Auto merge of #67670 - oli-obk:rollup-2dp08sd, r=oli-obk

Rollup of 15 pull requests

Successful merges:

 - #65244 (add IntoFuture trait and support for await)
 - #67576 (reuse `capacity` variable in slice::repeat)
 - #67588 (Use NonNull in slice::Iter and slice::IterMut.)
 - #67594 (Update libc to 0.2.66)
 - #67602 (Use issue = "none" instead of "0" in intrinsics)
 - #67604 (Add Scalar::to_(u|i)16 methods)
 - #67617 (Remove `compiler_builtins_lib` documentation)
 - #67621 (Use the correct type for static qualifs)
 - #67629 (Remove redundant link texts)
 - #67632 (Convert collapsed to shortcut reference links)
 - #67633 (Update .mailmap)
 - #67635 (Document safety of Path casting)
 - #67654 (Add regression test for old NLL ICE)
 - #67659 (Stabilize the `matches!` macro)
 - #67664 (Fix some mailmap entries)

Failed merges:

r? @ghost

46 files changed, 267 insertions, 174 deletions

diff --git a/.mailmap b/.mailmap
index a2e3c581eab..3e512377d03 100644
--- a/.mailmap
+++ b/.mailmap
@@ -54,9 +54,10 @@ Chris C Cerami <chrisccerami@users.noreply.github.com> Chris C Cerami <chrisccer
 Chris Pressey <cpressey@gmail.com>
 Chris Thorn <chris@thorn.co> Chris Thorn <thorn@thoughtbot.com>
 Chris Vittal <christopher.vittal@gmail.com> Christopher Vittal <christopher.vittal@gmail.com>
-Christian Poveda <christianpoveda@protonmail.com> <cn.poveda.ruiz@gmail.com>
-Christian Poveda <christianpoveda@protonmail.com> <z1mvader@protonmail.com>
-Christian Poveda <christianpoveda@protonmail.com> <cpovedar@fnal.gov>
+Christian Poveda <git@christianpoveda.xyz> <christianpoveda@protonmail.com>
+Christian Poveda <git@christianpoveda.xyz> <cn.poveda.ruiz@gmail.com>
+Christian Poveda <git@christianpoveda.xyz> <z1mvader@protonmail.com>
+Christian Poveda <git@christianpoveda.xyz> <cpovedar@fnal.gov>
 Clark Gaebel <cg.wowus.cg@gmail.com> <cgaebel@mozilla.com>
 Clinton Ryan <clint.ryan3@gmail.com>
 Corey Richardson <corey@octayn.net> Elaine "See More" Nemo <corey@octayn.net>
@@ -154,6 +155,7 @@ Lindsey Kuper <lindsey@composition.al> <lkuper@mozilla.com>
 Luke Metz <luke.metz@students.olin.edu>
 Luqman Aden <me@luqman.ca> <laden@csclub.uwaterloo.ca>
 Luqman Aden <me@luqman.ca> <laden@mozilla.com>
+Manish Goregaokar <manishsmail@gmail.com>
 Marcell Pardavi <marcell.pardavi@gmail.com>
 Margaret Meyerhofer <mmeyerho@andrew.cmu.edu> <mmeyerho@andrew>
 Mark Rousskov <mark.simulacrum@gmail.com>
@@ -185,6 +187,7 @@ Neil Pankey <npankey@gmail.com> <neil@wire.im>
 Nick Platt <platt.nicholas@gmail.com>
 Nicole Mazzuca <npmazzuca@gmail.com>
 Nif Ward <nif.ward@gmail.com>
+Nika Layzell <michael@thelayzells.com>
 Oliver Middleton <olliemail27@gmail.com> <ollie27@users.noreply.github.com>
 Oliver Scherer <oliver.schneider@kit.edu> <git-spam-no-reply9815368754983@oli-obk.de>
 Oliver Scherer <oliver.schneider@kit.edu> <git-spam9815368754983@oli-obk.de>
@@ -204,7 +207,6 @@ Paul Faria <paul_faria@ultimatesoftware.com> Paul Faria <Nashenas88@gmail.com>
 Peer Aramillo Irizar <peer.aramillo.irizar@gmail.com> parir <peer.aramillo.irizar@gmail.com>
 Peter Elmers <peter.elmers@yahoo.com> <peter.elmers@rice.edu>
 Peter Liniker <peter.liniker+github@gmail.com>
-Peter Zotov <whitequark@whitequark.org>
 Phil Dawes <phil@phildawes.net> Phil Dawes <pdawes@drw.com>
 Philipp Brüschweiler <blei42@gmail.com> <blei42@gmail.com>
 Philipp Brüschweiler <blei42@gmail.com> <bruphili@student.ethz.ch>
@@ -255,6 +257,7 @@ Ulrik Sverdrup <bluss@users.noreply.github.com> Ulrik Sverdrup <root@localhost>
 Vadim Petrochenkov <vadim.petrochenkov@gmail.com>
 Vadim Petrochenkov <vadim.petrochenkov@gmail.com> petrochenkov <vadim.petrochenkov@gmail.com>
 Vitali Haravy <HumaneProgrammer@gmail.com> Vitali Haravy <humaneprogrammer@gmail.com>
+whitequark <whitequark@whitequark.org>
 William Ting <io@williamting.com> <william.h.ting@gmail.com>
 Xuefeng Wu <benewu@gmail.com> Xuefeng Wu <xfwu@thoughtworks.com>
 Xuefeng Wu <benewu@gmail.com> XuefengWu <benewu@gmail.com>
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 8fbbd7c4a2e..fc8ca5d07b2 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -367,7 +367,7 @@ labels to triage issues:
   to fix the issue.
 
 * The dark blue **final-comment-period** label marks bugs that are using the
-  RFC signoff functionality of [rfcbot][rfcbot] and are currently in the final
+  RFC signoff functionality of [rfcbot] and are currently in the final
   comment period.
 
 * Red, **I**-prefixed labels indicate the **importance** of the issue. The
@@ -385,7 +385,7 @@ labels to triage issues:
   label.
 
 * The gray **proposed-final-comment-period** label marks bugs that are using
-  the RFC signoff functionality of [rfcbot][rfcbot] and are currently awaiting
+  the RFC signoff functionality of [rfcbot] and are currently awaiting
   signoff of all team members in order to enter the final comment period.
 
 * Pink, **regression**-prefixed labels track regressions from stable to the
diff --git a/Cargo.lock b/Cargo.lock
index f3fad1296bf..847a406985d 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1773,9 +1773,9 @@ checksum = "b294d6fa9ee409a054354afc4352b0b9ef7ca222c69b8812cbea9e7d2bf3783f"
 
 [[package]]
 name = "libc"
-version = "0.2.64"
+version = "0.2.66"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "74dfca3d9957906e8d1e6a0b641dc9a59848e793f1da2165889fd4f62d10d79c"
+checksum = "d515b1f41455adea1313a4a2ac8a8a477634fbae63cc6100e3aebb207ce61558"
 dependencies = [
  "rustc-std-workspace-core",
 ]
diff --git a/RELEASES.md b/RELEASES.md
index 5afc6f9bdc0..e3597473f62 100644
--- a/RELEASES.md
+++ b/RELEASES.md
@@ -4951,10 +4951,10 @@ Stabilized APIs
 ---------------
 
 * [`std::panic`]
-* [`std::panic::catch_unwind`][] (renamed from `recover`)
-* [`std::panic::resume_unwind`][] (renamed from `propagate`)
-* [`std::panic::AssertUnwindSafe`][] (renamed from `AssertRecoverSafe`)
-* [`std::panic::UnwindSafe`][] (renamed from `RecoverSafe`)
+* [`std::panic::catch_unwind`] (renamed from `recover`)
+* [`std::panic::resume_unwind`] (renamed from `propagate`)
+* [`std::panic::AssertUnwindSafe`] (renamed from `AssertRecoverSafe`)
+* [`std::panic::UnwindSafe`] (renamed from `RecoverSafe`)
 * [`str::is_char_boundary`]
 * [`<*const T>::as_ref`]
 * [`<*mut T>::as_ref`]
@@ -5234,18 +5234,18 @@ Libraries
 ---------
 
