Auto merge of #81578 - jonas-schievink:rollup-yhiyowl, r=jonas-schievink

Rollup of 18 pull requests

Successful merges:

 - #78044 (Implement io::Seek for io::Empty)
 - #79285 (Stabilize Arc::{increment,decrement}_strong_count)
 - #80053 (stabilise `cargo test -- --include-ignored`)
 - #80279 (Implement missing `AsMut<str>` for `str`)
 - #80470 (Stabilize by-value `[T; N]` iterator `core::array::IntoIter`)
 - #80945 (Add Box::downcast() for dyn Any + Send + Sync)
 - #81048 (Stabilize `core::slice::fill_with`)
 - #81198 (Remove requirement that forces symmetric and transitive PartialEq impls to exist)
 - #81422 (Account for existing `_` field pattern when suggesting `..`)
 - #81472 (Clone entire `TokenCursor` when collecting tokens)
 - #81484 (Optimize decimal formatting of 128-bit integers)
 - #81491 (Balance sidebar `Deref` cycle check with main content)
 - #81509 (Add a regression test for ICE of bad_placeholder_type)
 - #81547 (Edit rustc_typeck top-level docs)
 - #81550 (Replace predecessor with range in collections documentation)
 - #81558 (Fix ascii art text wrapping in mobile)
 - #81562 (Clarify that InPlaceIterable guarantees extend to all advancing iterator methods.)
 - #81563 (Improve docblock readability on small screen)

Failed merges:

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

35 files changed, 284 insertions, 118 deletions

diff --git a/compiler/rustc_arena/src/lib.rs b/compiler/rustc_arena/src/lib.rs
index 54552b499be..651f4c6fabd 100644
--- a/compiler/rustc_arena/src/lib.rs
+++ b/compiler/rustc_arena/src/lib.rs
@@ -11,11 +11,9 @@
     html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/",
     test(no_crate_inject, attr(deny(warnings)))
 )]
-#![feature(array_value_iter_slice)]
 #![feature(dropck_eyepatch)]
 #![feature(new_uninit)]
 #![feature(maybe_uninit_slice)]
-#![feature(array_value_iter)]
 #![cfg_attr(bootstrap, feature(min_const_generics))]
 #![feature(min_specialization)]
 #![cfg_attr(test, feature(test))]
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index 6d95da02151..8f2e49e299c 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -30,7 +30,6 @@
 //! get confused if the spans from leaf AST nodes occur in multiple places
 //! in the HIR, especially for multiple identifiers.
 
-#![feature(array_value_iter)]
 #![feature(crate_visibility_modifier)]
 #![feature(or_patterns)]
 #![recursion_limit = "256"]
diff --git a/compiler/rustc_hir/src/lib.rs b/compiler/rustc_hir/src/lib.rs
index 8b55ec6c705..efc516a662f 100644
--- a/compiler/rustc_hir/src/lib.rs
+++ b/compiler/rustc_hir/src/lib.rs
@@ -2,7 +2,6 @@
 //!
 //! [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/hir.html
 
-#![feature(array_value_iter)]
 #![feature(crate_visibility_modifier)]
 #![feature(const_fn)] // For the unsizing cast on `&[]`
 #![feature(const_panic)]
diff --git a/compiler/rustc_parse/src/parser/mod.rs b/compiler/rustc_parse/src/parser/mod.rs
index c575c821964..e2af63d1744 100644
--- a/compiler/rustc_parse/src/parser/mod.rs
+++ b/compiler/rustc_parse/src/parser/mod.rs
@@ -1254,15 +1254,7 @@ impl<'a> Parser<'a> {
         f: impl FnOnce(&mut Self) -> PResult<'a, (R, TrailingToken)>,
     ) -> PResult<'a, R> {
         let start_token = (self.token.clone(), self.token_spacing);
-        let cursor_snapshot = TokenCursor {
-            frame: self.token_cursor.frame.clone(),
-            // We only ever capture tokens within our current frame,
-            // so we can just use an empty frame stack
-            stack: vec![],
-            desugar_doc_comments: self.token_cursor.desugar_doc_comments,
-            num_next_calls: self.token_cursor.num_next_calls,
-            append_unglued_token: self.token_cursor.append_unglued_token.clone(),
-        };
+        let cursor_snapshot = self.token_cursor.clone();
 
         let (mut ret, trailing_token) = f(self)?;
 
diff --git a/compiler/rustc_trait_selection/src/lib.rs b/compiler/rustc_trait_selection/src/lib.rs
index 42509cd8975..e1f8d59991f 100644
--- a/compiler/rustc_trait_selection/src/lib.rs
+++ b/compiler/rustc_trait_selection/src/lib.rs
@@ -11,7 +11,6 @@
 //! This API is completely unstable and subject to change.
 
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
-#![feature(array_value_iter)]
 #![feature(bool_to_option)]
 #![feature(box_patterns)]
 #![feature(drain_filter)]
diff --git a/compiler/rustc_typeck/src/check/mod.rs b/compiler/rustc_typeck/src/check/mod.rs
index c8c6fa12fae..dc3e3b4e738 100644
--- a/compiler/rustc_typeck/src/check/mod.rs
+++ b/compiler/rustc_typeck/src/check/mod.rs
@@ -52,13 +52,13 @@ The types of top-level items, which never contain unbound type
 variables, are stored directly into the `tcx` typeck_results.
 
