Merge from rustc

alloc/src/collections/binary_heap/mod.rs

@@ -484,7 +484,7 @@ impl<T: Ord, A: Allocator> BinaryHeap<T, A> {
     /// heap.push(4);
     /// ```
     #[unstable(feature = "allocator_api", issue = "32838")]
-    #[rustc_const_unstable(feature = "const_binary_heap_new_in", issue = "112353")]
+    #[rustc_const_unstable(feature = "const_binary_heap_new_in", issue = "125961")]
     #[must_use]
     pub const fn new_in(alloc: A) -> BinaryHeap<T, A> {
         BinaryHeap { data: Vec::new_in(alloc) }

alloc/src/lib.rs

@@ -101,6 +101,7 @@
 #![feature(array_windows)]
 #![feature(ascii_char)]
 #![feature(assert_matches)]
+#![feature(async_closure)]
 #![feature(async_fn_traits)]
 #![feature(async_iterator)]
 #![feature(clone_to_uninit)]

alloc/src/rc.rs

@@ -259,7 +259,7 @@ use core::intrinsics::abort;
 #[cfg(not(no_global_oom_handling))]
 use core::iter;
 use core::marker::{PhantomData, Unsize};
-use core::mem::{self, align_of_val_raw, forget, ManuallyDrop};
+use core::mem::{self, align_of_val_raw, ManuallyDrop};
 use core::ops::{CoerceUnsized, Deref, DerefMut, DerefPure, DispatchFromDyn, Receiver};
 use core::panic::{RefUnwindSafe, UnwindSafe};
 #[cfg(not(no_global_oom_handling))]
@@ -908,19 +908,18 @@ impl<T, A: Allocator> Rc<T, A> {
     #[stable(feature = "rc_unique", since = "1.4.0")]
     pub fn try_unwrap(this: Self) -> Result<T, Self> {
         if Rc::strong_count(&this) == 1 {
-            unsafe {
-                let val = ptr::read(&*this); // copy the contained object
-                let alloc = ptr::read(&this.alloc); // copy the allocator
-
-                // Indicate to Weaks that they can't be promoted by decrementing
-                // the strong count, and then remove the implicit "strong weak"
-                // pointer while also handling drop logic by just crafting a
-                // fake Weak.
-                this.inner().dec_strong();
-                let _weak = Weak { ptr: this.ptr, alloc };
-                forget(this);
-                Ok(val)
-            }
+            let this = ManuallyDrop::new(this);
+
+            let val: T = unsafe { ptr::read(&**this) }; // copy the contained object
+            let alloc: A = unsafe { ptr::read(&this.alloc) }; // copy the allocator
+
+            // Indicate to Weaks that they can't be promoted by decrementing
+            // the strong count, and then remove the implicit "strong weak"
+            // pointer while also handling drop logic by just crafting a
+            // fake Weak.
+            this.inner().dec_strong();
+            let _weak = Weak { ptr: this.ptr, alloc };
+            Ok(val)
         } else {
             Err(this)
         }
@@ -1354,9 +1353,8 @@ impl<T: ?Sized, A: Allocator> Rc<T, A> {
     #[stable(feature = "rc_raw", since = "1.17.0")]
     #[rustc_never_returns_null_ptr]
     pub fn into_raw(this: Self) -> *const T {
-        let ptr = Self::as_ptr(&this);
-        mem::forget(this);
-        ptr
+        let this = ManuallyDrop::new(this);
+        Self::as_ptr(&*this)
     }
 
     /// Consumes the `Rc`, returning the wrapped pointer and allocator.
@@ -2127,7 +2125,7 @@ impl<T> Rc<[T]> {
             }
 
             // All clear. Forget the guard so it doesn't free the new RcBox.
-            forget(guard);
+            mem::forget(guard);
 
             Self::from_ptr(ptr)
         }
@@ -3080,9 +3078,7 @@ impl<T: ?Sized, A: Allocator> Weak<T, A> {
     #[must_use = "losing the pointer will leak memory"]
     #[stable(feature = "weak_into_raw", since = "1.45.0")]
     pub fn into_raw(self) -> *const T {
-        let result = self.as_ptr();
-        mem::forget(self);
-        result
+        mem::ManuallyDrop::new(self).as_ptr()
     }
 