 * Stabilized APIs:
-  * [`str::encode_utf16`][] (renamed from `utf16_units`)
-  * [`str::EncodeUtf16`][] (renamed from `Utf16Units`)
+  * [`str::encode_utf16`] (renamed from `utf16_units`)
+  * [`str::EncodeUtf16`] (renamed from `Utf16Units`)
   * [`Ref::map`]
   * [`RefMut::map`]
   * [`ptr::drop_in_place`]
   * [`time::Instant`]
   * [`time::SystemTime`]
   * [`Instant::now`]
-  * [`Instant::duration_since`][] (renamed from `duration_from_earlier`)
+  * [`Instant::duration_since`] (renamed from `duration_from_earlier`)
   * [`Instant::elapsed`]
   * [`SystemTime::now`]
-  * [`SystemTime::duration_since`][] (renamed from `duration_from_earlier`)
+  * [`SystemTime::duration_since`] (renamed from `duration_from_earlier`)
   * [`SystemTime::elapsed`]
   * Various `Add`/`Sub` impls for `Time` and `SystemTime`
   * [`SystemTimeError`]
@@ -5432,8 +5432,8 @@ Libraries
 
 * Stabilized APIs
   * `Path`
-    * [`Path::strip_prefix`][] (renamed from relative_from)
-    * [`path::StripPrefixError`][] (new error type returned from strip_prefix)
+    * [`Path::strip_prefix`] (renamed from relative_from)
+    * [`path::StripPrefixError`] (new error type returned from strip_prefix)
   * `Ipv4Addr`
     * [`Ipv4Addr::is_loopback`]
     * [`Ipv4Addr::is_private`]
@@ -5646,7 +5646,7 @@ Libraries
 
 * Stabilized APIs:
   [`Read::read_exact`],
-  [`ErrorKind::UnexpectedEof`][] (renamed from `UnexpectedEOF`),
+  [`ErrorKind::UnexpectedEof`] (renamed from `UnexpectedEOF`),
   [`fs::DirBuilder`], [`fs::DirBuilder::new`],
   [`fs::DirBuilder::recursive`], [`fs::DirBuilder::create`],
   [`os::unix::fs::DirBuilderExt`],
@@ -5659,11 +5659,11 @@ Libraries
   [`collections::hash_set::HashSet::drain`],
   [`collections::binary_heap::Drain`],
   [`collections::binary_heap::BinaryHeap::drain`],
-  [`Vec::extend_from_slice`][] (renamed from `push_all`),
+  [`Vec::extend_from_slice`] (renamed from `push_all`),
   [`Mutex::get_mut`], [`Mutex::into_inner`], [`RwLock::get_mut`],
   [`RwLock::into_inner`],
-  [`Iterator::min_by_key`][] (renamed from `min_by`),
-  [`Iterator::max_by_key`][] (renamed from `max_by`).
+  [`Iterator::min_by_key`] (renamed from `min_by`),
+  [`Iterator::max_by_key`] (renamed from `max_by`).
 * The [core library][1.6co] is stable, as are most of its APIs.
 * [The `assert_eq!` macro supports arguments that don't implement
   `Sized`][1.6ae], such as arrays. In this way it behaves more like
diff --git a/src/doc/unstable-book/src/language-features/lang-items.md b/src/doc/unstable-book/src/language-features/lang-items.md
index d4ad65e84b7..6f096e582f5 100644
--- a/src/doc/unstable-book/src/language-features/lang-items.md
+++ b/src/doc/unstable-book/src/language-features/lang-items.md
@@ -188,11 +188,7 @@ pub extern fn rust_begin_panic(info: &PanicInfo) -> ! {
 
 In many cases, you may need to manually link to the `compiler_builtins` crate
 when building a `no_std` binary. You may observe this via linker error messages
-such as "```undefined reference to `__rust_probestack'```". Using this crate
-also requires enabling the library feature `compiler_builtins_lib`. You can read
-more about this [here][compiler-builtins-lib].
-
-[compiler-builtins-lib]: ../library-features/compiler-builtins-lib.md
+such as "```undefined reference to `__rust_probestack'```".
 
 ## More about the language items
 
diff --git a/src/doc/unstable-book/src/library-features/compiler-builtins-lib.md b/src/doc/unstable-book/src/library-features/compiler-builtins-lib.md
deleted file mode 100644
index 6c71c3f2ce1..00000000000
--- a/src/doc/unstable-book/src/library-features/compiler-builtins-lib.md
+++ /dev/null
@@ -1,35 +0,0 @@
-# `compiler_builtins_lib`
-
-The tracking issue for this feature is: None.
-
-------------------------
-
-This feature is required to link to the `compiler_builtins` crate which contains
-"compiler intrinsics". Compiler intrinsics are software implementations of basic
-operations like multiplication of `u64`s. These intrinsics are only required on
-platforms where these operations don't directly map to a hardware instruction.
-
-You should never need to explicitly link to the `compiler_builtins` crate when
-building "std" programs as `compiler_builtins` is already in the dependency
-graph of `std`. But you may need it when building `no_std` **binary** crates. If
-you get a *linker* error like:
-
-``` text
-$PWD/src/main.rs:11: undefined reference to `__aeabi_lmul'
-$PWD/src/main.rs:11: undefined reference to `__aeabi_uldivmod'
-```
-
-That means that you need to link to this crate.
-
-When you link to this crate, make sure it only appears once in your crate
-dependency graph. Also, it doesn't matter where in the dependency graph you
-place the `compiler_builtins` crate.
-
-<!-- NOTE(ignore) doctests don't support `no_std` binaries -->
-
-``` rust,ignore
-#![feature(compiler_builtins_lib)]
-#![no_std]
-
-extern crate compiler_builtins;
-```
diff --git a/src/liballoc/collections/binary_heap.rs b/src/liballoc/collections/binary_heap.rs
index 0148711bb86..c527b378f74 100644
--- a/src/liballoc/collections/binary_heap.rs
+++ b/src/liballoc/collections/binary_heap.rs
@@ -1094,7 +1094,7 @@ impl<T> FusedIterator for Iter<'_, T> {}
 
 /// An owning iterator over the elements of a `BinaryHeap`.
 ///
-/// This `struct` is created by the [`into_iter`] method on [`BinaryHeap`][`BinaryHeap`]
+/// This `struct` is created by the [`into_iter`] method on [`BinaryHeap`]
 /// (provided by the `IntoIterator` trait). See its documentation for more.
 ///
 /// [`into_iter`]: struct.BinaryHeap.html#method.into_iter
diff --git a/src/liballoc/collections/btree/map.rs b/src/liballoc/collections/btree/map.rs
index 7d0a862d79e..fa8aae04011 100644
--- a/src/liballoc/collections/btree/map.rs
+++ b/src/liballoc/collections/btree/map.rs
@@ -283,7 +283,7 @@ pub struct IterMut<'a, K: 'a, V: 'a> {
 
 /// An owning iterator over the entries of a `BTreeMap`.
 ///
-/// This `struct` is created by the [`into_iter`] method on [`BTreeMap`][`BTreeMap`]
+/// This `struct` is created by the [`into_iter`] method on [`BTreeMap`]
 /// (provided by the `IntoIterator` trait). See its documentation for more.
 ///
 /// [`into_iter`]: struct.BTreeMap.html#method.into_iter
diff --git a/src/liballoc/collections/btree/set.rs b/src/liballoc/collections/btree/set.rs
index 282d163141b..f5487426814 100644
--- a/src/liballoc/collections/btree/set.rs
+++ b/src/liballoc/collections/btree/set.rs
@@ -83,7 +83,7 @@ impl<T: fmt::Debug> fmt::Debug for Iter<'_, T> {
 
 /// An owning iterator over the items of a `BTreeSet`.
 ///
-/// This `struct` is created by the [`into_iter`] method on [`BTreeSet`][`BTreeSet`]
+/// This `struct` is created by the [`into_iter`] method on [`BTreeSet`]
 /// (provided by the `IntoIterator` trait). See its documentation for more.
 ///
 /// [`BTreeSet`]: struct.BTreeSet.html
diff --git a/src/liballoc/collections/linked_list.rs b/src/liballoc/collections/linked_list.rs
index 4931093c55c..29bf2fdb30c 100644
--- a/src/liballoc/collections/linked_list.rs
+++ b/src/liballoc/collections/linked_list.rs
@@ -105,7 +105,7 @@ impl<T: fmt::Debug> fmt::Debug for IterMut<'_, T> {
 