 N.B., a type variable is not the same thing as a type parameter.  A
-type variable is rather an "instance" of a type parameter: that is,
-given a generic function `fn foo<T>(t: T)`: while checking the
+type variable is an instance of a type parameter. That is,
+given a generic function `fn foo<T>(t: T)`, while checking the
 function `foo`, the type `ty_param(0)` refers to the type `T`, which
-is treated in abstract.  When `foo()` is called, however, `T` will be
+is treated in abstract. However, when `foo()` is called, `T` will be
 substituted for a fresh type variable `N`.  This variable will
 eventually be resolved to some concrete type (which might itself be
-type parameter).
+a type parameter).
 
 */
 
diff --git a/compiler/rustc_typeck/src/check/pat.rs b/compiler/rustc_typeck/src/check/pat.rs
index 1c1f7f7886f..d7e69668e5e 100644
--- a/compiler/rustc_typeck/src/check/pat.rs
+++ b/compiler/rustc_typeck/src/check/pat.rs
@@ -1041,12 +1041,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 vec![(left, "(".to_string()), (right.shrink_to_hi(), ")".to_string())],
                 Applicability::MachineApplicable,
             );
-        } else if fields.len() > subpats.len() {
-            let after_fields_span = if pat_span == DUMMY_SP {
-                pat_span
-            } else {
-                pat_span.with_hi(pat_span.hi() - BytePos(1)).shrink_to_hi()
-            };
+        } else if fields.len() > subpats.len() && pat_span != DUMMY_SP {
+            let after_fields_span = pat_span.with_hi(pat_span.hi() - BytePos(1)).shrink_to_hi();
             let all_fields_span = match subpats {
                 [] => after_fields_span,
                 [field] => field.span,
@@ -1055,7 +1051,19 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
             // Check if all the fields in the pattern are wildcards.
             let all_wildcards = subpats.iter().all(|pat| matches!(pat.kind, PatKind::Wild));
+            let first_tail_wildcard =
+                subpats.iter().enumerate().fold(None, |acc, (pos, pat)| match (acc, &pat.kind) {
+                    (None, PatKind::Wild) => Some(pos),
+                    (Some(_), PatKind::Wild) => acc,
+                    _ => None,
+                });
+            let tail_span = match first_tail_wildcard {
+                None => after_fields_span,
+                Some(0) => subpats[0].span.to(after_fields_span),
+                Some(pos) => subpats[pos - 1].span.shrink_to_hi().to(after_fields_span),
+            };
 
+            // FIXME: heuristic-based suggestion to check current types for where to add `_`.
             let mut wildcard_sugg = vec!["_"; fields.len() - subpats.len()].join(", ");
             if !subpats.is_empty() {
                 wildcard_sugg = String::from(", ") + &wildcard_sugg;
@@ -1080,7 +1088,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     );
                 } else {
                     err.span_suggestion_verbose(
-                        after_fields_span,
+                        tail_span,
                         "use `..` to ignore the rest of the fields",
                         String::from(", .."),
                         Applicability::MaybeIncorrect,
diff --git a/compiler/rustc_typeck/src/lib.rs b/compiler/rustc_typeck/src/lib.rs
index ad92d816c98..fd44bafab6f 100644
--- a/compiler/rustc_typeck/src/lib.rs
+++ b/compiler/rustc_typeck/src/lib.rs
@@ -7,9 +7,9 @@ The type checker is responsible for:
 1. Determining the type of each expression.
 2. Resolving methods and traits.
 3. Guaranteeing that most type rules are met. ("Most?", you say, "why most?"
-   Well, dear reader, read on)
+   Well, dear reader, read on.)
 
-The main entry point is `check_crate()`. Type checking operates in
+The main entry point is [`check_crate()`]. Type checking operates in
 several major phases:
 
 1. The collect phase first passes over all items and determines their
@@ -25,7 +25,7 @@ several major phases:
    containing function).  Inference is used to supply types wherever
    they are unknown. The actual checking of a function itself has
    several phases (check, regionck, writeback), as discussed in the
-   documentation for the `check` module.
+   documentation for the [`check`] module.
 
 The type checker is defined into various submodules which are documented
 independently:
@@ -56,7 +56,6 @@ This API is completely unstable and subject to change.
 */
 
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
-#![feature(array_value_iter)]
 #![feature(bool_to_option)]
 #![feature(box_syntax)]
 #![feature(crate_visibility_modifier)]
diff --git a/library/alloc/src/boxed.rs b/library/alloc/src/boxed.rs
index a3c0be69813..949079e5b69 100644
--- a/library/alloc/src/boxed.rs
+++ b/library/alloc/src/boxed.rs
@@ -1372,6 +1372,39 @@ impl<A: Allocator> Box<dyn Any + Send, A> {
     }
 }
 
