Merge ref 'b3cfb8faf84c' from rust-lang/rust

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

Upstream ref: b3cfb8faf84c5f3b7909479a9f9b6a3290d5f4d7
Filtered ref: 8995aa7743caf019203bc853f27af6006705ae30
Upstream diff: https://github.com/rust-lang/rust/compare/9385c64c95d971329e62917adc4349c8ccdbafe0...b3cfb8faf84c5f3b7909479a9f9b6a3290d5f4d7

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

11 files changed, 334 insertions, 2 deletions

diff --git a/library/core/src/array/mod.rs b/library/core/src/array/mod.rs
index 4cdc046f71e..d14419a23a1 100644
--- a/library/core/src/array/mod.rs
+++ b/library/core/src/array/mod.rs
@@ -48,6 +48,7 @@ pub use iter::IntoIter;
 /// assert_eq!(strings, ["Hello there!", "Hello there!"]);
 /// ```
 #[inline]
+#[must_use = "cloning is often expensive and is not expected to have side effects"]
 #[stable(feature = "array_repeat", since = "CURRENT_RUSTC_VERSION")]
 pub fn repeat<T: Clone, const N: usize>(val: T) -> [T; N] {
     from_trusted_iterator(repeat_n(val, N))
diff --git a/library/core/src/intrinsics/fallback.rs b/library/core/src/intrinsics/fallback.rs
index eec5c4d646d..96928325328 100644
--- a/library/core/src/intrinsics/fallback.rs
+++ b/library/core/src/intrinsics/fallback.rs
@@ -148,3 +148,76 @@ impl_disjoint_bitor! {
     u8, u16, u32, u64, u128, usize,
     i8, i16, i32, i64, i128, isize,
 }
+
+#[const_trait]
+#[rustc_const_unstable(feature = "core_intrinsics_fallbacks", issue = "none")]
+pub trait FunnelShift: Copy + 'static {
+    /// See [`super::unchecked_funnel_shl`]; we just need the trait indirection to handle
+    /// different types since calling intrinsics with generics doesn't work.
+    unsafe fn unchecked_funnel_shl(self, rhs: Self, shift: u32) -> Self;
+
+    /// See [`super::unchecked_funnel_shr`]; we just need the trait indirection to handle
+    /// different types since calling intrinsics with generics doesn't work.
+    unsafe fn unchecked_funnel_shr(self, rhs: Self, shift: u32) -> Self;
+}
+
+macro_rules! impl_funnel_shifts {
+    ($($type:ident),*) => {$(
+        #[rustc_const_unstable(feature = "core_intrinsics_fallbacks", issue = "none")]
+        impl const FunnelShift for $type {
+            #[cfg_attr(miri, track_caller)]
+            #[inline]
+            unsafe fn unchecked_funnel_shl(self, rhs: Self, shift: u32) -> Self {
+                // This implementation is also used by Miri so we have to check the precondition.
+                // SAFETY: this is guaranteed by the caller
+                unsafe { super::assume(shift < $type::BITS) };
+                if shift == 0 {
+                    self
+                } else {
+                    // SAFETY:
+                    //  - `shift < T::BITS`, which satisfies `unchecked_shl`
+                    //  - this also ensures that `T::BITS - shift < T::BITS` (shift = 0 is checked
+                    //    above), which satisfies `unchecked_shr`
+                    //  - because the types are unsigned, the combination are disjoint bits (this is
+                    //    not true if they're signed, since SHR will fill in the empty space with a
+                    //    sign bit, not zero)
+                    unsafe {
+                        super::disjoint_bitor(
+                            super::unchecked_shl(self, shift),
+                            super::unchecked_shr(rhs, $type::BITS - shift),
+                        )
+                    }
+                }
+            }
+
+            #[cfg_attr(miri, track_caller)]
+            #[inline]
+            unsafe fn unchecked_funnel_shr(self, rhs: Self, shift: u32) -> Self {
+                // This implementation is also used by Miri so we have to check the precondition.