 /// An owning iterator over the elements of a `LinkedList`.
 ///
-/// This `struct` is created by the [`into_iter`] method on [`LinkedList`][`LinkedList`]
+/// This `struct` is created by the [`into_iter`] method on [`LinkedList`]
 /// (provided by the `IntoIterator` trait). See its documentation for more.
 ///
 /// [`into_iter`]: struct.LinkedList.html#method.into_iter
diff --git a/src/liballoc/collections/vec_deque.rs b/src/liballoc/collections/vec_deque.rs
index 9d2eec94a0c..2cc450bb68a 100644
--- a/src/liballoc/collections/vec_deque.rs
+++ b/src/liballoc/collections/vec_deque.rs
@@ -2474,7 +2474,7 @@ impl<T> FusedIterator for IterMut<'_, T> {}
 
 /// An owning iterator over the elements of a `VecDeque`.
 ///
-/// This `struct` is created by the [`into_iter`] method on [`VecDeque`][`VecDeque`]
+/// This `struct` is created by the [`into_iter`] method on [`VecDeque`]
 /// (provided by the `IntoIterator` trait). See its documentation for more.
 ///
 /// [`into_iter`]: struct.VecDeque.html#method.into_iter
diff --git a/src/liballoc/fmt.rs b/src/liballoc/fmt.rs
index 01d4913665c..e6162e0f571 100644
--- a/src/liballoc/fmt.rs
+++ b/src/liballoc/fmt.rs
@@ -330,7 +330,7 @@
 //!
 //! Additionally, the return value of this function is [`fmt::Result`] which is a
 //! type alias of [`Result`]`<(), `[`std::fmt::Error`]`>`. Formatting implementations
-//! should ensure that they propagate errors from the [`Formatter`][`Formatter`] (e.g., when
+//! should ensure that they propagate errors from the [`Formatter`] (e.g., when
 //! calling [`write!`]). However, they should never return errors spuriously. That
 //! is, a formatting implementation must and may only return an error if the
 //! passed-in [`Formatter`] returns an error. This is because, contrary to what
diff --git a/src/liballoc/slice.rs b/src/liballoc/slice.rs
index 2f6d10c027b..7b83658fca6 100644
--- a/src/liballoc/slice.rs
+++ b/src/liballoc/slice.rs
@@ -450,7 +450,8 @@ impl<T> [T] {
         // and `rem` is the remaining part of `n`.
 
         // Using `Vec` to access `set_len()`.
-        let mut buf = Vec::with_capacity(self.len().checked_mul(n).expect("capacity overflow"));
+        let capacity = self.len().checked_mul(n).expect("capacity overflow");
+        let mut buf = Vec::with_capacity(capacity);
 
         // `2^expn` repetition is done by doubling `buf` `expn`-times.
         buf.extend(self);
@@ -476,7 +477,7 @@ impl<T> [T] {
 
         // `rem` (`= n - 2^expn`) repetition is done by copying
         // first `rem` repetitions from `buf` itself.
-        let rem_len = self.len() * n - buf.len(); // `self.len() * rem`
+        let rem_len = capacity - buf.len(); // `self.len() * rem`
         if rem_len > 0 {
             // `buf.extend(buf[0 .. rem_len])`:
             unsafe {
@@ -487,8 +488,7 @@ impl<T> [T] {
                     rem_len,
                 );
                 // `buf.len() + rem_len` equals to `buf.capacity()` (`= self.len() * n`).
-                let buf_cap = buf.capacity();
-                buf.set_len(buf_cap);
+                buf.set_len(capacity);
             }
         }
         buf
diff --git a/src/liballoc/vec.rs b/src/liballoc/vec.rs
index dcd7dc49526..93a51ccb207 100644
--- a/src/liballoc/vec.rs
+++ b/src/liballoc/vec.rs
@@ -242,7 +242,7 @@ use crate::raw_vec::RawVec;
 /// ensures no unnecessary allocations or deallocations occur. Emptying a `Vec`
 /// and then filling it back up to the same [`len`] should incur no calls to
 /// the allocator. If you wish to free up unused memory, use
-/// [`shrink_to_fit`][`shrink_to_fit`].
+/// [`shrink_to_fit`].
 ///
 /// [`push`] and [`insert`] will never (re)allocate if the reported capacity is
 /// sufficient. [`push`] and [`insert`] *will* (re)allocate if
@@ -2461,7 +2461,7 @@ where
 
 /// An iterator that moves out of a vector.
 ///
-/// This `struct` is created by the `into_iter` method on [`Vec`][`Vec`] (provided
+/// This `struct` is created by the `into_iter` method on [`Vec`] (provided
 /// by the [`IntoIterator`] trait).
 ///
 /// [`Vec`]: struct.Vec.html
diff --git a/src/libcore/future/future.rs b/src/libcore/future/future.rs
index f14ed38b9b0..dcb819f9381 100644
--- a/src/libcore/future/future.rs
+++ b/src/libcore/future/future.rs
@@ -99,6 +99,21 @@ pub trait Future {
     fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output>;
 }
 
+/// Conversion into a `Future`.
+#[unstable(feature = "into_future", issue = "67644")]
+pub trait IntoFuture {
+    /// The output that the future will produce on completion.
+    #[unstable(feature = "into_future", issue = "67644")]
+    type Output;
+    /// Which kind of future are we turning this into?
+    #[unstable(feature = "into_future", issue = "67644")]
+    type Future: Future<Output = Self::Output>;
+
+    /// Creates a future from a value.
+    #[unstable(feature = "into_future", issue = "67644")]
+    fn into_future(self) -> Self::Future;
+}
+
 #[stable(feature = "futures_api", since = "1.36.0")]
 impl<F: ?Sized + Future + Unpin> Future for &mut F {
     type Output = F::Output;
@@ -119,3 +134,13 @@ where
         Pin::get_mut(self).as_mut().poll(cx)
     }
 }
+
+#[unstable(feature = "into_future", issue = "67644")]
+impl<F: Future> IntoFuture for F {
+    type Output = F::Output;
+    type Future = F;
+
+    fn into_future(self) -> Self::Future {
+        self
+    }
+}
diff --git a/src/libcore/future/mod.rs b/src/libcore/future/mod.rs
index 89ea4713cfd..aecd57b9ce7 100644
--- a/src/libcore/future/mod.rs
+++ b/src/libcore/future/mod.rs
@@ -5,3 +5,6 @@
 mod future;
 #[stable(feature = "futures_api", since = "1.36.0")]
 pub use self::future::Future;
+
+#[unstable(feature = "into_future", issue = "67644")]
+pub use self::future::IntoFuture;
diff --git a/src/libcore/intrinsics.rs b/src/libcore/intrinsics.rs
index 502090731f4..416c73f50bd 100644
--- a/src/libcore/intrinsics.rs
+++ b/src/libcore/intrinsics.rs
@@ -697,7 +697,7 @@ extern "rust-intrinsic" {
 
     #[rustc_const_stable(feature = "const_min_align_of", since = "1.40.0")]
     pub fn min_align_of<T>() -> usize;
-    #[rustc_const_unstable(feature = "const_pref_align_of", issue = "0")]
+    #[rustc_const_unstable(feature = "const_pref_align_of", issue = "none")]
     pub fn pref_align_of<T>() -> usize;
 
     /// The size of the referenced value in bytes.
@@ -708,13 +708,13 @@ extern "rust-intrinsic" {
     pub fn min_align_of_val<T: ?Sized>(_: &T) -> usize;
 
     /// Gets a static string slice containing the name of a type.
-    #[rustc_const_unstable(feature = "const_type_name", issue = "0")]
+    #[rustc_const_unstable(feature = "const_type_name", issue = "none")]
     pub fn type_name<T: ?Sized>() -> &'static str;
 
     /// 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.
-    #[rustc_const_unstable(feature = "const_type_id", issue = "0")]
+    #[rustc_const_unstable(feature = "const_type_id", issue = "none")]
     pub fn type_id<T: ?Sized + 'static>() -> u64;
 
     /// A guard for unsafe functions that cannot ever be executed if `T` is uninhabited:
@@ -1222,7 +1222,7 @@ extern "rust-intrinsic" {
     /// let num_leading = unsafe { ctlz_nonzero(x) };
     /// assert_eq!(num_leading, 3);
     /// ```
-    #[rustc_const_unstable(feature = "constctlz", issue = "0")]
+    #[rustc_const_unstable(feature = "constctlz", issue = "none")]
     pub fn ctlz_nonzero<T>(x: T) -> T;
 