+impl<A: Allocator> Box<dyn Any + Send + Sync, A> {
+    #[inline]
+    #[stable(feature = "box_send_sync_any_downcast", since = "1.51.0")]
+    /// Attempt to downcast the box to a concrete type.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::any::Any;
+    ///
+    /// fn print_if_string(value: Box<dyn Any + Send + Sync>) {
+    ///     if let Ok(string) = value.downcast::<String>() {
+    ///         println!("String ({}): {}", string.len(), string);
+    ///     }
+    /// }
+    ///
+    /// let my_string = "Hello World".to_string();
+    /// print_if_string(Box::new(my_string));
+    /// print_if_string(Box::new(0i8));
+    /// ```
+    pub fn downcast<T: Any>(self) -> Result<Box<T, A>, Self> {
+        if self.is::<T>() {
+            unsafe {
+                let (raw, alloc): (*mut (dyn Any + Send + Sync), _) =
+                    Box::into_raw_with_allocator(self);
+                Ok(Box::from_raw_in(raw as *mut T, alloc))
+            }
+        } else {
+            Err(self)
+        }
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: fmt::Display + ?Sized, A: Allocator> fmt::Display for Box<T, A> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
diff --git a/library/alloc/src/lib.rs b/library/alloc/src/lib.rs
index 0f9c5af4744..13f4d902d3b 100644
--- a/library/alloc/src/lib.rs
+++ b/library/alloc/src/lib.rs
@@ -78,7 +78,6 @@
 #![feature(allocator_api)]
 #![feature(array_chunks)]
 #![feature(array_methods)]
-#![feature(array_value_iter)]
 #![feature(array_windows)]
 #![feature(allow_internal_unstable)]
 #![feature(arbitrary_self_types)]
diff --git a/library/alloc/src/sync.rs b/library/alloc/src/sync.rs
index d0081097fe1..461ca85c030 100644
--- a/library/alloc/src/sync.rs
+++ b/library/alloc/src/sync.rs
@@ -962,15 +962,13 @@ impl<T: ?Sized> Arc<T> {
     /// # Examples
     ///
     /// ```
-    /// #![feature(arc_mutate_strong_count)]
-    ///
     /// use std::sync::Arc;
     ///
     /// let five = Arc::new(5);
     ///
     /// unsafe {
     ///     let ptr = Arc::into_raw(five);
-    ///     Arc::incr_strong_count(ptr);
+    ///     Arc::increment_strong_count(ptr);
     ///
     ///     // This assertion is deterministic because we haven't shared
     ///     // the `Arc` between threads.
@@ -979,8 +977,8 @@ impl<T: ?Sized> Arc<T> {
     /// }
     /// ```
     #[inline]
-    #[unstable(feature = "arc_mutate_strong_count", issue = "71983")]
-    pub unsafe fn incr_strong_count(ptr: *const T) {
+    #[stable(feature = "arc_mutate_strong_count", since = "1.51.0")]
+    pub unsafe fn increment_strong_count(ptr: *const T) {
         // Retain Arc, but don't touch refcount by wrapping in ManuallyDrop
         let arc = unsafe { mem::ManuallyDrop::new(Arc::<T>::from_raw(ptr)) };
         // Now increase refcount, but don't drop new refcount either
@@ -1001,27 +999,25 @@ impl<T: ?Sized> Arc<T> {
     /// # Examples
     ///
     /// ```
-    /// #![feature(arc_mutate_strong_count)]
-    ///
     /// use std::sync::Arc;
     ///
     /// let five = Arc::new(5);
     ///
     /// unsafe {
     ///     let ptr = Arc::into_raw(five);
-    ///     Arc::incr_strong_count(ptr);
+    ///     Arc::increment_strong_count(ptr);
     ///
     ///     // Those assertions are deterministic because we haven't shared
     ///     // the `Arc` between threads.
     ///     let five = Arc::from_raw(ptr);
     ///     assert_eq!(2, Arc::strong_count(&five));
-    ///     Arc::decr_strong_count(ptr);
+    ///     Arc::decrement_strong_count(ptr);
     ///     assert_eq!(1, Arc::strong_count(&five));
     /// }
     /// ```
     #[inline]
-    #[unstable(feature = "arc_mutate_strong_count", issue = "71983")]
-    pub unsafe fn decr_strong_count(ptr: *const T) {
+    #[stable(feature = "arc_mutate_strong_count", since = "1.51.0")]
+    pub unsafe fn decrement_strong_count(ptr: *const T) {
         unsafe { mem::drop(Arc::from_raw(ptr)) };
     }
 
diff --git a/library/alloc/src/task.rs b/library/alloc/src/task.rs
index 69690494196..a80550a9653 100644
--- a/library/alloc/src/task.rs
+++ b/library/alloc/src/task.rs
@@ -62,7 +62,7 @@ impl<W: Wake + Send + Sync + 'static> From<Arc<W>> for RawWaker {
 fn raw_waker<W: Wake + Send + Sync + 'static>(waker: Arc<W>) -> RawWaker {
     // Increment the reference count of the arc to clone it.
     unsafe fn clone_waker<W: Wake + Send + Sync + 'static>(waker: *const ()) -> RawWaker {
-        unsafe { Arc::incr_strong_count(waker as *const W) };
+        unsafe { Arc::increment_strong_count(waker as *const W) };
         RawWaker::new(
             waker as *const (),
             &RawWakerVTable::new(clone_waker::<W>, wake::<W>, wake_by_ref::<W>, drop_waker::<W>),
@@ -83,7 +83,7 @@ fn raw_waker<W: Wake + Send + Sync + 'static>(waker: Arc<W>) -> RawWaker {
 
     // Decrement the reference count of the Arc on drop
     unsafe fn drop_waker<W: Wake + Send + Sync + 'static>(waker: *const ()) {
-        unsafe { Arc::decr_strong_count(waker as *const W) };
+        unsafe { Arc::decrement_strong_count(waker as *const W) };
     }
 
