Auto merge of #89512 - Manishearth:rollup-meh9x7r, r=Manishearth

Rollup of 14 pull requests

Successful merges:

 - #86434 (Add `Ipv6Addr::is_benchmarking`)
 - #86828 (const fn for option copied, take & replace)
 - #87679 (BTree: refine some comments)
 - #87910 (Mark unsafe methods NonZero*::unchecked_(add|mul) as const.)
 - #88286 (Remove unnecessary unsafe block in `process_unix`)
 - #88305 (Manual Debug for Unix ExitCode ExitStatus ExitStatusError)
 - #88353 (Partially stabilize `array_methods`)
 - #88370 (Add missing `# Panics` section to `Vec` method)
 - #88481 (Remove some feature gates)
 - #89138 (Fix link in Ipv6Addr::to_ipv4 docs)
 - #89401 (Add truncate note to Vec::resize)
 - #89467 (Fix typos in rustdoc/lints)
 - #89472 (Only register `WSACleanup` if `WSAStartup` is actually ever called)
 - #89505 (Add regression test for spurious const error with NLL)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

30 files changed, 251 insertions, 135 deletions

diff --git a/compiler/rustc_borrowck/src/member_constraints.rs b/compiler/rustc_borrowck/src/member_constraints.rs
index 2e2578df011..f22d355e613 100644
--- a/compiler/rustc_borrowck/src/member_constraints.rs
+++ b/compiler/rustc_borrowck/src/member_constraints.rs
@@ -144,7 +144,7 @@ impl<R> MemberConstraintSet<'tcx, R>
 where
     R: Copy + Hash + Eq,
 {
-    crate fn all_indices(&self) -> impl Iterator<Item = NllMemberConstraintIndex> {
+    crate fn all_indices(&self) -> impl Iterator<Item = NllMemberConstraintIndex> + '_ {
         self.constraints.indices()
     }
 
diff --git a/compiler/rustc_borrowck/src/region_infer/mod.rs b/compiler/rustc_borrowck/src/region_infer/mod.rs
index 65d6e3a4ae5..734a5b4972b 100644
--- a/compiler/rustc_borrowck/src/region_infer/mod.rs
+++ b/compiler/rustc_borrowck/src/region_infer/mod.rs
@@ -497,7 +497,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     }
 
     /// Returns an iterator over all the region indices.
-    pub fn regions(&self) -> impl Iterator<Item = RegionVid> {
+    pub fn regions(&self) -> impl Iterator<Item = RegionVid> + '_ {
         self.definitions.indices()
     }
 
diff --git a/compiler/rustc_data_structures/src/lib.rs b/compiler/rustc_data_structures/src/lib.rs
index b1f04bfbf0a..370e8ffed72 100644
--- a/compiler/rustc_data_structures/src/lib.rs
+++ b/compiler/rustc_data_structures/src/lib.rs
@@ -7,7 +7,6 @@
 //! This API is completely unstable and subject to change.
 
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
-#![feature(allow_internal_unstable)]
 #![feature(array_windows)]
 #![feature(associated_type_bounds)]
 #![feature(auto_traits)]
diff --git a/compiler/rustc_index/src/lib.rs b/compiler/rustc_index/src/lib.rs
index 0093fa5e562..a72a27e07bd 100644
--- a/compiler/rustc_index/src/lib.rs
+++ b/compiler/rustc_index/src/lib.rs
@@ -2,9 +2,8 @@
 #![feature(bench_black_box)]
 #![feature(extend_one)]
 #![feature(iter_zip)]
-#![feature(unboxed_closures)]
+#![feature(min_specialization)]
 #![feature(test)]
-#![feature(fn_traits)]
 
 pub mod bit_set;
 pub mod vec;
diff --git a/compiler/rustc_index/src/vec.rs b/compiler/rustc_index/src/vec.rs
index 8535a7c866d..56ea04539e5 100644
--- a/compiler/rustc_index/src/vec.rs
+++ b/compiler/rustc_index/src/vec.rs
@@ -3,9 +3,9 @@ use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 use std::fmt;
 use std::fmt::Debug;
 use std::hash::Hash;
-use std::iter::{self, FromIterator};
+use std::iter::FromIterator;
 use std::marker::PhantomData;
-use std::ops::{Index, IndexMut, Range, RangeBounds};
+use std::ops::{Index, IndexMut, RangeBounds};
 use std::slice;
 use std::vec;
 
@@ -518,8 +518,6 @@ impl<I: Idx, T: fmt::Debug> fmt::Debug for IndexVec<I, T> {
     }
 }
 
-pub type Enumerated<I, J> = iter::Map<iter::Enumerate<J>, IntoIdx<I>>;
-
 impl<I: Idx, T> IndexVec<I, T> {
     #[inline]
     pub fn new() -> Self {
@@ -596,8 +594,10 @@ impl<I: Idx, T> IndexVec<I, T> {
     }
 
     #[inline]
-    pub fn into_iter_enumerated(self) -> Enumerated<I, vec::IntoIter<T>> {
-        self.raw.into_iter().enumerate().map(IntoIdx { _marker: PhantomData })
+    pub fn into_iter_enumerated(
+        self,
+    ) -> impl DoubleEndedIterator<Item = (I, T)> + ExactSizeIterator {
+        self.raw.into_iter().enumerate().map(|(n, t)| (I::new(n), t))
     }
 
     #[inline]
@@ -606,13 +606,15 @@ impl<I: Idx, T> IndexVec<I, T> {
     }
 
     #[inline]
-    pub fn iter_enumerated(&self) -> Enumerated<I, slice::Iter<'_, T>> {
-        self.raw.iter().enumerate().map(IntoIdx { _marker: PhantomData })
+    pub fn iter_enumerated(
+        &self,
+    ) -> impl DoubleEndedIterator<Item = (I, &T)> + ExactSizeIterator + '_ {
+        self.raw.iter().enumerate().map(|(n, t)| (I::new(n), t))
     }
 