     /// Returns the number of trailing unset bits (zeroes) in an integer type `T`.
@@ -1267,7 +1267,7 @@ extern "rust-intrinsic" {
     /// let num_trailing = unsafe { cttz_nonzero(x) };
     /// assert_eq!(num_trailing, 3);
     /// ```
-    #[rustc_const_unstable(feature = "const_cttz", issue = "0")]
+    #[rustc_const_unstable(feature = "const_cttz", issue = "none")]
     pub fn cttz_nonzero<T>(x: T) -> T;
 
     /// Reverses the bytes in an integer type `T`.
@@ -1396,7 +1396,7 @@ extern "rust-intrinsic" {
     pub fn nontemporal_store<T>(ptr: *mut T, val: T);
 
     /// See documentation of `<*const T>::offset_from` for details.
-    #[rustc_const_unstable(feature = "const_ptr_offset_from", issue = "0")]
+    #[rustc_const_unstable(feature = "const_ptr_offset_from", issue = "none")]
     pub fn ptr_offset_from<T>(ptr: *const T, base: *const T) -> isize;
 
     /// Internal hook used by Miri to implement unwinding.
diff --git a/src/libcore/macros/mod.rs b/src/libcore/macros/mod.rs
index e66d9c5bd2e..9a52823a454 100644
--- a/src/libcore/macros/mod.rs
+++ b/src/libcore/macros/mod.rs
@@ -252,8 +252,6 @@ macro_rules! debug_assert_ne {
 /// # Examples
 ///
 /// ```
-/// #![feature(matches_macro)]
-///
 /// let foo = 'f';
 /// assert!(matches!(foo, 'A'..='Z' | 'a'..='z'));
 ///
@@ -261,7 +259,7 @@ macro_rules! debug_assert_ne {
 /// assert!(matches!(bar, Some(x) if x > 2));
 /// ```
 #[macro_export]
-#[unstable(feature = "matches_macro", issue = "65721")]
+#[stable(feature = "matches_macro", since = "1.42.0")]
 macro_rules! matches {
     ($expression:expr, $( $pattern:pat )|+ $( if $guard: expr )?) => {
         match $expression {
diff --git a/src/libcore/marker.rs b/src/libcore/marker.rs
index 978d6221564..3b98bc1c272 100644
--- a/src/libcore/marker.rs
+++ b/src/libcore/marker.rs
@@ -142,7 +142,7 @@ pub trait Unsize<T: ?Sized> {
 /// In either of the two scenarios above, we reject usage of such a constant in
 /// a pattern match.
 ///
-/// See also the [structural match RFC][RFC1445], and [issue 63438][] which
+/// See also the [structural match RFC][RFC1445], and [issue 63438] which
 /// motivated migrating from attribute-based design to this trait.
 ///
 /// [RFC1445]: https://github.com/rust-lang/rfcs/blob/master/text/1445-restrict-constants-in-patterns.md
diff --git a/src/libcore/num/f32.rs b/src/libcore/num/f32.rs
index fd7b7cf0b34..f1f1bb13f0f 100644
--- a/src/libcore/num/f32.rs
+++ b/src/libcore/num/f32.rs
@@ -226,7 +226,7 @@ impl f32 {
     }
 
     /// Returns `true` if the number is neither zero, infinite,
-    /// [subnormal][subnormal], or `NaN`.
+    /// [subnormal], or `NaN`.
     ///
     /// ```
     /// use std::f32;
diff --git a/src/libcore/num/f64.rs b/src/libcore/num/f64.rs
index 540c6a529d7..5f9dc541b7d 100644
--- a/src/libcore/num/f64.rs
+++ b/src/libcore/num/f64.rs
@@ -226,7 +226,7 @@ impl f64 {
     }
 
     /// Returns `true` if the number is neither zero, infinite,
-    /// [subnormal][subnormal], or `NaN`.
+    /// [subnormal], or `NaN`.
     ///
     /// ```
     /// use std::f64;
diff --git a/src/libcore/ops/function.rs b/src/libcore/ops/function.rs
index 505a65cee3d..04c7789fa4f 100644
--- a/src/libcore/ops/function.rs
+++ b/src/libcore/ops/function.rs
@@ -2,12 +2,12 @@
 ///
 /// Instances of `Fn` can be called repeatedly without mutating state.
 ///
-/// *This trait (`Fn`) is not to be confused with [function pointers][]
+/// *This trait (`Fn`) is not to be confused with [function pointers]
 /// (`fn`).*
 ///
 /// `Fn` is implemented automatically by closures which only take immutable
 /// references to captured variables or don't capture anything at all, as well
-/// as (safe) [function pointers][] (with some caveats, see their documentation
+/// as (safe) [function pointers] (with some caveats, see their documentation
 /// for more details). Additionally, for any type `F` that implements `Fn`, `&F`
 /// implements `Fn`, too.
 ///
@@ -78,7 +78,7 @@ pub trait Fn<Args>: FnMut<Args> {
 ///
 /// `FnMut` is implemented automatically by closures which take mutable
 /// references to captured variables, as well as all types that implement
-/// [`Fn`], e.g., (safe) [function pointers][] (since `FnMut` is a supertrait of
+/// [`Fn`], e.g., (safe) [function pointers] (since `FnMut` is a supertrait of
 /// [`Fn`]). Additionally, for any type `F` that implements `FnMut`, `&mut F`
 /// implements `FnMut`, too.
 ///
@@ -162,7 +162,7 @@ pub trait FnMut<Args>: FnOnce<Args> {
 ///
 /// `FnOnce` is implemented automatically by closure that might consume captured
 /// variables, as well as all types that implement [`FnMut`], e.g., (safe)
-/// [function pointers][] (since `FnOnce` is a supertrait of [`FnMut`]).
+/// [function pointers] (since `FnOnce` is a supertrait of [`FnMut`]).
 ///
 /// Since both [`Fn`] and [`FnMut`] are subtraits of `FnOnce`, any instance of
 /// [`Fn`] or [`FnMut`] can be used where a `FnOnce` is expected.
diff --git a/src/libcore/result.rs b/src/libcore/result.rs
index ce4c8995a3c..5628658c5bd 100644
--- a/src/libcore/result.rs
+++ b/src/libcore/result.rs
@@ -1370,7 +1370,7 @@ unsafe impl<A> TrustedLen for IterMut<'_, A> {}
 /// The iterator yields one value if the result is [`Ok`], otherwise none.
 ///
 /// This struct is created by the [`into_iter`] method on
-/// [`Result`][`Result`] (provided by the [`IntoIterator`] trait).
+/// [`Result`] (provided by the [`IntoIterator`] trait).
 ///
 /// [`Ok`]: enum.Result.html#variant.Ok
 /// [`Result`]: enum.Result.html
diff --git a/src/libcore/slice/mod.rs b/src/libcore/slice/mod.rs
index 5ddf5d48965..9b4d2015732 100644
--- a/src/libcore/slice/mod.rs
+++ b/src/libcore/slice/mod.rs
@@ -34,7 +34,7 @@ use crate::mem;
 use crate::ops::{self, FnMut, Range};
 use crate::option::Option;
 use crate::option::Option::{None, Some};
-use crate::ptr;
+use crate::ptr::{self, NonNull};
 use crate::result::Result;
 use crate::result::Result::{Err, Ok};
 
@@ -628,7 +628,7 @@ impl<T> [T] {
                 ptr.add(self.len())
             };
 
-            Iter { ptr, end, _marker: marker::PhantomData }
+            Iter { ptr: NonNull::new_unchecked(ptr as *mut T), end, _marker: marker::PhantomData }
         }
     }
 
@@ -656,7 +656,7 @@ impl<T> [T] {
                 ptr.add(self.len())
             };
 
-            IterMut { ptr, end, _marker: marker::PhantomData }
+            IterMut { ptr: NonNull::new_unchecked(ptr), end, _marker: marker::PhantomData }
         }
     }
 