     RawWaker::new(
diff --git a/library/core/src/array/iter.rs b/library/core/src/array/iter.rs
index 706f865b4d1..535291471b1 100644
--- a/library/core/src/array/iter.rs
+++ b/library/core/src/array/iter.rs
@@ -11,7 +11,7 @@ use crate::{
 /// A by-value [array] iterator.
 ///
 /// [array]: ../../std/primitive.array.html
-#[unstable(feature = "array_value_iter", issue = "65798")]
+#[stable(feature = "array_value_iter", since = "1.51.0")]
 pub struct IntoIter<T, const N: usize> {
     /// This is the array we are iterating over.
     ///
@@ -38,10 +38,21 @@ pub struct IntoIter<T, const N: usize> {
 impl<T, const N: usize> IntoIter<T, N> {
     /// Creates a new iterator over the given `array`.
     ///
-    /// *Note*: this method might never get stabilized and/or removed in the
-    /// future as there will likely be another, preferred way of obtaining this
-    /// iterator (either via `IntoIterator` for arrays or via another way).
-    #[unstable(feature = "array_value_iter", issue = "65798")]
+    /// *Note*: this method might be deprecated in the future,
+    /// after [`IntoIterator` is implemented for arrays][array-into-iter].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::array;
+    ///
+    /// for value in array::IntoIter::new([1, 2, 3, 4, 5]) {
+    ///     // The type of `value` is a `i32` here, instead of `&i32`
+    ///     let _: i32 = value;
+    /// }
+    /// ```
+    /// [array-into-iter]: https://github.com/rust-lang/rust/pull/65819
+    #[stable(feature = "array_value_iter", since = "1.51.0")]
     pub fn new(array: [T; N]) -> Self {
         // SAFETY: The transmute here is actually safe. The docs of `MaybeUninit`
         // promise:
@@ -69,7 +80,7 @@ impl<T, const N: usize> IntoIter<T, N> {
 
     /// Returns an immutable slice of all elements that have not been yielded
     /// yet.
-    #[unstable(feature = "array_value_iter_slice", issue = "65798")]
+    #[stable(feature = "array_value_iter", since = "1.51.0")]
     pub fn as_slice(&self) -> &[T] {
         // SAFETY: We know that all elements within `alive` are properly initialized.
         unsafe {
@@ -79,7 +90,7 @@ impl<T, const N: usize> IntoIter<T, N> {
     }
 
     /// Returns a mutable slice of all elements that have not been yielded yet.
-    #[unstable(feature = "array_value_iter_slice", issue = "65798")]
+    #[stable(feature = "array_value_iter", since = "1.51.0")]
     pub fn as_mut_slice(&mut self) -> &mut [T] {
         // SAFETY: We know that all elements within `alive` are properly initialized.
         unsafe {
diff --git a/library/core/src/array/mod.rs b/library/core/src/array/mod.rs
index 85b1a47f4a9..d13061d2203 100644
--- a/library/core/src/array/mod.rs
+++ b/library/core/src/array/mod.rs
@@ -18,7 +18,7 @@ use crate::slice::{Iter, IterMut};
 
 mod iter;
 
-#[unstable(feature = "array_value_iter", issue = "65798")]
+#[stable(feature = "array_value_iter", since = "1.51.0")]
 pub use iter::IntoIter;
 
 /// Converts a reference to `T` into a reference to an array of length 1 (without copying).
diff --git a/library/core/src/cmp.rs b/library/core/src/cmp.rs
index b983f49eb17..4a15b185a83 100644
--- a/library/core/src/cmp.rs
+++ b/library/core/src/cmp.rs
@@ -31,14 +31,18 @@ use self::Ordering::*;
 /// equivalence relation. For example, in floating point numbers `NaN != NaN`,
 /// so floating point types implement `PartialEq` but not [`trait@Eq`].
 ///
-/// Formally, the equality must be (for all `a`, `b` and `c`):
+/// Formally, the equality must be (for all `a`, `b`, `c` of type `A`, `B`,
+/// `C`):
 ///
-/// - symmetric: `a == b` implies `b == a`; and
-/// - transitive: `a == b` and `b == c` implies `a == c`.
+/// - **Symmetric**: if `A: PartialEq<B>` and `B: PartialEq<A>`, then **`a == b`
+///   implies `b == a`**; and
+///
+/// - **Transitive**: if `A: PartialEq<B>` and `B: PartialEq<C>` and `A:
+///   PartialEq<C>`, then **`a == b` and `b == c` implies `a == c`**.
 ///
-/// Note that these requirements mean that the trait itself must be implemented
-/// symmetrically and transitively: if `T: PartialEq<U>` and `U: PartialEq<V>`
-/// then `U: PartialEq<T>` and `T: PartialEq<V>`.
+/// Note that the `B: PartialEq<A>` (symmetric) and `A: PartialEq<C>`
+/// (transitive) impls are not forced to exist, but these requirements apply
+/// whenever they do exist.
 ///
 /// ## Derivable
 ///
diff --git a/library/core/src/convert/mod.rs b/library/core/src/convert/mod.rs
index a6d3b5ef813..e1b19e4b73c 100644
--- a/library/core/src/convert/mod.rs
+++ b/library/core/src/convert/mod.rs
@@ -616,6 +616,14 @@ impl AsRef<str> for str {
     }
 }
 
+#[stable(feature = "as_mut_str_for_str", since = "1.51.0")]
+impl AsMut<str> for str {
+    #[inline]
+    fn as_mut(&mut self) -> &mut str {
+        self
+    }
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // THE NO-ERROR ERROR TYPE
 ////////////////////////////////////////////////////////////////////////////////
diff --git a/library/core/src/fmt/num.rs b/library/core/src/fmt/num.rs
index 7a98210995e..cdd731fdd4d 100644
--- a/library/core/src/fmt/num.rs
+++ b/library/core/src/fmt/num.rs
@@ -643,25 +643,42 @@ fn fmt_u128(n: u128, is_nonnegative: bool, f: &mut fmt::Formatter<'_>) -> fmt::R
 }
 