+                // SAFETY: this is guaranteed by the caller
+                unsafe { super::assume(shift < $type::BITS) };
+                if shift == 0 {
+                    rhs
+                } else {
+                    // SAFETY:
+                    //  - `shift < T::BITS`, which satisfies `unchecked_shr`
+                    //  - this also ensures that `T::BITS - shift < T::BITS` (shift = 0 is checked
+                    //    above), which satisfies `unchecked_shl`
+                    //  - because the types are unsigned, the combination are disjoint bits (this is
+                    //    not true if they're signed, since SHR will fill in the empty space with a
+                    //    sign bit, not zero)
+                    unsafe {
+                        super::disjoint_bitor(
+                            super::unchecked_shl(self, $type::BITS - shift),
+                            super::unchecked_shr(rhs, shift),
+                        )
+                    }
+                }
+            }
+        }
+    )*};
+}
+
+impl_funnel_shifts! {
+    u8, u16, u32, u64, u128, usize
+}
diff --git a/library/core/src/intrinsics/mod.rs b/library/core/src/intrinsics/mod.rs
index 904aa52c784..bffffbc29c1 100644
--- a/library/core/src/intrinsics/mod.rs
+++ b/library/core/src/intrinsics/mod.rs
@@ -2102,6 +2102,61 @@ pub const fn saturating_add<T: Copy>(a: T, b: T) -> T;
 #[rustc_intrinsic]
 pub const fn saturating_sub<T: Copy>(a: T, b: T) -> T;
 
+/// Funnel Shift left.
+///
+/// Concatenates `a` and `b` (with `a` in the most significant half),
+/// creating an integer twice as wide. Then shift this integer left
+/// by `shift`), and extract the most significant half. If `a` and `b`
+/// are the same, this is equivalent to a rotate left operation.
+///
+/// It is undefined behavior if `shift` is greater than or equal to the
+/// bit size of `T`.
+///
+/// Safe versions of this intrinsic are available on the integer primitives
+/// via the `funnel_shl` method. For example, [`u32::funnel_shl`].
+#[rustc_intrinsic]
+#[rustc_nounwind]
+#[rustc_const_unstable(feature = "funnel_shifts", issue = "145686")]
+#[unstable(feature = "funnel_shifts", issue = "145686")]
+#[track_caller]
+#[miri::intrinsic_fallback_is_spec]
+pub const unsafe fn unchecked_funnel_shl<T: [const] fallback::FunnelShift>(
+    a: T,
+    b: T,
+    shift: u32,
+) -> T {
+    // SAFETY: caller ensures that `shift` is in-range
+    unsafe { a.unchecked_funnel_shl(b, shift) }
+}
+
+/// Funnel Shift right.
+///
+/// Concatenates `a` and `b` (with `a` in the most significant half),
+/// creating an integer twice as wide. Then shift this integer right
+/// by `shift` (taken modulo the bit size of `T`), and extract the
+/// least significant half. If `a` and `b` are the same, this is equivalent
+/// to a rotate right operation.
+///
+/// It is undefined behavior if `shift` is greater than or equal to the
+/// bit size of `T`.
+///
+/// Safer versions of this intrinsic are available on the integer primitives
+/// via the `funnel_shr` method. For example, [`u32::funnel_shr`]
+#[rustc_intrinsic]
+#[rustc_nounwind]
+#[rustc_const_unstable(feature = "funnel_shifts", issue = "145686")]
+#[unstable(feature = "funnel_shifts", issue = "145686")]
+#[track_caller]
+#[miri::intrinsic_fallback_is_spec]
+pub const unsafe fn unchecked_funnel_shr<T: [const] fallback::FunnelShift>(
+    a: T,
+    b: T,
+    shift: u32,
+) -> T {
+    // SAFETY: caller ensures that `shift` is in-range
+    unsafe { a.unchecked_funnel_shr(b, shift) }
+}
+
 /// This is an implementation detail of [`crate::ptr::read`] and should
 /// not be used anywhere else.  See its comments for why this exists.
