Merge ref 'd36f96412516' from rust-lang/rust

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

Upstream ref: d36f964
Filtered ref: 92461731ae79cfe5044e4826160665b77c0363a2

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

Author: The rustc-josh-sync Cronjob Bot

Cargo.lock

@@ -59,4 +59,3 @@ rustflags = ["-Cpanic=abort"]
 rustc-std-workspace-core = { path = 'rustc-std-workspace-core' }
 rustc-std-workspace-alloc = { path = 'rustc-std-workspace-alloc' }
 rustc-std-workspace-std = { path = 'rustc-std-workspace-std' }
-compiler_builtins = { path = "compiler-builtins/compiler-builtins" }

Cargo.toml

@@ -17,6 +17,7 @@ unsafe extern "Rust" {
     #[rustc_allocator]
     #[rustc_nounwind]
     #[rustc_std_internal_symbol]
+    #[rustc_allocator_zeroed_variant = "__rust_alloc_zeroed"]
     fn __rust_alloc(size: usize, align: usize) -> *mut u8;
     #[rustc_deallocator]
     #[rustc_nounwind]

alloc/src/alloc.rs

@@ -1672,7 +1672,7 @@ unsafe impl<#[may_dangle] T: ?Sized, A: Allocator> Drop for Box<T, A> {
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: Default> Default for Box<T> {
-    /// Creates a `Box<T>`, with the `Default` value for T.
+    /// Creates a `Box<T>`, with the `Default` value for `T`.
     #[inline]
     fn default() -> Self {
         let mut x: Box<mem::MaybeUninit<T>> = Box::new_uninit();
@@ -1695,6 +1695,7 @@ impl<T: Default> Default for Box<T> {
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T> Default for Box<[T]> {
+    /// Creates an empty `[T]` inside a `Box`.
     #[inline]
     fn default() -> Self {
         let ptr: Unique<[T]> = Unique::<[T; 0]>::dangling();
@@ -1716,6 +1717,19 @@ impl Default for Box<str> {
     }
 }
 
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "pin_default_impls", since = "CURRENT_RUSTC_VERSION")]
+impl<T> Default for Pin<Box<T>>
+where
+    T: ?Sized,
+    Box<T>: Default,
+{
+    #[inline]
+    fn default() -> Self {
+        Box::into_pin(Box::<T>::default())
+    }
+}
+
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: Clone, A: Allocator + Clone> Clone for Box<T, A> {
@@ -2114,11 +2128,6 @@ impl<F: ?Sized + Future + Unpin, A: Allocator> Future for Box<F, A> {
 
 #[stable(feature = "box_error", since = "1.8.0")]
 impl<E: Error> Error for Box<E> {
-    #[allow(deprecated, deprecated_in_future)]
-    fn description(&self) -> &str {
-        Error::description(&**self)
-    }
-
     #[allow(deprecated)]
     fn cause(&self) -> Option<&dyn Error> {
         Error::cause(&**self)

alloc/src/boxed.rs

@@ -608,12 +608,7 @@ impl<'a> From<String> for Box<dyn Error + Send + Sync + 'a> {
     fn from(err: String) -> Box<dyn Error + Send + Sync + 'a> {
         struct StringError(String);
 
-        impl Error for StringError {
-            #[allow(deprecated)]
-            fn description(&self) -> &str {
-                &self.0
-            }
-        }
+        impl Error for StringError {}
 
         impl fmt::Display for StringError {
             fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {

alloc/src/boxed/convert.rs

@@ -40,30 +40,15 @@ pub(super) const MIN_LEN: usize = node::MIN_LEN_AFTER_SPLIT;
 
