Merge pull request #4513 from rust-lang/rustup-2025-08-04

Automatic Rustup

14 files changed, 222 insertions, 75 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.rs b/library/core/src/cell.rs
index d6d1bf2effa..d67408cae1b 100644
--- a/library/core/src/cell.rs
+++ b/library/core/src/cell.rs
@@ -2068,9 +2068,9 @@ impl<T: ?Sized + fmt::Display> fmt::Display for RefMut<'_, T> {
 /// implies exclusive access to its `T`:
 ///
 /// ```rust
-/// #![forbid(unsafe_code)] // with exclusive accesses,
-///                         // `UnsafeCell` is a transparent no-op wrapper,
-///                         // so no need for `unsafe` here.
+/// #![forbid(unsafe_code)]
+/// // with exclusive accesses, `UnsafeCell` is a transparent no-op wrapper, so no need for
+/// // `unsafe` here.
 /// use std::cell::UnsafeCell;
 ///
 /// let mut x: UnsafeCell<i32> = 42.into();
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/hint.rs b/library/core/src/hint.rs
index 696d323c66d..c72eeb9a9c9 100644
--- a/library/core/src/hint.rs
+++ b/library/core/src/hint.rs
@@ -649,8 +649,6 @@ pub const fn must_use<T>(value: T) -> T {
 ///     }
 /// }
 /// ```
-///
-///
 #[unstable(feature = "likely_unlikely", issue = "136873")]
 #[inline(always)]
 pub const fn likely(b: bool) -> bool {
diff --git a/library/core/src/iter/mod.rs b/library/core/src/iter/mod.rs
index 7ca41d224a0..56ca1305b60 100644
--- a/library/core/src/iter/mod.rs
+++ b/library/core/src/iter/mod.rs
@@ -233,10 +233,12 @@
 //!
 //! ```
 //! let mut values = vec![41];
-//! for x in &mut values { // same as `values.iter_mut()`
+//! for x in &mut values {
+//!     //   ^ same as `values.iter_mut()`
 //!     *x += 1;
 //! }
-//! for x in &values { // same as `values.iter()`
+//! for x in &values {
+//!     //   ^ same as `values.iter()`
 //!     assert_eq!(*x, 42);
 //! }
 //! assert_eq!(values.len(), 1);
diff --git a/library/core/src/iter/traits/iterator.rs b/library/core/src/iter/traits/iterator.rs
index 10f9d464f7d..29313867ff2 100644
--- a/library/core/src/iter/traits/iterator.rs
+++ b/library/core/src/iter/traits/iterator.rs
@@ -807,7 +807,7 @@ pub trait Iterator {
     /// might be preferable to keep a functional style with longer iterators:
     ///
     /// ```
-    /// (0..5).flat_map(|x| x * 100 .. x * 110)
+    /// (0..5).flat_map(|x| (x * 100)..(x * 110))
     ///       .enumerate()
     ///       .filter(|&(i, x)| (i + x) % 3 == 0)
     ///       .for_each(|(i, x)| println!("{i}:{x}"));
diff --git a/library/core/src/macros/mod.rs b/library/core/src/macros/mod.rs
index 3d57da63683..c59290a757b 100644
--- a/library/core/src/macros/mod.rs
+++ b/library/core/src/macros/mod.rs
@@ -271,7 +271,10 @@ pub macro cfg_select($($tt:tt)*) {
 /// // expression given.
 /// debug_assert!(true);
 ///
-/// fn some_expensive_computation() -> bool { true } // a very simple function
+/// fn some_expensive_computation() -> bool {
+///     // Some expensive computation here
+///     true
+/// }
 /// debug_assert!(some_expensive_computation());
 ///
 /// // assert with a custom message
@@ -1547,7 +1550,10 @@ pub(crate) mod builtin {
     /// // expression given.
     /// assert!(true);
     ///
-    /// fn some_computation() -> bool { true } // a very simple function
+    /// fn some_computation() -> bool {
+    ///     // Some expensive computation here
+    ///     true
+    /// }
     ///
     /// assert!(some_computation());
     ///
diff --git a/library/core/src/marker.rs b/library/core/src/marker.rs
index 45277a1c82d..ba00ee17b65 100644
--- a/library/core/src/marker.rs
+++ b/library/core/src/marker.rs
@@ -138,8 +138,7 @@ unsafe impl<T: Sync + PointeeSized> Send for &T {}