 /// Partition of `n` into n > 1e19 and rem <= 1e19
+///
+/// Integer division algorithm is based on the following paper:
+///
+///   T. Granlund and P. Montgomery, “Division by Invariant Integers Using Multiplication”
+///   in Proc. of the SIGPLAN94 Conference on Programming Language Design and
+///   Implementation, 1994, pp. 61–72
+///
 fn udiv_1e19(n: u128) -> (u128, u64) {
     const DIV: u64 = 1e19 as u64;
-    let high = (n >> 64) as u64;
-    if high == 0 {
-        let low = n as u64;
-        return ((low / DIV) as u128, low % DIV);
-    }
-    let sr = 65 - high.leading_zeros();
-    let mut q = n << (128 - sr);
-    let mut r = n >> sr;
-    let mut carry = 0;
-
-    for _ in 0..sr {
-        r = (r << 1) | (q >> 127);
-        q = (q << 1) | carry as u128;
-
-        let s = (DIV as u128).wrapping_sub(r).wrapping_sub(1) as i128 >> 127;
-        carry = (s & 1) as u64;
-        r -= (DIV as u128) & s as u128;
-    }
-    ((q << 1) | carry as u128, r as u64)
+    const FACTOR: u128 = 156927543384667019095894735580191660403;
+
+    let quot = if n < 1 << 83 {
+        ((n >> 19) as u64 / (DIV >> 19)) as u128
+    } else {
+        u128_mulhi(n, FACTOR) >> 62
+    };
+
+    let rem = (n - quot * DIV as u128) as u64;
+    (quot, rem)
+}
+
+/// Multiply unsigned 128 bit integers, return upper 128 bits of the result
+#[inline]
+fn u128_mulhi(x: u128, y: u128) -> u128 {
+    let x_lo = x as u64;
+    let x_hi = (x >> 64) as u64;
+    let y_lo = y as u64;
+    let y_hi = (y >> 64) as u64;
+
+    // handle possibility of overflow
+    let carry = (x_lo as u128 * y_lo as u128) >> 64;
+    let m = x_lo as u128 * y_hi as u128 + carry;
+    let high1 = m >> 64;
+
+    let m_lo = m as u64;
+    let high2 = (x_hi as u128 * y_lo as u128 + m_lo as u128) >> 64;
+
+    x_hi as u128 * y_hi as u128 + high1 + high2
 }
diff --git a/library/core/src/iter/traits/marker.rs b/library/core/src/iter/traits/marker.rs
index ed8eea672f8..c4e21b84863 100644
--- a/library/core/src/iter/traits/marker.rs
+++ b/library/core/src/iter/traits/marker.rs
@@ -43,12 +43,14 @@ unsafe impl<I: TrustedLen + ?Sized> TrustedLen for &mut I {}
 /// An iterator that when yielding an item will have taken at least one element
 /// from its underlying [`SourceIter`].
 ///
-/// Calling [`next()`] guarantees that at least one value of the iterator's underlying source
-/// has been moved out and the result of the iterator chain could be inserted in its place,
-/// assuming structural constraints of the source allow such an insertion.
+/// Calling any method that advances the iterator, e.g.  [`next()`] or [`try_fold()`],
+/// guarantees that for each step at least one value of the iterator's underlying source
+/// has been moved out and the result of the iterator chain could be inserted
+/// in its place, assuming structural constraints of the source allow such an insertion.
 /// In other words this trait indicates that an iterator pipeline can be collected in place.
 ///
 /// [`SourceIter`]: crate::iter::SourceIter
 /// [`next()`]: Iterator::next
+/// [`try_fold()`]: Iterator::try_fold
 #[unstable(issue = "none", feature = "inplace_iteration")]
 pub unsafe trait InPlaceIterable: Iterator {}
diff --git a/library/core/src/slice/mod.rs b/library/core/src/slice/mod.rs
index 315df83115d..19a3b45e568 100644
--- a/library/core/src/slice/mod.rs
+++ b/library/core/src/slice/mod.rs
@@ -2852,13 +2852,12 @@ impl<T> [T] {
     /// # Examples
     ///
     /// ```
-    /// #![feature(slice_fill_with)]
-    ///
     /// let mut buf = vec![1; 10];
     /// buf.fill_with(Default::default);
     /// assert_eq!(buf, vec![0; 10]);
     /// ```
-    #[unstable(feature = "slice_fill_with", issue = "79221")]
+    #[doc(alias = "memset")]
+    #[stable(feature = "slice_fill_with", since = "1.51.0")]
     pub fn fill_with<F>(&mut self, mut f: F)
     where
         F: FnMut() -> T,
diff --git a/library/core/tests/lib.rs b/library/core/tests/lib.rs
index b7a406c30e9..bc0e3e059c9 100644
--- a/library/core/tests/lib.rs
+++ b/library/core/tests/lib.rs
@@ -50,7 +50,6 @@
 #![feature(slice_internals)]
 #![feature(slice_partition_dedup)]
 #![feature(int_error_matching)]
-#![feature(array_value_iter)]
 #![feature(iter_advance_by)]
 #![feature(iter_partition_in_place)]
 #![feature(iter_intersperse)]
diff --git a/library/std/src/collections/mod.rs b/library/std/src/collections/mod.rs
index a1aab767eb2..80a13d52a2a 100644
--- a/library/std/src/collections/mod.rs
+++ b/library/std/src/collections/mod.rs
@@ -110,10 +110,10 @@
 //!
 //! For Sets, all operations have the cost of the equivalent Map operation.
 //!
-//! |              | get       | insert    | remove    | predecessor | append |
-//! |--------------|-----------|-----------|-----------|-------------|--------|
-//! | [`HashMap`]  | O(1)~     | O(1)~*    | O(1)~     | N/A         | N/A    |
-//! | [`BTreeMap`] | O(log(n)) | O(log(n)) | O(log(n)) | O(log(n))   | O(n+m) |
+//! |              | get       | insert    | remove    | range     | append |
+//! |--------------|-----------|-----------|-----------|-----------|--------|
+//! | [`HashMap`]  | O(1)~     | O(1)~*    | O(1)~     | N/A       | N/A    |
+//! | [`BTreeMap`] | O(log(n)) | O(log(n)) | O(log(n)) | O(log(n)) | O(n+m) |
 //!
 //! # Correct and Efficient Usage of Collections
 //!
diff --git a/library/std/src/io/util.rs b/library/std/src/io/util.rs
index db845457c96..e43ce4cdb4b 100644
--- a/library/std/src/io/util.rs
+++ b/library/std/src/io/util.rs
@@ -4,7 +4,7 @@
 mod tests;
 