     #[inline]
-    pub fn indices(&self) -> iter::Map<Range<usize>, IntoIdx<I>> {
-        (0..self.len()).map(IntoIdx { _marker: PhantomData })
+    pub fn indices(&self) -> impl DoubleEndedIterator<Item = I> + ExactSizeIterator + 'static {
+        (0..self.len()).map(|n| I::new(n))
     }
 
     #[inline]
@@ -621,8 +623,10 @@ impl<I: Idx, T> IndexVec<I, T> {
     }
 
     #[inline]
-    pub fn iter_enumerated_mut(&mut self) -> Enumerated<I, slice::IterMut<'_, T>> {
-        self.raw.iter_mut().enumerate().map(IntoIdx { _marker: PhantomData })
+    pub fn iter_enumerated_mut(
+        &mut self,
+    ) -> impl DoubleEndedIterator<Item = (I, &mut T)> + ExactSizeIterator + '_ {
+        self.raw.iter_mut().enumerate().map(|(n, t)| (I::new(n), t))
     }
 
     #[inline]
@@ -638,7 +642,7 @@ impl<I: Idx, T> IndexVec<I, T> {
         &'a mut self,
         range: R,
     ) -> impl Iterator<Item = (I, T)> + 'a {
-        self.raw.drain(range).enumerate().map(IntoIdx { _marker: PhantomData })
+        self.raw.drain(range).enumerate().map(|(n, t)| (I::new(n), t))
     }
 
     #[inline]
@@ -832,36 +836,5 @@ impl<'a, I: Idx, T> IntoIterator for &'a mut IndexVec<I, T> {
     }
 }
 
-pub struct IntoIdx<I: Idx> {
-    _marker: PhantomData<fn(&I)>,
-}
-impl<I: Idx, T> FnOnce<((usize, T),)> for IntoIdx<I> {
-    type Output = (I, T);
-
-    extern "rust-call" fn call_once(self, ((n, t),): ((usize, T),)) -> Self::Output {
-        (I::new(n), t)
-    }
-}
-
-impl<I: Idx, T> FnMut<((usize, T),)> for IntoIdx<I> {
-    extern "rust-call" fn call_mut(&mut self, ((n, t),): ((usize, T),)) -> Self::Output {
-        (I::new(n), t)
-    }
-}
-
-impl<I: Idx> FnOnce<(usize,)> for IntoIdx<I> {
-    type Output = I;
-
-    extern "rust-call" fn call_once(self, (n,): (usize,)) -> Self::Output {
-        I::new(n)
-    }
-}
-
-impl<I: Idx> FnMut<(usize,)> for IntoIdx<I> {
-    extern "rust-call" fn call_mut(&mut self, (n,): (usize,)) -> Self::Output {
-        I::new(n)
-    }
-}
-
 #[cfg(test)]
 mod tests;
diff --git a/compiler/rustc_lint/src/lib.rs b/compiler/rustc_lint/src/lib.rs
index 10285272130..17eb0054584 100644
--- a/compiler/rustc_lint/src/lib.rs
+++ b/compiler/rustc_lint/src/lib.rs
@@ -26,7 +26,6 @@
 //! This API is completely unstable and subject to change.
 
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
-#![cfg_attr(test, feature(test))]
 #![feature(array_windows)]
 #![feature(bool_to_option)]
 #![feature(box_patterns)]
diff --git a/compiler/rustc_middle/src/lib.rs b/compiler/rustc_middle/src/lib.rs
index 02f0294c8ad..1f2bfa5e7d9 100644
--- a/compiler/rustc_middle/src/lib.rs
+++ b/compiler/rustc_middle/src/lib.rs
@@ -41,13 +41,11 @@
 #![feature(once_cell)]
 #![feature(min_specialization)]
 #![feature(trusted_len)]
-#![feature(test)]
 #![feature(in_band_lifetimes)]
 #![feature(crate_visibility_modifier)]
 #![feature(associated_type_bounds)]
 #![feature(rustc_attrs)]
 #![feature(half_open_range_patterns)]
-#![feature(exclusive_range_pattern)]
 #![feature(control_flow_enum)]
 #![feature(associated_type_defaults)]
 #![feature(iter_zip)]
diff --git a/compiler/rustc_middle/src/ty/codec.rs b/compiler/rustc_middle/src/ty/codec.rs
index 8b70692960d..434008ecb1f 100644
--- a/compiler/rustc_middle/src/ty/codec.rs
+++ b/compiler/rustc_middle/src/ty/codec.rs
@@ -1,10 +1,10 @@
-// This module contains some shared code for encoding and decoding various
-// things from the `ty` module, and in particular implements support for
-// "shorthands" which allow to have pointers back into the already encoded
-// stream instead of re-encoding the same thing twice.
-//
-// The functionality in here is shared between persisting to crate metadata and
-// persisting to incr. comp. caches.
+//! This module contains some shared code for encoding and decoding various
+//! things from the `ty` module, and in particular implements support for
+//! "shorthands" which allow to have pointers back into the already encoded
+//! stream instead of re-encoding the same thing twice.
+//!
+//! The functionality in here is shared between persisting to crate metadata and
+//! persisting to incr. comp. caches.
 