 /// impl Bar for Impl { }
 ///
 /// let x: &dyn Foo = &Impl;    // OK
-/// // let y: &dyn Bar = &Impl; // error: the trait `Bar` cannot
-///                             // be made into an object
+/// // let y: &dyn Bar = &Impl; // error: the trait `Bar` cannot be made into an object
 /// ```
 ///
 /// [trait object]: ../../book/ch17-02-trait-objects.html
diff --git a/library/core/src/mem/maybe_uninit.rs b/library/core/src/mem/maybe_uninit.rs
index 34d8370da7e..c160360cfac 100644
--- a/library/core/src/mem/maybe_uninit.rs
+++ b/library/core/src/mem/maybe_uninit.rs
@@ -773,8 +773,7 @@ impl<T> MaybeUninit<T> {
     /// // Initialize the `MaybeUninit` using `Cell::set`:
     /// unsafe {
     ///     b.assume_init_ref().set(true);
-    ///    // ^^^^^^^^^^^^^^^
-    ///    // Reference to an uninitialized `Cell<bool>`: UB!
+    ///     //^^^^^^^^^^^^^^^ Reference to an uninitialized `Cell<bool>`: UB!
     /// }
     /// ```
     #[stable(feature = "maybe_uninit_ref", since = "1.55.0")]
@@ -864,9 +863,9 @@ impl<T> MaybeUninit<T> {
     /// {
     ///     let mut buffer = MaybeUninit::<[u8; 64]>::uninit();
     ///     reader.read_exact(unsafe { buffer.assume_init_mut() })?;
-    ///                             // ^^^^^^^^^^^^^^^^^^^^^^^^
-    ///                             // (mutable) reference to uninitialized memory!
-    ///                             // This is undefined behavior.
+    ///     //                         ^^^^^^^^^^^^^^^^^^^^^^^^
+    ///     // (mutable) reference to uninitialized memory!
+    ///     // This is undefined behavior.
     ///     Ok(unsafe { buffer.assume_init() })
     /// }
     /// ```
@@ -884,13 +883,13 @@ impl<T> MaybeUninit<T> {
     /// let foo: Foo = unsafe {
     ///     let mut foo = MaybeUninit::<Foo>::uninit();
     ///     ptr::write(&mut foo.assume_init_mut().a as *mut u32, 1337);
-    ///                  // ^^^^^^^^^^^^^^^^^^^^^
-    ///                  // (mutable) reference to uninitialized memory!
-    ///                  // This is undefined behavior.
+    ///     //              ^^^^^^^^^^^^^^^^^^^^^
+    ///     // (mutable) reference to uninitialized memory!
+    ///     // This is undefined behavior.
     ///     ptr::write(&mut foo.assume_init_mut().b as *mut u8, 42);
-    ///                  // ^^^^^^^^^^^^^^^^^^^^^
-    ///                  // (mutable) reference to uninitialized memory!
-    ///                  // This is undefined behavior.
+    ///     //              ^^^^^^^^^^^^^^^^^^^^^
+    ///     // (mutable) reference to uninitialized memory!
+    ///     // This is undefined behavior.
     ///     foo.assume_init()
     /// };
     /// ```
diff --git a/library/core/src/num/niche_types.rs b/library/core/src/num/niche_types.rs
index b92561c9e35..d57b1d433e5 100644
--- a/library/core/src/num/niche_types.rs
+++ b/library/core/src/num/niche_types.rs
@@ -46,11 +46,11 @@ macro_rules! define_valid_range_type {
             /// primitive without checking whether its zero.
             ///
             /// # Safety
-            /// Immediate language UB if `val == 0`, as it violates the validity
-            /// invariant of this type.
+            /// Immediate language UB if `val` is not within the valid range for this
+            /// type, as it violates the validity invariant.
             #[inline]
             pub const unsafe fn new_unchecked(val: $int) -> Self {
-                // SAFETY: Caller promised that `val` is non-zero.
+                // SAFETY: Caller promised that `val` is within the valid range.
                 unsafe { $name(val) }
             }
 
