Merge ref '6bcdcc73bd11' from rust-lang/rust

Pull recent changes from https://github.com/rust-lang/rust via Josh.

Upstream ref: 6bcdcc73bd11568fd85f5a38b58e1eda054ad1cd
Filtered ref: 6cc4ce79e1f8dc0ec5a2e18049b9c1a51dee3221

This merge was created using https://github.com/rust-lang/josh-sync.

8 files changed, 98 insertions, 42 deletions

diff --git a/library/core/src/array/equality.rs b/library/core/src/array/equality.rs
index bb668d2a673..1ad2cca64a3 100644
--- a/library/core/src/array/equality.rs
+++ b/library/core/src/array/equality.rs
@@ -22,18 +22,16 @@ where
 {
     #[inline]
     fn eq(&self, other: &[U]) -> bool {
-        let b: Result<&[U; N], _> = other.try_into();
-        match b {
-            Ok(b) => *self == *b,
-            Err(_) => false,
+        match other.as_array::<N>() {
+            Some(b) => *self == *b,
+            None => false,
         }
     }
     #[inline]
     fn ne(&self, other: &[U]) -> bool {
-        let b: Result<&[U; N], _> = other.try_into();
-        match b {
-            Ok(b) => *self != *b,
-            Err(_) => true,
+        match other.as_array::<N>() {
+            Some(b) => *self != *b,
+            None => true,
         }
     }
 }
@@ -45,18 +43,16 @@ where
 {
     #[inline]
     fn eq(&self, other: &[U; N]) -> bool {
-        let b: Result<&[T; N], _> = self.try_into();
-        match b {
-            Ok(b) => *b == *other,
-            Err(_) => false,
+        match self.as_array::<N>() {
+            Some(b) => *b == *other,
+            None => false,
         }
     }
     #[inline]
     fn ne(&self, other: &[U; N]) -> bool {
-        let b: Result<&[T; N], _> = self.try_into();
-        match b {
-            Ok(b) => *b != *other,
-            Err(_) => true,
+        match self.as_array::<N>() {
+            Some(b) => *b != *other,
+            None => true,
         }
     }
 }
diff --git a/library/core/src/cell/lazy.rs b/library/core/src/cell/lazy.rs
index 1758e84ad7c..a1bd4c85717 100644
--- a/library/core/src/cell/lazy.rs
+++ b/library/core/src/cell/lazy.rs
@@ -15,6 +15,22 @@ enum State<T, F> {
 ///
 /// [`std::sync::LazyLock`]: ../../std/sync/struct.LazyLock.html
 ///
+/// # Poisoning
+///
+/// If the initialization closure passed to [`LazyCell::new`] panics, the cell will be poisoned.
+/// Once the cell is poisoned, any threads that attempt to access this cell (via a dereference
+/// or via an explicit call to [`force()`]) will panic.
+///
+/// This concept is similar to that of poisoning in the [`std::sync::poison`] module. A key
+/// difference, however, is that poisoning in `LazyCell` is _unrecoverable_. All future accesses of
+/// the cell from other threads will panic, whereas a type in [`std::sync::poison`] like
+/// [`std::sync::poison::Mutex`] allows recovery via [`PoisonError::into_inner()`].
+///
+/// [`force()`]: LazyCell::force
+/// [`std::sync::poison`]: ../../std/sync/poison/index.html
+/// [`std::sync::poison::Mutex`]: ../../std/sync/poison/struct.Mutex.html
+/// [`PoisonError::into_inner()`]: ../../std/sync/poison/struct.PoisonError.html#method.into_inner
+///
 /// # Examples
 ///
 /// ```
@@ -64,6 +80,10 @@ impl<T, F: FnOnce() -> T> LazyCell<T, F> {
     ///
     /// Returns `Ok(value)` if `Lazy` is initialized and `Err(f)` otherwise.
     ///
+    /// # Panics
+    ///
+    /// Panics if the cell is poisoned.
+    ///
     /// # Examples
     ///
     /// ```
@@ -93,6 +113,15 @@ impl<T, F: FnOnce() -> T> LazyCell<T, F> {
     ///
     /// This is equivalent to the `Deref` impl, but is explicit.
     ///
+    /// # Panics
+    ///
+    /// If the initialization closure panics (the one that is passed to the [`new()`] method), the
+    /// panic is propagated to the caller, and the cell becomes poisoned. This will cause all future
+    /// accesses of the cell (via [`force()`] or a dereference) to panic.
+    ///
+    /// [`new()`]: LazyCell::new
+    /// [`force()`]: LazyCell::force
+    ///
     /// # Examples
     ///
     /// ```
@@ -123,6 +152,15 @@ impl<T, F: FnOnce() -> T> LazyCell<T, F> {
     /// Forces the evaluation of this lazy value and returns a mutable reference to
     /// the result.
     ///
+    /// # Panics
+    ///
+    /// If the initialization closure panics (the one that is passed to the [`new()`] method), the
+    /// panic is propagated to the caller, and the cell becomes poisoned. This will cause all future
+    /// accesses of the cell (via [`force()`] or a dereference) to panic.
+    ///
+    /// [`new()`]: LazyCell::new
+    /// [`force()`]: LazyCell::force
+    ///
     /// # Examples
     ///
     /// ```
@@ -219,7 +257,8 @@ impl<T, F: FnOnce() -> T> LazyCell<T, F> {
 }
 
