Rollup of 18 pull requests

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))]

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"]

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)]

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)?;
 

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)]

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).
 
 */
 

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,

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)]

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 {

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)]

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)) };
     }
 

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(

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 {

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).

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
 ///

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
 ////////////////////////////////////////////////////////////////////////////////