Merging upstream version 1.72.1+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

57 files changed, 992 insertions, 339 deletions

diff --git a/library/core/benches/iter.rs b/library/core/benches/iter.rs
index 60ef83223..5ec22e514 100644
--- a/library/core/benches/iter.rs
+++ b/library/core/benches/iter.rs
@@ -2,6 +2,7 @@ use core::borrow::Borrow;
 use core::iter::*;
 use core::mem;
 use core::num::Wrapping;
+use core::ops::Range;
 use test::{black_box, Bencher};
 
 #[bench]
@@ -69,6 +70,57 @@ fn bench_max(b: &mut Bencher) {
     })
 }
 
+#[bench]
+fn bench_range_step_by_sum_reducible(b: &mut Bencher) {
+    let r = 0u32..1024;
+    b.iter(|| {
+        let r = black_box(r.clone()).step_by(8);
+
+        let mut sum: u32 = 0;
+        for i in r {
+            sum += i;
+        }
+
+        sum
+    })
+}
+
+#[bench]
+fn bench_range_step_by_loop_u32(b: &mut Bencher) {
+    let r = 0..(u16::MAX as u32);
+    b.iter(|| {
+        let r = black_box(r.clone()).step_by(64);
+
+        let mut sum: u32 = 0;
+        for i in r {
+            let i = i ^ i.wrapping_sub(1);
+            sum = sum.wrapping_add(i);
+        }
+
+        sum
+    })
+}
+
+#[bench]
+fn bench_range_step_by_fold_usize(b: &mut Bencher) {
+    let r: Range<usize> = 0..(u16::MAX as usize);
+    b.iter(|| {
+        let r = black_box(r.clone());
+        r.step_by(64)
+            .map(|x: usize| x ^ (x.wrapping_sub(1)))
+            .fold(0usize, |acc, i| acc.wrapping_add(i))
+    })
+}
+
+#[bench]
+fn bench_range_step_by_fold_u16(b: &mut Bencher) {
+    let r: Range<u16> = 0..u16::MAX;
+    b.iter(|| {
+        let r = black_box(r.clone());
+        r.step_by(64).map(|x: u16| x ^ (x.wrapping_sub(1))).fold(0u16, |acc, i| acc.wrapping_add(i))
+    })
+}
+
 pub fn copy_zip(xs: &[u8], ys: &mut [u8]) {
     for (a, b) in ys.iter_mut().zip(xs) {
         *a = *b;
diff --git a/library/core/benches/slice.rs b/library/core/benches/slice.rs
index 9b86a0ca9..3bfb35e68 100644
--- a/library/core/benches/slice.rs
+++ b/library/core/benches/slice.rs
@@ -1,3 +1,4 @@
+use core::ptr::NonNull;
 use test::black_box;
 use test::Bencher;
 
@@ -162,3 +163,11 @@ fn fill_byte_sized(b: &mut Bencher) {
         black_box(slice.fill(black_box(NewType(42))));
     });
 }
+
+// Tests the ability of the compiler to recognize that only the last slice item is needed
+// based on issue #106288
+#[bench]
+fn fold_to_last(b: &mut Bencher) {
+    let slice: &[i32] = &[0; 1024];
+    b.iter(|| black_box(slice).iter().fold(None, |_, r| Some(NonNull::from(r))));
+}
diff --git a/library/core/src/alloc/mod.rs b/library/core/src/alloc/mod.rs
index d6ae2b821..78091c017 100644
--- a/library/core/src/alloc/mod.rs
+++ b/library/core/src/alloc/mod.rs
@@ -94,8 +94,9 @@ impl fmt::Display for AllocError {
 ///
 /// # Safety
 ///
-/// * Memory blocks returned from an allocator must point to valid memory and retain their validity
-///   until the instance and all of its copies and clones are dropped,
+/// * Memory blocks returned from an allocator that are [*currently allocated*] must point to
+///   valid memory and retain their validity while they are [*currently allocated*] and at
+///   least one of the instance and all of its clones has not been dropped.
 ///
 /// * copying, cloning, or moving the allocator must not invalidate memory blocks returned from this
 ///   allocator. A copied or cloned allocator must behave like the same allocator, and
diff --git a/library/core/src/any.rs b/library/core/src/any.rs
index 7969f4055..09f52d692 100644
--- a/library/core/src/any.rs
+++ b/library/core/src/any.rs
@@ -153,6 +153,7 @@
 #![stable(feature = "rust1", since = "1.0.0")]
 
 use crate::fmt;
+use crate::hash;
 use crate::intrinsics;
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -662,10 +663,10 @@ impl dyn Any + Send + Sync {
 /// While `TypeId` implements `Hash`, `PartialOrd`, and `Ord`, it is worth
 /// noting that the hashes and ordering will vary between Rust releases. Beware
 /// of relying on them inside of your code!
-#[derive(Clone, Copy, Debug, Hash, Eq, PartialOrd, Ord)]
+#[derive(Clone, Copy, Debug, Eq, PartialOrd, Ord)]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct TypeId {
-    t: u64,
+    t: u128,
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -696,7 +697,31 @@ impl TypeId {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_const_unstable(feature = "const_type_id", issue = "77125")]
     pub const fn of<T: ?Sized + 'static>() -> TypeId {
-        TypeId { t: intrinsics::type_id::<T>() }
+        #[cfg(bootstrap)]
+        let t = intrinsics::type_id::<T>() as u128;
+        #[cfg(not(bootstrap))]
+        let t: u128 = intrinsics::type_id::<T>();
+        TypeId { t }
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl hash::Hash for TypeId {
+    #[inline]
+    fn hash<H: hash::Hasher>(&self, state: &mut H) {
+        // We only hash the lower 64 bits of our (128 bit) internal numeric ID,
+        // because:
+        // - The hashing algorithm which backs `TypeId` is expected to be
+        //   unbiased and high quality, meaning further mixing would be somewhat
+        //   redundant compared to choosing (the lower) 64 bits arbitrarily.
+        // - `Hasher::finish` returns a u64 anyway, so the extra entropy we'd
+        //   get from hashing the full value would probably not be useful
+        //   (especially given the previous point about the lower 64 bits being
+        //   high quality on their own).
+        // - It is correct to do so -- only hashing a subset of `self` is still
+        //   with an `Eq` implementation that considers the entire value, as
+        //   ours does.
+        (self.t as u64).hash(state);
     }
 }
 
diff --git a/library/core/src/array/mod.rs b/library/core/src/array/mod.rs
index fec92320a..76b3589b9 100644
--- a/library/core/src/array/mod.rs
+++ b/library/core/src/array/mod.rs
@@ -538,29 +538,6 @@ impl<T, const N: usize> [T; N] {
         drain_array_with(self, |iter| try_from_trusted_iterator(iter.map(f)))
     }
 
-    /// 'Zips up' two arrays into a single array of pairs.
-    ///
-    /// `zip()` returns a new array where every element is a tuple where the
-    /// first element comes from the first array, and the second element comes
-    /// from the second array. In other words, it zips two arrays together,
-    /// into a single one.
-    ///
-    /// # Examples
-    ///
-    /// ```
-    /// #![feature(array_zip)]
-    /// let x = [1, 2, 3];
-    /// let y = [4, 5, 6];
-    /// let z = x.zip(y);
-    /// assert_eq!(z, [(1, 4), (2, 5), (3, 6)]);
-    /// ```
-    #[unstable(feature = "array_zip", issue = "80094")]
-    pub fn zip<U>(self, rhs: [U; N]) -> [(T, U); N] {
-        drain_array_with(self, |lhs| {
-            drain_array_with(rhs, |rhs| from_trusted_iterator(crate::iter::zip(lhs, rhs)))
-        })
-    }
-
     /// Returns a slice containing the entire array. Equivalent to `&s[..]`.
     #[stable(feature = "array_as_slice", since = "1.57.0")]
     #[rustc_const_stable(feature = "array_as_slice", since = "1.57.0")]
diff --git a/library/core/src/cell.rs b/library/core/src/cell.rs
index 744767aae..909b32547 100644
--- a/library/core/src/cell.rs
+++ b/library/core/src/cell.rs
@@ -59,7 +59,7 @@
 //! [`borrow`](`RefCell::borrow`), and a mutable borrow (`&mut T`) can be obtained with
 //! [`borrow_mut`](`RefCell::borrow_mut`). When these functions are called, they first verify that
 //! Rust's borrow rules will be satisfied: any number of immutable borrows are allowed or a
-//! single immutable borrow is allowed, but never both. If a borrow is attempted that would violate
+//! single mutable borrow is allowed, but never both. If a borrow is attempted that would violate
 //! these rules, the thread will panic.
 //!
 //! The corresponding [`Sync`] version of `RefCell<T>` is [`RwLock<T>`].
@@ -1374,7 +1374,7 @@ impl Clone for BorrowRef<'_> {
         debug_assert!(is_reading(borrow));
         // Prevent the borrow counter from overflowing into
         // a writing borrow.
-        assert!(borrow != isize::MAX);
+        assert!(borrow != BorrowFlag::MAX);
         self.borrow.set(borrow + 1);
         BorrowRef { borrow: self.borrow }
     }
@@ -1756,7 +1756,7 @@ impl<'b> BorrowRefMut<'b> {
         let borrow = self.borrow.get();
         debug_assert!(is_writing(borrow));
         // Prevent the borrow counter from underflowing.
-        assert!(borrow != isize::MIN);
+        assert!(borrow != BorrowFlag::MIN);
         self.borrow.set(borrow - 1);
         BorrowRefMut { borrow: self.borrow }
     }
diff --git a/library/core/src/convert/mod.rs b/library/core/src/convert/mod.rs
index 38a6d1ccd..ff5a4c913 100644
--- a/library/core/src/convert/mod.rs
+++ b/library/core/src/convert/mod.rs
@@ -495,8 +495,7 @@ pub trait Into<T>: Sized {
 /// By converting underlying error types to our own custom error type that encapsulates the
 /// underlying error type, we can return a single error type without losing information on the
 /// underlying cause. The '?' operator automatically converts the underlying error type to our
-/// custom error type by calling `Into<CliError>::into` which is automatically provided when
-/// implementing `From`. The compiler then infers which implementation of `Into` should be used.
+/// custom error type with `From::from`.
 ///
 /// ```
 /// use std::fs;
@@ -533,7 +532,7 @@ pub trait Into<T>: Sized {
 #[rustc_diagnostic_item = "From"]
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_on_unimplemented(on(
-    all(_Self = "&str", T = "std::string::String"),
+    all(_Self = "&str", any(T = "alloc::string::String", T = "std::string::String")),
     note = "to coerce a `{T}` into a `{Self}`, use `&*` as a prefix",
 ))]
 pub trait From<T>: Sized {
diff --git a/library/core/src/default.rs b/library/core/src/default.rs
index 09dbc9581..1f7be85d3 100644
--- a/library/core/src/default.rs
+++ b/library/core/src/default.rs
@@ -190,7 +190,7 @@ macro_rules! default_impl {
     ($t:ty, $v:expr, $doc:tt) => {
         #[stable(feature = "rust1", since = "1.0.0")]
         impl Default for $t {
-            #[inline]
+            #[inline(always)]
             #[doc = $doc]
             fn default() -> $t {
                 $v
diff --git a/library/core/src/ffi/c_str.rs b/library/core/src/ffi/c_str.rs
index e1e1a9b40..39f795c1f 100644
--- a/library/core/src/ffi/c_str.rs
+++ b/library/core/src/ffi/c_str.rs
@@ -81,7 +81,7 @@ use crate::str;
 #[derive(Hash)]
 #[stable(feature = "core_c_str", since = "1.64.0")]
 #[rustc_has_incoherent_inherent_impls]
-#[cfg_attr(not(bootstrap), lang = "CStr")]
+#[lang = "CStr"]
 // FIXME:
 // `fn from` in `impl From<&CStr> for Box<CStr>` current implementation relies
 // on `CStr` being layout-compatible with `[u8]`.
@@ -241,7 +241,7 @@ impl CStr {
     /// ```
     ///
     /// ```
-    /// #![feature(const_cstr_methods)]
+    /// #![feature(const_cstr_from_ptr)]
     ///
     /// use std::ffi::{c_char, CStr};
     ///
@@ -256,7 +256,7 @@ impl CStr {
     #[inline]
     #[must_use]
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_const_unstable(feature = "const_cstr_methods", issue = "101719")]
+    #[rustc_const_unstable(feature = "const_cstr_from_ptr", issue = "101719")]
     pub const unsafe fn from_ptr<'a>(ptr: *const c_char) -> &'a CStr {
         // SAFETY: The caller has provided a pointer that points to a valid C
         // string with a NUL terminator of size less than `isize::MAX`, whose
@@ -377,7 +377,7 @@ impl CStr {
     /// assert!(cstr.is_err());
     /// ```
     #[stable(feature = "cstr_from_bytes", since = "1.10.0")]
-    #[rustc_const_unstable(feature = "const_cstr_methods", issue = "101719")]
+    #[rustc_const_stable(feature = "const_cstr_methods", since = "1.72.0")]
     pub const fn from_bytes_with_nul(bytes: &[u8]) -> Result<&Self, FromBytesWithNulError> {
         let nul_pos = memchr::memchr(0, bytes);
         match nul_pos {
@@ -561,10 +561,12 @@ impl CStr {
     #[must_use = "this returns the result of the operation, \
                   without modifying the original"]
     #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn to_bytes(&self) -> &[u8] {
+    #[rustc_const_stable(feature = "const_cstr_methods", since = "1.72.0")]
+    pub const fn to_bytes(&self) -> &[u8] {
         let bytes = self.to_bytes_with_nul();
+        // FIXME(const-hack) replace with range index
         // SAFETY: to_bytes_with_nul returns slice with length at least 1
-        unsafe { bytes.get_unchecked(..bytes.len() - 1) }
+        unsafe { slice::from_raw_parts(bytes.as_ptr(), bytes.len() - 1) }
     }
 