 impl<T, F> LazyCell<T, F> {
-    /// Returns a mutable reference to the value if initialized, or `None` if not.
+    /// Returns a mutable reference to the value if initialized. Otherwise (if uninitialized or
+    /// poisoned), returns `None`.
     ///
     /// # Examples
     ///
@@ -245,7 +284,8 @@ impl<T, F> LazyCell<T, F> {
         }
     }
 
-    /// Returns a reference to the value if initialized, or `None` if not.
+    /// Returns a reference to the value if initialized. Otherwise (if uninitialized or poisoned),
+    /// returns `None`.
     ///
     /// # Examples
     ///
@@ -278,6 +318,15 @@ impl<T, F> LazyCell<T, F> {
 #[stable(feature = "lazy_cell", since = "1.80.0")]
 impl<T, F: FnOnce() -> T> Deref for LazyCell<T, F> {
     type Target = T;
+
+    /// # Panics
+    ///
+    /// If the initialization closure panics (the one that is passed to the [`new()`] method), the
+    /// panic is propagated to the caller, and the cell becomes poisoned. This will cause all future
+    /// accesses of the cell (via [`force()`] or a dereference) to panic.
+    ///
+    /// [`new()`]: LazyCell::new
+    /// [`force()`]: LazyCell::force
     #[inline]
     fn deref(&self) -> &T {
         LazyCell::force(self)
@@ -286,6 +335,14 @@ impl<T, F: FnOnce() -> T> Deref for LazyCell<T, F> {
 
 #[stable(feature = "lazy_deref_mut", since = "1.89.0")]
 impl<T, F: FnOnce() -> T> DerefMut for LazyCell<T, F> {
+    /// # Panics
+    ///
+    /// If the initialization closure panics (the one that is passed to the [`new()`] method), the
+    /// panic is propagated to the caller, and the cell becomes poisoned. This will cause all future
+    /// accesses of the cell (via [`force()`] or a dereference) to panic.
+    ///
+    /// [`new()`]: LazyCell::new
+    /// [`force()`]: LazyCell::force
     #[inline]
     fn deref_mut(&mut self) -> &mut T {
         LazyCell::force_mut(self)
diff --git a/library/core/src/intrinsics/mod.rs b/library/core/src/intrinsics/mod.rs
index 106cc725fee..c6b92df5fe1 100644
--- a/library/core/src/intrinsics/mod.rs
+++ b/library/core/src/intrinsics/mod.rs
@@ -2667,7 +2667,7 @@ pub unsafe fn vtable_align(ptr: *const ()) -> usize;
 /// More specifically, this is the offset in bytes between successive
 /// items of the same type, including alignment padding.
 ///
-/// The stabilized version of this intrinsic is [`size_of`].
+/// The stabilized version of this intrinsic is [`core::mem::size_of`].
 #[rustc_nounwind]
 #[unstable(feature = "core_intrinsics", issue = "none")]
 #[rustc_intrinsic_const_stable_indirect]
@@ -2681,7 +2681,7 @@ pub const fn size_of<T>() -> usize;
 /// Therefore, implementations must not require the user to uphold
 /// any safety invariants.
 ///
-/// The stabilized version of this intrinsic is [`align_of`].
+/// The stabilized version of this intrinsic is [`core::mem::align_of`].
 #[rustc_nounwind]
 #[unstable(feature = "core_intrinsics", issue = "none")]
 #[rustc_intrinsic_const_stable_indirect]
@@ -2704,7 +2704,7 @@ pub const fn variant_count<T>() -> usize;
 
 /// The size of the referenced value in bytes.
 ///
-/// The stabilized version of this intrinsic is [`size_of_val`].
+/// The stabilized version of this intrinsic is [`core::mem::size_of_val`].
 ///
 /// # Safety
 ///
@@ -2717,7 +2717,7 @@ pub const unsafe fn size_of_val<T: ?Sized>(ptr: *const T) -> usize;
 