     /// Consumes the `Weak<T>`, returning the wrapped pointer and allocator.
@@ -3762,10 +3758,11 @@ impl<T: ?Sized, A: Allocator> UniqueRcUninit<T, A> {
     /// # Safety
     ///
     /// The data must have been initialized (by writing to [`Self::data_ptr()`]).
-    unsafe fn into_rc(mut self) -> Rc<T, A> {
-        let ptr = self.ptr;
-        let alloc = self.alloc.take().unwrap();
-        mem::forget(self);
+    unsafe fn into_rc(self) -> Rc<T, A> {
+        let mut this = ManuallyDrop::new(self);
+        let ptr = this.ptr;
+        let alloc = this.alloc.take().unwrap();
+
         // SAFETY: The pointer is valid as per `UniqueRcUninit::new`, and the caller is responsible
         // for having initialized the data.
         unsafe { Rc::from_ptr_in(ptr.as_ptr(), alloc) }

alloc/src/str.rs

@@ -269,7 +269,7 @@ impl str {
                   without modifying the original"]
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
-    pub fn replace<'a, P: Pattern<'a>>(&'a self, from: P, to: &str) -> String {
+    pub fn replace<P: Pattern>(&self, from: P, to: &str) -> String {
         let mut result = String::new();
         let mut last_end = 0;
         for (start, part) in self.match_indices(from) {
@@ -309,7 +309,7 @@ impl str {
     #[must_use = "this returns the replaced string as a new allocation, \
                   without modifying the original"]
     #[stable(feature = "str_replacen", since = "1.16.0")]
-    pub fn replacen<'a, P: Pattern<'a>>(&'a self, pat: P, to: &str, count: usize) -> String {
+    pub fn replacen<P: Pattern>(&self, pat: P, to: &str, count: usize) -> String {
         // Hope to reduce the times of re-allocation
         let mut result = String::with_capacity(32);
         let mut last_end = 0;

alloc/src/string.rs

@@ -1497,10 +1497,7 @@ impl String {
     /// ```
     #[cfg(not(no_global_oom_handling))]
     #[unstable(feature = "string_remove_matches", reason = "new API", issue = "72826")]
-    pub fn remove_matches<'a, P>(&'a mut self, pat: P)
-    where
-        P: for<'x> Pattern<'x>,
-    {
+    pub fn remove_matches<P: Pattern>(&mut self, pat: P) {
         use core::str::pattern::Searcher;
 
         let rejections = {
@@ -2288,35 +2285,41 @@ impl<'a> Extend<Cow<'a, str>> for String {
     reason = "API not fully fleshed out and ready to be stabilized",
     issue = "27721"
 )]
-impl<'a, 'b> Pattern<'a> for &'b String {
-    type Searcher = <&'b str as Pattern<'a>>::Searcher;
+impl<'b> Pattern for &'b String {
+    type Searcher<'a> = <&'b str as Pattern>::Searcher<'a>;
 
-    fn into_searcher(self, haystack: &'a str) -> <&'b str as Pattern<'a>>::Searcher {
+    fn into_searcher(self, haystack: &str) -> <&'b str as Pattern>::Searcher<'_> {
         self[..].into_searcher(haystack)
     }
 
     #[inline]
-    fn is_contained_in(self, haystack: &'a str) -> bool {
+    fn is_contained_in(self, haystack: &str) -> bool {
         self[..].is_contained_in(haystack)
     }
 
     #[inline]
-    fn is_prefix_of(self, haystack: &'a str) -> bool {
+    fn is_prefix_of(self, haystack: &str) -> bool {
         self[..].is_prefix_of(haystack)
     }
 
     #[inline]
-    fn strip_prefix_of(self, haystack: &'a str) -> Option<&'a str> {
+    fn strip_prefix_of(self, haystack: &str) -> Option<&str> {
         self[..].strip_prefix_of(haystack)
     }
 
     #[inline]
-    fn is_suffix_of(self, haystack: &'a str) -> bool {
+    fn is_suffix_of<'a>(self, haystack: &'a str) -> bool
+    where
+        Self::Searcher<'a>: core::str::pattern::ReverseSearcher<'a>,
+    {
         self[..].is_suffix_of(haystack)
     }
 