 ///
diff --git a/library/core/src/iter/adapters/chain.rs b/library/core/src/iter/adapters/chain.rs
index 943b88e2330..3ebdf7b4727 100644
--- a/library/core/src/iter/adapters/chain.rs
+++ b/library/core/src/iter/adapters/chain.rs
@@ -321,6 +321,7 @@ impl<A: Default, B: Default> Default for Chain<A, B> {
     ///
     /// // take requires `Default`
     /// let _: Chain<_, _> = mem::take(&mut foo.0);
+    /// ```
     fn default() -> Self {
         Chain::new(Default::default(), Default::default())
     }
diff --git a/library/core/src/iter/adapters/peekable.rs b/library/core/src/iter/adapters/peekable.rs
index a6522659620..a55de75d56c 100644
--- a/library/core/src/iter/adapters/peekable.rs
+++ b/library/core/src/iter/adapters/peekable.rs
@@ -317,6 +317,108 @@ impl<I: Iterator> Peekable<I> {
     {
         self.next_if(|next| next == expected)
     }
+
+    /// Consumes the next value of this iterator and applies a function `f` on it,
+    /// returning the result if the closure returns `Ok`.
+    ///
+    /// Otherwise if the closure returns `Err` the value is put back for the next iteration.
+    ///
+    /// The content of the `Err` variant is typically the original value of the closure,
+    /// but this is not required. If a different value is returned,
+    /// the next `peek()` or `next()` call will result in this new value.
+    /// This is similar to modifying the output of `peek_mut()`.
+    ///
+    /// If the closure panics, the next value will always be consumed and dropped
+    /// even if the panic is caught, because the closure never returned an `Err` value to put back.
+    ///
+    /// # Examples
+    ///
+    /// Parse the leading decimal number from an iterator of characters.
+    /// ```
+    /// #![feature(peekable_next_if_map)]
+    /// let mut iter = "125 GOTO 10".chars().peekable();
+    /// let mut line_num = 0_u32;
+    /// while let Some(digit) = iter.next_if_map(|c| c.to_digit(10).ok_or(c)) {
+    ///     line_num = line_num * 10 + digit;
+    /// }
+    /// assert_eq!(line_num, 125);
+    /// assert_eq!(iter.collect::<String>(), " GOTO 10");
+    /// ```
+    ///
+    /// Matching custom types.
+    /// ```
+    /// #![feature(peekable_next_if_map)]
+    ///
+    /// #[derive(Debug, PartialEq, Eq)]
+    /// enum Node {
+    ///     Comment(String),
+    ///     Red(String),
+    ///     Green(String),
+    ///     Blue(String),
+    /// }
+    ///
+    /// /// Combines all consecutive `Comment` nodes into a single one.
+    /// fn combine_comments(nodes: Vec<Node>) -> Vec<Node> {
+    ///     let mut result = Vec::with_capacity(nodes.len());
+    ///     let mut iter = nodes.into_iter().peekable();
+    ///     let mut comment_text = None::<String>;
+    ///     loop {
+    ///         // Typically the closure in .next_if_map() matches on the input,
+    ///         //  extracts the desired pattern into an `Ok`,
+    ///         //  and puts the rest into an `Err`.
+    ///         while let Some(text) = iter.next_if_map(|node| match node {
+    ///             Node::Comment(text) => Ok(text),
+    ///             other => Err(other),
+    ///         }) {
+    ///             comment_text.get_or_insert_default().push_str(&text);
+    ///         }
+    ///
+    ///         if let Some(text) = comment_text.take() {
+    ///             result.push(Node::Comment(text));
+    ///         }
+    ///         if let Some(node) = iter.next() {
+    ///             result.push(node);
+    ///         } else {
+    ///             break;
+    ///         }
+    ///     }
+    ///     result
+    /// }
+    ///# assert_eq!( // hiding the test to avoid cluttering the documentation.