     /// Converts this C string to a byte slice containing the trailing 0 byte.
@@ -588,7 +590,7 @@ impl CStr {
     #[must_use = "this returns the result of the operation, \
                   without modifying the original"]
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_const_unstable(feature = "const_cstr_methods", issue = "101719")]
+    #[rustc_const_stable(feature = "const_cstr_methods", since = "1.72.0")]
     pub const fn to_bytes_with_nul(&self) -> &[u8] {
         // SAFETY: Transmuting a slice of `c_char`s to a slice of `u8`s
         // is safe on all supported targets.
@@ -612,7 +614,8 @@ impl CStr {
     /// assert_eq!(cstr.to_str(), Ok("foo"));
     /// ```
     #[stable(feature = "cstr_to_str", since = "1.4.0")]
-    pub fn to_str(&self) -> Result<&str, str::Utf8Error> {
+    #[rustc_const_stable(feature = "const_cstr_methods", since = "1.72.0")]
+    pub const fn to_str(&self) -> Result<&str, str::Utf8Error> {
         // N.B., when `CStr` is changed to perform the length check in `.to_bytes()`
         // instead of in `from_ptr()`, it may be worth considering if this should
         // be rewritten to do the UTF-8 check inline with the length calculation
diff --git a/library/core/src/ffi/mod.rs b/library/core/src/ffi/mod.rs
index b73abbbac..0488c8076 100644
--- a/library/core/src/ffi/mod.rs
+++ b/library/core/src/ffi/mod.rs
@@ -132,7 +132,12 @@ mod c_char_definition {
             ),
             all(
                 target_os = "netbsd",
-                any(target_arch = "aarch64", target_arch = "arm", target_arch = "powerpc")
+                any(
+                    target_arch = "aarch64",
+                    target_arch = "arm",
+                    target_arch = "powerpc",
+                    target_arch = "riscv64"
+                )
             ),
             all(
                 target_os = "vxworks",
@@ -202,7 +207,7 @@ mod c_long_definition {
 //     would be uninhabited and at least dereferencing such pointers would
 //     be UB.
 #[doc = include_str!("c_void.md")]
-#[cfg_attr(not(bootstrap), lang = "c_void")]
+#[lang = "c_void"]
 #[cfg_attr(not(doc), repr(u8))] // work around https://github.com/rust-lang/rust/issues/90435
 #[stable(feature = "core_c_void", since = "1.30.0")]
 pub enum c_void {
@@ -238,7 +243,7 @@ impl fmt::Debug for c_void {
         not(target_arch = "s390x"),
         not(target_arch = "x86_64")
     ),
-    all(target_arch = "aarch64", any(target_os = "macos", target_os = "ios")),
+    all(target_arch = "aarch64", any(target_os = "macos", target_os = "ios", target_os = "tvos")),
     target_family = "wasm",
     target_arch = "asmjs",
     target_os = "uefi",
@@ -267,7 +272,7 @@ pub struct VaListImpl<'f> {
         not(target_arch = "s390x"),
         not(target_arch = "x86_64")
     ),
-    all(target_arch = "aarch64", any(target_os = "macos", target_os = "ios")),
+    all(target_arch = "aarch64", any(target_os = "macos", target_os = "ios", target_os = "tvos")),
     target_family = "wasm",
     target_arch = "asmjs",
     target_os = "uefi",
@@ -292,7 +297,7 @@ impl<'f> fmt::Debug for VaListImpl<'f> {
 /// http://infocenter.arm.com/help/topic/com.arm.doc.ihi0055b/IHI0055B_aapcs64.pdf
 #[cfg(all(
     target_arch = "aarch64",
-    not(any(target_os = "macos", target_os = "ios")),
+    not(any(target_os = "macos", target_os = "ios", target_os = "tvos")),
     not(target_os = "uefi"),
     not(windows),
 ))]
@@ -389,7 +394,10 @@ pub struct VaList<'a, 'f: 'a> {
             not(target_arch = "s390x"),
             not(target_arch = "x86_64")
         ),
-        all(target_arch = "aarch64", any(target_os = "macos", target_os = "ios")),
+        all(
+            target_arch = "aarch64",
+            any(target_os = "macos", target_os = "ios", target_os = "tvos")
+        ),
         target_family = "wasm",
         target_arch = "asmjs",
         target_os = "uefi",
@@ -404,7 +412,10 @@ pub struct VaList<'a, 'f: 'a> {
             target_arch = "s390x",
             target_arch = "x86_64"
         ),
-        any(not(target_arch = "aarch64"), not(any(target_os = "macos", target_os = "ios"))),
+        any(
+            not(target_arch = "aarch64"),
+            not(any(target_os = "macos", target_os = "ios", target_os = "tvos"))
+        ),
         not(target_family = "wasm"),
         not(target_arch = "asmjs"),
         not(target_os = "uefi"),
@@ -422,7 +433,7 @@ pub struct VaList<'a, 'f: 'a> {
         not(target_arch = "s390x"),
         not(target_arch = "x86_64")
     ),
-    all(target_arch = "aarch64", any(target_os = "macos", target_os = "ios")),
+    all(target_arch = "aarch64", any(target_os = "macos", target_os = "ios", target_os = "tvos")),
     target_family = "wasm",
     target_arch = "asmjs",
     target_os = "uefi",
@@ -449,7 +460,10 @@ impl<'f> VaListImpl<'f> {
         target_arch = "s390x",
         target_arch = "x86_64"
     ),
-    any(not(target_arch = "aarch64"), not(any(target_os = "macos", target_os = "ios"))),
+    any(
+        not(target_arch = "aarch64"),
+        not(any(target_os = "macos", target_os = "ios", target_os = "tvos"))
+    ),
     not(target_family = "wasm"),
     not(target_arch = "asmjs"),
     not(target_os = "uefi"),
diff --git a/library/core/src/future/poll_fn.rs b/library/core/src/future/poll_fn.rs
index 90cb79739..d27a9dfc1 100644
--- a/library/core/src/future/poll_fn.rs
+++ b/library/core/src/future/poll_fn.rs
@@ -24,6 +24,93 @@ use crate::task::{Context, Poll};
 /// assert_eq!(read_future.await, "Hello, World!".to_owned());
 /// # }
 /// ```
+///
+/// ## Capturing a pinned state
+///
+/// Example of a closure wrapping inner futures:
+///
+/// ```
+/// # async fn run() {
+/// use core::future::{self, Future};
+/// use core::task::Poll;
+///
+/// /// Resolves to the first future that completes. In the event of a tie, `a` wins.
+/// fn naive_select<T>(
+///     a: impl Future<Output = T>,
+///     b: impl Future<Output = T>,
+/// ) -> impl Future<Output = T>
+/// {
+///     let (mut a, mut b) = (Box::pin(a), Box::pin(b));
+///     future::poll_fn(move |cx| {
+///         if let Poll::Ready(r) = a.as_mut().poll(cx) {
+///             Poll::Ready(r)
+///         } else if let Poll::Ready(r) = b.as_mut().poll(cx) {
+///             Poll::Ready(r)
+///         } else {
+///             Poll::Pending
+///         }
+///     })
+/// }
+///
+/// let a = async { 42 };
+/// let b = future::pending();
+/// let v = naive_select(a, b).await;
+/// assert_eq!(v, 42);
+///
+/// let a = future::pending();
+/// let b = async { 27 };
+/// let v = naive_select(a, b).await;
+/// assert_eq!(v, 27);
+///
+/// let a = async { 42 };
+/// let b = async { 27 };
+/// let v = naive_select(a, b).await;
+/// assert_eq!(v, 42); // biased towards `a` in case of tie!
+/// # }
+/// ```
+///
+/// This time without [`Box::pin`]ning:
+///
+/// [`Box::pin`]: ../../std/boxed/struct.Box.html#method.pin
+///
+/// ```
+/// # async fn run() {
+/// use core::future::{self, Future};
+/// use core::pin::pin;
+/// use core::task::Poll;
+///
+/// /// Resolves to the first future that completes. In the event of a tie, `a` wins.
+/// fn naive_select<T>(
+///     a: impl Future<Output = T>,
+///     b: impl Future<Output = T>,
+/// ) -> impl Future<Output = T>
+/// {
+///     async {
+///         let (mut a, mut b) = (pin!(a), pin!(b));
+///         future::poll_fn(move |cx| {
+///             if let Poll::Ready(r) = a.as_mut().poll(cx) {
+///                 Poll::Ready(r)
+///             } else if let Poll::Ready(r) = b.as_mut().poll(cx) {
+///                 Poll::Ready(r)
+///             } else {
+///                 Poll::Pending
+///             }
+///         }).await
+///     }
+/// }
+///
+/// let a = async { 42 };
+/// let b = future::pending();
+/// let v = naive_select(a, b).await;
+/// assert_eq!(v, 42);
+/// # }
+/// ```
+///
+///   - Notice how, by virtue of being in an `async` context, we have been able to make the [`pin!`]
+///     macro work, thereby avoiding any need for the `unsafe`
+///     <code>[Pin::new_unchecked](&mut fut)</code> constructor.
+///
+/// [`pin!`]: crate::pin::pin!
 #[stable(feature = "future_poll_fn", since = "1.64.0")]
 pub fn poll_fn<T, F>(f: F) -> PollFn<F>
 where
diff --git a/library/core/src/intrinsics.rs b/library/core/src/intrinsics.rs
index f5c5dd29f..5a9a7013a 100644
--- a/library/core/src/intrinsics.rs
+++ b/library/core/src/intrinsics.rs
@@ -1057,8 +1057,25 @@ extern "rust-intrinsic" {
     #[rustc_const_unstable(feature = "const_type_id", issue = "77125")]
     #[rustc_safe_intrinsic]
     #[rustc_nounwind]
+    #[cfg(bootstrap)]
     pub fn type_id<T: ?Sized + 'static>() -> u64;
 
+    /// Gets an identifier which is globally unique to the specified type. This
+    /// function will return the same value for a type regardless of whichever
+    /// crate it is invoked in.
+    ///
+    /// Note that, unlike most intrinsics, this is safe to call;
+    /// it does not require an `unsafe` block.
+    /// Therefore, implementations must not require the user to uphold
+    /// any safety invariants.
+    ///
+    /// The stabilized version of this intrinsic is [`core::any::TypeId::of`].
+    #[rustc_const_unstable(feature = "const_type_id", issue = "77125")]
+    #[rustc_safe_intrinsic]
+    #[rustc_nounwind]
+    #[cfg(not(bootstrap))]
+    pub fn type_id<T: ?Sized + 'static>() -> u128;
+
     /// A guard for unsafe functions that cannot ever be executed if `T` is uninhabited:
     /// This will statically either panic, or do nothing.
     ///
@@ -1385,7 +1402,6 @@ extern "rust-intrinsic" {
     ///
     /// This is not expected to ever be exposed directly to users, rather it
     /// may eventually be exposed through some more-constrained API.
-    #[cfg(not(bootstrap))]
     #[rustc_const_stable(feature = "const_transmute", since = "1.56.0")]
     #[rustc_nounwind]
     pub fn transmute_unchecked<Src, Dst>(src: Src) -> Dst;
@@ -1425,19 +1441,11 @@ extern "rust-intrinsic" {
     /// returned value will result in undefined behavior.
     ///
     /// The stabilized version of this intrinsic is [`pointer::offset`].
-    #[cfg(not(bootstrap))]
     #[must_use = "returns a new pointer rather than modifying its argument"]
     #[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
     #[rustc_nounwind]
     pub fn offset<Ptr, Delta>(dst: Ptr, offset: Delta) -> Ptr;
 
-    /// The bootstrap version of this is more restricted.
-    #[cfg(bootstrap)]
-    #[must_use = "returns a new pointer rather than modifying its argument"]
-    #[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
-    #[rustc_nounwind]
-    pub fn offset<T>(dst: *const T, offset: isize) -> *const T;
-
     /// Calculates the offset from a pointer, potentially wrapping.
     ///
     /// This is implemented as an intrinsic to avoid converting to and from an
@@ -2270,7 +2278,6 @@ extern "rust-intrinsic" {
     /// This intrinsic can *only* be called where the pointer is a local without
     /// projections (`write_via_move(ptr, x)`, not `write_via_move(*ptr, x)`) so
     /// that it trivially obeys runtime-MIR rules about derefs in operands.
-    #[cfg(not(bootstrap))]
     #[rustc_const_unstable(feature = "const_ptr_write", issue = "86302")]
     #[rustc_nounwind]
     pub fn write_via_move<T>(ptr: *mut T, value: T);
@@ -2650,7 +2657,7 @@ pub(crate) fn is_nonoverlapping<T>(src: *const T, dst: *const T, count: usize) -
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_allowed_through_unstable_modules]
 #[rustc_const_stable(feature = "const_intrinsic_copy", since = "1.63.0")]
-#[inline]
+#[inline(always)]
 #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
 pub const unsafe fn copy_nonoverlapping<T>(src: *const T, dst: *mut T, count: usize) {
     extern "rust-intrinsic" {
@@ -2741,7 +2748,7 @@ pub const unsafe fn copy_nonoverlapping<T>(src: *const T, dst: *mut T, count: us
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_allowed_through_unstable_modules]
 #[rustc_const_stable(feature = "const_intrinsic_copy", since = "1.63.0")]
-#[inline]
+#[inline(always)]
 #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
 pub const unsafe fn copy<T>(src: *const T, dst: *mut T, count: usize) {
     extern "rust-intrinsic" {
@@ -2814,7 +2821,7 @@ pub const unsafe fn copy<T>(src: *const T, dst: *mut T, count: usize) {
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_allowed_through_unstable_modules]
 #[rustc_const_unstable(feature = "const_ptr_write", issue = "86302")]
-#[inline]
+#[inline(always)]
 #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
 pub const unsafe fn write_bytes<T>(dst: *mut T, val: u8, count: usize) {
     extern "rust-intrinsic" {
@@ -2832,24 +2839,3 @@ pub const unsafe fn write_bytes<T>(dst: *mut T, val: u8, count: usize) {
         write_bytes(dst, val, count)
     }
 }
-
-/// Polyfill for bootstrap
-#[cfg(bootstrap)]
-pub const unsafe fn transmute_unchecked<Src, Dst>(src: Src) -> Dst {
-    use crate::mem::*;
-    // SAFETY: It's a transmute -- the caller promised it's fine.
-    unsafe { transmute_copy(&ManuallyDrop::new(src)) }
-}
-
-/// Polyfill for bootstrap
-#[cfg(bootstrap)]
-pub const unsafe fn write_via_move<T>(ptr: *mut T, value: T) {
-    use crate::mem::*;
-    // SAFETY: the caller must guarantee that `dst` is valid for writes.
-    // `dst` cannot overlap `src` because the caller has mutable access
-    // to `dst` while `src` is owned by this function.
-    unsafe {
-        copy_nonoverlapping::<T>(&value, ptr, 1);
-        forget(value);
-    }
-}
diff --git a/library/core/src/iter/adapters/flatten.rs b/library/core/src/iter/adapters/flatten.rs
index 2568aaf34..d3e454563 100644
--- a/library/core/src/iter/adapters/flatten.rs
+++ b/library/core/src/iter/adapters/flatten.rs
@@ -310,7 +310,7 @@ where
 /// Real logic of both `Flatten` and `FlatMap` which simply delegate to
 /// this type.
 #[derive(Clone, Debug)]
-#[unstable(feature = "trusted_len", issue = "37572")]
+#[cfg_attr(bootstrap, unstable(feature = "trusted_len", issue = "37572"))]
 struct FlattenCompat<I, U> {
     iter: Fuse<I>,
     frontiter: Option<U>,
@@ -464,7 +464,7 @@ where
     }
 }
 
-#[unstable(feature = "trusted_len", issue = "37572")]
+#[cfg_attr(bootstrap, unstable(feature = "trusted_len", issue = "37572"))]
 impl<I, U> Iterator for FlattenCompat<I, U>
 where
     I: Iterator<Item: IntoIterator<IntoIter = U, Item = U::Item>>,
@@ -579,7 +579,7 @@ where
     }
 }
 
-#[unstable(feature = "trusted_len", issue = "37572")]
+#[cfg_attr(bootstrap, unstable(feature = "trusted_len", issue = "37572"))]
 impl<I, U> DoubleEndedIterator for FlattenCompat<I, U>
 where
     I: DoubleEndedIterator<Item: IntoIterator<IntoIter = U, Item = U::Item>>,
@@ -649,7 +649,7 @@ where
     }
 }
 