 /// The required alignment of the referenced value.
 ///
-/// The stabilized version of this intrinsic is [`align_of_val`].
+/// The stabilized version of this intrinsic is [`core::mem::align_of_val`].
 ///
 /// # Safety
 ///
diff --git a/library/core/src/num/int_macros.rs b/library/core/src/num/int_macros.rs
index 5683d5ec92d..10efb8aff4a 100644
--- a/library/core/src/num/int_macros.rs
+++ b/library/core/src/num/int_macros.rs
@@ -177,14 +177,14 @@ macro_rules! int_impl {
         ///
         #[doc = concat!("let n: ", stringify!($SelfT), " = 0b_01100100;")]
         ///
-        /// assert_eq!(n.isolate_most_significant_one(), 0b_01000000);
-        #[doc = concat!("assert_eq!(0_", stringify!($SelfT), ".isolate_most_significant_one(), 0);")]
+        /// assert_eq!(n.isolate_highest_one(), 0b_01000000);
+        #[doc = concat!("assert_eq!(0_", stringify!($SelfT), ".isolate_highest_one(), 0);")]
         /// ```
         #[unstable(feature = "isolate_most_least_significant_one", issue = "136909")]
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline(always)]
-        pub const fn isolate_most_significant_one(self) -> Self {
+        pub const fn isolate_highest_one(self) -> Self {
             self & (((1 as $SelfT) << (<$SelfT>::BITS - 1)).wrapping_shr(self.leading_zeros()))
         }
 
@@ -198,14 +198,14 @@ macro_rules! int_impl {
         ///
         #[doc = concat!("let n: ", stringify!($SelfT), " = 0b_01100100;")]
         ///
-        /// assert_eq!(n.isolate_least_significant_one(), 0b_00000100);
-        #[doc = concat!("assert_eq!(0_", stringify!($SelfT), ".isolate_least_significant_one(), 0);")]
+        /// assert_eq!(n.isolate_lowest_one(), 0b_00000100);
+        #[doc = concat!("assert_eq!(0_", stringify!($SelfT), ".isolate_lowest_one(), 0);")]
         /// ```
         #[unstable(feature = "isolate_most_least_significant_one", issue = "136909")]
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline(always)]
-        pub const fn isolate_least_significant_one(self) -> Self {
+        pub const fn isolate_lowest_one(self) -> Self {
             self & self.wrapping_neg()
         }
 
diff --git a/library/core/src/num/nonzero.rs b/library/core/src/num/nonzero.rs
index f793602de50..2d3a680b348 100644
--- a/library/core/src/num/nonzero.rs
+++ b/library/core/src/num/nonzero.rs
@@ -629,7 +629,7 @@ macro_rules! nonzero_integer {
             #[doc = concat!("let a = NonZero::<", stringify!($Int), ">::new(0b_01100100)?;")]
             #[doc = concat!("let b = NonZero::<", stringify!($Int), ">::new(0b_01000000)?;")]
             ///
-            /// assert_eq!(a.isolate_most_significant_one(), b);
+            /// assert_eq!(a.isolate_highest_one(), b);
             /// # Some(())
             /// # }
             /// ```
@@ -637,7 +637,7 @@ macro_rules! nonzero_integer {
             #[must_use = "this returns the result of the operation, \
                         without modifying the original"]
             #[inline(always)]
-            pub const fn isolate_most_significant_one(self) -> Self {
+            pub const fn isolate_highest_one(self) -> Self {
                 let n = self.get() & (((1 as $Int) << (<$Int>::BITS - 1)).wrapping_shr(self.leading_zeros()));
 
                 // SAFETY:
@@ -659,7 +659,7 @@ macro_rules! nonzero_integer {
             #[doc = concat!("let a = NonZero::<", stringify!($Int), ">::new(0b_01100100)?;")]
             #[doc = concat!("let b = NonZero::<", stringify!($Int), ">::new(0b_00000100)?;")]
             ///
-            /// assert_eq!(a.isolate_least_significant_one(), b);
+            /// assert_eq!(a.isolate_lowest_one(), b);
             /// # Some(())
             /// # }
             /// ```
@@ -667,7 +667,7 @@ macro_rules! nonzero_integer {
             #[must_use = "this returns the result of the operation, \
                         without modifying the original"]
             #[inline(always)]
-            pub const fn isolate_least_significant_one(self) -> Self {
+            pub const fn isolate_lowest_one(self) -> Self {
                 let n = self.get();
                 let n = n & n.wrapping_neg();
 