+    ///#     combine_comments(vec![
+    ///#         Node::Comment("The".to_owned()),
+    ///#         Node::Comment("Quick".to_owned()),
+    ///#         Node::Comment("Brown".to_owned()),
+    ///#         Node::Red("Fox".to_owned()),
+    ///#         Node::Green("Jumped".to_owned()),
+    ///#         Node::Comment("Over".to_owned()),
+    ///#         Node::Blue("The".to_owned()),
+    ///#         Node::Comment("Lazy".to_owned()),
+    ///#         Node::Comment("Dog".to_owned()),
+    ///#     ]),
+    ///#     vec![
+    ///#         Node::Comment("TheQuickBrown".to_owned()),
+    ///#         Node::Red("Fox".to_owned()),
+    ///#         Node::Green("Jumped".to_owned()),
+    ///#         Node::Comment("Over".to_owned()),
+    ///#         Node::Blue("The".to_owned()),
+    ///#         Node::Comment("LazyDog".to_owned()),
+    ///#     ],
+    ///# )
+    /// ```
+    #[unstable(feature = "peekable_next_if_map", issue = "143702")]
+    pub fn next_if_map<R>(&mut self, f: impl FnOnce(I::Item) -> Result<R, I::Item>) -> Option<R> {
+        let unpeek = if let Some(item) = self.next() {
+            match f(item) {
+                Ok(result) => return Some(result),
+                Err(item) => Some(item),
+            }
+        } else {
+            None
+        };
+        self.peeked = Some(unpeek);
+        None
+    }
 }
 
 #[unstable(feature = "trusted_len", issue = "37572")]
diff --git a/library/core/src/lib.rs b/library/core/src/lib.rs
index 82506379cac..c306011bdda 100644
--- a/library/core/src/lib.rs
+++ b/library/core/src/lib.rs
@@ -156,6 +156,7 @@
 #![feature(f128)]
 #![feature(freeze_impls)]
 #![feature(fundamental)]
+#![feature(funnel_shifts)]
 #![feature(if_let_guard)]
 #![feature(intra_doc_pointers)]
 #![feature(intrinsics)]
diff --git a/library/core/src/num/int_macros.rs b/library/core/src/num/int_macros.rs
index 25864db5fea..db70fb65d44 100644
--- a/library/core/src/num/int_macros.rs
+++ b/library/core/src/num/int_macros.rs
@@ -1285,7 +1285,7 @@ macro_rules! int_impl {
         ///
         /// ```should_panic
         #[doc = concat!("let _ = ", stringify!($SelfT), "::MIN.strict_neg();")]
-        ///
+        /// ```
         #[stable(feature = "strict_overflow_ops", since = "CURRENT_RUSTC_VERSION")]
         #[rustc_const_stable(feature = "strict_overflow_ops", since = "CURRENT_RUSTC_VERSION")]
         #[must_use = "this returns the result of the operation, \
diff --git a/library/core/src/num/mod.rs b/library/core/src/num/mod.rs
index 69c6a7dbd89..54d5a63633c 100644
--- a/library/core/src/num/mod.rs
+++ b/library/core/src/num/mod.rs
@@ -454,6 +454,9 @@ impl u8 {
         rot = 2,
         rot_op = "0x82",
         rot_result = "0xa",
+        fsh_op = "0x36",
+        fshl_result = "0x8",
+        fshr_result = "0x8d",
         swap_op = "0x12",
         swapped = "0x12",
         reversed = "0x48",
@@ -1088,6 +1091,9 @@ impl u16 {
         rot = 4,
         rot_op = "0xa003",
         rot_result = "0x3a",
+        fsh_op = "0x2de",
+        fshl_result = "0x30",
+        fshr_result = "0x302d",
         swap_op = "0x1234",
         swapped = "0x3412",
         reversed = "0x2c48",
@@ -1135,6 +1141,9 @@ impl u32 {
         rot = 8,
         rot_op = "0x10000b3",
         rot_result = "0xb301",
+        fsh_op = "0x2fe78e45",
+        fshl_result = "0xb32f",
+        fshr_result = "0xb32fe78e",
         swap_op = "0x12345678",
         swapped = "0x78563412",
         reversed = "0x1e6a2c48",
@@ -1158,6 +1167,9 @@ impl u64 {
         rot = 12,
         rot_op = "0xaa00000000006e1",
         rot_result = "0x6e10aa",
+        fsh_op = "0x2fe78e45983acd98",
+        fshl_result = "0x6e12fe",
+        fshr_result = "0x6e12fe78e45983ac",
         swap_op = "0x1234567890123456",
         swapped = "0x5634129078563412",
         reversed = "0x6a2c48091e6a2c48",
@@ -1181,6 +1193,9 @@ impl u128 {
         rot = 16,
         rot_op = "0x13f40000000000000000000000004f76",
         rot_result = "0x4f7613f4",