 /// An ordered map based on a [B-Tree].
 ///
-/// B-Trees represent a fundamental compromise between cache-efficiency and actually minimizing
-/// the amount of work performed in a search. In theory, a binary search tree (BST) is the optimal
-/// choice for a sorted map, as a perfectly balanced BST performs the theoretical minimum amount of
-/// comparisons necessary to find an element (log<sub>2</sub>n). However, in practice the way this
-/// is done is *very* inefficient for modern computer architectures. In particular, every element
-/// is stored in its own individually heap-allocated node. This means that every single insertion
-/// triggers a heap-allocation, and every single comparison should be a cache-miss. Since these
-/// are both notably expensive things to do in practice, we are forced to, at the very least,
-/// reconsider the BST strategy.
-///
-/// A B-Tree instead makes each node contain B-1 to 2B-1 elements in a contiguous array. By doing
-/// this, we reduce the number of allocations by a factor of B, and improve cache efficiency in
-/// searches. However, this does mean that searches will have to do *more* comparisons on average.
-/// The precise number of comparisons depends on the node search strategy used. For optimal cache
-/// efficiency, one could search the nodes linearly. For optimal comparisons, one could search
-/// the node using binary search. As a compromise, one could also perform a linear search
-/// that initially only checks every i<sup>th</sup> element for some choice of i.
+/// Given a key type with a [total order], an ordered map stores its entries in key order.
+/// That means that keys must be of a type that implements the [`Ord`] trait,
+/// such that two keys can always be compared to determine their [`Ordering`].
+/// Examples of keys with a total order are strings with lexicographical order,
+/// and numbers with their natural order.
 ///
-/// Currently, our implementation simply performs naive linear search. This provides excellent
-/// performance on *small* nodes of elements which are cheap to compare. However in the future we
-/// would like to further explore choosing the optimal search strategy based on the choice of B,
-/// and possibly other factors. Using linear search, searching for a random element is expected
-/// to take B * log(n) comparisons, which is generally worse than a BST. In practice,
-/// however, performance is excellent.
+/// Iterators obtained from functions such as [`BTreeMap::iter`], [`BTreeMap::into_iter`], [`BTreeMap::values`], or
+/// [`BTreeMap::keys`] produce their items in key order, and take worst-case logarithmic and
+/// amortized constant time per item returned.
 ///
 /// It is a logic error for a key to be modified in such a way that the key's ordering relative to
 /// any other key, as determined by the [`Ord`] trait, changes while it is in the map. This is
@@ -72,14 +57,6 @@ pub(super) const MIN_LEN: usize = node::MIN_LEN_AFTER_SPLIT;
 /// `BTreeMap` that observed the logic error and not result in undefined behavior. This could
 /// include panics, incorrect results, aborts, memory leaks, and non-termination.
 ///
-/// Iterators obtained from functions such as [`BTreeMap::iter`], [`BTreeMap::into_iter`], [`BTreeMap::values`], or
-/// [`BTreeMap::keys`] produce their items in order by key, and take worst-case logarithmic and
-/// amortized constant time per item returned.
-///
-/// [B-Tree]: https://en.wikipedia.org/wiki/B-tree
-/// [`Cell`]: core::cell::Cell
-/// [`RefCell`]: core::cell::RefCell
-///
 /// # Examples
 ///
 /// ```
@@ -135,6 +112,8 @@ pub(super) const MIN_LEN: usize = node::MIN_LEN_AFTER_SPLIT;
 /// ]);
 /// ```
 ///
+/// ## `Entry` API
+///
 /// `BTreeMap` implements an [`Entry API`], which allows for complex
 /// methods of getting, setting, updating and removing keys and their values:
 ///
@@ -167,6 +146,43 @@ pub(super) const MIN_LEN: usize = node::MIN_LEN_AFTER_SPLIT;
 /// // modify an entry before an insert with in-place mutation
 /// player_stats.entry("mana").and_modify(|mana| *mana += 200).or_insert(100);
 /// ```
+///
+/// # Background
+///
+/// A B-tree is (like) a [binary search tree], but adapted to the natural granularity that modern
+/// machines like to consume data at. This means that each node contains an entire array of elements,
+/// instead of just a single element.
+///
+/// B-Trees represent a fundamental compromise between cache-efficiency and actually minimizing
+/// the amount of work performed in a search. In theory, a binary search tree (BST) is the optimal
+/// choice for a sorted map, as a perfectly balanced BST performs the theoretical minimum number of
+/// comparisons necessary to find an element (log<sub>2</sub>n). However, in practice the way this
+/// is done is *very* inefficient for modern computer architectures. In particular, every element
+/// is stored in its own individually heap-allocated node. This means that every single insertion
+/// triggers a heap-allocation, and every comparison is a potential cache-miss due to the indirection.
+/// Since both heap-allocations and cache-misses are notably expensive in practice, we are forced to,
+/// at the very least, reconsider the BST strategy.
+///
+/// A B-Tree instead makes each node contain B-1 to 2B-1 elements in a contiguous array. By doing
+/// this, we reduce the number of allocations by a factor of B, and improve cache efficiency in
+/// searches. However, this does mean that searches will have to do *more* comparisons on average.
+/// The precise number of comparisons depends on the node search strategy used. For optimal cache
+/// efficiency, one could search the nodes linearly. For optimal comparisons, one could search
+/// the node using binary search. As a compromise, one could also perform a linear search
+/// that initially only checks every i<sup>th</sup> element for some choice of i.
+///
+/// Currently, our implementation simply performs naive linear search. This provides excellent
+/// performance on *small* nodes of elements which are cheap to compare. However in the future we
+/// would like to further explore choosing the optimal search strategy based on the choice of B,
+/// and possibly other factors. Using linear search, searching for a random element is expected
+/// to take B * log(n) comparisons, which is generally worse than a BST. In practice,
+/// however, performance is excellent.
+///
+/// [B-Tree]: https://en.wikipedia.org/wiki/B-tree
+/// [binary search tree]: https://en.wikipedia.org/wiki/Binary_search_tree
+/// [total order]: https://en.wikipedia.org/wiki/Total_order
+/// [`Cell`]: core::cell::Cell
+/// [`RefCell`]: core::cell::RefCell
 #[stable(feature = "rust1", since = "1.0.0")]
 #[cfg_attr(not(test), rustc_diagnostic_item = "BTreeMap")]
 #[rustc_insignificant_dtor]