-#[unstable(feature = "trusted_len", issue = "37572")]
+#[cfg_attr(bootstrap, unstable(feature = "trusted_len", issue = "37572"))]
 unsafe impl<const N: usize, I, T> TrustedLen
     for FlattenCompat<I, <[T; N] as IntoIterator>::IntoIter>
 where
@@ -657,7 +657,7 @@ where
 {
 }
 
-#[unstable(feature = "trusted_len", issue = "37572")]
+#[cfg_attr(bootstrap, unstable(feature = "trusted_len", issue = "37572"))]
 unsafe impl<'a, const N: usize, I, T> TrustedLen
     for FlattenCompat<I, <&'a [T; N] as IntoIterator>::IntoIter>
 where
@@ -665,7 +665,7 @@ where
 {
 }
 
-#[unstable(feature = "trusted_len", issue = "37572")]
+#[cfg_attr(bootstrap, unstable(feature = "trusted_len", issue = "37572"))]
 unsafe impl<'a, const N: usize, I, T> TrustedLen
     for FlattenCompat<I, <&'a mut [T; N] as IntoIterator>::IntoIter>
 where
diff --git a/library/core/src/iter/adapters/step_by.rs b/library/core/src/iter/adapters/step_by.rs
index 4252c34a0..7f58f7d17 100644
--- a/library/core/src/iter/adapters/step_by.rs
+++ b/library/core/src/iter/adapters/step_by.rs
@@ -1,4 +1,9 @@
-use crate::{intrinsics, iter::from_fn, ops::Try};
+use crate::convert::TryFrom;
+use crate::{
+    intrinsics,
+    iter::{from_fn, TrustedLen},
+    ops::{Range, Try},
+};
 
 /// An iterator for stepping iterators by a custom amount.
 ///
@@ -11,14 +16,22 @@ use crate::{intrinsics, iter::from_fn, ops::Try};
 #[stable(feature = "iterator_step_by", since = "1.28.0")]
 #[derive(Clone, Debug)]
 pub struct StepBy<I> {
+    /// This field is guaranteed to be preprocessed by the specialized `SpecRangeSetup::setup`
+    /// in the constructor.
+    /// For most iterators that processing is a no-op, but for Range<{integer}> types it is lossy
+    /// which means the inner iterator cannot be returned to user code.
+    /// Additionally this type-dependent preprocessing means specialized implementations
+    /// cannot be used interchangeably.
     iter: I,
     step: usize,
     first_take: bool,
 }
 
 impl<I> StepBy<I> {
+    #[inline]
     pub(in crate::iter) fn new(iter: I, step: usize) -> StepBy<I> {
         assert!(step != 0);
+        let iter = <I as SpecRangeSetup<I>>::setup(iter, step);
         StepBy { iter, step: step - 1, first_take: true }
     }
 }
@@ -32,16 +45,174 @@ where
 
     #[inline]
     fn next(&mut self) -> Option<Self::Item> {
+        self.spec_next()
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.spec_size_hint()
+    }
+
+    #[inline]
+    fn nth(&mut self, n: usize) -> Option<Self::Item> {
+        self.spec_nth(n)
+    }
+
+    fn try_fold<Acc, F, R>(&mut self, acc: Acc, f: F) -> R
+    where
+        F: FnMut(Acc, Self::Item) -> R,
+        R: Try<Output = Acc>,
+    {
+        self.spec_try_fold(acc, f)
+    }
+
+    #[inline]
+    fn fold<Acc, F>(self, acc: Acc, f: F) -> Acc
+    where
+        F: FnMut(Acc, Self::Item) -> Acc,
+    {
+        self.spec_fold(acc, f)
+    }
+}
+
+impl<I> StepBy<I>
+where
+    I: ExactSizeIterator,
+{
+    // The zero-based index starting from the end of the iterator of the
+    // last element. Used in the `DoubleEndedIterator` implementation.
+    fn next_back_index(&self) -> usize {
+        let rem = self.iter.len() % (self.step + 1);
         if self.first_take {
-            self.first_take = false;
-            self.iter.next()
+            if rem == 0 { self.step } else { rem - 1 }
         } else {
-            self.iter.nth(self.step)
+            rem
         }
     }
+}
 
+#[stable(feature = "double_ended_step_by_iterator", since = "1.38.0")]
+impl<I> DoubleEndedIterator for StepBy<I>
+where
+    I: DoubleEndedIterator + ExactSizeIterator,
+{
     #[inline]
-    fn size_hint(&self) -> (usize, Option<usize>) {
+    fn next_back(&mut self) -> Option<Self::Item> {
+        self.spec_next_back()
+    }
+
+    #[inline]
+    fn nth_back(&mut self, n: usize) -> Option<Self::Item> {
+        self.spec_nth_back(n)
+    }
+
+    fn try_rfold<Acc, F, R>(&mut self, init: Acc, f: F) -> R
+    where
+        F: FnMut(Acc, Self::Item) -> R,
+        R: Try<Output = Acc>,
+    {
+        self.spec_try_rfold(init, f)
+    }
+
+    #[inline]
+    fn rfold<Acc, F>(self, init: Acc, f: F) -> Acc
+    where
+        Self: Sized,
+        F: FnMut(Acc, Self::Item) -> Acc,
+    {
+        self.spec_rfold(init, f)
+    }
+}
+
+// StepBy can only make the iterator shorter, so the len will still fit.
+#[stable(feature = "iterator_step_by", since = "1.28.0")]
+impl<I> ExactSizeIterator for StepBy<I> where I: ExactSizeIterator {}
+
+trait SpecRangeSetup<T> {
+    fn setup(inner: T, step: usize) -> T;
+}
+
+impl<T> SpecRangeSetup<T> for T {
+    #[inline]
+    default fn setup(inner: T, _step: usize) -> T {
+        inner
+    }
+}
+
+/// Specialization trait to optimize `StepBy<Range<{integer}>>` iteration.
+///
+/// # Safety
+///
+/// Technically this is safe to implement (look ma, no unsafe!), but in reality
+/// a lot of unsafe code relies on ranges over integers being correct.
+///
+/// For correctness *all* public StepBy methods must be specialized
+/// because `setup` drastically alters the meaning of the struct fields so that mixing
+/// different implementations would lead to incorrect results.
+unsafe trait StepByImpl<I> {
+    type Item;
+
+    fn spec_next(&mut self) -> Option<Self::Item>;
+
+    fn spec_size_hint(&self) -> (usize, Option<usize>);
+
+    fn spec_nth(&mut self, n: usize) -> Option<Self::Item>;
+
+    fn spec_try_fold<Acc, F, R>(&mut self, acc: Acc, f: F) -> R
+    where
+        F: FnMut(Acc, Self::Item) -> R,
+        R: Try<Output = Acc>;
+
+    fn spec_fold<Acc, F>(self, acc: Acc, f: F) -> Acc
+    where
+        F: FnMut(Acc, Self::Item) -> Acc;
+}
+
+/// Specialization trait for double-ended iteration.
+///
+/// See also: `StepByImpl`
+///
+/// # Safety
+///
+/// The specializations must be implemented together with `StepByImpl`
+/// where applicable. I.e. if `StepBy` does support backwards iteration
+/// for a given iterator and that is specialized for forward iteration then
+/// it must also be specialized for backwards iteration.
+unsafe trait StepByBackImpl<I> {
+    type Item;
+
+    fn spec_next_back(&mut self) -> Option<Self::Item>
+    where
+        I: DoubleEndedIterator + ExactSizeIterator;
+
+    fn spec_nth_back(&mut self, n: usize) -> Option<Self::Item>
+    where
+        I: DoubleEndedIterator + ExactSizeIterator;
+
+    fn spec_try_rfold<Acc, F, R>(&mut self, init: Acc, f: F) -> R
+    where
+        I: DoubleEndedIterator + ExactSizeIterator,
+        F: FnMut(Acc, Self::Item) -> R,
+        R: Try<Output = Acc>;
+
+    fn spec_rfold<Acc, F>(self, init: Acc, f: F) -> Acc
+    where
+        I: DoubleEndedIterator + ExactSizeIterator,
+        F: FnMut(Acc, Self::Item) -> Acc;
+}
+
+unsafe impl<I: Iterator> StepByImpl<I> for StepBy<I> {
+    type Item = I::Item;
+
+    #[inline]
+    default fn spec_next(&mut self) -> Option<I::Item> {
+        let step_size = if self.first_take { 0 } else { self.step };
+        self.first_take = false;
+        self.iter.nth(step_size)
+    }
+
+    #[inline]
+    default fn spec_size_hint(&self) -> (usize, Option<usize>) {
         #[inline]
         fn first_size(step: usize) -> impl Fn(usize) -> usize {
             move |n| if n == 0 { 0 } else { 1 + (n - 1) / (step + 1) }
@@ -64,7 +235,7 @@ where
     }
 
     #[inline]
-    fn nth(&mut self, mut n: usize) -> Option<Self::Item> {
+    default fn spec_nth(&mut self, mut n: usize) -> Option<I::Item> {
         if self.first_take {
             self.first_take = false;
             let first = self.iter.next();
@@ -108,7 +279,7 @@ where
         }
     }
 
-    fn try_fold<Acc, F, R>(&mut self, mut acc: Acc, mut f: F) -> R
+    default fn spec_try_fold<Acc, F, R>(&mut self, mut acc: Acc, mut f: F) -> R
     where
         F: FnMut(Acc, Self::Item) -> R,
         R: Try<Output = Acc>,
@@ -128,7 +299,7 @@ where
         from_fn(nth(&mut self.iter, self.step)).try_fold(acc, f)
     }
 
-    fn fold<Acc, F>(mut self, mut acc: Acc, mut f: F) -> Acc
+    default fn spec_fold<Acc, F>(mut self, mut acc: Acc, mut f: F) -> Acc
     where
         F: FnMut(Acc, Self::Item) -> Acc,
     {
@@ -148,34 +319,16 @@ where
     }
 }
 
-impl<I> StepBy<I>
-where
-    I: ExactSizeIterator,
-{
-    // The zero-based index starting from the end of the iterator of the
-    // last element. Used in the `DoubleEndedIterator` implementation.
-    fn next_back_index(&self) -> usize {
-        let rem = self.iter.len() % (self.step + 1);
-        if self.first_take {
-            if rem == 0 { self.step } else { rem - 1 }
-        } else {
-            rem
-        }
-    }
-}
+unsafe impl<I: DoubleEndedIterator + ExactSizeIterator> StepByBackImpl<I> for StepBy<I> {
+    type Item = I::Item;
 
-#[stable(feature = "double_ended_step_by_iterator", since = "1.38.0")]
-impl<I> DoubleEndedIterator for StepBy<I>
-where
-    I: DoubleEndedIterator + ExactSizeIterator,
-{
     #[inline]
-    fn next_back(&mut self) -> Option<Self::Item> {
+    default fn spec_next_back(&mut self) -> Option<Self::Item> {
         self.iter.nth_back(self.next_back_index())
     }
 
     #[inline]
-    fn nth_back(&mut self, n: usize) -> Option<Self::Item> {
+    default fn spec_nth_back(&mut self, n: usize) -> Option<I::Item> {
         // `self.iter.nth_back(usize::MAX)` does the right thing here when `n`
         // is out of bounds because the length of `self.iter` does not exceed
         // `usize::MAX` (because `I: ExactSizeIterator`) and `nth_back` is
@@ -184,7 +337,7 @@ where
         self.iter.nth_back(n)
     }
 
-    fn try_rfold<Acc, F, R>(&mut self, init: Acc, mut f: F) -> R
+    default fn spec_try_rfold<Acc, F, R>(&mut self, init: Acc, mut f: F) -> R
     where
         F: FnMut(Acc, Self::Item) -> R,
         R: Try<Output = Acc>,
@@ -207,10 +360,10 @@ where
     }
 
     #[inline]
-    fn rfold<Acc, F>(mut self, init: Acc, mut f: F) -> Acc
+    default fn spec_rfold<Acc, F>(mut self, init: Acc, mut f: F) -> Acc
     where
         Self: Sized,
-        F: FnMut(Acc, Self::Item) -> Acc,
+        F: FnMut(Acc, I::Item) -> Acc,
     {
         #[inline]
         fn nth_back<I: DoubleEndedIterator>(
@@ -230,6 +383,192 @@ where
     }
 }
 