 use crate::arena::ArenaAllocatable;
 use crate::infer::canonical::{CanonicalVarInfo, CanonicalVarInfos};
diff --git a/compiler/rustc_mir_dataflow/src/move_paths/mod.rs b/compiler/rustc_mir_dataflow/src/move_paths/mod.rs
index 699ec4bbff8..f2b34159382 100644
--- a/compiler/rustc_mir_dataflow/src/move_paths/mod.rs
+++ b/compiler/rustc_mir_dataflow/src/move_paths/mod.rs
@@ -1,6 +1,5 @@
-use core::slice::Iter;
 use rustc_data_structures::fx::FxHashMap;
-use rustc_index::vec::{Enumerated, IndexVec};
+use rustc_index::vec::IndexVec;
 use rustc_middle::mir::*;
 use rustc_middle::ty::{ParamEnv, Ty, TyCtxt};
 use rustc_span::Span;
@@ -337,7 +336,9 @@ impl MovePathLookup {
 
     /// An enumerated iterator of `local`s and their associated
     /// `MovePathIndex`es.
-    pub fn iter_locals_enumerated(&self) -> Enumerated<Local, Iter<'_, MovePathIndex>> {
+    pub fn iter_locals_enumerated(
+        &self,
+    ) -> impl DoubleEndedIterator<Item = (Local, &MovePathIndex)> + ExactSizeIterator {
         self.locals.iter_enumerated()
     }
 }
diff --git a/compiler/rustc_target/src/lib.rs b/compiler/rustc_target/src/lib.rs
index e75c52555b9..23d5d575d94 100644
--- a/compiler/rustc_target/src/lib.rs
+++ b/compiler/rustc_target/src/lib.rs
@@ -15,7 +15,6 @@
 #![feature(exhaustive_patterns)]
 #![feature(min_specialization)]
 #![feature(step_trait)]
-#![feature(unchecked_math)]
 
 use std::path::{Path, PathBuf};
 
diff --git a/compiler/rustc_ty_utils/src/lib.rs b/compiler/rustc_ty_utils/src/lib.rs
index 313571274c3..60f8e196bcb 100644
--- a/compiler/rustc_ty_utils/src/lib.rs
+++ b/compiler/rustc_ty_utils/src/lib.rs
@@ -6,8 +6,6 @@
 
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![feature(control_flow_enum)]
-#![feature(half_open_range_patterns)]
-#![feature(exclusive_range_pattern)]
 #![feature(nll)]
 #![recursion_limit = "256"]
 
diff --git a/library/alloc/src/collections/btree/map.rs b/library/alloc/src/collections/btree/map.rs
index 3b7c92818f6..11b0ca4b421 100644
--- a/library/alloc/src/collections/btree/map.rs
+++ b/library/alloc/src/collections/btree/map.rs
@@ -19,16 +19,16 @@ mod entry;
 pub use entry::{Entry, OccupiedEntry, OccupiedError, VacantEntry};
 use Entry::*;
 
-/// Minimum number of elements in nodes that are not a root.
+/// Minimum number of elements in a node that is not a root.
 /// We might temporarily have fewer elements during methods.
 pub(super) const MIN_LEN: usize = node::MIN_LEN_AFTER_SPLIT;
 
 // A tree in a `BTreeMap` is a tree in the `node` module with additional invariants:
 // - Keys must appear in ascending order (according to the key's type).
-// - If the root node is internal, it must contain at least 1 element.
+// - Every non-leaf node contains at least 1 element (has at least 2 children).
 // - Every non-root node contains at least MIN_LEN elements.
 //
-// An empty map may be represented both by the absence of a root node or by a
+// An empty map is represented either by the absence of a root node or by a
 // root node that is an empty leaf.
 
 /// A map based on a [B-Tree].
@@ -1735,8 +1735,8 @@ impl<'a, K: 'a, V: 'a> DrainFilterInner<'a, K, V> {
     pub(super) fn size_hint(&self) -> (usize, Option<usize>) {
         // In most of the btree iterators, `self.length` is the number of elements
         // yet to be visited. Here, it includes elements that were visited and that
-        // the predicate decided not to drain. Making this upper bound more accurate
-        // requires maintaining an extra field and is not worth while.
+        // the predicate decided not to drain. Making this upper bound more tight
+        // during iteration would require an extra field.
         (0, Some(*self.length))
     }
 }
diff --git a/library/alloc/src/collections/btree/navigate.rs b/library/alloc/src/collections/btree/navigate.rs
index 7b1d4d68c4f..9d0db345009 100644
--- a/library/alloc/src/collections/btree/navigate.rs
+++ b/library/alloc/src/collections/btree/navigate.rs
@@ -440,8 +440,7 @@ impl<K, V> Handle<NodeRef<marker::Dying, K, V, marker::Leaf>, marker::Edge> {
     /// - The given edge must not have been previously returned by counterpart
     ///   `deallocating_next_back`.
     /// - The returned KV handle is only valid to access the key and value,
-    ///   and only valid until the next call to this method or counterpart
-    ///   `deallocating_next_back`.
+    ///   and only valid until the next call to a `deallocating_` method.
     unsafe fn deallocating_next(
         self,
     ) -> Option<(Self, Handle<NodeRef<marker::Dying, K, V, marker::LeafOrInternal>, marker::KV>)>
@@ -470,8 +469,7 @@ impl<K, V> Handle<NodeRef<marker::Dying, K, V, marker::Leaf>, marker::Edge> {
     /// - The given edge must not have been previously returned by counterpart
     ///   `deallocating_next`.
     /// - The returned KV handle is only valid to access the key and value,
-    ///   and only valid until the next call to this method or counterpart
-    ///   `deallocating_next`.
+    ///   and only valid until the next call to a `deallocating_` method.
     unsafe fn deallocating_next_back(
         self,
     ) -> Option<(Self, Handle<NodeRef<marker::Dying, K, V, marker::LeafOrInternal>, marker::KV>)>
diff --git a/library/alloc/src/collections/btree/node.rs b/library/alloc/src/collections/btree/node.rs
index a73f00a083a..dfce98f97bd 100644
--- a/library/alloc/src/collections/btree/node.rs
+++ b/library/alloc/src/collections/btree/node.rs
@@ -574,7 +574,7 @@ impl<K, V> NodeRef<marker::Owned, K, V, marker::LeafOrInternal> {
     /// no cleanup is done on any of the keys, values and other children.
     /// This decreases the height by 1 and is the opposite of `push_internal_level`.
     ///
-    /// Requires exclusive access to the `Root` object but not to the root node;
+    /// Requires exclusive access to the `NodeRef` object but not to the root node;
     /// it will not invalidate other handles or references to the root node.
     ///
     /// Panics if there is no internal level, i.e., if the root node is a leaf.
diff --git a/library/alloc/src/vec/mod.rs b/library/alloc/src/vec/mod.rs
index f3a30d09825..320347e58e1 100644
--- a/library/alloc/src/vec/mod.rs
+++ b/library/alloc/src/vec/mod.rs
@@ -2137,6 +2137,7 @@ impl<T: Clone, A: Allocator> Vec<T, A> {
     /// in order to be able to clone the passed value.
     /// If you need more flexibility (or want to rely on [`Default`] instead of
     /// [`Clone`]), use [`Vec::resize_with`].
+    /// If you only need to resize to a smaller size, use [`Vec::truncate`].
     ///
     /// # Examples
     ///
@@ -2188,7 +2189,12 @@ impl<T: Clone, A: Allocator> Vec<T, A> {
 