diff --git a/library/core/src/num/uint_macros.rs b/library/core/src/num/uint_macros.rs
index 584cd60fbe5..5a41a302916 100644
--- a/library/core/src/num/uint_macros.rs
+++ b/library/core/src/num/uint_macros.rs
@@ -229,14 +229,14 @@ macro_rules! uint_impl {
         ///
         #[doc = concat!("let n: ", stringify!($SelfT), " = 0b_01100100;")]
         ///
-        /// assert_eq!(n.isolate_most_significant_one(), 0b_01000000);
-        #[doc = concat!("assert_eq!(0_", stringify!($SelfT), ".isolate_most_significant_one(), 0);")]
+        /// assert_eq!(n.isolate_highest_one(), 0b_01000000);
+        #[doc = concat!("assert_eq!(0_", stringify!($SelfT), ".isolate_highest_one(), 0);")]
         /// ```
         #[unstable(feature = "isolate_most_least_significant_one", issue = "136909")]
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline(always)]
-        pub const fn isolate_most_significant_one(self) -> Self {
+        pub const fn isolate_highest_one(self) -> Self {
             self & (((1 as $SelfT) << (<$SelfT>::BITS - 1)).wrapping_shr(self.leading_zeros()))
         }
 
@@ -250,14 +250,14 @@ macro_rules! uint_impl {
         ///
         #[doc = concat!("let n: ", stringify!($SelfT), " = 0b_01100100;")]
         ///
-        /// assert_eq!(n.isolate_least_significant_one(), 0b_00000100);
-        #[doc = concat!("assert_eq!(0_", stringify!($SelfT), ".isolate_least_significant_one(), 0);")]
+        /// assert_eq!(n.isolate_lowest_one(), 0b_00000100);
+        #[doc = concat!("assert_eq!(0_", stringify!($SelfT), ".isolate_lowest_one(), 0);")]
         /// ```
         #[unstable(feature = "isolate_most_least_significant_one", issue = "136909")]
         #[must_use = "this returns the result of the operation, \
                       without modifying the original"]
         #[inline(always)]
-        pub const fn isolate_least_significant_one(self) -> Self {
+        pub const fn isolate_lowest_one(self) -> Self {
             self & self.wrapping_neg()
         }
 
diff --git a/library/core/src/ptr/alignment.rs b/library/core/src/ptr/alignment.rs
index bd5b4e21baa..402634e49b3 100644
--- a/library/core/src/ptr/alignment.rs
+++ b/library/core/src/ptr/alignment.rs
@@ -1,3 +1,5 @@
+#![allow(clippy::enum_clike_unportable_variant)]
+
 use crate::num::NonZero;
 use crate::ub_checks::assert_unsafe_precondition;
 use crate::{cmp, fmt, hash, mem, num};
@@ -241,7 +243,7 @@ impl const Default for Alignment {
 
 #[cfg(target_pointer_width = "16")]
 #[derive(Copy, Clone, PartialEq, Eq)]
-#[repr(u16)]
+#[repr(usize)]
 enum AlignmentEnum {
     _Align1Shl0 = 1 << 0,
     _Align1Shl1 = 1 << 1,
@@ -263,7 +265,7 @@ enum AlignmentEnum {
 
 #[cfg(target_pointer_width = "32")]
 #[derive(Copy, Clone, PartialEq, Eq)]
-#[repr(u32)]
+#[repr(usize)]
 enum AlignmentEnum {
     _Align1Shl0 = 1 << 0,
     _Align1Shl1 = 1 << 1,
@@ -301,7 +303,7 @@ enum AlignmentEnum {
 
 #[cfg(target_pointer_width = "64")]
 #[derive(Copy, Clone, PartialEq, Eq)]
-#[repr(u64)]
+#[repr(usize)]
 enum AlignmentEnum {
     _Align1Shl0 = 1 << 0,
     _Align1Shl1 = 1 << 1,
diff --git a/library/core/src/slice/mod.rs b/library/core/src/slice/mod.rs
index 14042997bc2..1dddc48e68e 100644
--- a/library/core/src/slice/mod.rs
+++ b/library/core/src/slice/mod.rs
@@ -3974,8 +3974,9 @@ impl<T> [T] {
     ///
     /// [`split_at_mut`]: slice::split_at_mut
     #[stable(feature = "swap_with_slice", since = "1.27.0")]
+    #[rustc_const_unstable(feature = "const_swap_with_slice", issue = "142204")]
     #[track_caller]
-    pub fn swap_with_slice(&mut self, other: &mut [T]) {
+    pub const fn swap_with_slice(&mut self, other: &mut [T]) {
         assert!(self.len() == other.len(), "destination and source slices have different lengths");
         // SAFETY: `self` is valid for `self.len()` elements by definition, and `src` was
         // checked to have the same length. The slices cannot overlap because