     #[inline]
-    fn strip_suffix_of(self, haystack: &'a str) -> Option<&'a str> {
+    fn strip_suffix_of<'a>(self, haystack: &'a str) -> Option<&str>
+    where
+        Self::Searcher<'a>: core::str::pattern::ReverseSearcher<'a>,
+    {
         self[..].strip_suffix_of(haystack)
     }
 }

alloc/src/sync.rs

@@ -20,7 +20,7 @@ use core::intrinsics::abort;
 #[cfg(not(no_global_oom_handling))]
 use core::iter;
 use core::marker::{PhantomData, Unsize};
-use core::mem::{self, align_of_val_raw};
+use core::mem::{self, align_of_val_raw, ManuallyDrop};
 use core::ops::{CoerceUnsized, Deref, DerefPure, DispatchFromDyn, Receiver};
 use core::panic::{RefUnwindSafe, UnwindSafe};
 use core::pin::Pin;
@@ -960,16 +960,14 @@ impl<T, A: Allocator> Arc<T, A> {
 
         acquire!(this.inner().strong);
 
-        unsafe {
-            let elem = ptr::read(&this.ptr.as_ref().data);
-            let alloc = ptr::read(&this.alloc); // copy the allocator
+        let this = ManuallyDrop::new(this);
+        let elem: T = unsafe { ptr::read(&this.ptr.as_ref().data) };
+        let alloc: A = unsafe { ptr::read(&this.alloc) }; // copy the allocator
 
-            // Make a weak pointer to clean up the implicit strong-weak reference
-            let _weak = Weak { ptr: this.ptr, alloc };
-            mem::forget(this);
+        // Make a weak pointer to clean up the implicit strong-weak reference
+        let _weak = Weak { ptr: this.ptr, alloc };
 
-            Ok(elem)
-        }
+        Ok(elem)
     }
 
     /// Returns the inner value, if the `Arc` has exactly one strong reference.
@@ -1493,9 +1491,8 @@ impl<T: ?Sized, A: Allocator> Arc<T, A> {
     #[stable(feature = "rc_raw", since = "1.17.0")]
     #[rustc_never_returns_null_ptr]
     pub fn into_raw(this: Self) -> *const T {
-        let ptr = Self::as_ptr(&this);
-        mem::forget(this);
-        ptr
+        let this = ManuallyDrop::new(this);
+        Self::as_ptr(&*this)
     }
 
     /// Consumes the `Arc`, returning the wrapped pointer and allocator.
@@ -2801,9 +2798,7 @@ impl<T: ?Sized, A: Allocator> Weak<T, A> {
     #[must_use = "losing the pointer will leak memory"]
     #[stable(feature = "weak_into_raw", since = "1.45.0")]
     pub fn into_raw(self) -> *const T {
-        let result = self.as_ptr();
-        mem::forget(self);
-        result
+        ManuallyDrop::new(self).as_ptr()
     }
 
     /// Consumes the `Weak<T>`, returning the wrapped pointer and allocator.
@@ -3875,13 +3870,14 @@ impl<T: ?Sized, A: Allocator> UniqueArcUninit<T, A> {
     /// # Safety
     ///
     /// The data must have been initialized (by writing to [`Self::data_ptr()`]).
-    unsafe fn into_arc(mut self) -> Arc<T, A> {
-        let ptr = self.ptr;
-        let alloc = self.alloc.take().unwrap();
-        mem::forget(self);
+    unsafe fn into_arc(self) -> Arc<T, A> {
+        let mut this = ManuallyDrop::new(self);
+        let ptr = this.ptr.as_ptr();
+        let alloc = this.alloc.take().unwrap();
+
         // SAFETY: The pointer is valid as per `UniqueArcUninit::new`, and the caller is responsible
         // for having initialized the data.
-        unsafe { Arc::from_ptr_in(ptr.as_ptr(), alloc) }
+        unsafe { Arc::from_ptr_in(ptr, alloc) }
     }
 }
 

alloc/tests/str.rs

@@ -1927,12 +1927,10 @@ mod pattern {
         }
     }
 
-    fn cmp_search_to_vec<'a>(
-        rev: bool,
-        pat: impl Pattern<'a, Searcher: ReverseSearcher<'a>>,
-        haystack: &'a str,
-        right: Vec<SearchStep>,
-    ) {
+    fn cmp_search_to_vec<P>(rev: bool, pat: P, haystack: &str, right: Vec<SearchStep>)
+    where
+        P: for<'a> Pattern<Searcher<'a>: ReverseSearcher<'a>>,
+    {
         let mut searcher = pat.into_searcher(haystack);
         let mut v = vec![];
         loop {
@@ -2191,9 +2189,9 @@ generate_iterator_test! {
 fn different_str_pattern_forwarding_lifetimes() {
     use std::str::pattern::Pattern;
 