     /// Copies elements from `src` range to the end of the vector.
     ///
-    /// ## Examples
+    /// # Panics
+    ///
+    /// Panics if the starting point is greater than the end point or if
+    /// the end point is greater than the length of the vector.
+    ///
+    /// # Examples
     ///
     /// ```
     /// let mut vec = vec![0, 1, 2, 3, 4];
diff --git a/library/core/src/array/mod.rs b/library/core/src/array/mod.rs
index 8c33a43ab33..09329247f94 100644
--- a/library/core/src/array/mod.rs
+++ b/library/core/src/array/mod.rs
@@ -368,14 +368,14 @@ impl<T, const N: usize> [T; N] {
     }
 
     /// Returns a slice containing the entire array. Equivalent to `&s[..]`.
-    #[unstable(feature = "array_methods", issue = "76118")]
-    pub fn as_slice(&self) -> &[T] {
+    #[stable(feature = "array_as_slice", since = "1.57.0")]
+    pub const fn as_slice(&self) -> &[T] {
         self
     }
 
     /// Returns a mutable slice containing the entire array. Equivalent to
     /// `&mut s[..]`.
-    #[unstable(feature = "array_methods", issue = "76118")]
+    #[stable(feature = "array_as_slice", since = "1.57.0")]
     pub fn as_mut_slice(&mut self) -> &mut [T] {
         self
     }
diff --git a/library/core/src/lib.rs b/library/core/src/lib.rs
index 2230461b5f4..45ef1fcde2a 100644
--- a/library/core/src/lib.rs
+++ b/library/core/src/lib.rs
@@ -91,6 +91,7 @@
 #![feature(const_maybe_uninit_assume_init)]
 #![feature(const_option)]
 #![feature(const_pin)]
+#![feature(const_replace)]
 #![feature(const_ptr_offset)]
 #![feature(const_ptr_offset_from)]
 #![feature(const_ptr_read)]
diff --git a/library/core/src/num/nonzero.rs b/library/core/src/num/nonzero.rs
index dd9b9330aee..e44597279ba 100644
--- a/library/core/src/num/nonzero.rs
+++ b/library/core/src/num/nonzero.rs
@@ -379,7 +379,7 @@ macro_rules! nonzero_unsigned_operations {
                 /// ```
                 #[unstable(feature = "nonzero_ops", issue = "84186")]
                 #[inline]
-                pub unsafe fn unchecked_add(self, other: $Int) -> $Ty {
+                pub const unsafe fn unchecked_add(self, other: $Int) -> $Ty {
                     // SAFETY: The caller ensures there is no overflow.
                     unsafe { $Ty::new_unchecked(self.get().unchecked_add(other)) }
                 }
@@ -750,7 +750,7 @@ macro_rules! nonzero_unsigned_signed_operations {
                 /// ```
                 #[unstable(feature = "nonzero_ops", issue = "84186")]
                 #[inline]
-                pub unsafe fn unchecked_mul(self, other: $Ty) -> $Ty {
+                pub const unsafe fn unchecked_mul(self, other: $Ty) -> $Ty {
                     // SAFETY: The caller ensures there is no overflow.
                     unsafe { $Ty::new_unchecked(self.get().unchecked_mul(other.get())) }
                 }
diff --git a/library/core/src/option.rs b/library/core/src/option.rs
index b2cc7145702..3259e142a0c 100644
--- a/library/core/src/option.rs
+++ b/library/core/src/option.rs
@@ -544,8 +544,8 @@ impl<T> Option<T> {
     /// ```
     #[must_use = "if you intended to assert that this has a value, consider `.unwrap()` instead"]
     #[inline]
-    #[rustc_const_stable(feature = "const_option", since = "1.48.0")]
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[rustc_const_stable(feature = "const_option", since = "1.48.0")]
     pub const fn is_some(&self) -> bool {
         matches!(*self, Some(_))
     }
@@ -564,8 +564,8 @@ impl<T> Option<T> {
     #[must_use = "if you intended to assert that this doesn't have a value, consider \
                   `.and_then(|_| panic!(\"`Option` had a value when expected `None`\"))` instead"]
     #[inline]
-    #[rustc_const_stable(feature = "const_option", since = "1.48.0")]
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[rustc_const_stable(feature = "const_option", since = "1.48.0")]
     pub const fn is_none(&self) -> bool {
         !self.is_some()
     }
@@ -1318,8 +1318,10 @@ impl<T> Option<T> {
     /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn take(&mut self) -> Option<T> {
-        mem::take(self)
+    #[rustc_const_unstable(feature = "const_option", issue = "67441")]
+    pub const fn take(&mut self) -> Option<T> {
+        // FIXME replace `mem::replace` by `mem::take` when the latter is const ready
+        mem::replace(self, None)
     }
 