-// StepBy can only make the iterator shorter, so the len will still fit.
-#[stable(feature = "iterator_step_by", since = "1.28.0")]
-impl<I> ExactSizeIterator for StepBy<I> where I: ExactSizeIterator {}
+/// For these implementations, `SpecRangeSetup` calculates the number
+/// of iterations that will be needed and stores that in `iter.end`.
+///
+/// The various iterator implementations then rely on that to not need
+/// overflow checking, letting loops just be counted instead.
+///
+/// These only work for unsigned types, and will need to be reworked
+/// if you want to use it to specialize on signed types.
+///
+/// Currently these are only implemented for integers up to usize due to
+/// correctness issues around ExactSizeIterator impls on 16bit platforms.
+/// And since ExactSizeIterator is a prerequisite for backwards iteration
+/// and we must consistently specialize backwards and forwards iteration
+/// that makes the situation complicated enough that it's not covered
+/// for now.
+macro_rules! spec_int_ranges {
+    ($($t:ty)*) => ($(
+
+        const _: () = assert!(usize::BITS >= <$t>::BITS);
+
+        impl SpecRangeSetup<Range<$t>> for Range<$t> {
+            #[inline]
+            fn setup(mut r: Range<$t>, step: usize) -> Range<$t> {
+                let inner_len = r.size_hint().0;
+                // If step exceeds $t::MAX, then the count will be at most 1 and
+                // thus always fit into $t.
+                let yield_count = inner_len.div_ceil(step);
+                // Turn the range end into an iteration counter
+                r.end = yield_count as $t;
+                r
+            }
+        }
+
+        unsafe impl StepByImpl<Range<$t>> for StepBy<Range<$t>> {
+            #[inline]
+            fn spec_next(&mut self) -> Option<$t> {
+                // if a step size larger than the type has been specified fall back to
+                // t::MAX, in which case remaining will be at most 1.
+                // The `+ 1` can't overflow since the constructor substracted 1 from the original value.
+                let step = <$t>::try_from(self.step + 1).unwrap_or(<$t>::MAX);
+                let remaining = self.iter.end;
+                if remaining > 0 {
+                    let val = self.iter.start;
+                    // this can only overflow during the last step, after which the value
+                    // will not be used
+                    self.iter.start = val.wrapping_add(step);
+                    self.iter.end = remaining - 1;
+                    Some(val)
+                } else {
+                    None
+                }
+            }
+
+            #[inline]
+            fn spec_size_hint(&self) -> (usize, Option<usize>) {
+                let remaining = self.iter.end as usize;
+                (remaining, Some(remaining))
+            }
+
+            // The methods below are all copied from the Iterator trait default impls.
+            // We have to repeat them here so that the specialization overrides the StepByImpl defaults
+
+            #[inline]
+            fn spec_nth(&mut self, n: usize) -> Option<Self::Item> {
+                self.advance_by(n).ok()?;
+                self.next()
+            }
+
+            #[inline]
+            fn spec_try_fold<Acc, F, R>(&mut self, init: Acc, mut f: F) -> R
+                where
+                    F: FnMut(Acc, Self::Item) -> R,
+                    R: Try<Output = Acc>
+            {
+                let mut accum = init;
+                while let Some(x) = self.next() {
+                    accum = f(accum, x)?;
+                }
+                try { accum }
+            }
+
+            #[inline]
+            fn spec_fold<Acc, F>(self, init: Acc, mut f: F) -> Acc
+                where
+                    F: FnMut(Acc, Self::Item) -> Acc
+            {
+                // if a step size larger than the type has been specified fall back to
+                // t::MAX, in which case remaining will be at most 1.
+                let step = <$t>::try_from(self.step + 1).unwrap_or(<$t>::MAX);
+                let remaining = self.iter.end;
+                let mut acc = init;
+                let mut val = self.iter.start;
+                for _ in 0..remaining {
+                    acc = f(acc, val);
+                    // this can only overflow during the last step, after which the value
+                    // will no longer be used
+                    val = val.wrapping_add(step);
+                }
+                acc
+            }
+        }
+
+        /// Safety: This macro is only applied to ranges over types <= usize
+        /// which means the inner length is guaranteed to fit into a usize and so
+        /// the outer length calculation won't encounter clamped values
+        #[unstable(feature = "trusted_len", issue = "37572")]
+        unsafe impl TrustedLen for StepBy<Range<$t>> {}
+    )*)
+}
+
+macro_rules! spec_int_ranges_r {
+    ($($t:ty)*) => ($(
+        const _: () = assert!(usize::BITS >= <$t>::BITS);
+
+        unsafe impl StepByBackImpl<Range<$t>> for StepBy<Range<$t>> {
+
+            #[inline]
+            fn spec_next_back(&mut self) -> Option<Self::Item>
+                where Range<$t>: DoubleEndedIterator + ExactSizeIterator,
+            {
+                let step = (self.step + 1) as $t;
+                let remaining = self.iter.end;
+                if remaining > 0 {
+                    let start = self.iter.start;
+                    self.iter.end = remaining - 1;
+                    Some(start + step * (remaining - 1))
+                } else {
+                    None
+                }
+            }
+
+            // The methods below are all copied from the Iterator trait default impls.
+            // We have to repeat them here so that the specialization overrides the StepByImplBack defaults
+
+            #[inline]
+            fn spec_nth_back(&mut self, n: usize) -> Option<Self::Item>
+                where Self: DoubleEndedIterator,
+            {
+                if self.advance_back_by(n).is_err() {
+                    return None;
+                }
+                self.next_back()
+            }
+
+            #[inline]
+            fn spec_try_rfold<Acc, F, R>(&mut self, init: Acc, mut f: F) -> R
+                where
+                    Self: DoubleEndedIterator,
+                    F: FnMut(Acc, Self::Item) -> R,
+                    R: Try<Output = Acc>
+            {
+                let mut accum = init;
+                while let Some(x) = self.next_back() {
+                    accum = f(accum, x)?;
+                }
+                try { accum }
+            }
+
+            #[inline]
+            fn spec_rfold<Acc, F>(mut self, init: Acc, mut f: F) -> Acc
+                where
+                    Self: DoubleEndedIterator,
+                    F: FnMut(Acc, Self::Item) -> Acc
+            {
+                let mut accum = init;
+                while let Some(x) = self.next_back() {
+                    accum = f(accum, x);
+                }
+                accum
+            }
+        }
+    )*)
+}
+
+#[cfg(target_pointer_width = "64")]
+spec_int_ranges!(u8 u16 u32 u64 usize);
+// DoubleEndedIterator requires ExactSizeIterator, which isn't implemented for Range<u64>
+#[cfg(target_pointer_width = "64")]
+spec_int_ranges_r!(u8 u16 u32 usize);
+
+#[cfg(target_pointer_width = "32")]
+spec_int_ranges!(u8 u16 u32 usize);
+#[cfg(target_pointer_width = "32")]
+spec_int_ranges_r!(u8 u16 u32 usize);
+
+#[cfg(target_pointer_width = "16")]
+spec_int_ranges!(u8 u16 usize);
+#[cfg(target_pointer_width = "16")]
+spec_int_ranges_r!(u8 u16 usize);
diff --git a/library/core/src/iter/range.rs b/library/core/src/iter/range.rs
index 0171d8981..462f7170a 100644
--- a/library/core/src/iter/range.rs
+++ b/library/core/src/iter/range.rs
@@ -619,9 +619,10 @@ impl<T: TrustedStep> RangeIteratorImpl for ops::Range<T> {
     #[inline]
     fn spec_next(&mut self) -> Option<T> {
         if self.start < self.end {
+            let old = self.start;
             // SAFETY: just checked precondition
-            let n = unsafe { Step::forward_unchecked(self.start.clone(), 1) };
-            Some(mem::replace(&mut self.start, n))
+            self.start = unsafe { Step::forward_unchecked(old, 1) };
+            Some(old)
         } else {
             None
         }
@@ -629,15 +630,15 @@ impl<T: TrustedStep> RangeIteratorImpl for ops::Range<T> {
 
     #[inline]
     fn spec_nth(&mut self, n: usize) -> Option<T> {
-        if let Some(plus_n) = Step::forward_checked(self.start.clone(), n) {
+        if let Some(plus_n) = Step::forward_checked(self.start, n) {
             if plus_n < self.end {
                 // SAFETY: just checked precondition
-                self.start = unsafe { Step::forward_unchecked(plus_n.clone(), 1) };
+                self.start = unsafe { Step::forward_unchecked(plus_n, 1) };
                 return Some(plus_n);
             }
         }
 
-        self.start = self.end.clone();
+        self.start = self.end;
         None
     }
 
@@ -655,7 +656,7 @@ impl<T: TrustedStep> RangeIteratorImpl for ops::Range<T> {
         // then steps_between either returns a bound to which we clamp or returns None which
         // together with the initial inequality implies more than usize::MAX steps.
         // Otherwise 0 is returned which always safe to use.
-        self.start = unsafe { Step::forward_unchecked(self.start.clone(), taken) };
+        self.start = unsafe { Step::forward_unchecked(self.start, taken) };
 
         NonZeroUsize::new(n - taken).map_or(Ok(()), Err)
     }
@@ -664,8 +665,8 @@ impl<T: TrustedStep> RangeIteratorImpl for ops::Range<T> {
     fn spec_next_back(&mut self) -> Option<T> {
         if self.start < self.end {
             // SAFETY: just checked precondition
-            self.end = unsafe { Step::backward_unchecked(self.end.clone(), 1) };
-            Some(self.end.clone())
+            self.end = unsafe { Step::backward_unchecked(self.end, 1) };
+            Some(self.end)
         } else {
             None
         }
@@ -673,15 +674,15 @@ impl<T: TrustedStep> RangeIteratorImpl for ops::Range<T> {
 
     #[inline]
     fn spec_nth_back(&mut self, n: usize) -> Option<T> {
-        if let Some(minus_n) = Step::backward_checked(self.end.clone(), n) {
+        if let Some(minus_n) = Step::backward_checked(self.end, n) {
             if minus_n > self.start {
                 // SAFETY: just checked precondition
                 self.end = unsafe { Step::backward_unchecked(minus_n, 1) };
-                return Some(self.end.clone());
+                return Some(self.end);
             }
         }
 
-        self.end = self.start.clone();
+        self.end = self.start;
         None
     }
 
@@ -696,7 +697,7 @@ impl<T: TrustedStep> RangeIteratorImpl for ops::Range<T> {
         let taken = available.min(n);
 
         // SAFETY: same as the spec_advance_by() implementation
-        self.end = unsafe { Step::backward_unchecked(self.end.clone(), taken) };
+        self.end = unsafe { Step::backward_unchecked(self.end, taken) };
 
         NonZeroUsize::new(n - taken).map_or(Ok(()), Err)
     }
diff --git a/library/core/src/iter/sources/successors.rs b/library/core/src/iter/sources/successors.rs
index 99f058a90..6a6cbe905 100644
--- a/library/core/src/iter/sources/successors.rs
+++ b/library/core/src/iter/sources/successors.rs
@@ -22,7 +22,7 @@ where
     Successors { next: first, succ }
 }
 
-/// An new iterator where each successive item is computed based on the preceding one.
+/// A new iterator where each successive item is computed based on the preceding one.
 ///
 /// This `struct` is created by the [`iter::successors()`] function.
 /// See its documentation for more.
diff --git a/library/core/src/iter/traits/iterator.rs b/library/core/src/iter/traits/iterator.rs
index dabfce144..988352283 100644
--- a/library/core/src/iter/traits/iterator.rs
+++ b/library/core/src/iter/traits/iterator.rs
@@ -26,13 +26,13 @@ fn _assert_is_object_safe(_: &dyn Iterator<Item = ()>) {}
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_on_unimplemented(
     on(
-        _Self = "std::ops::RangeTo<Idx>",
+        any(_Self = "core::ops::RangeTo<Idx>", _Self = "std::ops::RangeTo<Idx>"),
         label = "if you meant to iterate until a value, add a starting value",
         note = "`..end` is a `RangeTo`, which cannot be iterated on; you might have meant to have a \
               bounded `Range`: `0..end`"
     ),
     on(
-        _Self = "std::ops::RangeToInclusive<Idx>",
+        any(_Self = "core::ops::RangeToInclusive<Idx>", _Self = "std::ops::RangeToInclusive<Idx>"),
         label = "if you meant to iterate until a value (including it), add a starting value",
         note = "`..=end` is a `RangeToInclusive`, which cannot be iterated on; you might have meant \
               to have a bounded `RangeInclusive`: `0..=end`"
@@ -43,7 +43,7 @@ fn _assert_is_object_safe(_: &dyn Iterator<Item = ()>) {}
     ),
     on(_Self = "&[]", label = "`{Self}` is not an iterator; try calling `.iter()`"),
     on(
-        _Self = "std::vec::Vec<T, A>",
+        any(_Self = "alloc::vec::Vec<T, A>", _Self = "std::vec::Vec<T, A>"),
         label = "`{Self}` is not an iterator; try calling `.into_iter()` or `.iter()`"
     ),
     on(
@@ -51,7 +51,7 @@ fn _assert_is_object_safe(_: &dyn Iterator<Item = ()>) {}
         label = "`{Self}` is not an iterator; try calling `.chars()` or `.bytes()`"
     ),
     on(
-        _Self = "std::string::String",
+        any(_Self = "alloc::string::String", _Self = "std::string::String"),
         label = "`{Self}` is not an iterator; try calling `.chars()` or `.bytes()`"
     ),
     on(
diff --git a/library/core/src/iter/traits/marker.rs b/library/core/src/iter/traits/marker.rs
index af0284823..c21a2aac1 100644
--- a/library/core/src/iter/traits/marker.rs
+++ b/library/core/src/iter/traits/marker.rs
@@ -86,4 +86,4 @@ pub unsafe trait InPlaceIterable: Iterator {}
 /// for details. Consumers are free to rely on the invariants in unsafe code.
 #[unstable(feature = "trusted_step", issue = "85731")]
 #[rustc_specialization_trait]
-pub unsafe trait TrustedStep: Step {}
+pub unsafe trait TrustedStep: Step + Copy {}
diff --git a/library/core/src/lib.rs b/library/core/src/lib.rs
index 6c419eb16..05876f5fc 100644
--- a/library/core/src/lib.rs
+++ b/library/core/src/lib.rs
@@ -113,7 +113,6 @@
 #![feature(const_caller_location)]
 #![feature(const_cell_into_inner)]
 #![feature(const_char_from_u32_unchecked)]
-#![feature(const_cstr_methods)]
 #![feature(const_discriminant)]
 #![feature(const_eval_select)]
 #![feature(const_exact_div)]
diff --git a/library/core/src/macros/mod.rs b/library/core/src/macros/mod.rs
index c4134dbcd..45e5b7627 100644
--- a/library/core/src/macros/mod.rs
+++ b/library/core/src/macros/mod.rs
@@ -960,6 +960,8 @@ pub(crate) mod builtin {
     ///
     /// A compile time error is never emitted when using this macro regardless
     /// of whether the environment variable is present or not.
+    /// To emit a compile error if the environment variable is not present,
+    /// use the [`env!`] macro instead.
     ///
     /// # Examples
     ///
diff --git a/library/core/src/marker.rs b/library/core/src/marker.rs
index 8dab8d1a6..e251015dd 100644
--- a/library/core/src/marker.rs
+++ b/library/core/src/marker.rs
@@ -140,7 +140,8 @@ unsafe impl<T: Sync + ?Sized> Send for &T {}
 )]
 #[fundamental] // for Default, for example, which requires that `[T]: !Default` be evaluatable
 #[rustc_specialization_trait]
-#[rustc_deny_explicit_impl]
+#[cfg_attr(not(bootstrap), rustc_deny_explicit_impl(implement_via_object = false))]
+#[cfg_attr(bootstrap, rustc_deny_explicit_impl)]
 #[rustc_coinductive]
 pub trait Sized {
     // Empty.
@@ -173,7 +174,8 @@ pub trait Sized {
 /// [nomicon-coerce]: ../../nomicon/coercions.html
 #[unstable(feature = "unsize", issue = "18598")]
 #[lang = "unsize"]
-#[rustc_deny_explicit_impl]
+#[cfg_attr(not(bootstrap), rustc_deny_explicit_impl(implement_via_object = false))]
+#[cfg_attr(bootstrap, rustc_deny_explicit_impl)]
 pub trait Unsize<T: ?Sized> {
     // Empty.
 }
@@ -205,6 +207,20 @@ pub trait StructuralPartialEq {
     // Empty.
 }
 