 use crate::fmt;
-use crate::io::{self, BufRead, Initializer, IoSlice, IoSliceMut, Read, Write};
+use crate::io::{self, BufRead, Initializer, IoSlice, IoSliceMut, Read, Seek, SeekFrom, Write};
 
 /// A reader which is always at EOF.
 ///
@@ -58,6 +58,21 @@ impl BufRead for Empty {
     fn consume(&mut self, _n: usize) {}
 }
 
+#[stable(feature = "empty_seek", since = "1.51.0")]
+impl Seek for Empty {
+    fn seek(&mut self, _pos: SeekFrom) -> io::Result<u64> {
+        Ok(0)
+    }
+
+    fn stream_len(&mut self) -> io::Result<u64> {
+        Ok(0)
+    }
+
+    fn stream_position(&mut self) -> io::Result<u64> {
+        Ok(0)
+    }
+}
+
 #[stable(feature = "std_debug", since = "1.16.0")]
 impl fmt::Debug for Empty {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
diff --git a/library/std/src/io/util/tests.rs b/library/std/src/io/util/tests.rs
index 9450b1ee124..df34e27d136 100644
--- a/library/std/src/io/util/tests.rs
+++ b/library/std/src/io/util/tests.rs
@@ -1,5 +1,5 @@
 use crate::io::prelude::*;
-use crate::io::{copy, empty, repeat, sink, Empty, Repeat, Sink};
+use crate::io::{copy, empty, repeat, sink, Empty, Repeat, SeekFrom, Sink};
 
 #[test]
 fn copy_copies() {
@@ -30,6 +30,26 @@ fn empty_reads() {
 }
 
 #[test]
+fn empty_seeks() {
+    let mut e = empty();
+    assert!(matches!(e.seek(SeekFrom::Start(0)), Ok(0)));
+    assert!(matches!(e.seek(SeekFrom::Start(1)), Ok(0)));
+    assert!(matches!(e.seek(SeekFrom::Start(u64::MAX)), Ok(0)));
+
+    assert!(matches!(e.seek(SeekFrom::End(i64::MIN)), Ok(0)));
+    assert!(matches!(e.seek(SeekFrom::End(-1)), Ok(0)));
+    assert!(matches!(e.seek(SeekFrom::End(0)), Ok(0)));
+    assert!(matches!(e.seek(SeekFrom::End(1)), Ok(0)));
+    assert!(matches!(e.seek(SeekFrom::End(i64::MAX)), Ok(0)));
+
+    assert!(matches!(e.seek(SeekFrom::Current(i64::MIN)), Ok(0)));
+    assert!(matches!(e.seek(SeekFrom::Current(-1)), Ok(0)));
+    assert!(matches!(e.seek(SeekFrom::Current(0)), Ok(0)));
+    assert!(matches!(e.seek(SeekFrom::Current(1)), Ok(0)));
+    assert!(matches!(e.seek(SeekFrom::Current(i64::MAX)), Ok(0)));
+}
+
+#[test]
 fn repeat_repeats() {
     let mut r = repeat(4);
     let mut b = [0; 1024];
diff --git a/library/test/src/cli.rs b/library/test/src/cli.rs
index 97a659f22d7..02c529252e0 100644
--- a/library/test/src/cli.rs
+++ b/library/test/src/cli.rs
@@ -230,9 +230,9 @@ fn parse_opts_impl(matches: getopts::Matches) -> OptRes {
     // Unstable flags
     let force_run_in_process = unstable_optflag!(matches, allow_unstable, "force-run-in-process");
     let exclude_should_panic = unstable_optflag!(matches, allow_unstable, "exclude-should-panic");
-    let include_ignored = unstable_optflag!(matches, allow_unstable, "include-ignored");
     let time_options = get_time_options(&matches, allow_unstable)?;
 
+    let include_ignored = matches.opt_present("include-ignored");
     let quiet = matches.opt_present("quiet");
     let exact = matches.opt_present("exact");
     let list = matches.opt_present("list");
diff --git a/library/test/src/tests.rs b/library/test/src/tests.rs
index a629829b885..99e12c973c4 100644
--- a/library/test/src/tests.rs
+++ b/library/test/src/tests.rs
@@ -391,12 +391,7 @@ fn parse_show_output_flag() {
 