-    fn foo<'a, P>(p: P)
+    fn foo<P>(p: P)
     where
-        for<'b> &'b P: Pattern<'a>,
+        for<'b> &'b P: Pattern,
     {
         for _ in 0..3 {
             "asdf".find(&p);

core/src/alloc/layout.rs

@@ -183,6 +183,8 @@ impl Layout {
     ///     - a [slice], then the length of the slice tail must be an initialized
     ///       integer, and the size of the *entire value*
     ///       (dynamic tail length + statically sized prefix) must fit in `isize`.
+    ///       For the special case where the dynamic tail length is 0, this function
+    ///       is safe to call.
     ///     - a [trait object], then the vtable part of the pointer must point
     ///       to a valid vtable for the type `T` acquired by an unsizing coercion,
     ///       and the size of the *entire value*

core/src/error.rs

@@ -506,7 +506,7 @@ where
 /// ```
 ///
 #[unstable(feature = "error_generic_member_access", issue = "99301")]
-#[cfg_attr(not(doc), repr(transparent))] // work around https://github.com/rust-lang/rust/issues/90435
+#[repr(transparent)]
 pub struct Request<'a>(Tagged<dyn Erased<'a> + 'a>);
 
 impl<'a> Request<'a> {

core/src/ffi/c_str.rs

@@ -103,7 +103,7 @@ use crate::str;
 // However, `CStr` layout is considered an implementation detail and must not be relied upon. We
 // want `repr(transparent)` but we don't want it to show up in rustdoc, so we hide it under
 // `cfg(doc)`. This is an ad-hoc implementation of attribute privacy.
-#[cfg_attr(not(doc), repr(transparent))]
+#[repr(transparent)]
 #[allow(clippy::derived_hash_with_manual_eq)]
 pub struct CStr {
     // FIXME: this should not be represented with a DST slice but rather with

core/src/ffi/mod.rs

@@ -191,7 +191,7 @@ mod c_long_definition {
 //     be UB.
 #[doc = include_str!("c_void.md")]
 #[lang = "c_void"]
-#[cfg_attr(not(doc), repr(u8))] // work around https://github.com/rust-lang/rust/issues/90435
+#[cfg_attr(not(doc), repr(u8))] // An implementation detail we don't want to show up in rustdoc
 #[stable(feature = "core_c_void", since = "1.30.0")]
 pub enum c_void {
     #[unstable(

core/src/ffi/va_list.rs

@@ -23,7 +23,7 @@ use crate::ops::{Deref, DerefMut};
     target_os = "uefi",
     windows,
 ))]
-#[cfg_attr(not(doc), repr(transparent))] // work around https://github.com/rust-lang/rust/issues/90435
+#[repr(transparent)]
 #[lang = "va_list"]
 pub struct VaListImpl<'f> {
     ptr: *mut c_void,
@@ -115,7 +115,7 @@ pub struct VaListImpl<'f> {
 }
 
 /// A wrapper for a `va_list`
-#[cfg_attr(not(doc), repr(transparent))] // work around https://github.com/rust-lang/rust/issues/90435
+#[repr(transparent)]
 #[derive(Debug)]
 pub struct VaList<'a, 'f: 'a> {
     #[cfg(any(

core/src/mem/mod.rs

@@ -359,6 +359,12 @@ pub const fn size_of_val<T: ?Sized>(val: &T) -> usize {
 ///     - a [slice], then the length of the slice tail must be an initialized
 ///       integer, and the size of the *entire value*
 ///       (dynamic tail length + statically sized prefix) must fit in `isize`.
+///       For the special case where the dynamic tail length is 0, this function
+///       is safe to call.
+//        NOTE: the reason this is safe is that if an overflow were to occur already with size 0,
+//        then we would stop compilation as even the "statically known" part of the type would
+//        already be too big (or the call may be in dead code and optimized away, but then it
+//        doesn't matter).
 ///     - a [trait object], then the vtable part of the pointer must point
 ///       to a valid vtable acquired by an unsizing coercion, and the size
 ///       of the *entire value* (dynamic tail length + statically sized prefix)
@@ -506,6 +512,8 @@ pub const fn align_of_val<T: ?Sized>(val: &T) -> usize {
 ///     - a [slice], then the length of the slice tail must be an initialized
 ///       integer, and the size of the *entire value*
 ///       (dynamic tail length + statically sized prefix) must fit in `isize`.
+///       For the special case where the dynamic tail length is 0, this function
+///       is safe to call.
 ///     - a [trait object], then the vtable part of the pointer must point
 ///       to a valid vtable acquired by an unsizing coercion, and the size
 ///       of the *entire value* (dynamic tail length + statically sized prefix)