     /// Replaces the actual value in the option by the value given in parameter,
@@ -1340,8 +1342,9 @@ impl<T> Option<T> {
     /// assert_eq!(old, None);
     /// ```
     #[inline]
+    #[rustc_const_unstable(feature = "const_option", issue = "67441")]
     #[stable(feature = "option_replace", since = "1.31.0")]
-    pub fn replace(&mut self, value: T) -> Option<T> {
+    pub const fn replace(&mut self, value: T) -> Option<T> {
         mem::replace(self, Some(value))
     }
 
@@ -1446,8 +1449,14 @@ impl<T: Copy> Option<&T> {
     /// assert_eq!(copied, Some(12));
     /// ```
     #[stable(feature = "copied", since = "1.35.0")]
-    pub fn copied(self) -> Option<T> {
-        self.map(|&t| t)
+    #[rustc_const_unstable(feature = "const_option", issue = "67441")]
+    pub const fn copied(self) -> Option<T> {
+        // FIXME: this implementation, which sidesteps using `Option::map` since it's not const
+        // ready yet, should be reverted when possible to avoid code repetition
+        match self {
+            Some(&v) => Some(v),
+            None => None,
+        }
     }
 }
 
diff --git a/library/core/tests/option.rs b/library/core/tests/option.rs
index cd8fdebe36a..8995f96b123 100644
--- a/library/core/tests/option.rs
+++ b/library/core/tests/option.rs
@@ -367,6 +367,19 @@ fn option_const() {
 
     const IS_NONE: bool = OPTION.is_none();
     assert!(!IS_NONE);
+
+    const COPIED: Option<usize> = OPTION.as_ref().copied();
+    assert_eq!(COPIED, OPTION);
+}
+
+#[test]
+const fn option_const_mut() {
+    // test that the methods of `Option` that take mutable references are usable in a const context
+
+    let mut option: Option<usize> = Some(32);
+
+    let _take = option.take();
+    let _replace = option.replace(42);
 }
 
 #[test]
diff --git a/library/std/src/net/ip.rs b/library/std/src/net/ip.rs
index 9cf7ba9d574..c05a32742ba 100644
--- a/library/std/src/net/ip.rs
+++ b/library/std/src/net/ip.rs
@@ -340,6 +340,30 @@ impl IpAddr {
         }
     }
 
+    /// Returns [`true`] if this address is in a range designated for benchmarking.
+    ///
+    /// See the documentation for [`Ipv4Addr::is_benchmarking()`] and
+    /// [`Ipv6Addr::is_benchmarking()`] for more details.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(ip)]
+    ///
+    /// use std::net::{IpAddr, Ipv4Addr, Ipv6Addr};
+    ///
+    /// assert_eq!(IpAddr::V4(Ipv4Addr::new(198, 19, 255, 255)).is_benchmarking(), true);
+    /// assert_eq!(IpAddr::V6(Ipv6Addr::new(0x2001, 0x2, 0, 0, 0, 0, 0, 0)).is_benchmarking(), true);
+    /// ```
+    #[unstable(feature = "ip", issue = "27709")]
+    #[inline]
+    pub const fn is_benchmarking(&self) -> bool {
+        match self {
+            IpAddr::V4(ip) => ip.is_benchmarking(),
+            IpAddr::V6(ip) => ip.is_benchmarking(),
+        }
+    }
+
     /// Returns [`true`] if this address is an [`IPv4` address], and [`false`]
     /// otherwise.
     ///
@@ -1449,6 +1473,28 @@ impl Ipv6Addr {
         (self.segments()[0] == 0x2001) && (self.segments()[1] == 0xdb8)
     }
 
+    /// Returns [`true`] if this is an address reserved for benchmarking (`2001:2::/48`).
+    ///
+    /// This property is defined in [IETF RFC 5180], where it is mistakenly specified as covering the range `2001:0200::/48`.
+    /// This is corrected in [IETF RFC Errata 1752] to `2001:0002::/48`.
+    ///
+    /// [IETF RFC 5180]: https://tools.ietf.org/html/rfc5180
+    /// [IETF RFC Errata 1752]: https://www.rfc-editor.org/errata_search.php?eid=1752
+    ///
+    /// ```
+    /// #![feature(ip)]
+    ///
+    /// use std::net::Ipv6Addr;
+    ///
+    /// assert_eq!(Ipv6Addr::new(0, 0, 0, 0, 0, 0xffff, 0xc613, 0x0).is_benchmarking(), false);
+    /// assert_eq!(Ipv6Addr::new(0x2001, 0x2, 0, 0, 0, 0, 0, 0).is_benchmarking(), true);
+    /// ```
+    #[unstable(feature = "ip", issue = "27709")]
+    #[inline]
+    pub const fn is_benchmarking(&self) -> bool {
+        (self.segments()[0] == 0x2001) && (self.segments()[1] == 0x2) && (self.segments()[2] == 0)
+    }
+
     /// Returns [`true`] if the address is a globally routable unicast address.
     ///
     /// The following return false:
@@ -1589,7 +1635,7 @@ impl Ipv6Addr {
     /// `::a.b.c.d` and `::ffff:a.b.c.d` become `a.b.c.d`
     /// All addresses *not* starting with either all zeroes or `::ffff` will return `None`.
     ///
-    /// [IPv4 address]: Ipv4Addr
+    /// [`IPv4` address]: Ipv4Addr
     /// [IPv4-compatible]: Ipv6Addr#ipv4-compatible-ipv6-addresses
     /// [IPv4-mapped]: Ipv6Addr#ipv4-mapped-ipv6-addresses
     /// [IETF RFC 4291 section 2.5.5.1]: https://tools.ietf.org/html/rfc4291#section-2.5.5.1
diff --git a/library/std/src/net/ip/tests.rs b/library/std/src/net/ip/tests.rs
index dbfab9dde40..babc854cd1d 100644
--- a/library/std/src/net/ip/tests.rs
+++ b/library/std/src/net/ip/tests.rs
@@ -224,6 +224,7 @@ fn ip_properties() {
             let global: u8 = 1 << 2;
             let multicast: u8 = 1 << 3;
             let doc: u8 = 1 << 4;
+            let benchmarking: u8 = 1 << 5;
 