diff --git a/library/core/src/primitive_docs.rs b/library/core/src/primitive_docs.rs
index 9a1ba7d1728..1c824e336be 100644
--- a/library/core/src/primitive_docs.rs
+++ b/library/core/src/primitive_docs.rs
@@ -271,6 +271,7 @@ mod prim_bool {}
 /// When the compiler sees a value of type `!` in a [coercion site], it implicitly inserts a
 /// coercion to allow the type checker to infer any type:
 ///
+// FIXME: use `core::convert::absurd` here instead, once it's merged
 /// ```rust,ignore (illustrative-and-has-placeholders)
 /// // this
 /// let x: u8 = panic!();
@@ -281,7 +282,6 @@ mod prim_bool {}
 /// // where absurd is a function with the following signature
 /// // (it's sound, because `!` always marks unreachable code):
 /// fn absurd<T>(_: !) -> T { ... }
-// FIXME: use `core::convert::absurd` here instead, once it's merged
 /// ```
 ///
 /// This can lead to compilation errors if the type cannot be inferred:
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/result.rs b/library/core/src/result.rs
index f65257ff59b..474f86395ae 100644
--- a/library/core/src/result.rs
+++ b/library/core/src/result.rs
@@ -534,6 +534,7 @@
 #![stable(feature = "rust1", since = "1.0.0")]
 
 use crate::iter::{self, FusedIterator, TrustedLen};
+use crate::marker::Destruct;
 use crate::ops::{self, ControlFlow, Deref, DerefMut};
 use crate::{convert, fmt, hint};
 