+marker_impls! {
+    #[unstable(feature = "structural_match", issue = "31434")]
+    StructuralPartialEq for
+        usize, u8, u16, u32, u64, u128,
+        isize, i8, i16, i32, i64, i128,
+        bool,
+        char,
+        str /* Technically requires `[u8]: StructuralEq` */,
+        (),
+        {T, const N: usize} [T; N],
+        {T} [T],
+        {T: ?Sized} &T,
+}
+
 /// Required trait for constants used in pattern matches.
 ///
 /// Any type that derives `Eq` automatically implements this trait, *regardless*
@@ -267,6 +283,7 @@ marker_impls! {
         bool,
         char,
         str /* Technically requires `[u8]: StructuralEq` */,
+        (),
         {T, const N: usize} [T; N],
         {T} [T],
         {T: ?Sized} &T,
@@ -558,59 +575,59 @@ impl<T: ?Sized> Copy for &T {}
 #[lang = "sync"]
 #[rustc_on_unimplemented(
     on(
-        _Self = "std::cell::OnceCell<T>",
+        any(_Self = "core::cell:OnceCell<T>", _Self = "std::cell::OnceCell<T>"),
         note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::OnceLock` instead"
     ),
     on(
-        _Self = "std::cell::Cell<u8>",
+        any(_Self = "core::cell::Cell<u8>", _Self = "std::cell::Cell<u8>"),
         note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicU8` instead",
     ),
     on(
-        _Self = "std::cell::Cell<u16>",
+        any(_Self = "core::cell::Cell<u16>", _Self = "std::cell::Cell<u16>"),
         note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicU16` instead",
     ),
     on(
-        _Self = "std::cell::Cell<u32>",
+        any(_Self = "core::cell::Cell<u32>", _Self = "std::cell::Cell<u32>"),
         note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicU32` instead",
     ),
     on(
-        _Self = "std::cell::Cell<u64>",
+        any(_Self = "core::cell::Cell<u64>", _Self = "std::cell::Cell<u64>"),
         note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicU64` instead",
     ),
     on(
-        _Self = "std::cell::Cell<usize>",
+        any(_Self = "core::cell::Cell<usize>", _Self = "std::cell::Cell<usize>"),
         note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicUsize` instead",
     ),
     on(
-        _Self = "std::cell::Cell<i8>",
+        any(_Self = "core::cell::Cell<i8>", _Self = "std::cell::Cell<i8>"),
         note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicI8` instead",
     ),
     on(
-        _Self = "std::cell::Cell<i16>",
+        any(_Self = "core::cell::Cell<i16>", _Self = "std::cell::Cell<i16>"),
         note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicI16` instead",
     ),
     on(
-        _Self = "std::cell::Cell<i32>",
+        any(_Self = "core::cell::Cell<i32>", _Self = "std::cell::Cell<i32>"),
         note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicI32` instead",
     ),
     on(
-        _Self = "std::cell::Cell<i64>",
+        any(_Self = "core::cell::Cell<i64>", _Self = "std::cell::Cell<i64>"),
         note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicI64` instead",
     ),
     on(
-        _Self = "std::cell::Cell<isize>",
+        any(_Self = "core::cell::Cell<isize>", _Self = "std::cell::Cell<isize>"),
         note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicIsize` instead",
     ),
     on(
-        _Self = "std::cell::Cell<bool>",
+        any(_Self = "core::cell::Cell<bool>", _Self = "std::cell::Cell<bool>"),
         note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicBool` instead",
     ),
     on(
-        _Self = "std::cell::Cell<T>",
+        any(_Self = "core::cell::Cell<T>", _Self = "std::cell::Cell<T>"),
         note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock`",
     ),
     on(
-        _Self = "std::cell::RefCell<T>",
+        any(_Self = "core::cell::RefCell<T>", _Self = "std::cell::RefCell<T>"),
         note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` instead",
     ),
     message = "`{Self}` cannot be shared between threads safely",
@@ -839,7 +856,8 @@ impl<T: ?Sized> StructuralEq for PhantomData<T> {}
     reason = "this trait is unlikely to ever be stabilized, use `mem::discriminant` instead"
 )]
 #[lang = "discriminant_kind"]
-#[rustc_deny_explicit_impl]
+#[cfg_attr(not(bootstrap), rustc_deny_explicit_impl(implement_via_object = false))]
+#[cfg_attr(bootstrap, rustc_deny_explicit_impl)]
 pub trait DiscriminantKind {
     /// The type of the discriminant, which must satisfy the trait
     /// bounds required by `mem::Discriminant`.
@@ -944,7 +962,8 @@ marker_impls! {
 #[unstable(feature = "const_trait_impl", issue = "67792")]
 #[lang = "destruct"]
 #[rustc_on_unimplemented(message = "can't drop `{Self}`", append_const_msg)]
-#[rustc_deny_explicit_impl]
+#[cfg_attr(not(bootstrap), rustc_deny_explicit_impl(implement_via_object = false))]
+#[cfg_attr(bootstrap, rustc_deny_explicit_impl)]
 #[const_trait]
 pub trait Destruct {}
 
@@ -955,7 +974,8 @@ pub trait Destruct {}
 #[unstable(feature = "tuple_trait", issue = "none")]
 #[lang = "tuple_trait"]
 #[rustc_on_unimplemented(message = "`{Self}` is not a tuple")]
-#[rustc_deny_explicit_impl]
+#[cfg_attr(not(bootstrap), rustc_deny_explicit_impl(implement_via_object = false))]
+#[cfg_attr(bootstrap, rustc_deny_explicit_impl)]
 pub trait Tuple {}
 
 /// A marker for pointer-like types.
@@ -971,21 +991,20 @@ pub trait Tuple {}
 pub trait PointerLike {}
 
 /// A marker for types which can be used as types of `const` generic parameters.
-#[cfg_attr(not(bootstrap), lang = "const_param_ty")]
+#[lang = "const_param_ty"]
 #[unstable(feature = "adt_const_params", issue = "95174")]
 #[rustc_on_unimplemented(message = "`{Self}` can't be used as a const parameter type")]
-pub trait ConstParamTy: StructuralEq {}
+#[allow(multiple_supertrait_upcastable)]
+pub trait ConstParamTy: StructuralEq + StructuralPartialEq {}
 
 /// Derive macro generating an impl of the trait `ConstParamTy`.
 #[rustc_builtin_macro]
 #[unstable(feature = "adt_const_params", issue = "95174")]
-#[cfg(not(bootstrap))]
 pub macro ConstParamTy($item:item) {
     /* compiler built-in */
 }
 
-// FIXME(generic_const_parameter_types): handle `ty::FnDef`/`ty::Closure`
-// FIXME(generic_const_parameter_types): handle `ty::Tuple`
+// FIXME(adt_const_params): handle `ty::FnDef`/`ty::Closure`
 marker_impls! {
     #[unstable(feature = "adt_const_params", issue = "95174")]
     ConstParamTy for
@@ -999,6 +1018,11 @@ marker_impls! {
         {T: ?Sized + ConstParamTy} &T,
 }
 
+// FIXME(adt_const_params): Add to marker_impls call above once not in bootstrap
+#[unstable(feature = "adt_const_params", issue = "95174")]
+#[cfg(not(bootstrap))]
+impl ConstParamTy for () {}
+
 /// A common trait implemented by all function pointers.
 #[unstable(
     feature = "fn_ptr_trait",
@@ -1006,7 +1030,8 @@ marker_impls! {
     reason = "internal trait for implementing various traits for all function pointers"
 )]
 #[lang = "fn_ptr_trait"]
-#[rustc_deny_explicit_impl]
+#[cfg_attr(not(bootstrap), rustc_deny_explicit_impl(implement_via_object = false))]
+#[cfg_attr(bootstrap, rustc_deny_explicit_impl)]
 pub trait FnPtr: Copy + Clone {
     /// Returns the address of the function pointer.
     #[lang = "fn_ptr_addr"]
diff --git a/library/core/src/mem/mod.rs b/library/core/src/mem/mod.rs
index afbfd6d36..2fff3f0ef 100644
--- a/library/core/src/mem/mod.rs
+++ b/library/core/src/mem/mod.rs
@@ -968,7 +968,7 @@ pub const fn replace<T>(dest: &mut T, src: T) -> T {
 /// Integers and other types implementing [`Copy`] are unaffected by `drop`.
 ///
 /// ```
-/// # #![cfg_attr(not(bootstrap), allow(dropping_copy_types))]
+/// # #![allow(dropping_copy_types)]
 /// #[derive(Copy, Clone)]
 /// struct Foo(u8);
 ///
@@ -1316,9 +1316,9 @@ impl<T> SizedTypeProperties for T {}
 ///
 /// assert_eq!(mem::offset_of!(NestedA, b.0), 0);
 /// ```
-#[cfg(not(bootstrap))]
 #[unstable(feature = "offset_of", issue = "106655")]
-#[allow_internal_unstable(builtin_syntax)]
+#[allow_internal_unstable(builtin_syntax, hint_must_use)]
 pub macro offset_of($Container:ty, $($fields:tt).+ $(,)?) {
-    builtin # offset_of($Container, $($fields).+)
+    // The `{}` is for better error messages
+    crate::hint::must_use({builtin # offset_of($Container, $($fields).+)})
 }
diff --git a/library/core/src/mem/transmutability.rs b/library/core/src/mem/transmutability.rs
index 87ae30619..3805d149b 100644
--- a/library/core/src/mem/transmutability.rs
+++ b/library/core/src/mem/transmutability.rs
@@ -1,3 +1,5 @@
+use crate::marker::ConstParamTy;
+
 /// Are values of a type transmutable into values of another type?
 ///
 /// This trait is implemented on-the-fly by the compiler for types `Src` and `Self` when the bits of
@@ -5,6 +7,8 @@
 /// notwithstanding whatever safety checks you have asked the compiler to [`Assume`] are satisfied.
 #[unstable(feature = "transmutability", issue = "99571")]
 #[lang = "transmute_trait"]
+#[cfg_attr(not(bootstrap), rustc_deny_explicit_impl(implement_via_object = false))]
+#[cfg_attr(bootstrap, rustc_deny_explicit_impl)]
 pub unsafe trait BikeshedIntrinsicFrom<Src, Context, const ASSUME: Assume = { Assume::NOTHING }>
 where
     Src: ?Sized,
@@ -33,6 +37,9 @@ pub struct Assume {
     pub validity: bool,
 }
 
+#[unstable(feature = "transmutability", issue = "99571")]
+impl ConstParamTy for Assume {}
+
 impl Assume {
     /// Do not assume that *you* have ensured any safety properties are met.
     #[unstable(feature = "transmutability", issue = "99571")]
diff --git a/library/core/src/net/ip_addr.rs b/library/core/src/net/ip_addr.rs
index 954d88d54..c51913fa8 100644
--- a/library/core/src/net/ip_addr.rs
+++ b/library/core/src/net/ip_addr.rs
@@ -1770,14 +1770,8 @@ impl fmt::Display for Ipv6Addr {
                 f.write_str("::")
             } else if self.is_loopback() {
                 f.write_str("::1")
-            } else if let Some(ipv4) = self.to_ipv4() {
-                match segments[5] {
-                    // IPv4 Compatible address
-                    0 => write!(f, "::{}", ipv4),
-                    // IPv4 Mapped address
-                    0xffff => write!(f, "::ffff:{}", ipv4),
-                    _ => unreachable!(),
-                }
+            } else if let Some(ipv4) = self.to_ipv4_mapped() {
+                write!(f, "::ffff:{}", ipv4)
             } else {
                 #[derive(Copy, Clone, Default)]
                 struct Span {
diff --git a/library/core/src/num/f32.rs b/library/core/src/num/f32.rs
index 4a035ad61..d050d21c8 100644
--- a/library/core/src/num/f32.rs
+++ b/library/core/src/num/f32.rs
@@ -403,6 +403,7 @@ impl f32 {
     /// and the stability of its representation over Rust versions
     /// and target platforms isn't guaranteed.
     #[stable(feature = "assoc_int_consts", since = "1.43.0")]
+    #[rustc_diagnostic_item = "f32_nan"]
     pub const NAN: f32 = 0.0_f32 / 0.0_f32;
     /// Infinity (∞).
     #[stable(feature = "assoc_int_consts", since = "1.43.0")]
diff --git a/library/core/src/num/f64.rs b/library/core/src/num/f64.rs
index 3aafc435f..d9a738191 100644
--- a/library/core/src/num/f64.rs
+++ b/library/core/src/num/f64.rs
@@ -401,6 +401,7 @@ impl f64 {
     /// This constant isn't guaranteed to equal to any specific NaN bitpattern,
     /// and the stability of its representation over Rust versions
     /// and target platforms isn't guaranteed.
+    #[rustc_diagnostic_item = "f64_nan"]
     #[stable(feature = "assoc_int_consts", since = "1.43.0")]
     pub const NAN: f64 = 0.0_f64 / 0.0_f64;
     /// Infinity (∞).
diff --git a/library/core/src/num/mod.rs b/library/core/src/num/mod.rs
index c9baa09f4..95dcaf5dd 100644
--- a/library/core/src/num/mod.rs
+++ b/library/core/src/num/mod.rs
@@ -3,7 +3,6 @@
 #![stable(feature = "rust1", since = "1.0.0")]
 
 use crate::ascii;
-use crate::convert::TryInto;
 use crate::intrinsics;
 use crate::mem;
 use crate::ops::{Add, Mul, Sub};
@@ -278,18 +277,12 @@ macro_rules! widening_impl {
 
 macro_rules! conv_rhs_for_unchecked_shift {
     ($SelfT:ty, $x:expr) => {{
-        #[inline]
-        fn conv(x: u32) -> $SelfT {
-            // FIXME(const-hack) replace with `.try_into().ok().unwrap_unchecked()`.
-            // SAFETY: Any legal shift amount must be losslessly representable in the self type.
-            unsafe { x.try_into().ok().unwrap_unchecked() }
-        }
-        #[inline]
-        const fn const_conv(x: u32) -> $SelfT {
-            x as _
+        // If the `as` cast will truncate, ensure we still tell the backend
+        // that the pre-truncation value was also small.
+        if <$SelfT>::BITS < 32 {
+            intrinsics::assume($x <= (<$SelfT>::MAX as u32));
         }
-
-        intrinsics::const_eval_select(($x,), const_conv, conv)
+        $x as $SelfT
     }};
 }
 
diff --git a/library/core/src/num/nonzero.rs b/library/core/src/num/nonzero.rs
index 7f06e170a..5939dedbd 100644
--- a/library/core/src/num/nonzero.rs
+++ b/library/core/src/num/nonzero.rs
@@ -348,7 +348,7 @@ macro_rules! nonzero_unsigned_operations {
                 }
 
                 /// Adds an unsigned integer to a non-zero value.
-                #[doc = concat!("Return [`", stringify!($Int), "::MAX`] on overflow.")]
+                #[doc = concat!("Return [`", stringify!($Ty), "::MAX`] on overflow.")]
                 ///
                 /// # Examples
                 ///
@@ -579,7 +579,7 @@ macro_rules! nonzero_signed_operations {
 
                 /// Checked absolute value.
                 /// Checks for overflow and returns [`None`] if
-                #[doc = concat!("`self == ", stringify!($Int), "::MIN`.")]
+                #[doc = concat!("`self == ", stringify!($Ty), "::MIN`.")]
                 /// The result cannot be zero.
                 ///
                 /// # Example
@@ -800,7 +800,8 @@ macro_rules! nonzero_signed_operations {
                     self.get().is_negative()
                 }
 
-                /// Checked negation. Computes `-self`, returning `None` if `self == i32::MIN`.
+                /// Checked negation. Computes `-self`,
+                #[doc = concat!("returning `None` if `self == ", stringify!($Ty), "::MIN`.")]
                 ///
                 /// # Example
                 ///
@@ -859,8 +860,10 @@ macro_rules! nonzero_signed_operations {
                     ((unsafe { $Ty::new_unchecked(result) }), overflow)
                 }
 
-                /// Saturating negation. Computes `-self`, returning `MAX` if
-                /// `self == i32::MIN` instead of overflowing.
+                /// Saturating negation. Computes `-self`,
+                #[doc = concat!("returning [`", stringify!($Ty), "::MAX`]")]
+                #[doc = concat!("if `self == ", stringify!($Ty), "::MIN`")]
+                /// instead of overflowing.
                 ///
                 /// # Example
                 ///
@@ -993,7 +996,7 @@ macro_rules! nonzero_unsigned_signed_operations {
                 }
 