 #[test]
 fn parse_include_ignored_flag() {
-    let args = vec![
-        "progname".to_string(),
-        "filter".to_string(),
-        "-Zunstable-options".to_string(),
-        "--include-ignored".to_string(),
-    ];
+    let args = vec!["progname".to_string(), "filter".to_string(), "--include-ignored".to_string()];
     let opts = parse_opts(&args).unwrap().unwrap();
     assert_eq!(opts.run_ignored, RunIgnored::Yes);
 }
diff --git a/src/librustdoc/html/render/mod.rs b/src/librustdoc/html/render/mod.rs
index daaa2c719b0..6909ab870db 100644
--- a/src/librustdoc/html/render/mod.rs
+++ b/src/librustdoc/html/render/mod.rs
@@ -3510,6 +3510,7 @@ fn render_assoc_items(
                     "deref-methods-{:#}",
                     type_.print(cx.cache())
                 )));
+                debug!("Adding {} to deref id map", type_.print(cx.cache()));
                 cx.deref_id_map
                     .borrow_mut()
                     .insert(type_.def_id_full(cx.cache()).unwrap(), id.clone());
@@ -3626,6 +3627,7 @@ fn render_deref_methods(
             _ => None,
         })
         .expect("Expected associated type binding");
+    debug!("Render deref methods for {:#?}, target {:#?}", impl_.inner_impl().for_, target);
     let what =
         AssocItemRender::DerefFor { trait_: deref_type, type_: real_target, deref_mut_: deref_mut };
     if let Some(did) = target.def_id_full(cx.cache()) {
@@ -4416,6 +4418,15 @@ fn sidebar_deref_methods(cx: &Context<'_>, out: &mut Buffer, impl_: &Impl, v: &V
         })
     {
         debug!("found target, real_target: {:?} {:?}", target, real_target);
+        if let Some(did) = target.def_id_full(cx.cache()) {
+            if let Some(type_did) = impl_.inner_impl().for_.def_id_full(cx.cache()) {
+                // `impl Deref<Target = S> for S`
+                if did == type_did {
+                    // Avoid infinite cycles
+                    return;
+                }
+            }
+        }
         let deref_mut = v
             .iter()
             .filter(|i| i.inner_impl().trait_.is_some())
@@ -4464,13 +4475,6 @@ fn sidebar_deref_methods(cx: &Context<'_>, out: &mut Buffer, impl_: &Impl, v: &V
                     .filter(|i| i.inner_impl().trait_.is_some())
                     .find(|i| i.inner_impl().trait_.def_id_full(cx.cache()) == c.deref_trait_did)
                 {
-                    if let Some(type_did) = impl_.inner_impl().for_.def_id_full(cx.cache()) {
-                        // `impl Deref<Target = S> for S`
-                        if target_did == type_did {
-                            // Avoid infinite cycles
-                            return;
-                        }
-                    }
                     sidebar_deref_methods(cx, out, target_deref_impl, target_impls);
                 }
             }
diff --git a/src/librustdoc/html/static/rustdoc.css b/src/librustdoc/html/static/rustdoc.css
index 8dad26dced9..cb16dc588d3 100644
--- a/src/librustdoc/html/static/rustdoc.css
+++ b/src/librustdoc/html/static/rustdoc.css
@@ -156,6 +156,7 @@ code, pre, a.test-arrow {
 }
 .docblock pre code, .docblock-short pre code, .docblock code.spotlight {
 	padding: 0;
+	padding-right: 1ex;
 }
 .docblock code.spotlight :last-child {
 	padding-bottom: 0.6em;
@@ -404,7 +405,7 @@ nav.sub {
 	text-overflow: ellipsis;
 	margin: 0;
 }
-.docblock code, .docblock-short code {
+.docblock-short code {
 	white-space: pre-wrap;
 }
 
@@ -1624,6 +1625,10 @@ h4 > .notable-traits {
 	#settings-menu {
 		top: 7px;
 	}
+
+	.docblock {
+		margin-left: 12px;
+	}
 }
 
 h3.notable {
diff --git a/src/test/rustdoc-ui/deref-generic.rs b/src/test/rustdoc-ui/deref-generic.rs
new file mode 100644
index 00000000000..bc64beb1b93
--- /dev/null
+++ b/src/test/rustdoc-ui/deref-generic.rs
@@ -0,0 +1,15 @@
+// check-pass
+// #81395: Fix ICE when recursing into Deref target only differing in type args
+
+pub struct Generic<T>(T);
+
+impl<'a> std::ops::Deref for Generic<&'a mut ()> {
+    type Target = Generic<&'a ()>;
+    fn deref(&self) -> &Self::Target {
+        unimplemented!()
+    }
+}
+
+impl<'a> Generic<&'a ()> {
+    pub fn some_method(&self) {}
+}
diff --git a/src/test/ui/const-generics/array-impls/into-iter-impls-length-32.rs b/src/test/ui/const-generics/array-impls/into-iter-impls-length-32.rs
index 0aeba8607e8..6ba1b2813a1 100644
--- a/src/test/ui/const-generics/array-impls/into-iter-impls-length-32.rs
+++ b/src/test/ui/const-generics/array-impls/into-iter-impls-length-32.rs
@@ -1,6 +1,5 @@
 // check-pass
 
-#![feature(array_value_iter)]
 #![feature(trusted_len)]
 
 use std::{
diff --git a/src/test/ui/const-generics/array-impls/into-iter-impls-length-33.rs b/src/test/ui/const-generics/array-impls/into-iter-impls-length-33.rs
index 5503813c7aa..deafde2912b 100644
--- a/src/test/ui/const-generics/array-impls/into-iter-impls-length-33.rs
+++ b/src/test/ui/const-generics/array-impls/into-iter-impls-length-33.rs
@@ -1,6 +1,5 @@
 // check-pass
 