@@ -606,7 +607,13 @@ impl<T, E> Result<T, E> {
     #[must_use]
     #[inline]
     #[stable(feature = "is_some_and", since = "1.70.0")]
-    pub fn is_ok_and(self, f: impl FnOnce(T) -> bool) -> bool {
+    #[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
+    pub const fn is_ok_and<F>(self, f: F) -> bool
+    where
+        F: ~const FnOnce(T) -> bool + ~const Destruct,
+        T: ~const Destruct,
+        E: ~const Destruct,
+    {
         match self {
             Err(_) => false,
             Ok(x) => f(x),
@@ -655,7 +662,13 @@ impl<T, E> Result<T, E> {
     #[must_use]
     #[inline]
     #[stable(feature = "is_some_and", since = "1.70.0")]
-    pub fn is_err_and(self, f: impl FnOnce(E) -> bool) -> bool {
+    #[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
+    pub const fn is_err_and<F>(self, f: F) -> bool
+    where
+        F: ~const FnOnce(E) -> bool + ~const Destruct,
+        E: ~const Destruct,
+        T: ~const Destruct,
+    {
         match self {
             Ok(_) => false,
             Err(e) => f(e),
@@ -682,8 +695,13 @@ impl<T, E> Result<T, E> {
     /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
     #[rustc_diagnostic_item = "result_ok_method"]
-    pub fn ok(self) -> Option<T> {
+    pub const fn ok(self) -> Option<T>
+    where
+        T: ~const Destruct,
+        E: ~const Destruct,
+    {
         match self {
             Ok(x) => Some(x),
             Err(_) => None,
@@ -706,7 +724,12 @@ impl<T, E> Result<T, E> {
     /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn err(self) -> Option<E> {
+    #[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
+    pub const fn err(self) -> Option<E>
+    where
+        T: ~const Destruct,
+        E: ~const Destruct,
+    {
         match self {
             Ok(_) => None,
             Err(x) => Some(x),
@@ -796,7 +819,11 @@ impl<T, E> Result<T, E> {
     /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn map<U, F: FnOnce(T) -> U>(self, op: F) -> Result<U, E> {
+    #[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
+    pub const fn map<U, F>(self, op: F) -> Result<U, E>
+    where
+        F: ~const FnOnce(T) -> U + ~const Destruct,
+    {
         match self {
             Ok(t) => Ok(op(t)),
             Err(e) => Err(e),
@@ -823,8 +850,15 @@ impl<T, E> Result<T, E> {
     /// ```
     #[inline]
     #[stable(feature = "result_map_or", since = "1.41.0")]
+    #[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
     #[must_use = "if you don't need the returned value, use `if let` instead"]
-    pub fn map_or<U, F: FnOnce(T) -> U>(self, default: U, f: F) -> U {
+    pub const fn map_or<U, F>(self, default: U, f: F) -> U
+    where
+        F: ~const FnOnce(T) -> U + ~const Destruct,
+        T: ~const Destruct,
+        E: ~const Destruct,
+        U: ~const Destruct,
+    {
         match self {
             Ok(t) => f(t),
             Err(_) => default,
@@ -851,7 +885,12 @@ impl<T, E> Result<T, E> {
     /// ```
     #[inline]
     #[stable(feature = "result_map_or_else", since = "1.41.0")]
-    pub fn map_or_else<U, D: FnOnce(E) -> U, F: FnOnce(T) -> U>(self, default: D, f: F) -> U {
+    #[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
+    pub const fn map_or_else<U, D, F>(self, default: D, f: F) -> U
+    where
+        D: ~const FnOnce(E) -> U + ~const Destruct,
+        F: ~const FnOnce(T) -> U + ~const Destruct,
+    {
         match self {
             Ok(t) => f(t),
             Err(e) => default(e),
@@ -877,10 +916,13 @@ impl<T, E> Result<T, E> {
     /// [default value]: Default::default
     #[inline]
     #[unstable(feature = "result_option_map_or_default", issue = "138099")]
-    pub fn map_or_default<U, F>(self, f: F) -> U
+    #[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
+    pub const fn map_or_default<U, F>(self, f: F) -> U
     where
-        U: Default,
-        F: FnOnce(T) -> U,
+        F: ~const FnOnce(T) -> U + ~const Destruct,
+        U: ~const Default,
+        T: ~const Destruct,
+        E: ~const Destruct,
     {
         match self {
             Ok(t) => f(t),
@@ -908,7 +950,11 @@ impl<T, E> Result<T, E> {
     /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn map_err<F, O: FnOnce(E) -> F>(self, op: O) -> Result<T, F> {
+    #[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
+    pub const fn map_err<F, O>(self, op: O) -> Result<T, F>
+    where
+        O: ~const FnOnce(E) -> F + ~const Destruct,
+    {
         match self {
             Ok(t) => Ok(t),
             Err(e) => Err(op(e)),
@@ -930,7 +976,11 @@ impl<T, E> Result<T, E> {
     /// ```
     #[inline]
     #[stable(feature = "result_option_inspect", since = "1.76.0")]
-    pub fn inspect<F: FnOnce(&T)>(self, f: F) -> Self {
+    #[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
+    pub const fn inspect<F>(self, f: F) -> Self
+    where
+        F: ~const FnOnce(&T) + ~const Destruct,
+    {
         if let Ok(ref t) = self {
             f(t);
         }
@@ -954,7 +1004,11 @@ impl<T, E> Result<T, E> {
     /// ```
     #[inline]
     #[stable(feature = "result_option_inspect", since = "1.76.0")]
-    pub fn inspect_err<F: FnOnce(&E)>(self, f: F) -> Self {
+    #[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
+    pub const fn inspect_err<F>(self, f: F) -> Self
+    where
+        F: ~const FnOnce(&E) + ~const Destruct,
+    {
         if let Err(ref e) = self {
             f(e);
         }
@@ -1033,7 +1087,8 @@ impl<T, E> Result<T, E> {
     /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn iter(&self) -> Iter<'_, T> {
+    #[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
+    pub const fn iter(&self) -> Iter<'_, T> {
         Iter { inner: self.as_ref().ok() }
     }
 
@@ -1056,7 +1111,8 @@ impl<T, E> Result<T, E> {
     /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn iter_mut(&mut self) -> IterMut<'_, T> {
+    #[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
+    pub const fn iter_mut(&mut self) -> IterMut<'_, T> {
         IterMut { inner: self.as_mut().ok() }
     }
 