+        fsh_op = "0x2fe78e45983acd98039000008736273",
+        fshl_result = "0x4f7602fe",
+        fshr_result = "0x4f7602fe78e45983acd9803900000873",
         swap_op = "0x12345678901234567890123456789012",
         swapped = "0x12907856341290785634129078563412",
         reversed = "0x48091e6a2c48091e6a2c48091e6a2c48",
@@ -1207,6 +1222,9 @@ impl usize {
         rot = 4,
         rot_op = "0xa003",
         rot_result = "0x3a",
+        fsh_op = "0x2fe78e45983acd98039000008736273",
+        fshl_result = "0x4f7602fe",
+        fshr_result = "0x4f7602fe78e45983acd9803900000873",
         swap_op = "0x1234",
         swapped = "0x3412",
         reversed = "0x2c48",
@@ -1231,6 +1249,9 @@ impl usize {
         rot = 8,
         rot_op = "0x10000b3",
         rot_result = "0xb301",
+        fsh_op = "0x2fe78e45",
+        fshl_result = "0xb32f",
+        fshr_result = "0xb32fe78e",
         swap_op = "0x12345678",
         swapped = "0x78563412",
         reversed = "0x1e6a2c48",
@@ -1255,6 +1276,9 @@ impl usize {
         rot = 12,
         rot_op = "0xaa00000000006e1",
         rot_result = "0x6e10aa",
+        fsh_op = "0x2fe78e45983acd98",
+        fshl_result = "0x6e12fe",
+        fshr_result = "0x6e12fe78e45983ac",
         swap_op = "0x1234567890123456",
         swapped = "0x5634129078563412",
         reversed = "0x6a2c48091e6a2c48",
diff --git a/library/core/src/num/uint_macros.rs b/library/core/src/num/uint_macros.rs
index c1e656fdea2..0ce9c259c40 100644
--- a/library/core/src/num/uint_macros.rs
+++ b/library/core/src/num/uint_macros.rs
@@ -14,6 +14,9 @@ macro_rules! uint_impl {
         rot = $rot:literal,
         rot_op = $rot_op:literal,
         rot_result = $rot_result:literal,
+        fsh_op = $fsh_op:literal,
+        fshl_result = $fshl_result:literal,
+        fshr_result = $fshr_result:literal,
         swap_op = $swap_op:literal,
         swapped = $swapped:literal,
         reversed = $reversed:literal,
@@ -375,6 +378,76 @@ macro_rules! uint_impl {
             return intrinsics::rotate_right(self, n);
         }
 
+        /// Performs a left funnel shift (concatenates `self` with `rhs`, with `self`
+        /// making up the most significant half, then shifts the combined value left
+        /// by `n`, and most significant half is extracted to produce the result).
+        ///
+        /// Please note this isn't the same operation as the `<<` shifting operator or
+        /// [`rotate_left`](Self::rotate_left), although `a.funnel_shl(a, n)` is *equivalent*
+        /// to `a.rotate_left(n)`.
+        ///
+        /// # Panics
+        ///
+        /// If `n` is greater than or equal to the number of bits in `self`
+        ///
+        /// # Examples
+        ///
+        /// Basic usage:
+        ///
+        /// ```
+        /// #![feature(funnel_shifts)]
+        #[doc = concat!("let a = ", $rot_op, stringify!($SelfT), ";")]
+        #[doc = concat!("let b = ", $fsh_op, stringify!($SelfT), ";")]
+        #[doc = concat!("let m = ", $fshl_result, ";")]
+        ///
+        #[doc = concat!("assert_eq!(a.funnel_shl(b, ", $rot, "), m);")]
+        /// ```
+        #[rustc_const_unstable(feature = "funnel_shifts", issue = "145686")]
+        #[unstable(feature = "funnel_shifts", issue = "145686")]
+        #[must_use = "this returns the result of the operation, \
+                      without modifying the original"]
+        #[inline(always)]
+        pub const fn funnel_shl(self, rhs: Self, n: u32) -> Self {
+            assert!(n < Self::BITS, "attempt to funnel shift left with overflow");
+            // SAFETY: just checked that `shift` is in-range
+            unsafe { intrinsics::unchecked_funnel_shl(self, rhs, n) }
+        }
+
+        /// Performs a right funnel shift (concatenates `self` and `rhs`, with `self`
+        /// making up the most significant half, then shifts the combined value right
+        /// by `n`, and least significant half is extracted to produce the result).
