e643940d017 100644
--- a/library/alloc/src/vec/drain.rs
+++ b/library/alloc/src/vec/drain.rs
@@ -52,6 +52,7 @@ impl<'a, T, A: Allocator> Drain<'a, T, A> {
     /// let _ = drain.next().unwrap();
     /// assert_eq!(drain.as_slice(), &['b', 'c']);
     /// ```
+    #[must_use]
     #[stable(feature = "vec_drain_as_slice", since = "1.46.0")]
     pub fn as_slice(&self) -> &[T] {
         self.iter.as_slice()