@@ -3095,7 +3095,7 @@ macro_rules! is_empty {
     // The way we encode the length of a ZST iterator, this works both for ZST
     // and non-ZST.
     ($self: ident) => {
-        $self.ptr == $self.end
+        $self.ptr.as_ptr() as *const T == $self.end
     };
 }
 // To get rid of some bounds checks (see `position`), we compute the length in a somewhat
@@ -3105,17 +3105,17 @@ macro_rules! len {
         #![allow(unused_unsafe)] // we're sometimes used within an unsafe block
 
         let start = $self.ptr;
-        let size = size_from_ptr(start);
+        let size = size_from_ptr(start.as_ptr());
         if size == 0 {
             // This _cannot_ use `unchecked_sub` because we depend on wrapping
             // to represent the length of long ZST slice iterators.
-            ($self.end as usize).wrapping_sub(start as usize)
+            ($self.end as usize).wrapping_sub(start.as_ptr() as usize)
         } else {
             // We know that `start <= end`, so can do better than `offset_from`,
             // which needs to deal in signed.  By setting appropriate flags here
             // we can tell LLVM this, which helps it remove bounds checks.
             // SAFETY: By the type invariant, `start <= end`
-            let diff = unsafe { unchecked_sub($self.end as usize, start as usize) };
+            let diff = unsafe { unchecked_sub($self.end as usize, start.as_ptr() as usize) };
             // By also telling LLVM that the pointers are apart by an exact
             // multiple of the type size, it can optimize `len() == 0` down to
             // `start == end` instead of `(end - start) < size`.
@@ -3161,7 +3161,7 @@ macro_rules! iterator {
             // Helper function for creating a slice from the iterator.
             #[inline(always)]
             fn make_slice(&self) -> &'a [T] {
-                unsafe { from_raw_parts(self.ptr, len!(self)) }
+                unsafe { from_raw_parts(self.ptr.as_ptr(), len!(self)) }
             }
 
             // Helper function for moving the start of the iterator forwards by `offset` elements,
@@ -3171,10 +3171,10 @@ macro_rules! iterator {
             unsafe fn post_inc_start(&mut self, offset: isize) -> * $raw_mut T {
                 if mem::size_of::<T>() == 0 {
                     zst_shrink!(self, offset);
-                    self.ptr
+                    self.ptr.as_ptr()
                 } else {
-                    let old = self.ptr;
-                    self.ptr = self.ptr.offset(offset);
+                    let old = self.ptr.as_ptr();
+                    self.ptr = NonNull::new_unchecked(self.ptr.as_ptr().offset(offset));
                     old
                 }
             }
@@ -3186,7 +3186,7 @@ macro_rules! iterator {
             unsafe fn pre_dec_end(&mut self, offset: isize) -> * $raw_mut T {
                 if mem::size_of::<T>() == 0 {
                     zst_shrink!(self, offset);
-                    self.ptr
+                    self.ptr.as_ptr()
                 } else {
                     self.end = self.end.offset(-offset);
                     self.end
@@ -3215,7 +3215,7 @@ macro_rules! iterator {
             fn next(&mut self) -> Option<$elem> {
                 // could be implemented with slices, but this avoids bounds checks
                 unsafe {
-                    assume(!self.ptr.is_null());
+                    assume(!self.ptr.as_ptr().is_null());
                     if mem::size_of::<T>() != 0 {
                         assume(!self.end.is_null());
                     }
@@ -3245,9 +3245,12 @@ macro_rules! iterator {
                     if mem::size_of::<T>() == 0 {
                         // We have to do it this way as `ptr` may never be 0, but `end`
                         // could be (due to wrapping).
-                        self.end = self.ptr;
+                        self.end = self.ptr.as_ptr();
                     } else {
-                        self.ptr = self.end;
+                        unsafe {
+                            // End can't be 0 if T isn't ZST because ptr isn't 0 and end >= ptr
+                            self.ptr = NonNull::new_unchecked(self.end as *mut T);
+                        }
                     }
                     return None;
                 }
@@ -3308,7 +3311,7 @@ macro_rules! iterator {
             fn next_back(&mut self) -> Option<$elem> {
                 // could be implemented with slices, but this avoids bounds checks
                 unsafe {
-                    assume(!self.ptr.is_null());
+                    assume(!self.ptr.as_ptr().is_null());
                     if mem::size_of::<T>() != 0 {
                         assume(!self.end.is_null());
                     }
@@ -3324,7 +3327,7 @@ macro_rules! iterator {
             fn nth_back(&mut self, n: usize) -> Option<$elem> {
                 if n >= len!(self) {
                     // This iterator is now empty.
-                    self.end = self.ptr;
+                    self.end = self.ptr.as_ptr();
                     return None;
                 }
                 // We are in bounds. `pre_dec_end` does the right thing even for ZSTs.
@@ -3365,7 +3368,7 @@ macro_rules! iterator {
 /// [slices]: ../../std/primitive.slice.html
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Iter<'a, T: 'a> {
-    ptr: *const T,
+    ptr: NonNull<T>,
     end: *const T, // If T is a ZST, this is actually ptr+len.  This encoding is picked so that
     // ptr == end is a quick test for the Iterator being empty, that works
     // for both ZST and non-ZST.
@@ -3467,7 +3470,7 @@ impl<T> AsRef<[T]> for Iter<'_, T> {
 /// [slices]: ../../std/primitive.slice.html
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct IterMut<'a, T: 'a> {
-    ptr: *mut T,
+    ptr: NonNull<T>,
     end: *mut T, // If T is a ZST, this is actually ptr+len.  This encoding is picked so that
     // ptr == end is a quick test for the Iterator being empty, that works
     // for both ZST and non-ZST.
@@ -3522,7 +3525,7 @@ impl<'a, T> IterMut<'a, T> {
     /// ```
     #[stable(feature = "iter_to_slice", since = "1.4.0")]
     pub fn into_slice(self) -> &'a mut [T] {
-        unsafe { from_raw_parts_mut(self.ptr, len!(self)) }
+        unsafe { from_raw_parts_mut(self.ptr.as_ptr(), len!(self)) }
     }
 
     /// Views the underlying data as a subslice of the original data.
@@ -5682,7 +5685,7 @@ impl_marker_for!(BytewiseEquality,
 #[doc(hidden)]
 unsafe impl<'a, T> TrustedRandomAccess for Iter<'a, T> {
     unsafe fn get_unchecked(&mut self, i: usize) -> &'a T {
-        &*self.ptr.add(i)
+        &*self.ptr.as_ptr().add(i)
     }
     fn may_have_side_effect() -> bool {
         false
@@ -5692,7 +5695,7 @@ unsafe impl<'a, T> TrustedRandomAccess for Iter<'a, T> {
 #[doc(hidden)]
 unsafe impl<'a, T> TrustedRandomAccess for IterMut<'a, T> {
     unsafe fn get_unchecked(&mut self, i: usize) -> &'a mut T {
-        &mut *self.ptr.add(i)
+        &mut *self.ptr.as_ptr().add(i)
     }
     fn may_have_side_effect() -> bool {
         false
diff --git a/src/librustc/hir/lowering.rs b/src/librustc/hir/lowering.rs
index ed84bd118f7..5fca5f061ca 100644
--- a/src/librustc/hir/lowering.rs
+++ b/src/librustc/hir/lowering.rs
@@ -168,6 +168,7 @@ pub struct LoweringContext<'a, 'hir: 'a> {
 
     allow_try_trait: Option<Lrc<[Symbol]>>,
     allow_gen_future: Option<Lrc<[Symbol]>>,
+    allow_into_future: Option<Lrc<[Symbol]>>,
 }
 
 pub trait Resolver {
@@ -300,6 +301,7 @@ pub fn lower_crate<'a, 'hir>(
         in_scope_lifetimes: Vec::new(),
         allow_try_trait: Some([sym::try_trait][..].into()),
         allow_gen_future: Some([sym::gen_future][..].into()),
+        allow_into_future: Some([sym::into_future][..].into()),
     }
     .lower_crate(krate)
 }
diff --git a/src/librustc/hir/lowering/expr.rs b/src/librustc/hir/lowering/expr.rs
index 8a9614c6cb2..dbfa351b918 100644
--- a/src/librustc/hir/lowering/expr.rs
+++ b/src/librustc/hir/lowering/expr.rs
@@ -529,7 +529,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
     /// Desugar `<expr>.await` into:
     /// ```rust
-    /// match <expr> {
+    /// match ::std::future::IntoFuture::into_future(<expr>) {
     ///     mut pinned => loop {
     ///         match ::std::future::poll_with_tls_context(unsafe {
     ///             <::std::pin::Pin>::new_unchecked(&mut pinned)
@@ -653,11 +653,27 @@ impl<'hir> LoweringContext<'_, 'hir> {
         // mut pinned => loop { ... }
         let pinned_arm = self.arm(pinned_pat, loop_expr);
 