-#![feature(array_value_iter)]
 #![feature(trusted_len)]
 
 use std::{
diff --git a/src/test/ui/pattern/pat-tuple-underfield.stderr b/src/test/ui/pattern/pat-tuple-underfield.stderr
index 76323d9a7bf..70c21dbafe9 100644
--- a/src/test/ui/pattern/pat-tuple-underfield.stderr
+++ b/src/test/ui/pattern/pat-tuple-underfield.stderr
@@ -122,8 +122,8 @@ LL |         Point4(   a   ,     _    , _, _) => {}
    |                                  ^^^^^^
 help: use `..` to ignore the rest of the fields
    |
-LL |         Point4(   a   ,     _    , ..) => {}
-   |                                  ^^^^
+LL |         Point4(   a, ..) => {}
+   |                    ^^^^
 
 error: aborting due to 8 previous errors
 
diff --git a/src/test/ui/proc-macro/auxiliary/nonterminal-recollect-attr.rs b/src/test/ui/proc-macro/auxiliary/nonterminal-recollect-attr.rs
new file mode 100644
index 00000000000..a6903283aa1
--- /dev/null
+++ b/src/test/ui/proc-macro/auxiliary/nonterminal-recollect-attr.rs
@@ -0,0 +1,23 @@
+// force-host
+// no-prefer-dynamic
+
+#![crate_type = "proc-macro"]
+#![feature(proc_macro_quote)]
+
+extern crate proc_macro;
+use proc_macro::{TokenStream, quote};
+
+#[proc_macro_attribute]
+pub fn first_attr(_: TokenStream, input: TokenStream) -> TokenStream {
+    let recollected: TokenStream = input.into_iter().collect();
+    quote! {
+        #[second_attr]
+        $recollected
+    }
+}
+
+#[proc_macro_attribute]
+pub fn second_attr(_: TokenStream, input: TokenStream) -> TokenStream {
+    let _recollected: TokenStream = input.into_iter().collect();
+    TokenStream::new()
+}
diff --git a/src/test/ui/proc-macro/nonterminal-recollect-attr.rs b/src/test/ui/proc-macro/nonterminal-recollect-attr.rs
new file mode 100644
index 00000000000..5d4649b78c2
--- /dev/null
+++ b/src/test/ui/proc-macro/nonterminal-recollect-attr.rs
@@ -0,0 +1,17 @@
+// check-pass
+// aux-build:nonterminal-recollect-attr.rs
+
+extern crate nonterminal_recollect_attr;
+use nonterminal_recollect_attr::*;
+
+macro_rules! my_macro {
+    ($v:ident) => {
+        #[first_attr]
+        $v struct Foo {
+            field: u8
+        }
+    }
+}
+
+my_macro!(pub);
+fn main() {}
diff --git a/src/test/ui/typeck/typeck_type_placeholder_item_help.rs b/src/test/ui/typeck/typeck_type_placeholder_item_help.rs
index 905fc35350e..0c890f88c60 100644
--- a/src/test/ui/typeck/typeck_type_placeholder_item_help.rs
+++ b/src/test/ui/typeck/typeck_type_placeholder_item_help.rs
@@ -10,15 +10,18 @@ const TEST2: _ = 42u32;
 const TEST3: _ = Some(42);
 //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
 
-trait Test4 {
-    const TEST4: _ = 42;
+const TEST4: fn() -> _ = 42;
+//~^ ERROR the type placeholder `_` is not allowed within types on item signatures
+
+trait Test5 {
+    const TEST5: _ = 42;
     //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
 }
 
-struct Test5;
+struct Test6;
 
-impl Test5 {
-    const TEST5: _ = 13;
+impl Test6 {
+    const TEST6: _ = 13;
     //~^ ERROR the type placeholder `_` is not allowed within types on item signatures
 }
 
diff --git a/src/test/ui/typeck/typeck_type_placeholder_item_help.stderr b/src/test/ui/typeck/typeck_type_placeholder_item_help.stderr
index 88133814d29..0121e186316 100644
--- a/src/test/ui/typeck/typeck_type_placeholder_item_help.stderr
+++ b/src/test/ui/typeck/typeck_type_placeholder_item_help.stderr
@@ -26,23 +26,32 @@ LL | const TEST3: _ = Some(42);
    |              help: replace `_` with the correct type: `Option<i32>`
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item_help.rs:14:18
+  --> $DIR/typeck_type_placeholder_item_help.rs:13:22
    |
-LL |     const TEST4: _ = 42;
+LL | const TEST4: fn() -> _ = 42;
+   |                      ^
+   |                      |
+   |                      not allowed in type signatures
+   |                      help: use type parameters instead: `T`
+
+error[E0121]: the type placeholder `_` is not allowed within types on item signatures
+  --> $DIR/typeck_type_placeholder_item_help.rs:17:18
+   |
+LL |     const TEST5: _ = 42;
    |                  ^
    |                  |
    |                  not allowed in type signatures
    |                  help: replace `_` with the correct type: `i32`
 
 error[E0121]: the type placeholder `_` is not allowed within types on item signatures
-  --> $DIR/typeck_type_placeholder_item_help.rs:21:18
+  --> $DIR/typeck_type_placeholder_item_help.rs:24:18
    |
-LL |     const TEST5: _ = 13;
+LL |     const TEST6: _ = 13;
    |                  ^
    |                  |
    |                  not allowed in type signatures
    |                  help: replace `_` with the correct type: `i32`
 
-error: aborting due to 5 previous errors
+error: aborting due to 6 previous errors
 
 For more information about this error, try `rustc --explain E0121`.