alloc/src/collections/btree/map.rs

@@ -136,10 +136,6 @@ impl<'a, K: Debug + Ord, V: Debug, A: Allocator + Clone> fmt::Display
 impl<'a, K: core::fmt::Debug + Ord, V: core::fmt::Debug> core::error::Error
     for crate::collections::btree_map::OccupiedError<'a, K, V>
 {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "key already exists"
-    }
 }
 
 impl<'a, K: Ord, V, A: Allocator + Clone> Entry<'a, K, V, A> {

alloc/src/collections/btree/map/entry.rs

@@ -1061,17 +1061,10 @@ impl IntoStringError {
     }
 }
 
-impl IntoStringError {
-    fn description(&self) -> &str {
-        "C string contained non-utf8 bytes"
-    }
-}
-
 #[stable(feature = "cstring_into", since = "1.7.0")]
 impl fmt::Display for IntoStringError {
-    #[allow(deprecated, deprecated_in_future)]
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        self.description().fmt(f)
+        "C string contained non-utf8 bytes".fmt(f)
     }
 }
 
@@ -1291,23 +1284,13 @@ impl PartialEq<CString> for Cow<'_, CStr> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl core::error::Error for NulError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "nul byte found in data"
-    }
-}
+impl core::error::Error for NulError {}
 
 #[stable(feature = "cstring_from_vec_with_nul", since = "1.58.0")]
 impl core::error::Error for FromVecWithNulError {}
 
 #[stable(feature = "cstring_into", since = "1.7.0")]
 impl core::error::Error for IntoStringError {
-    #[allow(deprecated)]
-    fn description(&self) -> &str {
-        "C string contained non-utf8 bytes"
-    }
-
     fn source(&self) -> Option<&(dyn core::error::Error + 'static)> {
         Some(&self.error)
     }

alloc/src/ffi/c_str.rs

@@ -102,6 +102,7 @@
 #![feature(async_iterator)]
 #![feature(bstr)]
 #![feature(bstr_internals)]
+#![feature(cast_maybe_uninit)]
 #![feature(char_internals)]
 #![feature(char_max_len)]
 #![feature(clone_to_uninit)]
@@ -158,6 +159,7 @@
 #![feature(unicode_internals)]
 #![feature(unsize)]
 #![feature(unwrap_infallible)]
+#![feature(wtf8_internals)]
 // tidy-alphabetical-end
 //
 // Language features:
@@ -231,6 +233,8 @@ pub mod sync;
 #[cfg(all(not(no_global_oom_handling), not(no_rc), not(no_sync)))]
 pub mod task;
 pub mod vec;
+#[cfg(all(not(no_rc), not(no_sync), not(no_global_oom_handling)))]
+pub mod wtf8;
 
 #[doc(hidden)]
 #[unstable(feature = "liballoc_internals", issue = "none", reason = "implementation detail")]

alloc/src/lib.rs

@@ -155,7 +155,7 @@ impl RawVecInner<Global> {
 }
 
 // Tiny Vecs are dumb. Skip to:
-// - 8 if the element size is 1, because any heap allocators is likely
+// - 8 if the element size is 1, because any heap allocator is likely
 //   to round up a request of less than 8 bytes to at least 8 bytes.
 // - 4 if elements are moderate-sized (<= 1 KiB).
 // - 1 otherwise, to avoid wasting too much space for very short Vecs.