+        ///
+        /// Please note this isn't the same operation as the `>>` shifting operator or
+        /// [`rotate_right`](Self::rotate_right), although `a.funnel_shr(a, n)` is *equivalent*
+        /// to `a.rotate_right(n)`.
+        ///
+        /// # Panics
+        ///
+        /// If `n` is greater than or equal to the number of bits in `self`
+        ///
+        /// # Examples
+        ///
+        /// Basic usage:
+        ///
+        /// ```
+        /// #![feature(funnel_shifts)]
+        #[doc = concat!("let a = ", $rot_op, stringify!($SelfT), ";")]
+        #[doc = concat!("let b = ", $fsh_op, stringify!($SelfT), ";")]
+        #[doc = concat!("let m = ", $fshr_result, ";")]
+        ///
+        #[doc = concat!("assert_eq!(a.funnel_shr(b, ", $rot, "), m);")]
+        /// ```
+        #[rustc_const_unstable(feature = "funnel_shifts", issue = "145686")]
+        #[unstable(feature = "funnel_shifts", issue = "145686")]
+        #[must_use = "this returns the result of the operation, \
+                      without modifying the original"]
+        #[inline(always)]
+        pub const fn funnel_shr(self, rhs: Self, n: u32) -> Self {
+            assert!(n < Self::BITS, "attempt to funnel shift right with overflow");
+            // SAFETY: just checked that `shift` is in-range
+            unsafe { intrinsics::unchecked_funnel_shr(self, rhs, n) }
+        }
+
         /// Reverses the byte order of the integer.
         ///
         /// # Examples
@@ -1620,7 +1693,7 @@ macro_rules! uint_impl {
         ///
         /// ```should_panic
         #[doc = concat!("let _ = 1", stringify!($SelfT), ".strict_neg();")]
-        ///
+        /// ```
         #[stable(feature = "strict_overflow_ops", since = "CURRENT_RUSTC_VERSION")]
         #[rustc_const_stable(feature = "strict_overflow_ops", since = "CURRENT_RUSTC_VERSION")]
         #[must_use = "this returns the result of the operation, \
diff --git a/library/core/src/ops/range.rs b/library/core/src/ops/range.rs
index c0a27775694..58a9431bd84 100644
--- a/library/core/src/ops/range.rs
+++ b/library/core/src/ops/range.rs
@@ -836,6 +836,7 @@ pub trait RangeBounds<T: ?Sized> {
     /// assert!(!(0.0..1.0).contains(&f32::NAN));
     /// assert!(!(0.0..f32::NAN).contains(&0.5));
     /// assert!(!(f32::NAN..1.0).contains(&0.5));
+    /// ```
     #[inline]
     #[stable(feature = "range_contains", since = "1.35.0")]
     fn contains<U>(&self, item: &U) -> bool
diff --git a/library/core/src/ptr/mut_ptr.rs b/library/core/src/ptr/mut_ptr.rs
index 3fe4b08d459..ce6eee4f911 100644
--- a/library/core/src/ptr/mut_ptr.rs
+++ b/library/core/src/ptr/mut_ptr.rs
@@ -106,6 +106,7 @@ impl<T: PointeeSized> *mut T {
     ///
     /// // This dereference is UB. The pointer only has provenance for `x` but points to `y`.
     /// println!("{:?}", unsafe { &*bad });
+    /// ```
     #[unstable(feature = "set_ptr_value", issue = "75091")]
     #[must_use = "returns a new pointer rather than modifying its argument"]
     #[inline]