-        // match <expr> {
+        // `match ::std::future::IntoFuture::into_future(<expr>) { ... }`
+        let into_future_span = self.mark_span_with_reason(
+            DesugaringKind::Await,
+            await_span,
+            self.allow_into_future.clone(),
+        );
+        let expr = self.lower_expr_mut(expr);
+        let into_future_expr = self.expr_call_std_path(
+            into_future_span,
+            &[sym::future, sym::IntoFuture, sym::into_future],
+            arena_vec![self; expr],
+        );
+
+        // match <into_future_expr> {
         //     mut pinned => loop { .. }
         // }
-        let expr = self.lower_expr(expr);
-        hir::ExprKind::Match(expr, arena_vec![self; pinned_arm], hir::MatchSource::AwaitDesugar)
+        hir::ExprKind::Match(
+            into_future_expr,
+            arena_vec![self; pinned_arm],
+            hir::MatchSource::AwaitDesugar,
+        )
     }
 
     fn lower_expr_closure(
diff --git a/src/librustc/mir/interpret/value.rs b/src/librustc/mir/interpret/value.rs
index 93f167cdb9e..2be36ad418a 100644
--- a/src/librustc/mir/interpret/value.rs
+++ b/src/librustc/mir/interpret/value.rs
@@ -416,22 +416,30 @@ impl<'tcx, Tag> Scalar<Tag> {
         }
     }
 
+    #[inline]
+    fn to_unsigned_with_bit_width(self, bits: u64) -> InterpResult<'static, u128> {
+        let sz = Size::from_bits(bits);
+        self.to_bits(sz)
+    }
+
+    /// Converts the scalar to produce an `u8`. Fails if the scalar is a pointer.
     pub fn to_u8(self) -> InterpResult<'static, u8> {
-        let sz = Size::from_bits(8);
-        let b = self.to_bits(sz)?;
-        Ok(b as u8)
+        self.to_unsigned_with_bit_width(8).map(|v| v as u8)
+    }
+
+    /// Converts the scalar to produce an `u16`. Fails if the scalar is a pointer.
+    pub fn to_u16(self) -> InterpResult<'static, u16> {
+        self.to_unsigned_with_bit_width(16).map(|v| v as u16)
     }
 
+    /// Converts the scalar to produce an `u32`. Fails if the scalar is a pointer.
     pub fn to_u32(self) -> InterpResult<'static, u32> {
-        let sz = Size::from_bits(32);
-        let b = self.to_bits(sz)?;
-        Ok(b as u32)
+        self.to_unsigned_with_bit_width(32).map(|v| v as u32)
     }
 
+    /// Converts the scalar to produce an `u64`. Fails if the scalar is a pointer.
     pub fn to_u64(self) -> InterpResult<'static, u64> {
-        let sz = Size::from_bits(64);
-        let b = self.to_bits(sz)?;
-        Ok(b as u64)
+        self.to_unsigned_with_bit_width(64).map(|v| v as u64)
     }
 
     pub fn to_machine_usize(self, cx: &impl HasDataLayout) -> InterpResult<'static, u64> {
@@ -439,25 +447,31 @@ impl<'tcx, Tag> Scalar<Tag> {
         Ok(b as u64)
     }
 
-    pub fn to_i8(self) -> InterpResult<'static, i8> {
-        let sz = Size::from_bits(8);
+    #[inline]
+    fn to_signed_with_bit_width(self, bits: u64) -> InterpResult<'static, i128> {
+        let sz = Size::from_bits(bits);
         let b = self.to_bits(sz)?;
-        let b = sign_extend(b, sz) as i128;
-        Ok(b as i8)
+        Ok(sign_extend(b, sz) as i128)
+    }
+
+    /// Converts the scalar to produce an `i8`. Fails if the scalar is a pointer.
+    pub fn to_i8(self) -> InterpResult<'static, i8> {
+        self.to_signed_with_bit_width(8).map(|v| v as i8)
+    }
+
+    /// Converts the scalar to produce an `i16`. Fails if the scalar is a pointer.
+    pub fn to_i16(self) -> InterpResult<'static, i16> {
+        self.to_signed_with_bit_width(16).map(|v| v as i16)
     }
 
+    /// Converts the scalar to produce an `i32`. Fails if the scalar is a pointer.
     pub fn to_i32(self) -> InterpResult<'static, i32> {
-        let sz = Size::from_bits(32);
-        let b = self.to_bits(sz)?;
-        let b = sign_extend(b, sz) as i128;
-        Ok(b as i32)
+        self.to_signed_with_bit_width(32).map(|v| v as i32)
     }
 
+    /// Converts the scalar to produce an `i64`. Fails if the scalar is a pointer.
     pub fn to_i64(self) -> InterpResult<'static, i64> {
-        let sz = Size::from_bits(64);
-        let b = self.to_bits(sz)?;
-        let b = sign_extend(b, sz) as i128;
-        Ok(b as i64)
+        self.to_signed_with_bit_width(64).map(|v| v as i64)
     }
 
     pub fn to_machine_isize(self, cx: &impl HasDataLayout) -> InterpResult<'static, i64> {
diff --git a/src/librustc_data_structures/graph/iterate/mod.rs b/src/librustc_data_structures/graph/iterate/mod.rs
index 53475cdf4ba..d9d4c7e321f 100644
--- a/src/librustc_data_structures/graph/iterate/mod.rs
+++ b/src/librustc_data_structures/graph/iterate/mod.rs
@@ -101,14 +101,14 @@ pub enum ControlFlow<T> {
 pub enum NodeStatus {
     /// This node has been examined by the depth-first search but is not yet `Settled`.
     ///
-    /// Also referred to as "gray" or "discovered" nodes in [CLR][].
+    /// Also referred to as "gray" or "discovered" nodes in [CLR].
     ///
     /// [CLR]: https://en.wikipedia.org/wiki/Introduction_to_Algorithms
     Visited,
 
     /// This node and all nodes reachable from it have been examined by the depth-first search.
     ///
-    /// Also referred to as "black" or "finished" nodes in [CLR][].
+    /// Also referred to as "black" or "finished" nodes in [CLR].
     ///
     /// [CLR]: https://en.wikipedia.org/wiki/Introduction_to_Algorithms
     Settled,
@@ -122,13 +122,13 @@ struct Event<N> {
 /// A depth-first search that also tracks when all successors of a node have been examined.
 ///
 /// This is based on the DFS described in [Introduction to Algorithms (1st ed.)][CLR], hereby
-/// referred to as **CLR**. However, we use the terminology in [`NodeStatus`][] above instead of
+/// referred to as **CLR**. However, we use the terminology in [`NodeStatus`] above instead of
 /// "discovered"/"finished" or "white"/"grey"/"black". Each node begins the search with no status,
 /// becomes `Visited` when it is first examined by the DFS and is `Settled` when all nodes
 /// reachable from it have been examined. This allows us to differentiate between "tree", "back"
 /// and "forward" edges (see [`TriColorVisitor::node_examined`]).
 ///
-/// Unlike the pseudocode in [CLR][], this implementation is iterative and does not use timestamps.
+/// Unlike the pseudocode in [CLR], this implementation is iterative and does not use timestamps.
 /// We accomplish this by storing `Event`s on the stack that result in a (possible) state change
 /// for each node. A `Visited` event signifies that we should examine this node if it has not yet
 /// been `Visited` or `Settled`. When a node is examined for the first time, we mark it as
@@ -246,7 +246,7 @@ where
     /// By checking the value of `prior_status`, this visitor can determine whether the edge
     /// leading to this node was a tree edge (`None`), forward edge (`Some(Settled)`) or back edge
     /// (`Some(Visited)`). For a full explanation of each edge type, see the "Depth-first Search"
-    /// chapter in [CLR][] or [wikipedia][].
+    /// chapter in [CLR] or [wikipedia].
     ///
     /// If you want to know *both* nodes linked by each edge, you'll need to modify
     /// `TriColorDepthFirstSearch` to store a `source` node for each `Visited` event.
diff --git a/src/librustc_lint/lib.rs b/src/librustc_lint/lib.rs
index e4dd2f006ab..617e56ffe36 100644
--- a/src/librustc_lint/lib.rs
+++ b/src/librustc_lint/lib.rs
@@ -15,7 +15,6 @@
 #![feature(box_patterns)]
 #![feature(box_syntax)]
 #![feature(nll)]
-#![feature(matches_macro)]
 #![recursion_limit = "256"]
 