                 /// Multiplies two non-zero integers together.
-                #[doc = concat!("Return [`", stringify!($Int), "::MAX`] on overflow.")]
+                #[doc = concat!("Return [`", stringify!($Ty), "::MAX`] on overflow.")]
                 ///
                 /// # Examples
                 ///
@@ -1102,11 +1105,11 @@ macro_rules! nonzero_unsigned_signed_operations {
                 #[doc = sign_dependent_expr!{
                     $signedness ?
                     if signed {
-                        concat!("Return [`", stringify!($Int), "::MIN`] ",
-                                    "or [`", stringify!($Int), "::MAX`] on overflow.")
+                        concat!("Return [`", stringify!($Ty), "::MIN`] ",
+                                    "or [`", stringify!($Ty), "::MAX`] on overflow.")
                     }
                     if unsigned {
-                        concat!("Return [`", stringify!($Int), "::MAX`] on overflow.")
+                        concat!("Return [`", stringify!($Ty), "::MAX`] on overflow.")
                     }
                 }]
                 ///
diff --git a/library/core/src/ops/index.rs b/library/core/src/ops/index.rs
index 1f1784ec9..f4649be54 100644
--- a/library/core/src/ops/index.rs
+++ b/library/core/src/ops/index.rs
@@ -153,7 +153,7 @@ see chapter in The Book <https://doc.rust-lang.org/book/ch08-02-strings.html#ind
 see chapter in The Book <https://doc.rust-lang.org/book/ch08-02-strings.html#indexing-into-strings>"
     ),
     on(
-        _Self = "std::string::String",
+        any(_Self = "alloc::string::String", _Self = "std::string::String"),
         note = "you can use `.chars().nth()` or `.bytes().nth()`
 see chapter in The Book <https://doc.rust-lang.org/book/ch08-02-strings.html#indexing-into-strings>"
     ),
diff --git a/library/core/src/ops/try_trait.rs b/library/core/src/ops/try_trait.rs
index b4f69d0b2..17625dacc 100644
--- a/library/core/src/ops/try_trait.rs
+++ b/library/core/src/ops/try_trait.rs
@@ -226,8 +226,14 @@ pub trait Try: FromResidual {
     on(
         all(
             from_desugaring = "QuestionMark",
-            _Self = "std::result::Result<T, E>",
-            R = "std::option::Option<std::convert::Infallible>"
+            any(
+                _Self = "core::result::Result<T, E>",
+                _Self = "std::result::Result<T, E>",
+            ),
+            any(
+                R = "core::option::Option<core::convert::Infallible>",
+                R = "std::option::Option<std::convert::Infallible>",
+            )
         ),
         message = "the `?` operator can only be used on `Result`s, not `Option`s, \
             in {ItemContext} that returns `Result`",
@@ -237,7 +243,10 @@ pub trait Try: FromResidual {
     on(
         all(
             from_desugaring = "QuestionMark",
-            _Self = "std::result::Result<T, E>",
+            any(
+                _Self = "core::result::Result<T, E>",
+                _Self = "std::result::Result<T, E>",
+            )
         ),
         // There's a special error message in the trait selection code for
         // `From` in `?`, so this is not shown for result-in-result errors,
@@ -250,8 +259,14 @@ pub trait Try: FromResidual {
     on(
         all(
             from_desugaring = "QuestionMark",
-            _Self = "std::option::Option<T>",
-            R = "std::result::Result<T, E>",
+            any(
+                _Self = "core::option::Option<T>",
+                _Self = "std::option::Option<T>",
+            ),
+            any(
+                R = "core::result::Result<T, E>",
+                R = "std::result::Result<T, E>",
+            )
         ),
         message = "the `?` operator can only be used on `Option`s, not `Result`s, \
             in {ItemContext} that returns `Option`",
@@ -261,7 +276,10 @@ pub trait Try: FromResidual {
     on(
         all(
             from_desugaring = "QuestionMark",
-            _Self = "std::option::Option<T>",
+            any(
+                _Self = "core::option::Option<T>",
+                _Self = "std::option::Option<T>",
+            )
         ),
         // `Option`-in-`Option` always works, as there's only one possible
         // residual, so this can also be phrased strongly.
@@ -273,8 +291,14 @@ pub trait Try: FromResidual {
     on(
         all(
             from_desugaring = "QuestionMark",
-            _Self = "std::ops::ControlFlow<B, C>",
-            R = "std::ops::ControlFlow<B, C>",
+            any(
+                _Self = "core::ops::ControlFlow<B, C>",
+                _Self = "std::ops::ControlFlow<B, C>",
+            ),
+            any(
+                R = "core::ops::ControlFlow<B, C>",
+                R = "std::ops::ControlFlow<B, C>",
+            )
         ),
         message = "the `?` operator in {ItemContext} that returns `ControlFlow<B, _>` \
             can only be used on other `ControlFlow<B, _>`s (with the same Break type)",
@@ -285,7 +309,10 @@ pub trait Try: FromResidual {
     on(
         all(
             from_desugaring = "QuestionMark",
-            _Self = "std::ops::ControlFlow<B, C>",
+            any(
+                _Self = "core::ops::ControlFlow<B, C>",
+                _Self = "std::ops::ControlFlow<B, C>",
+            )
             // `R` is not a `ControlFlow`, as that case was matched previously
         ),
         message = "the `?` operator can only be used on `ControlFlow`s \
diff --git a/library/core/src/option.rs b/library/core/src/option.rs
index ec1ef3cf4..9b6ff76b2 100644
--- a/library/core/src/option.rs
+++ b/library/core/src/option.rs
@@ -1138,7 +1138,7 @@ impl<T> Option<T> {
     /// Computes a default function result (if none), or
     /// applies a different function to the contained value (if any).
     ///
-    /// # Examples
+    /// # Basic examples
     ///
     /// ```
     /// let k = 21;
@@ -1149,6 +1149,25 @@ impl<T> Option<T> {
     /// let x: Option<&str> = None;
     /// assert_eq!(x.map_or_else(|| 2 * k, |v| v.len()), 42);
     /// ```
+    ///
+    /// # Handling a Result-based fallback
+    ///
+    /// A somewhat common occurrence when dealing with optional values
+    /// in combination with [`Result<T, E>`] is the case where one wants to invoke
+    /// a fallible fallback if the option is not present.  This example
+    /// parses a command line argument (if present), or the contents of a file to
+    /// an integer.  However, unlike accessing the command line argument, reading
+    /// the file is fallible, so it must be wrapped with `Ok`.
+    ///
+    /// ```no_run
+    /// # fn main() -> Result<(), Box<dyn std::error::Error>> {
+    /// let v: u64 = std::env::args()
+    ///    .nth(1)
+    ///    .map_or_else(|| std::fs::read_to_string("/etc/someconfig.conf"), Ok)?
+    ///    .parse()?;
+    /// #   Ok(())
+    /// # }
+    /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn map_or_else<U, D, F>(self, default: D, f: F) -> U
@@ -1383,6 +1402,7 @@ impl<T> Option<T> {
     /// let item_2_0 = arr_2d.get(2).and_then(|row| row.get(0));
     /// assert_eq!(item_2_0, None);
     /// ```
+    #[doc(alias = "flatmap")]
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn and_then<U, F>(self, f: F) -> Option<U>
diff --git a/library/core/src/panicking.rs b/library/core/src/panicking.rs
index 81be3fb22..f0fcdab00 100644
--- a/library/core/src/panicking.rs
+++ b/library/core/src/panicking.rs
@@ -166,14 +166,15 @@ fn panic_bounds_check(index: usize, len: usize) -> ! {
 #[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
 #[track_caller]
 #[lang = "panic_misaligned_pointer_dereference"] // needed by codegen for panic on misaligned pointer deref
+#[rustc_nounwind] // `CheckAlignment` MIR pass requires this function to never unwind
 fn panic_misaligned_pointer_dereference(required: usize, found: usize) -> ! {
     if cfg!(feature = "panic_immediate_abort") {
         super::intrinsics::abort()
     }
 
-    panic!(
+    panic_nounwind_fmt(format_args!(
         "misaligned pointer dereference: address must be a multiple of {required:#x} but is {found:#x}"
-    )
+    ))
 }
 
 /// Panic because we cannot unwind out of a function.
diff --git a/library/core/src/primitive_docs.rs b/library/core/src/primitive_docs.rs
index 8266e8990..80289ca08 100644
--- a/library/core/src/primitive_docs.rs
+++ b/library/core/src/primitive_docs.rs
@@ -308,7 +308,7 @@ mod prim_never {}
 ///
 /// ```no_run
 /// // Undefined behaviour
-/// unsafe { char::from_u32_unchecked(0x110000) };
+/// let _ = unsafe { char::from_u32_unchecked(0x110000) };
 /// ```
 ///
 /// USVs are also the exact set of values that may be encoded in UTF-8. Because
diff --git a/library/core/src/ptr/const_ptr.rs b/library/core/src/ptr/const_ptr.rs
index 6e1e862d3..926189a17 100644
--- a/library/core/src/ptr/const_ptr.rs
+++ b/library/core/src/ptr/const_ptr.rs
@@ -104,6 +104,7 @@ impl<T: ?Sized> *const T {
     /// refactored.
     #[stable(feature = "ptr_const_cast", since = "1.65.0")]
     #[rustc_const_stable(feature = "ptr_const_cast", since = "1.65.0")]
+    #[rustc_diagnostic_item = "ptr_cast_mut"]
     #[inline(always)]
     pub const fn cast_mut(self) -> *mut T {
         self as _
@@ -916,16 +917,8 @@ impl<T: ?Sized> *const T {
     where
         T: Sized,
     {
-        #[cfg(bootstrap)]
         // SAFETY: the caller must uphold the safety contract for `offset`.
-        unsafe {
-            self.offset(count as isize)
-        }
-        #[cfg(not(bootstrap))]
-        // SAFETY: the caller must uphold the safety contract for `offset`.
-        unsafe {
-            intrinsics::offset(self, count)
-        }
+        unsafe { intrinsics::offset(self, count) }
     }
 
     /// Calculates the offset from a pointer in bytes (convenience for `.byte_offset(count as isize)`).
diff --git a/library/core/src/ptr/metadata.rs b/library/core/src/ptr/metadata.rs
index 2ea032d4a..daaa44b1d 100644
--- a/library/core/src/ptr/metadata.rs
+++ b/library/core/src/ptr/metadata.rs
@@ -50,7 +50,8 @@ use crate::hash::{Hash, Hasher};
 ///
 /// [`to_raw_parts`]: *const::to_raw_parts
 #[lang = "pointee_trait"]
-#[rustc_deny_explicit_impl]
+#[cfg_attr(not(bootstrap), rustc_deny_explicit_impl(implement_via_object = false))]
+#[cfg_attr(bootstrap, rustc_deny_explicit_impl)]
 pub trait Pointee {
     /// The type for metadata in pointers and references to `Self`.
     #[lang = "metadata_type"]
diff --git a/library/core/src/ptr/mod.rs b/library/core/src/ptr/mod.rs
index d0cb2f715..acc9ca29d 100644
--- a/library/core/src/ptr/mod.rs
+++ b/library/core/src/ptr/mod.rs
@@ -698,6 +698,7 @@ where
 #[inline(always)]
 #[must_use]
 #[unstable(feature = "ptr_from_ref", issue = "106116")]
+#[rustc_diagnostic_item = "ptr_from_ref"]
 pub const fn from_ref<T: ?Sized>(r: &T) -> *const T {
     r
 }
diff --git a/library/core/src/ptr/mut_ptr.rs b/library/core/src/ptr/mut_ptr.rs
index 2fe5164c3..c6f438578 100644
--- a/library/core/src/ptr/mut_ptr.rs
+++ b/library/core/src/ptr/mut_ptr.rs
@@ -473,20 +473,10 @@ impl<T: ?Sized> *mut T {
     where
         T: Sized,
     {
-        #[cfg(bootstrap)]
         // SAFETY: the caller must uphold the safety contract for `offset`.
         // The obtained pointer is valid for writes since the caller must
         // guarantee that it points to the same allocated object as `self`.
-        unsafe {
-            intrinsics::offset(self, count) as *mut T
-        }
-        #[cfg(not(bootstrap))]
-        // SAFETY: the caller must uphold the safety contract for `offset`.
-        // The obtained pointer is valid for writes since the caller must
-        // guarantee that it points to the same allocated object as `self`.
-        unsafe {
-            intrinsics::offset(self, count)
-        }
+        unsafe { intrinsics::offset(self, count) }
     }
 
     /// Calculates the offset from a pointer in bytes.
@@ -1026,16 +1016,8 @@ impl<T: ?Sized> *mut T {
     where
         T: Sized,
     {
-        #[cfg(bootstrap)]
-        // SAFETY: the caller must uphold the safety contract for `offset`.
-        unsafe {
-            self.offset(count as isize)
-        }
-        #[cfg(not(bootstrap))]
         // SAFETY: the caller must uphold the safety contract for `offset`.
-        unsafe {
-            intrinsics::offset(self, count)
-        }
+        unsafe { intrinsics::offset(self, count) }
     }
 
     /// Calculates the offset from a pointer in bytes (convenience for `.byte_offset(count as isize)`).
diff --git a/library/core/src/ptr/unique.rs b/library/core/src/ptr/unique.rs
index a853f15ed..ff7e91d3e 100644
--- a/library/core/src/ptr/unique.rs
+++ b/library/core/src/ptr/unique.rs
@@ -32,6 +32,8 @@ use crate::ptr::NonNull;
 )]
 #[doc(hidden)]
 #[repr(transparent)]
+// Lang item used experimentally by Miri to define the semantics of `Unique`.
+#[cfg_attr(not(bootstrap), lang = "ptr_unique")]
 pub struct Unique<T: ?Sized> {
     pointer: NonNull<T>,
     // NOTE: this marker has no consequences for variance, but is necessary
diff --git a/library/core/src/slice/index.rs b/library/core/src/slice/index.rs
index 6ef9f9c95..e1e3bcc05 100644
--- a/library/core/src/slice/index.rs
+++ b/library/core/src/slice/index.rs
@@ -152,7 +152,10 @@ mod private_slice_index {
 #[rustc_on_unimplemented(
     on(T = "str", label = "string indices are ranges of `usize`",),
     on(
-        all(any(T = "str", T = "&str", T = "std::string::String"), _Self = "{integer}"),
+        all(
+            any(T = "str", T = "&str", T = "alloc::string::String", T = "std::string::String"),
+            _Self = "{integer}"
+        ),
         note = "you can use `.chars().nth()` or `.bytes().nth()`\n\
                 for more information, see chapter 8 in The Book: \
                 <https://doc.rust-lang.org/book/ch08-02-strings.html#indexing-into-strings>"
diff --git a/library/core/src/slice/iter/macros.rs b/library/core/src/slice/iter/macros.rs
index 3462c0e02..96a145e22 100644
--- a/library/core/src/slice/iter/macros.rs
+++ b/library/core/src/slice/iter/macros.rs
@@ -191,6 +191,39 @@ macro_rules! iterator {
                 self.next_back()
             }
 