             if ($mask & unspec) == unspec {
                 assert!(ip!($s).is_unspecified());
@@ -254,6 +255,12 @@ fn ip_properties() {
             } else {
                 assert!(!ip!($s).is_documentation());
             }
+
+            if ($mask & benchmarking) == benchmarking {
+                assert!(ip!($s).is_benchmarking());
+            } else {
+                assert!(!ip!($s).is_benchmarking());
+            }
         }};
     }
 
@@ -262,6 +269,7 @@ fn ip_properties() {
     let global: u8 = 1 << 2;
     let multicast: u8 = 1 << 3;
     let doc: u8 = 1 << 4;
+    let benchmarking: u8 = 1 << 5;
 
     check!("0.0.0.0", unspec);
     check!("0.0.0.1");
@@ -280,9 +288,9 @@ fn ip_properties() {
     check!("239.255.255.255", global | multicast);
     check!("255.255.255.255");
     // make sure benchmarking addresses are not global
-    check!("198.18.0.0");
-    check!("198.18.54.2");
-    check!("198.19.255.255");
+    check!("198.18.0.0", benchmarking);
+    check!("198.18.54.2", benchmarking);
+    check!("198.19.255.255", benchmarking);
     // make sure addresses reserved for protocol assignment are not global
     check!("192.0.0.0");
     check!("192.0.0.255");
@@ -313,6 +321,7 @@ fn ip_properties() {
     check!("ff08::", multicast);
     check!("ff0e::", global | multicast);
     check!("2001:db8:85a3::8a2e:370:7334", doc);
+    check!("2001:2::ac32:23ff:21", global | benchmarking);
     check!("102:304:506:708:90a:b0c:d0e:f10", global);
 }
 
@@ -467,21 +476,22 @@ fn ipv6_properties() {
             assert_eq!(&ip!($s).octets(), octets);
             assert_eq!(Ipv6Addr::from(*octets), ip!($s));
 
-            let unspecified: u16 = 1 << 0;
-            let loopback: u16 = 1 << 1;
-            let unique_local: u16 = 1 << 2;
-            let global: u16 = 1 << 3;
-            let unicast_link_local: u16 = 1 << 4;
-            let unicast_global: u16 = 1 << 7;
-            let documentation: u16 = 1 << 8;
-            let multicast_interface_local: u16 = 1 << 9;
-            let multicast_link_local: u16 = 1 << 10;
-            let multicast_realm_local: u16 = 1 << 11;
-            let multicast_admin_local: u16 = 1 << 12;
-            let multicast_site_local: u16 = 1 << 13;
-            let multicast_organization_local: u16 = 1 << 14;
-            let multicast_global: u16 = 1 << 15;
-            let multicast: u16 = multicast_interface_local
+            let unspecified: u32 = 1 << 0;
+            let loopback: u32 = 1 << 1;
+            let unique_local: u32 = 1 << 2;
+            let global: u32 = 1 << 3;
+            let unicast_link_local: u32 = 1 << 4;
+            let unicast_global: u32 = 1 << 7;
+            let documentation: u32 = 1 << 8;
+            let benchmarking: u32 = 1 << 16;
+            let multicast_interface_local: u32 = 1 << 9;
+            let multicast_link_local: u32 = 1 << 10;
+            let multicast_realm_local: u32 = 1 << 11;
+            let multicast_admin_local: u32 = 1 << 12;
+            let multicast_site_local: u32 = 1 << 13;
+            let multicast_organization_local: u32 = 1 << 14;
+            let multicast_global: u32 = 1 << 15;
+            let multicast: u32 = multicast_interface_local
                 | multicast_admin_local
                 | multicast_global
                 | multicast_link_local
@@ -524,6 +534,11 @@ fn ipv6_properties() {
             } else {
                 assert!(!ip!($s).is_documentation());
             }
+            if ($mask & benchmarking) == benchmarking {
+                assert!(ip!($s).is_benchmarking());
+            } else {
+                assert!(!ip!($s).is_benchmarking());
+            }
             if ($mask & multicast) != 0 {
                 assert!(ip!($s).multicast_scope().is_some());
                 assert!(ip!($s).is_multicast());
@@ -562,20 +577,21 @@ fn ipv6_properties() {
         }
     }
 