 #[macro_use]
diff --git a/src/librustc_mir/dataflow/generic.rs b/src/librustc_mir/dataflow/generic.rs
index 659ebeab650..7eb6f5cc073 100644
--- a/src/librustc_mir/dataflow/generic.rs
+++ b/src/librustc_mir/dataflow/generic.rs
@@ -10,7 +10,7 @@
 //! interface, but make `Engine` and `ResultsCursor` the canonical way to perform and inspect a
 //! dataflow analysis. This requires porting the graphviz debugging logic to this module, deciding
 //! on a way to handle the `before` methods in `BitDenotation` and creating an adapter so that
-//! gen-kill problems can still be evaluated efficiently. See the discussion in [#64566][] for more
+//! gen-kill problems can still be evaluated efficiently. See the discussion in [#64566] for more
 //! information.
 //!
 //! [gk]: https://en.wikipedia.org/wiki/Data-flow_analysis#Bit_vector_problems
diff --git a/src/librustc_mir/lib.rs b/src/librustc_mir/lib.rs
index 30db1ce345a..32b35c4139d 100644
--- a/src/librustc_mir/lib.rs
+++ b/src/librustc_mir/lib.rs
@@ -29,7 +29,6 @@ Rust MIR: a lowered representation of Rust. Also: an experiment!
 #![feature(range_is_empty)]
 #![feature(stmt_expr_attributes)]
 #![feature(trait_alias)]
-#![feature(matches_macro)]
 #![recursion_limit = "256"]
 
 #[macro_use]
diff --git a/src/librustc_mir/transform/check_consts/qualifs.rs b/src/librustc_mir/transform/check_consts/qualifs.rs
index 746d83b05c6..bd895171e35 100644
--- a/src/librustc_mir/transform/check_consts/qualifs.rs
+++ b/src/librustc_mir/transform/check_consts/qualifs.rs
@@ -1,6 +1,5 @@
 //! A copy of the `Qualif` trait in `qualify_consts.rs` that is suitable for the new validator.
 
-use rustc::hir::def_id::DefId;
 use rustc::mir::*;
 use rustc::ty::{self, Ty};
 use syntax_pos::DUMMY_SP;
@@ -33,12 +32,6 @@ pub trait Qualif {
     /// of the type.
     fn in_any_value_of_ty(_cx: &ConstCx<'_, 'tcx>, _ty: Ty<'tcx>) -> bool;
 
-    fn in_static(cx: &ConstCx<'_, 'tcx>, def_id: DefId) -> bool {
-        // `mir_const_qualif` does return the qualifs in the final value of a `static`, so we could
-        // use value-based qualification here, but we shouldn't do this without a good reason.
-        Self::in_any_value_of_ty(cx, cx.tcx.type_of(def_id))
-    }
-
     fn in_projection_structurally(
         cx: &ConstCx<'_, 'tcx>,
         per_local: &impl Fn(Local) -> bool,
@@ -101,8 +94,14 @@ pub trait Qualif {
             }
 
             Operand::Constant(ref constant) => {
-                if let Some(static_) = constant.check_static_ptr(cx.tcx) {
-                    Self::in_static(cx, static_)
+                if constant.check_static_ptr(cx.tcx).is_some() {
+                    // `mir_const_qualif` does return the qualifs in the final value of a `static`,
+                    // so we could use value-based qualification here, but we shouldn't do this
+                    // without a good reason.
+                    //
+                    // Note: this uses `constant.literal.ty` which is a reference or pointer to the
+                    // type of the actual `static` item.
+                    Self::in_any_value_of_ty(cx, constant.literal.ty)
                 } else if let ty::ConstKind::Unevaluated(def_id, _) = constant.literal.val {
                     // Don't peek inside trait associated constants.
                     if cx.tcx.trait_of_item(def_id).is_some() {
diff --git a/src/libstd/collections/hash/map.rs b/src/libstd/collections/hash/map.rs
index a928867d9de..fdc587ba5da 100644
--- a/src/libstd/collections/hash/map.rs
+++ b/src/libstd/collections/hash/map.rs
@@ -1076,7 +1076,7 @@ impl<'a, K, V> IterMut<'a, K, V> {
 
 /// An owning iterator over the entries of a `HashMap`.
 ///
-/// This `struct` is created by the [`into_iter`] method on [`HashMap`][`HashMap`]
+/// This `struct` is created by the [`into_iter`] method on [`HashMap`]
 /// (provided by the `IntoIterator` trait). See its documentation for more.
 ///
 /// [`into_iter`]: struct.HashMap.html#method.into_iter
diff --git a/src/libstd/collections/hash/set.rs b/src/libstd/collections/hash/set.rs
index fff64e9fc90..566e5146cf8 100644
--- a/src/libstd/collections/hash/set.rs
+++ b/src/libstd/collections/hash/set.rs
@@ -1101,7 +1101,7 @@ pub struct Iter<'a, K: 'a> {
 
 /// An owning iterator over the items of a `HashSet`.
 ///
-/// This `struct` is created by the [`into_iter`] method on [`HashSet`][`HashSet`]
+/// This `struct` is created by the [`into_iter`] method on [`HashSet`]
 /// (provided by the `IntoIterator` trait). See its documentation for more.
 ///
 /// [`HashSet`]: struct.HashSet.html
diff --git a/src/libstd/future.rs b/src/libstd/future.rs
index 9c7422c2b20..908736c6393 100644
--- a/src/libstd/future.rs
+++ b/src/libstd/future.rs
@@ -10,7 +10,11 @@ use core::task::{Context, Poll};
 
 #[doc(inline)]
 #[stable(feature = "futures_api", since = "1.36.0")]
-pub use core::future::*;
+pub use core::future::Future;
+
+#[doc(inline)]
+#[unstable(feature = "into_future", issue = "67644")]
+pub use core::future::IntoFuture;
 
 /// Wrap a generator in a future.
 ///
diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs
index 9e9df5ab9b6..930bf397bc4 100644
--- a/src/libstd/lib.rs
+++ b/src/libstd/lib.rs
@@ -269,6 +269,7 @@
 #![feature(hashmap_internals)]
 #![feature(int_error_internals)]
 #![feature(int_error_matching)]
+#![feature(into_future)]
 #![feature(integer_atomics)]
 #![feature(lang_items)]
 #![feature(libc)]
@@ -276,7 +277,6 @@
 #![feature(linkage)]
 #![feature(log_syntax)]
 #![feature(manually_drop_take)]
-#![feature(matches_macro)]
 #![feature(maybe_uninit_ref)]
 #![feature(maybe_uninit_slice)]
 #![feature(needs_panic_runtime)]
diff --git a/src/libstd/path.rs b/src/libstd/path.rs
index 580ff1610ac..f308d511cf8 100644
--- a/src/libstd/path.rs
+++ b/src/libstd/path.rs
@@ -2,7 +2,7 @@
 
 //! Cross-platform path manipulation.
 //!
-//! This module provides two types, [`PathBuf`] and [`Path`][`Path`] (akin to [`String`]
+//! This module provides two types, [`PathBuf`] and [`Path`] (akin to [`String`]
 //! and [`str`]), for working with paths abstractly. These types are thin wrappers
 //! around [`OsString`] and [`OsStr`] respectively, meaning that they work directly
 //! on strings according to the local platform's path syntax.
@@ -296,6 +296,13 @@ where
 }
 
 // See note at the top of this module to understand why these are used:
+//
+// These casts are safe as OsStr is internally a wrapper around [u8] on all
+// platforms.
+//
+// Note that currently this relies on the special knowledge that libstd has;
+// these types are single-element structs but are not marked repr(transparent)
+// or repr(C) which would make these casts allowable outside std.
 fn os_str_as_u8_slice(s: &OsStr) -> &[u8] {
     unsafe { &*(s as *const OsStr as *const [u8]) }
 }
diff --git a/src/libstd/sync/mpsc/mod.rs b/src/libstd/sync/mpsc/mod.rs
index 0e334c191e7..e70204d6839 100644
--- a/src/libstd/sync/mpsc/mod.rs
+++ b/src/libstd/sync/mpsc/mod.rs
@@ -286,7 +286,7 @@ mod sync;
 
 mod cache_aligned;
 