+            #[inline]
+            fn fold<B, F>(self, init: B, mut f: F) -> B
+                where
+                    F: FnMut(B, Self::Item) -> B,
+            {
+                // this implementation consists of the following optimizations compared to the
+                // default implementation:
+                // - do-while loop, as is llvm's preferred loop shape,
+                //   see https://releases.llvm.org/16.0.0/docs/LoopTerminology.html#more-canonical-loops
+                // - bumps an index instead of a pointer since the latter case inhibits
+                //   some optimizations, see #111603
+                // - avoids Option wrapping/matching
+                if is_empty!(self) {
+                    return init;
+                }
+                let mut acc = init;
+                let mut i = 0;
+                let len = len!(self);
+                loop {
+                    // SAFETY: the loop iterates `i in 0..len`, which always is in bounds of
+                    // the slice allocation
+                    acc = f(acc, unsafe { & $( $mut_ )? *self.ptr.add(i).as_ptr() });
+                    // SAFETY: `i` can't overflow since it'll only reach usize::MAX if the
+                    // slice had that length, in which case we'll break out of the loop
+                    // after the increment
+                    i = unsafe { i.unchecked_add(1) };
+                    if i == len {
+                        break;
+                    }
+                }
+                acc
+            }
+
             // We override the default implementation, which uses `try_fold`,
             // because this simple implementation generates less LLVM IR and is
             // faster to compile.
diff --git a/library/core/src/slice/mod.rs b/library/core/src/slice/mod.rs
index ea0181e35..e2a2428fb 100644
--- a/library/core/src/slice/mod.rs
+++ b/library/core/src/slice/mod.rs
@@ -851,6 +851,8 @@ impl<T> [T] {
 
     /// Swaps two elements in the slice.
     ///
+    /// If `a` equals to `b`, it's guaranteed that elements won't change value.
+    ///
     /// # Arguments
     ///
     /// * a - The index of the first element
@@ -2995,7 +2997,7 @@ impl<T> [T] {
     /// This reordering has the additional property that any value at position `i < index` will be
     /// less than or equal to any value at a position `j > index`. Additionally, this reordering is
     /// unstable (i.e. any number of equal elements may end up at position `index`), in-place
-    /// (i.e. does not allocate), and *O*(*n*) on average. The worst-case performance is *O*(*n* log *n*).
+    /// (i.e. does not allocate), and runs in *O*(*n*) time.
     /// This function is also known as "kth element" in other libraries.
     ///
     /// It returns a triplet of the following from the reordered slice:
@@ -3045,9 +3047,8 @@ impl<T> [T] {
     /// This reordering has the additional property that any value at position `i < index` will be
     /// less than or equal to any value at a position `j > index` using the comparator function.
     /// Additionally, this reordering is unstable (i.e. any number of equal elements may end up at
-    /// position `index`), in-place (i.e. does not allocate), and *O*(*n*) on average.
-    /// The worst-case performance is *O*(*n* log *n*). This function is also known as
-    /// "kth element" in other libraries.
+    /// position `index`), in-place (i.e. does not allocate), and runs in *O*(*n*) time.
+    /// This function is also known as "kth element" in other libraries.
     ///
     /// It returns a triplet of the following from
     /// the slice reordered according to the provided comparator function: the subslice prior to
@@ -3101,8 +3102,7 @@ impl<T> [T] {
     /// This reordering has the additional property that any value at position `i < index` will be
     /// less than or equal to any value at a position `j > index` using the key extraction function.
     /// Additionally, this reordering is unstable (i.e. any number of equal elements may end up at
-    /// position `index`), in-place (i.e. does not allocate), and *O*(*n*) on average.
-    /// The worst-case performance is *O*(*n* log *n*).
+    /// position `index`), in-place (i.e. does not allocate), and runs in *O*(*n*) time.
     /// This function is also known as "kth element" in other libraries.
     ///
     /// It returns a triplet of the following from
@@ -3113,8 +3113,9 @@ impl<T> [T] {
     ///
     /// # Current implementation
     ///
-    /// The current algorithm is based on the quickselect portion of the same quicksort algorithm
-    /// used for [`sort_unstable`].
+    /// The current algorithm is an introselect implementation based on Pattern Defeating Quicksort, which is also
+    /// the basis for [`sort_unstable`]. The fallback algorithm is Median of Medians using Tukey's Ninther for
+    /// pivot selection, which guarantees linear runtime for all inputs.
     ///
     /// [`sort_unstable`]: slice::sort_unstable
     ///
diff --git a/library/core/src/slice/raw.rs b/library/core/src/slice/raw.rs
index 052fd34d0..48a6eb03b 100644
--- a/library/core/src/slice/raw.rs
+++ b/library/core/src/slice/raw.rs
@@ -32,7 +32,8 @@ use crate::ptr;
 /// * The memory referenced by the returned slice must not be mutated for the duration
 ///   of lifetime `'a`, except inside an `UnsafeCell`.
 ///
-/// * The total size `len * mem::size_of::<T>()` of the slice must be no larger than `isize::MAX`.
+/// * The total size `len * mem::size_of::<T>()` of the slice must be no larger than `isize::MAX`,
+///   and adding that size to `data` must not "wrap around" the address space.
 ///   See the safety documentation of [`pointer::offset`].
 ///
 /// # Caveat
@@ -125,7 +126,8 @@ pub const unsafe fn from_raw_parts<'a, T>(data: *const T, len: usize) -> &'a [T]
 ///   (not derived from the return value) for the duration of lifetime `'a`.
 ///   Both read and write accesses are forbidden.
 ///
-/// * The total size `len * mem::size_of::<T>()` of the slice must be no larger than `isize::MAX`.
+/// * The total size `len * mem::size_of::<T>()` of the slice must be no larger than `isize::MAX`,
+///   and adding that size to `data` must not "wrap around" the address space.
 ///   See the safety documentation of [`pointer::offset`].
 ///
 /// [valid]: ptr#safety
@@ -179,15 +181,16 @@ pub const fn from_mut<T>(s: &mut T) -> &mut [T] {
 ///   the last element, such that the offset from the end to the start pointer is
 ///   the length of the slice.
 ///
-/// * The range must contain `N` consecutive properly initialized values of type `T`:
+/// * The entire memory range of this slice must be contained within a single allocated object!
+///   Slices can never span across multiple allocated objects.
 ///
-///     * The entire memory range of this slice must be contained within a single allocated object!
-///       Slices can never span across multiple allocated objects.
+/// * The range must contain `N` consecutive properly initialized values of type `T`.
 ///
 /// * The memory referenced by the returned slice must not be mutated for the duration
 ///   of lifetime `'a`, except inside an `UnsafeCell`.
 ///
-/// * The total length of the range must be no larger than `isize::MAX`.
+/// * The total length of the range must be no larger than `isize::MAX`,
+///   and adding that size to `data` must not "wrap around" the address space.
 ///   See the safety documentation of [`pointer::offset`].
 ///
 /// Note that a range created from [`slice::as_ptr_range`] fulfills these requirements.
@@ -247,16 +250,17 @@ pub const unsafe fn from_ptr_range<'a, T>(range: Range<*const T>) -> &'a [T] {
 ///   the last element, such that the offset from the end to the start pointer is
 ///   the length of the slice.
 ///
-/// * The range must contain `N` consecutive properly initialized values of type `T`:
+/// * The entire memory range of this slice must be contained within a single allocated object!
+///   Slices can never span across multiple allocated objects.
 ///
-///     * The entire memory range of this slice must be contained within a single allocated object!
-///       Slices can never span across multiple allocated objects.
+/// * The range must contain `N` consecutive properly initialized values of type `T`.
 ///
 /// * The memory referenced by the returned slice must not be accessed through any other pointer
 ///   (not derived from the return value) for the duration of lifetime `'a`.
 ///   Both read and write accesses are forbidden.
 ///
-/// * The total length of the range must be no larger than `isize::MAX`.
+/// * The total length of the range must be no larger than `isize::MAX`,
+///   and adding that size to `data` must not "wrap around" the address space.
 ///   See the safety documentation of [`pointer::offset`].
 ///
 /// Note that a range created from [`slice::as_mut_ptr_range`] fulfills these requirements.
diff --git a/library/core/src/str/converts.rs b/library/core/src/str/converts.rs
index 5f8748206..0f23cf7ae 100644
--- a/library/core/src/str/converts.rs
+++ b/library/core/src/str/converts.rs
@@ -84,6 +84,7 @@ use super::Utf8Error;
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_const_stable(feature = "const_str_from_utf8_shared", since = "1.63.0")]
 #[rustc_allow_const_fn_unstable(str_internals)]
+#[rustc_diagnostic_item = "str_from_utf8"]
 pub const fn from_utf8(v: &[u8]) -> Result<&str, Utf8Error> {
     // FIXME: This should use `?` again, once it's `const`
     match run_utf8_validation(v) {
@@ -127,6 +128,7 @@ pub const fn from_utf8(v: &[u8]) -> Result<&str, Utf8Error> {
 /// errors that can be returned.
 #[stable(feature = "str_mut_extras", since = "1.20.0")]
 #[rustc_const_unstable(feature = "const_str_from_utf8", issue = "91006")]
+#[rustc_diagnostic_item = "str_from_utf8_mut"]
 pub const fn from_utf8_mut(v: &mut [u8]) -> Result<&mut str, Utf8Error> {
     // This should use `?` again, once it's `const`
     match run_utf8_validation(v) {
@@ -167,6 +169,7 @@ pub const fn from_utf8_mut(v: &mut [u8]) -> Result<&mut str, Utf8Error> {
 #[must_use]
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_const_stable(feature = "const_str_from_utf8_unchecked", since = "1.55.0")]
+#[rustc_diagnostic_item = "str_from_utf8_unchecked"]
 pub const unsafe fn from_utf8_unchecked(v: &[u8]) -> &str {
     // SAFETY: the caller must guarantee that the bytes `v` are valid UTF-8.
     // Also relies on `&str` and `&[u8]` having the same layout.
@@ -194,6 +197,7 @@ pub const unsafe fn from_utf8_unchecked(v: &[u8]) -> &str {
 #[must_use]
 #[stable(feature = "str_mut_extras", since = "1.20.0")]
 #[rustc_const_unstable(feature = "const_str_from_utf8_unchecked_mut", issue = "91005")]
+#[rustc_diagnostic_item = "str_from_utf8_unchecked_mut"]
 pub const unsafe fn from_utf8_unchecked_mut(v: &mut [u8]) -> &mut str {
     // SAFETY: the caller must guarantee that the bytes `v`
     // are valid UTF-8, thus the cast to `*mut str` is safe.
diff --git a/library/core/src/str/mod.rs b/library/core/src/str/mod.rs
index ef05b25fd..9a93bb729 100644
--- a/library/core/src/str/mod.rs
+++ b/library/core/src/str/mod.rs
@@ -144,8 +144,6 @@ impl str {
     ///
     /// # Examples
     ///
-    /// Basic usage:
-    ///
     /// ```
     /// let len = "foo".len();
     /// assert_eq!(3, len);
@@ -165,8 +163,6 @@ impl str {
     ///
     /// # Examples
     ///
-    /// Basic usage:
-    ///
     /// ```
     /// let s = "";
     /// assert!(s.is_empty());
@@ -311,8 +307,6 @@ impl str {
     ///
     /// # Examples
     ///
-    /// Basic usage:
-    ///
     /// ```
     /// let bytes = "bors".as_bytes();
     /// assert_eq!(b"bors", bytes);
@@ -387,8 +381,6 @@ impl str {
     ///
     /// # Examples
     ///
-    /// Basic usage:
-    ///
     /// ```
     /// let s = "Hello";
     /// let ptr = s.as_ptr();
@@ -570,8 +562,6 @@ impl str {
     ///
     /// # Examples
     ///
-    /// Basic usage:
-    ///
     /// ```
     /// let s = "Löwe 老虎 Léopard";
     ///
@@ -649,8 +639,6 @@ impl str {
     ///
     /// # Examples
     ///
-    /// Basic usage:
-    ///
     /// ```
     /// let s = "Per Martin-Löf";
     ///
@@ -691,8 +679,6 @@ impl str {
     ///
     /// # Examples
     ///
-    /// Basic usage:
-    ///
     /// ```
     /// let mut s = "Per Martin-Löf".to_string();
     /// {
@@ -840,8 +826,6 @@ impl str {
     ///
     /// # Examples
     ///
-    /// Basic usage:
-    ///
     /// ```
     /// let mut bytes = "bors".bytes();
     ///
@@ -1020,8 +1004,6 @@ impl str {
     ///
     /// # Examples
     ///
-    /// Basic usage:
-    ///
     /// ```
     /// let text = "Zażółć gęślą jaźń";
     ///
@@ -1050,8 +1032,6 @@ impl str {
     ///
     /// # Examples
     ///
-    /// Basic usage:
-    ///
     /// ```
     /// let bananas = "bananas";
     ///
@@ -1077,8 +1057,6 @@ impl str {
     ///
     /// # Examples
     ///
-    /// Basic usage:
-    ///
     /// ```
     /// let bananas = "bananas";
     ///
@@ -1103,8 +1081,6 @@ impl str {
     ///
     /// # Examples
     ///
-    /// Basic usage:
-    ///
     /// ```
     /// let bananas = "bananas";
     ///
@@ -1463,8 +1439,6 @@ impl str {
     ///
     /// # Examples
     ///
-    /// Basic usage:
-    ///
     /// ```
     /// let v: Vec<&str> = "A.B.".split_terminator('.').collect();
     /// assert_eq!(v, ["A", "B"]);
@@ -1696,8 +1670,6 @@ impl str {
     ///
     /// # Examples
     ///
-    /// Basic usage:
-    ///
     /// ```
     /// let v: Vec<&str> = "abcXXXabcYYYabc".matches("abc").collect();
     /// assert_eq!(v, ["abc", "abc", "abc"]);
@@ -1732,8 +1704,6 @@ impl str {
     ///
     /// # Examples
     ///
-    /// Basic usage:
-    ///
     /// ```
     /// let v: Vec<&str> = "abcXXXabcYYYabc".rmatches("abc").collect();
     /// assert_eq!(v, ["abc", "abc", "abc"]);
@@ -1775,8 +1745,6 @@ impl str {
     ///
     /// # Examples
     ///
-    /// Basic usage:
-    ///
     /// ```
     /// let v: Vec<_> = "abcXXXabcYYYabc".match_indices("abc").collect();
     /// assert_eq!(v, [(0, "abc"), (6, "abc"), (12, "abc")]);
@@ -1817,8 +1785,6 @@ impl str {
     ///
     /// # Examples
     ///
-    /// Basic usage:
-    ///
     /// ```
     /// let v: Vec<_> = "abcXXXabcYYYabc".rmatch_indices("abc").collect();
     /// assert_eq!(v, [(12, "abc"), (6, "abc"), (0, "abc")]);
@@ -1845,8 +1811,6 @@ impl str {
     ///
     /// # Examples
     ///
-    /// Basic usage:
-    ///
     /// ```
     /// let s = "\n Hello\tworld\t\n";
     ///
@@ -2085,8 +2049,6 @@ impl str {
     ///
     /// # Examples
     ///
-    /// Basic usage:
-    ///
     /// ```
     /// assert_eq!("11foo1bar11".trim_start_matches('1'), "foo1bar11");
     /// assert_eq!("123foo1bar123".trim_start_matches(char::is_numeric), "foo1bar123");
@@ -2232,8 +2194,6 @@ impl str {
     ///
     /// # Examples
     ///
-    /// Basic usage:
-    ///
     /// ```
     /// assert_eq!("11foo1bar11".trim_left_matches('1'), "foo1bar11");
     /// assert_eq!("123foo1bar123".trim_left_matches(char::is_numeric), "foo1bar123");
diff --git a/library/core/src/task/wake.rs b/library/core/src/task/wake.rs
index 7043ab5ff..b63fd5c90 100644
--- a/library/core/src/task/wake.rs
+++ b/library/core/src/task/wake.rs
@@ -2,6 +2,7 @@
 
 use crate::fmt;
 use crate::marker::{PhantomData, Unpin};
+use crate::ptr;
 