-    let unspecified: u16 = 1 << 0;
-    let loopback: u16 = 1 << 1;
-    let unique_local: u16 = 1 << 2;
-    let global: u16 = 1 << 3;
-    let unicast_link_local: u16 = 1 << 4;
-    let unicast_global: u16 = 1 << 7;
-    let documentation: u16 = 1 << 8;
-    let multicast_interface_local: u16 = 1 << 9;
-    let multicast_link_local: u16 = 1 << 10;
-    let multicast_realm_local: u16 = 1 << 11;
-    let multicast_admin_local: u16 = 1 << 12;
-    let multicast_site_local: u16 = 1 << 13;
-    let multicast_organization_local: u16 = 1 << 14;
-    let multicast_global: u16 = 1 << 15;
+    let unspecified: u32 = 1 << 0;
+    let loopback: u32 = 1 << 1;
+    let unique_local: u32 = 1 << 2;
+    let global: u32 = 1 << 3;
+    let unicast_link_local: u32 = 1 << 4;
+    let unicast_global: u32 = 1 << 7;
+    let documentation: u32 = 1 << 8;
+    let benchmarking: u32 = 1 << 16;
+    let multicast_interface_local: u32 = 1 << 9;
+    let multicast_link_local: u32 = 1 << 10;
+    let multicast_realm_local: u32 = 1 << 11;
+    let multicast_admin_local: u32 = 1 << 12;
+    let multicast_site_local: u32 = 1 << 13;
+    let multicast_organization_local: u32 = 1 << 14;
+    let multicast_global: u32 = 1 << 15;
 
     check!("::", &[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0], unspecified);
 
@@ -672,6 +688,12 @@ fn ipv6_properties() {
     );
 
     check!(
+        "2001:2::ac32:23ff:21",
+        &[0x20, 1, 0, 2, 0, 0, 0, 0, 0, 0, 0xac, 0x32, 0x23, 0xff, 0, 0x21],
+        global | unicast_global | benchmarking
+    );
+
+    check!(
         "102:304:506:708:90a:b0c:d0e:f10",
         &[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16],
         global | unicast_global
@@ -874,6 +896,9 @@ fn ipv6_const() {
     const IS_DOCUMENTATION: bool = IP_ADDRESS.is_documentation();
     assert!(!IS_DOCUMENTATION);
 
+    const IS_BENCHMARKING: bool = IP_ADDRESS.is_benchmarking();
+    assert!(!IS_BENCHMARKING);
+
     const IS_UNICAST_GLOBAL: bool = IP_ADDRESS.is_unicast_global();
     assert!(!IS_UNICAST_GLOBAL);
 
diff --git a/library/std/src/sys/unix/process/process_common.rs b/library/std/src/sys/unix/process/process_common.rs
index 7b261a302c3..7ac2f9d8af7 100644
--- a/library/std/src/sys/unix/process/process_common.rs
+++ b/library/std/src/sys/unix/process/process_common.rs
@@ -457,9 +457,15 @@ impl fmt::Debug for Command {
     }
 }
 
-#[derive(PartialEq, Eq, Clone, Copy, Debug)]
+#[derive(PartialEq, Eq, Clone, Copy)]
 pub struct ExitCode(u8);
 
+impl fmt::Debug for ExitCode {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_tuple("unix_exit_status").field(&self.0).finish()
+    }
+}
+
 impl ExitCode {
     pub const SUCCESS: ExitCode = ExitCode(EXIT_SUCCESS as _);
     pub const FAILURE: ExitCode = ExitCode(EXIT_FAILURE as _);
diff --git a/library/std/src/sys/unix/process/process_unix.rs b/library/std/src/sys/unix/process/process_unix.rs
index 12edf04a4e2..8c33051cfa4 100644
--- a/library/std/src/sys/unix/process/process_unix.rs
+++ b/library/std/src/sys/unix/process/process_unix.rs
@@ -552,8 +552,7 @@ impl Process {
         use crate::os::unix::io::FromRawFd;
         use crate::sys_common::FromInner;
         // Safety: If `pidfd` is nonnegative, we assume it's valid and otherwise unowned.
-        let pidfd = (pidfd >= 0)
-            .then(|| PidFd::from_inner(unsafe { sys::fd::FileDesc::from_raw_fd(pidfd) }));
+        let pidfd = (pidfd >= 0).then(|| PidFd::from_inner(sys::fd::FileDesc::from_raw_fd(pidfd)));
         Process { pid, status: None, pidfd }
     }
 
@@ -607,9 +606,15 @@ impl Process {
 }
 
 /// Unix exit statuses
-#[derive(PartialEq, Eq, Clone, Copy, Debug)]
+#[derive(PartialEq, Eq, Clone, Copy)]
 pub struct ExitStatus(c_int);
 
+impl fmt::Debug for ExitStatus {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_tuple("unix_wait_status").field(&self.0).finish()
+    }
+}
+
 impl ExitStatus {
     pub fn new(status: c_int) -> ExitStatus {
         ExitStatus(status)
@@ -683,7 +688,7 @@ impl fmt::Display for ExitStatus {
     }
 }
 
-#[derive(PartialEq, Eq, Clone, Copy, Debug)]
+#[derive(PartialEq, Eq, Clone, Copy)]
 pub struct ExitStatusError(NonZero_c_int);
 
 impl Into<ExitStatus> for ExitStatusError {
@@ -692,6 +697,12 @@ impl Into<ExitStatus> for ExitStatusError {
     }
 }
 