@@ -1195,9 +1251,11 @@ impl<T, E> Result<T, E> {
     /// [`FromStr`]: crate::str::FromStr
     #[inline]
     #[stable(feature = "result_unwrap_or_default", since = "1.16.0")]
-    pub fn unwrap_or_default(self) -> T
+    #[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
+    pub const fn unwrap_or_default(self) -> T
     where
-        T: Default,
+        T: ~const Default + ~const Destruct,
+        E: ~const Destruct,
     {
         match self {
             Ok(x) => x,
@@ -1370,7 +1428,13 @@ impl<T, E> Result<T, E> {
     /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn and<U>(self, res: Result<U, E>) -> Result<U, E> {
+    #[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
+    pub const fn and<U>(self, res: Result<U, E>) -> Result<U, E>
+    where
+        T: ~const Destruct,
+        E: ~const Destruct,
+        U: ~const Destruct,
+    {
         match self {
             Ok(_) => res,
             Err(e) => Err(e),
@@ -1409,8 +1473,12 @@ impl<T, E> Result<T, E> {
     /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
     #[rustc_confusables("flat_map", "flatmap")]
-    pub fn and_then<U, F: FnOnce(T) -> Result<U, E>>(self, op: F) -> Result<U, E> {
+    pub const fn and_then<U, F>(self, op: F) -> Result<U, E>
+    where
+        F: ~const FnOnce(T) -> Result<U, E> + ~const Destruct,
+    {
         match self {
             Ok(t) => op(t),
             Err(e) => Err(e),
@@ -1446,7 +1514,13 @@ impl<T, E> Result<T, E> {
     /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn or<F>(self, res: Result<T, F>) -> Result<T, F> {
+    #[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
+    pub const fn or<F>(self, res: Result<T, F>) -> Result<T, F>
+    where
+        T: ~const Destruct,
+        E: ~const Destruct,
+        F: ~const Destruct,
+    {
         match self {
             Ok(v) => Ok(v),
             Err(_) => res,
@@ -1471,7 +1545,11 @@ impl<T, E> Result<T, E> {
     /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn or_else<F, O: FnOnce(E) -> Result<T, F>>(self, op: O) -> Result<T, F> {
+    #[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
+    pub const fn or_else<F, O>(self, op: O) -> Result<T, F>
+    where
+        O: ~const FnOnce(E) -> Result<T, F> + ~const Destruct,
+    {
         match self {
             Ok(t) => Ok(t),
             Err(e) => op(e),
@@ -1498,7 +1576,12 @@ impl<T, E> Result<T, E> {
     /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn unwrap_or(self, default: T) -> T {
+    #[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
+    pub const fn unwrap_or(self, default: T) -> T
+    where
+        T: ~const Destruct,
+        E: ~const Destruct,
+    {
         match self {
             Ok(t) => t,
             Err(_) => default,
@@ -1519,7 +1602,11 @@ impl<T, E> Result<T, E> {
     #[inline]
     #[track_caller]
     #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn unwrap_or_else<F: FnOnce(E) -> T>(self, op: F) -> T {
+    #[rustc_const_unstable(feature = "const_result_trait_fn", issue = "144211")]
+    pub const fn unwrap_or_else<F>(self, op: F) -> T
+    where
+        F: ~const FnOnce(E) -> T + ~const Destruct,
+    {
         match self {
             Ok(t) => t,
             Err(e) => op(e),
@@ -1544,7 +1631,7 @@ impl<T, E> Result<T, E> {
     ///
     /// ```no_run
     /// let x: Result<u32, &str> = Err("emergency failure");
-    /// unsafe { x.unwrap_unchecked(); } // Undefined behavior!
+    /// unsafe { x.unwrap_unchecked() }; // Undefined behavior!
     /// ```
     #[inline]
     #[track_caller]
@@ -1762,7 +1849,7 @@ impl<T, E> Result<Result<T, E>, E> {
 #[cold]
 #[track_caller]
 fn unwrap_failed(msg: &str, error: &dyn fmt::Debug) -> ! {
-    panic!("{msg}: {error:?}")
+    panic!("{msg}: {error:?}");
 }
 
 // This is a separate function to avoid constructing a `dyn Debug`
@@ -1773,7 +1860,7 @@ fn unwrap_failed(msg: &str, error: &dyn fmt::Debug) -> ! {
 #[inline]
 #[cold]
 #[track_caller]
-fn unwrap_failed<T>(_msg: &str, _error: &T) -> ! {
+const fn unwrap_failed<T>(_msg: &str, _error: &T) -> ! {
     panic!()
 }
 
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