-/// The receiving half of Rust's [`channel`][] (or [`sync_channel`]) type.
+/// The receiving half of Rust's [`channel`] (or [`sync_channel`]) type.
 /// This half can only be owned by one thread.
 ///
 /// Messages sent to the channel can be retrieved using [`recv`].
@@ -558,7 +558,7 @@ pub struct SendError<T>(#[stable(feature = "rust1", since = "1.0.0")] pub T);
 /// An error returned from the [`recv`] function on a [`Receiver`].
 ///
 /// The [`recv`] operation can only fail if the sending half of a
-/// [`channel`][`channel`] (or [`sync_channel`]) is disconnected, implying that no further
+/// [`channel`] (or [`sync_channel`]) is disconnected, implying that no further
 /// messages will ever be received.
 ///
 /// [`recv`]: struct.Receiver.html#method.recv
@@ -1108,7 +1108,7 @@ impl<T> Receiver<T> {
     ///
     /// This function will always block the current thread if there is no data
     /// available and it's possible for more data to be sent. Once a message is
-    /// sent to the corresponding [`Sender`][] (or [`SyncSender`]), then this
+    /// sent to the corresponding [`Sender`] (or [`SyncSender`]), then this
     /// receiver will wake up and return that message.
     ///
     /// If the corresponding [`Sender`] has disconnected, or it disconnects while
@@ -1194,7 +1194,7 @@ impl<T> Receiver<T> {
     ///
     /// This function will always block the current thread if there is no data
     /// available and it's possible for more data to be sent. Once a message is
-    /// sent to the corresponding [`Sender`][] (or [`SyncSender`]), then this
+    /// sent to the corresponding [`Sender`] (or [`SyncSender`]), then this
     /// receiver will wake up and return that message.
     ///
     /// If the corresponding [`Sender`] has disconnected, or it disconnects while
@@ -1295,7 +1295,7 @@ impl<T> Receiver<T> {
     ///
     /// This function will always block the current thread if there is no data
     /// available and it's possible for more data to be sent. Once a message is
-    /// sent to the corresponding [`Sender`][] (or [`SyncSender`]), then this
+    /// sent to the corresponding [`Sender`] (or [`SyncSender`]), then this
     /// receiver will wake up and return that message.
     ///
     /// If the corresponding [`Sender`] has disconnected, or it disconnects while
diff --git a/src/libstd/sync/rwlock.rs b/src/libstd/sync/rwlock.rs
index 2ff36133a7c..fdd29af8581 100644
--- a/src/libstd/sync/rwlock.rs
+++ b/src/libstd/sync/rwlock.rs
@@ -25,7 +25,7 @@ use crate::sys_common::rwlock as sys;
 /// The type parameter `T` represents the data that this lock protects. It is
 /// required that `T` satisfies [`Send`] to be shared across threads and
 /// [`Sync`] to allow concurrent access through readers. The RAII guards
-/// returned from the locking methods implement [`Deref`][] (and [`DerefMut`]
+/// returned from the locking methods implement [`Deref`] (and [`DerefMut`]
 /// for the `write` methods) to allow access to the content of the lock.
 ///
 /// # Poisoning
diff --git a/src/libsyntax/lib.rs b/src/libsyntax/lib.rs
index 31370e2c92e..7b8819377e6 100644
--- a/src/libsyntax/lib.rs
+++ b/src/libsyntax/lib.rs
@@ -11,7 +11,6 @@
 #![feature(const_transmute)]
 #![feature(crate_visibility_modifier)]
 #![feature(label_break_value)]
-#![feature(matches_macro)]
 #![feature(nll)]
 #![feature(try_trait)]
 #![feature(slice_patterns)]
diff --git a/src/libsyntax_pos/symbol.rs b/src/libsyntax_pos/symbol.rs
index 8fdc199d9ed..7ae037faf15 100644
--- a/src/libsyntax_pos/symbol.rs
+++ b/src/libsyntax_pos/symbol.rs
@@ -379,6 +379,8 @@ symbols! {
         infer_static_outlives_requirements,
         inline,
         intel,
+        into_future,
+        IntoFuture,
         into_iter,
         IntoIterator,
         into_result,
diff --git a/src/test/ui/async-await/async-fn-size-moved-locals.rs b/src/test/ui/async-await/async-fn-size-moved-locals.rs
index 4a413381aa3..f2469de7394 100644
--- a/src/test/ui/async-await/async-fn-size-moved-locals.rs
+++ b/src/test/ui/async-await/async-fn-size-moved-locals.rs
@@ -112,7 +112,7 @@ async fn mixed_sizes() {
 fn main() {
     assert_eq!(1028, std::mem::size_of_val(&single()));
     assert_eq!(1032, std::mem::size_of_val(&single_with_noop()));
-    assert_eq!(3084, std::mem::size_of_val(&joined()));
-    assert_eq!(3084, std::mem::size_of_val(&joined_with_noop()));
-    assert_eq!(7188, std::mem::size_of_val(&mixed_sizes()));
+    assert_eq!(3080, std::mem::size_of_val(&joined()));
+    assert_eq!(3080, std::mem::size_of_val(&joined_with_noop()));
+    assert_eq!(6164, std::mem::size_of_val(&mixed_sizes()));
 }
diff --git a/src/test/ui/async-await/await-into-future.rs b/src/test/ui/async-await/await-into-future.rs
new file mode 100644
index 00000000000..d5ff0eb3049
--- /dev/null
+++ b/src/test/ui/async-await/await-into-future.rs
@@ -0,0 +1,28 @@
+// check-pass
+
+// edition:2018
+
+#![feature(into_future)]
+
+use std::{future::{Future, IntoFuture}, pin::Pin};
+
+struct AwaitMe;
+
+impl IntoFuture for AwaitMe {
+    type Output = i32;
+    type Future = Pin<Box<dyn Future<Output = i32>>>;
+
+    fn into_future(self) -> Self::Future {
+        Box::pin(me())
+    }
+}
+
+async fn me() -> i32 {
+    41
+}
+
+async fn run() {
+    assert_eq!(AwaitMe.await, 41);
+}
+
+fn main() {}
diff --git a/src/test/ui/async-await/issues/issue-62009-1.stderr b/src/test/ui/async-await/issues/issue-62009-1.stderr
index 3a49a5a97de..e31904b6c1f 100644
--- a/src/test/ui/async-await/issues/issue-62009-1.stderr
+++ b/src/test/ui/async-await/issues/issue-62009-1.stderr
@@ -32,11 +32,8 @@ error[E0277]: the trait bound `[closure@$DIR/issue-62009-1.rs:13:5: 13:15]: std:
    |
 LL |     (|_| 2333).await;
    |     ^^^^^^^^^^^^^^^^ the trait `std::future::Future` is not implemented for `[closure@$DIR/issue-62009-1.rs:13:5: 13:15]`
-   | 
-  ::: $SRC_DIR/libstd/future.rs:LL:COL
    |
-LL |     F: Future,
-   |        ------ required by this bound in `std::future::poll_with_tls_context`
+   = note: required by `std::future::IntoFuture::into_future`
 
 error: aborting due to 4 previous errors
 
diff --git a/src/test/ui/consts/const-eval/promote-static.rs b/src/test/ui/consts/const-eval/promote-static.rs
new file mode 100644
index 00000000000..d3c663c53e9
--- /dev/null
+++ b/src/test/ui/consts/const-eval/promote-static.rs
@@ -0,0 +1,14 @@
+// regression test for #67609.
+
+// check-pass
+
+static NONE: Option<String> = None;
+
+static NONE_REF_REF: &&Option<String> = {
+    let x = &&NONE;
+    x
+};
+
+fn main() {
+    println!("{:?}", NONE_REF_REF);
+}
diff --git a/src/test/ui/issues/issue-51770.rs b/src/test/ui/issues/issue-51770.rs
new file mode 100644
index 00000000000..bcb37a5f4ff
--- /dev/null
+++ b/src/test/ui/issues/issue-51770.rs
@@ -0,0 +1,20 @@
+// check-pass
+
+#![crate_type = "lib"]
+
+// In an older version, when NLL was still a feature, the following previously did not compile
+// #![feature(nll)]
+
+use std::ops::Index;
+
+pub struct Test<T> {
+    a: T,
+}
+
+impl<T> Index<usize> for Test<T> {
+    type Output = T;
+
+    fn index(&self, _index: usize) -> &Self::Output {
+        &self.a
+    }
+}