+impl fmt::Debug for ExitStatusError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_tuple("unix_wait_status").field(&self.0).finish()
+    }
+}
+
 impl ExitStatusError {
     pub fn code(self) -> Option<NonZeroI32> {
         ExitStatus(self.0.into()).code().map(|st| st.try_into().unwrap())
diff --git a/library/std/src/sys/windows/net.rs b/library/std/src/sys/windows/net.rs
index 33152cc97ab..9c631e7e51c 100644
--- a/library/std/src/sys/windows/net.rs
+++ b/library/std/src/sys/windows/net.rs
@@ -2,13 +2,13 @@
 
 use crate::cmp;
 use crate::io::{self, IoSlice, IoSliceMut, Read};
+use crate::lazy::SyncOnceCell;
 use crate::mem;
 use crate::net::{Shutdown, SocketAddr};
 use crate::os::windows::io::{
     AsRawSocket, AsSocket, BorrowedSocket, FromRawSocket, IntoRawSocket, OwnedSocket, RawSocket,
 };
 use crate::ptr;
-use crate::sync::Once;
 use crate::sys;
 use crate::sys::c;
 use crate::sys_common::net;
@@ -29,26 +29,31 @@ pub mod netc {
 
 pub struct Socket(OwnedSocket);
 
-static INIT: Once = Once::new();
+static WSA_CLEANUP: SyncOnceCell<unsafe extern "system" fn() -> i32> = SyncOnceCell::new();
 
 /// Checks whether the Windows socket interface has been started already, and
 /// if not, starts it.
 pub fn init() {
-    INIT.call_once(|| unsafe {
+    let _ = WSA_CLEANUP.get_or_init(|| unsafe {
         let mut data: c::WSADATA = mem::zeroed();
         let ret = c::WSAStartup(
             0x202, // version 2.2
             &mut data,
         );
         assert_eq!(ret, 0);
+
+        // Only register `WSACleanup` if `WSAStartup` is actually ever called.
+        // Workaround to prevent linking to `WS2_32.dll` when no network functionality is used.
+        // See issue #85441.
+        c::WSACleanup
     });
 }
 
 pub fn cleanup() {
-    if INIT.is_completed() {
-        // only close the socket interface if it has actually been started
+    // only perform cleanup if network functionality was actually initialized
+    if let Some(cleanup) = WSA_CLEANUP.get() {
         unsafe {
-            c::WSACleanup();
+            cleanup();
         }
     }
 }
diff --git a/src/doc/rustdoc/src/lints.md b/src/doc/rustdoc/src/lints.md
index d5981dd83de..1773c15464a 100644
--- a/src/doc/rustdoc/src/lints.md
+++ b/src/doc/rustdoc/src/lints.md
@@ -70,7 +70,7 @@ This lint **warns by default**. This lint detects when [intra-doc links] from pu
 For example:
 
 ```rust
-#![warn(rustdoc::private_intra_doc_links)] // note: unecessary - warns by default.
+#![warn(rustdoc::private_intra_doc_links)] // note: unnecessary - warns by default.
 
 /// [private]
 pub fn public() {}
@@ -229,7 +229,7 @@ This lint **warns by default**. It detects code block attributes in
 documentation examples that have potentially mis-typed values. For example:
 
 ```rust
-#![warn(rustdoc::invalid_codeblock_attributes)]  // note: unecessary - warns by default.
+#![warn(rustdoc::invalid_codeblock_attributes)]  // note: unnecessary - warns by default.
 
 /// Example.
 ///
@@ -348,7 +348,7 @@ This lint is **warn-by-default**. It detects URLs which are not links.
 For example:
 
 ```rust
-#![warn(rustdoc::bare_urls)] // note: unecessary - warns by default.
+#![warn(rustdoc::bare_urls)] // note: unnecessary - warns by default.
 
 /// http://example.org
 /// [http://example.net]
diff --git a/src/test/run-make/issue-85441/Makefile b/src/test/run-make/issue-85441/Makefile
new file mode 100644
index 00000000000..c7ae708c173
--- /dev/null
+++ b/src/test/run-make/issue-85441/Makefile
@@ -0,0 +1,9 @@
+# only-windows-msvc
+
+-include ../../run-make-fulldeps/tools.mk
+
+# Tests that WS2_32.dll is not unnecessarily linked, see issue #85441
+
+all:
+	$(RUSTC) empty.rs
+	objdump -p $(TMPDIR)/empty.exe | $(CGREP) -v -i "WS2_32.dll"
diff --git a/src/test/run-make/issue-85441/empty.rs b/src/test/run-make/issue-85441/empty.rs
new file mode 100644
index 00000000000..f328e4d9d04
--- /dev/null
+++ b/src/test/run-make/issue-85441/empty.rs
@@ -0,0 +1 @@
+fn main() {}
diff --git a/src/test/ui/nll/issue-55825-const-fn.rs b/src/test/ui/nll/issue-55825-const-fn.rs
new file mode 100644
index 00000000000..c9efccd15b7
--- /dev/null
+++ b/src/test/ui/nll/issue-55825-const-fn.rs
@@ -0,0 +1,8 @@
+// Regression test for issue #55825
+// Tests that we don't emit a spurious warning in NLL mode
+
+#![feature(nll)]
+
+const fn no_dyn_trait_ret() -> &'static dyn std::fmt::Debug { &() } //~ ERROR const
+
+fn main() { }
diff --git a/src/test/ui/nll/issue-55825-const-fn.stderr b/src/test/ui/nll/issue-55825-const-fn.stderr
new file mode 100644
index 00000000000..9af5180343b
--- /dev/null
+++ b/src/test/ui/nll/issue-55825-const-fn.stderr
@@ -0,0 +1,12 @@
+error[E0658]: trait objects in const fn are unstable
+  --> $DIR/issue-55825-const-fn.rs:6:32
+   |
+LL | const fn no_dyn_trait_ret() -> &'static dyn std::fmt::Debug { &() }
+   |                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: see issue #57563 <https://github.com/rust-lang/rust/issues/57563> for more information
+   = help: add `#![feature(const_fn_trait_bound)]` to the crate attributes to enable
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0658`.