 /// A `RawWaker` allows the implementor of a task executor to create a [`Waker`]
 /// which provides customized wakeup behavior.
@@ -322,6 +323,45 @@ impl Waker {
         Waker { waker }
     }
 
+    /// Creates a new `Waker` that does nothing when `wake` is called.
+    ///
+    /// This is mostly useful for writing tests that need a [`Context`] to poll
+    /// some futures, but are not expecting those futures to wake the waker or
+    /// do not need to do anything specific if it happens.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(noop_waker)]
+    ///
+    /// use std::future::Future;
+    /// use std::task;
+    ///
+    /// let waker = task::Waker::noop();
+    /// let mut cx = task::Context::from_waker(&waker);
+    ///
+    /// let mut future = Box::pin(async { 10 });
+    /// assert_eq!(future.as_mut().poll(&mut cx), task::Poll::Ready(10));
+    /// ```
+    #[inline]
+    #[must_use]
+    #[unstable(feature = "noop_waker", issue = "98286")]
+    pub const fn noop() -> Waker {
+        const VTABLE: RawWakerVTable = RawWakerVTable::new(
+            // Cloning just returns a new no-op raw waker
+            |_| RAW,
+            // `wake` does nothing
+            |_| {},
+            // `wake_by_ref` does nothing
+            |_| {},
+            // Dropping does nothing as we don't allocate anything
+            |_| {},
+        );
+        const RAW: RawWaker = RawWaker::new(ptr::null(), &VTABLE);
+
+        Waker { waker: RAW }
+    }
+
     /// Get a reference to the underlying [`RawWaker`].
     #[inline]
     #[must_use]
diff --git a/library/core/src/tuple.rs b/library/core/src/tuple.rs
index a1388dfee..ac8d04a82 100644
--- a/library/core/src/tuple.rs
+++ b/library/core/src/tuple.rs
@@ -1,6 +1,9 @@
 // See src/libstd/primitive_docs.rs for documentation.
 
 use crate::cmp::Ordering::{self, *};
+#[cfg(not(bootstrap))]
+use crate::marker::ConstParamTy;
+use crate::marker::{StructuralEq, StructuralPartialEq};
 
 // Recursive macro for implementing n-ary tuple functions and operations
 //
@@ -47,6 +50,28 @@ macro_rules! tuple_impls {
 
         maybe_tuple_doc! {
             $($T)+ @
+            #[unstable(feature = "structural_match", issue = "31434")]
+            #[cfg(not(bootstrap))]
+            impl<$($T: ConstParamTy),+> ConstParamTy for ($($T,)+)
+            {}
+        }
+
+        maybe_tuple_doc! {
+            $($T)+ @
+            #[unstable(feature = "structural_match", issue = "31434")]
+            impl<$($T),+> StructuralPartialEq for ($($T,)+)
+            {}
+        }
+
+        maybe_tuple_doc! {
+            $($T)+ @
+            #[unstable(feature = "structural_match", issue = "31434")]
+            impl<$($T),+> StructuralEq for ($($T,)+)
+            {}
+        }
+
+        maybe_tuple_doc! {
+            $($T)+ @
             #[stable(feature = "rust1", since = "1.0.0")]
             impl<$($T: PartialOrd),+> PartialOrd for ($($T,)+)
             where
diff --git a/library/core/src/unicode/printable.py b/library/core/src/unicode/printable.py
index 7c37f5f09..4d39ace06 100755
--- a/library/core/src/unicode/printable.py
+++ b/library/core/src/unicode/printable.py
@@ -119,7 +119,7 @@ def print_singletons(uppers, lowers, uppersname, lowersname):
     print("#[rustfmt::skip]")
     print("const {}: &[u8] = &[".format(lowersname))
     for i in range(0, len(lowers), 8):
-        print("    {}".format(" ".join("{:#04x},".format(l) for l in lowers[i:i+8])))
+        print("    {}".format(" ".join("{:#04x},".format(x) for x in lowers[i:i+8])))
     print("];")
 
 def print_normal(normal, normalname):
diff --git a/library/core/tests/array.rs b/library/core/tests/array.rs
index 0869644c0..982d7853f 100644
--- a/library/core/tests/array.rs
+++ b/library/core/tests/array.rs
@@ -257,14 +257,8 @@ fn iterator_drops() {
     assert_eq!(i.get(), 5);
 }
 
-// This test does not work on targets without panic=unwind support.
-// To work around this problem, test is marked is should_panic, so it will
-// be automagically skipped on unsuitable targets, such as
-// wasm32-unknown-unknown.
-//
-// It means that we use panic for indicating success.
-#[test]
-#[should_panic(expected = "test succeeded")]
+#[test]
+#[cfg_attr(not(panic = "unwind"), ignore = "test requires unwinding support")]
 fn array_default_impl_avoids_leaks_on_panic() {
     use core::sync::atomic::{AtomicUsize, Ordering::Relaxed};
     static COUNTER: AtomicUsize = AtomicUsize::new(0);
@@ -296,7 +290,6 @@ fn array_default_impl_avoids_leaks_on_panic() {
     assert_eq!(*panic_msg, "bomb limit exceeded");
     // check that all bombs are successfully dropped
     assert_eq!(COUNTER.load(Relaxed), 0);
-    panic!("test succeeded")
 }
 
 #[test]
@@ -317,9 +310,8 @@ fn array_map() {
     assert_eq!(b, [1, 2, 3]);
 }
 
-// See note on above test for why `should_panic` is used.
 #[test]
-#[should_panic(expected = "test succeeded")]
+#[cfg_attr(not(panic = "unwind"), ignore = "test requires unwinding support")]
 fn array_map_drop_safety() {
     static DROPPED: AtomicUsize = AtomicUsize::new(0);
     struct DropCounter;
@@ -341,7 +333,6 @@ fn array_map_drop_safety() {
     });
     assert!(success.is_err());
     assert_eq!(DROPPED.load(Ordering::SeqCst), num_to_create);
-    panic!("test succeeded")
 }
 
 #[test]
diff --git a/library/core/tests/clone.rs b/library/core/tests/clone.rs
index aafe5ced2..64193e115 100644
--- a/library/core/tests/clone.rs
+++ b/library/core/tests/clone.rs
@@ -1,5 +1,5 @@
 #[test]
-#[cfg_attr(not(bootstrap), allow(suspicious_double_ref_op))]
+#[allow(suspicious_double_ref_op)]
 fn test_borrowed_clone() {
     let x = 5;
     let y: &i32 = &x;
diff --git a/library/core/tests/future.rs b/library/core/tests/future.rs
index 74b6f74e4..db417256d 100644
--- a/library/core/tests/future.rs
+++ b/library/core/tests/future.rs
@@ -30,7 +30,6 @@ fn poll_n(val: usize, num: usize) -> PollN {
 }
 
 #[test]
-#[cfg_attr(miri, ignore)] // self-referential generators do not work with Miri's aliasing checks
 fn test_join() {
     block_on(async move {
         let x = join!(async { 0 }).await;
diff --git a/library/core/tests/iter/adapters/step_by.rs b/library/core/tests/iter/adapters/step_by.rs
index 94f2fa8c2..4c5b1dd9a 100644
--- a/library/core/tests/iter/adapters/step_by.rs
+++ b/library/core/tests/iter/adapters/step_by.rs
@@ -244,3 +244,58 @@ fn test_step_by_skip() {
     assert_eq!((0..=50).step_by(10).nth(3), Some(30));
     assert_eq!((200..=255u8).step_by(10).nth(3), Some(230));
 }
+
+
+struct DeOpt<I: Iterator>(I);
+
+impl<I: Iterator> Iterator for DeOpt<I> {
+    type Item = I::Item;
+
+    fn next(&mut self) -> core::option::Option<Self::Item> {
+        self.0.next()
+    }
+}
+
+impl<I: DoubleEndedIterator> DoubleEndedIterator for DeOpt<I> {
+    fn next_back(&mut self) -> core::option::Option<Self::Item> {
+        self.0.next_back()
+    }
+}
+
+#[test]
+fn test_step_by_fold_range_specialization() {
+    macro_rules! t {
+        ($range:expr, $var: ident, $body:tt) => {
+            {
+                // run the same tests for the non-optimized version
+                let mut $var = DeOpt($range);
+                $body
+            }
+            {
+                let mut $var = $range;
+                $body
+            }
+        }
+    }
+
+    t!((1usize..5).step_by(1), r, {
+        assert_eq!(r.next_back(), Some(4));
+        assert_eq!(r.sum::<usize>(), 6);
+    });
+
+    t!((0usize..4).step_by(2), r, {
+        assert_eq!(r.next(), Some(0));
+        assert_eq!(r.sum::<usize>(), 2);
+    });
+
+
+    t!((0usize..5).step_by(2), r, {
+        assert_eq!(r.next(), Some(0));
+        assert_eq!(r.sum::<usize>(), 6);
+    });
+
+    t!((usize::MAX - 6 .. usize::MAX).step_by(5), r, {
+        assert_eq!(r.next(), Some(usize::MAX - 6));
+        assert_eq!(r.sum::<usize>(), usize::MAX - 1);
+    });
+}
diff --git a/library/core/tests/lib.rs b/library/core/tests/lib.rs
index 3933e3289..3e6d31fcd 100644
--- a/library/core/tests/lib.rs
+++ b/library/core/tests/lib.rs
@@ -109,7 +109,7 @@
 #![feature(utf8_chunks)]
 #![feature(is_ascii_octdigit)]
 #![feature(get_many_mut)]
-#![cfg_attr(not(bootstrap), feature(offset_of))]
+#![feature(offset_of)]
 #![deny(unsafe_op_in_unsafe_fn)]
 #![deny(fuzzy_provenance_casts)]
 
diff --git a/library/core/tests/manually_drop.rs b/library/core/tests/manually_drop.rs
index 9eac27973..22d72d219 100644
--- a/library/core/tests/manually_drop.rs
+++ b/library/core/tests/manually_drop.rs
@@ -1,3 +1,5 @@
+#![cfg_attr(not(bootstrap), allow(undropped_manually_drops))]
+
 use core::mem::ManuallyDrop;
 
 #[test]
diff --git a/library/core/tests/mem.rs b/library/core/tests/mem.rs
index aee9c89b5..5c2e18745 100644
--- a/library/core/tests/mem.rs
+++ b/library/core/tests/mem.rs
@@ -366,7 +366,6 @@ fn const_maybe_uninit() {
 }
 
 #[test]
-#[cfg(not(bootstrap))]
 fn offset_of() {
     #[repr(C)]
     struct Foo {
@@ -391,7 +390,7 @@ fn offset_of() {
     struct Generic<T> {
         x: u8,
         y: u32,
-        z: T
+        z: T,
     }
 
     trait Trait {}
@@ -409,7 +408,6 @@ fn offset_of() {
 }
 
 #[test]
-#[cfg(not(bootstrap))]
 fn offset_of_union() {
     #[repr(C)]
     union Foo {
@@ -429,7 +427,6 @@ fn offset_of_union() {
 }
 
 #[test]
-#[cfg(not(bootstrap))]
 fn offset_of_dst() {
     #[repr(C)]
     struct Alpha {
@@ -469,7 +466,6 @@ fn offset_of_dst() {
 }
 
 #[test]
-#[cfg(not(bootstrap))]
 fn offset_of_packed() {
     #[repr(C, packed)]
     struct Foo {
@@ -482,7 +478,6 @@ fn offset_of_packed() {
 }
 
 #[test]
-#[cfg(not(bootstrap))]
 fn offset_of_projection() {
     #[repr(C)]
     struct Foo {
@@ -503,7 +498,6 @@ fn offset_of_projection() {
 }
 
 #[test]
-#[cfg(not(bootstrap))]
 fn offset_of_alias() {
     #[repr(C)]
     struct Foo {
@@ -518,7 +512,6 @@ fn offset_of_alias() {
 }
 
 #[test]
-#[cfg(not(bootstrap))]
 fn const_offset_of() {
     #[repr(C)]
     struct Foo {
@@ -534,7 +527,6 @@ fn const_offset_of() {
 }
 
 #[test]
-#[cfg(not(bootstrap))]
 fn offset_of_without_const_promotion() {
     #[repr(C)]
     struct Foo<SuppressConstPromotion> {
@@ -555,7 +547,6 @@ fn offset_of_without_const_promotion() {
 }
 
 #[test]
-#[cfg(not(bootstrap))]
 fn offset_of_addr() {
     #[repr(C)]
     struct Foo {
diff --git a/library/core/tests/net/ip_addr.rs b/library/core/tests/net/ip_addr.rs
index 5a6ac08c0..7530fc084 100644
--- a/library/core/tests/net/ip_addr.rs
+++ b/library/core/tests/net/ip_addr.rs
@@ -139,7 +139,7 @@ fn ipv6_addr_to_string() {
 
     // ipv4-compatible address
     let a1 = Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0xc000, 0x280);
-    assert_eq!(a1.to_string(), "::192.0.2.128");
+    assert_eq!(a1.to_string(), "::c000:280");
 
     // v6 address with no zero segments
     assert_eq!(Ipv6Addr::new(8, 9, 10, 11, 12, 13, 14, 15).to_string(), "8:9:a:b:c:d:e:f");
@@ -316,7 +316,7 @@ fn ip_properties() {
 
     check!("::", unspec);
     check!("::1", loopback);
-    check!("::0.0.0.2", global);
+    check!("::2", global);
     check!("1::", global);
     check!("fc00::");
     check!("fdff:ffff::");
@@ -607,7 +607,7 @@ fn ipv6_properties() {
 
     check!("::1", &[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1], loopback);
 
-    check!("::0.0.0.2", &[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2], global | unicast_global);
+    check!("::2", &[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2], global | unicast_global);
 
     check!("1::", &[0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0], global | unicast_global);
 
diff --git a/library/core/tests/net/socket_addr.rs b/library/core/tests/net/socket_addr.rs
index 68c7cd94d..35a69cead 100644
--- a/library/core/tests/net/socket_addr.rs
+++ b/library/core/tests/net/socket_addr.rs
@@ -34,7 +34,7 @@ fn ipv6_socket_addr_to_string() {
     // IPv4-compatible address.
     assert_eq!(
         SocketAddrV6::new(Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0xc000, 0x280), 8080, 0, 0).to_string(),
-        "[::192.0.2.128]:8080"
+        "[::c000:280]:8080"
     );
 
     // IPv6 address with no zero segments.
diff --git a/library/core/tests/ptr.rs b/library/core/tests/ptr.rs
index c02cd99cc..ee885adfe 100644
--- a/library/core/tests/ptr.rs
+++ b/library/core/tests/ptr.rs
@@ -1001,7 +1001,7 @@ fn nonnull_tagged_pointer_with_provenance() {
     assert_eq!(p.tag(), 3);
     assert_eq!(unsafe { *p.pointer().as_ptr() }, 10);
 
-    unsafe { Box::from_raw(p.pointer().as_ptr()) };
+    unsafe { drop(Box::from_raw(p.pointer().as_ptr())) };
 
     /// A non-null pointer type which carries several bits of metadata and maintains provenance.
     #[repr(transparent)]