Merge pull request #2215 from Kobzol/pull

rustc pull

11 files changed, 76 insertions, 83 deletions

diff --git a/library/alloc/Cargo.toml b/library/alloc/Cargo.toml
index 07596fa16f9..96caac890a3 100644
--- a/library/alloc/Cargo.toml
+++ b/library/alloc/Cargo.toml
@@ -10,7 +10,7 @@ edition = "2021"
 
 [dependencies]
 core = { path = "../core" }
-compiler_builtins = { version = "=0.1.140", features = ['rustc-dep-of-std'] }
+compiler_builtins = { version = "=0.1.143", features = ['rustc-dep-of-std'] }
 
 [dev-dependencies]
 rand = { version = "0.8.5", default-features = false, features = ["alloc"] }
diff --git a/library/alloc/src/boxed.rs b/library/alloc/src/boxed.rs
index 0f66217b5cb..1b5e44a9134 100644
--- a/library/alloc/src/boxed.rs
+++ b/library/alloc/src/boxed.rs
@@ -2028,8 +2028,7 @@ impl<Args: Tuple, F: Fn<Args> + ?Sized, A: Allocator> Fn<Args> for Box<F, A> {
     }
 }
 
-#[cfg_attr(bootstrap, unstable(feature = "async_closure", issue = "62290"))]
-#[cfg_attr(not(bootstrap), stable(feature = "async_closure", since = "CURRENT_RUSTC_VERSION"))]
+#[stable(feature = "async_closure", since = "1.85.0")]
 impl<Args: Tuple, F: AsyncFnOnce<Args> + ?Sized, A: Allocator> AsyncFnOnce<Args> for Box<F, A> {
     type Output = F::Output;
     type CallOnceFuture = F::CallOnceFuture;
@@ -2039,8 +2038,7 @@ impl<Args: Tuple, F: AsyncFnOnce<Args> + ?Sized, A: Allocator> AsyncFnOnce<Args>
     }
 }
 
-#[cfg_attr(bootstrap, unstable(feature = "async_closure", issue = "62290"))]
-#[cfg_attr(not(bootstrap), stable(feature = "async_closure", since = "CURRENT_RUSTC_VERSION"))]
+#[stable(feature = "async_closure", since = "1.85.0")]
 impl<Args: Tuple, F: AsyncFnMut<Args> + ?Sized, A: Allocator> AsyncFnMut<Args> for Box<F, A> {
     type CallRefFuture<'a>
         = F::CallRefFuture<'a>
@@ -2052,8 +2050,7 @@ impl<Args: Tuple, F: AsyncFnMut<Args> + ?Sized, A: Allocator> AsyncFnMut<Args> f
     }
 }
 
-#[cfg_attr(bootstrap, unstable(feature = "async_closure", issue = "62290"))]
-#[cfg_attr(not(bootstrap), stable(feature = "async_closure", since = "CURRENT_RUSTC_VERSION"))]
+#[stable(feature = "async_closure", since = "1.85.0")]
 impl<Args: Tuple, F: AsyncFn<Args> + ?Sized, A: Allocator> AsyncFn<Args> for Box<F, A> {
     extern "rust-call" fn async_call(&self, args: Args) -> Self::CallRefFuture<'_> {
         F::async_call(self, args)
diff --git a/library/alloc/src/collections/btree/node.rs b/library/alloc/src/collections/btree/node.rs
index 0c93eff0d20..4057657632b 100644
--- a/library/alloc/src/collections/btree/node.rs
+++ b/library/alloc/src/collections/btree/node.rs
@@ -383,9 +383,7 @@ impl<'a, K: 'a, V: 'a, Type> NodeRef<marker::Immut<'a>, K, V, Type> {
     /// Borrows a view into the keys stored in the node.
     pub fn keys(&self) -> &[K] {
         let leaf = self.into_leaf();
-        unsafe {
-            MaybeUninit::slice_assume_init_ref(leaf.keys.get_unchecked(..usize::from(leaf.len)))
-        }
+        unsafe { leaf.keys.get_unchecked(..usize::from(leaf.len)).assume_init_ref() }
     }
 }
 
diff --git a/library/alloc/src/lib.rs b/library/alloc/src/lib.rs
index aff90f5abb3..b4f08debc93 100644
--- a/library/alloc/src/lib.rs
+++ b/library/alloc/src/lib.rs
@@ -91,7 +91,6 @@
 //
 // Library features:
 // tidy-alphabetical-start
-#![cfg_attr(bootstrap, feature(async_closure))]
 #![cfg_attr(test, feature(str_as_str))]
 #![feature(alloc_layout_extra)]
 #![feature(allocator_api)]
@@ -127,6 +126,7 @@
 #![feature(local_waker)]
 #![feature(maybe_uninit_slice)]
 #![feature(maybe_uninit_uninit_array_transpose)]
+#![feature(nonnull_provenance)]
 #![feature(panic_internals)]
 #![feature(pattern)]
 #![feature(pin_coerce_unsized_trait)]
@@ -143,6 +143,7 @@
 #![feature(slice_range)]
 #![feature(std_internals)]
 #![feature(str_internals)]
+#![feature(temporary_niche_types)]
 #![feature(trusted_fused)]
 #![feature(trusted_len)]
 #![feature(trusted_random_access)]
diff --git a/library/alloc/src/macros.rs b/library/alloc/src/macros.rs
index 6ee3907cc8e..c000fd6f4ef 100644
--- a/library/alloc/src/macros.rs
+++ b/library/alloc/src/macros.rs
@@ -48,8 +48,8 @@ macro_rules! vec {
     );
     ($($x:expr),+ $(,)?) => (
         <[_]>::into_vec(
-            // Using the intrinsic produces a dramatic improvement in compile
-            // time when constructing arrays with many elements.
+            // Using the intrinsic produces a dramatic improvement in stack usage for
+            // unoptimized programs using this code path to construct large Vecs.
             $crate::boxed::box_new([$($x),+])
         )
     );
diff --git a/library/alloc/src/raw_vec.rs b/library/alloc/src/raw_vec.rs
index e93ff2f9023..ad86bf4bf07 100644
--- a/library/alloc/src/raw_vec.rs
+++ b/library/alloc/src/raw_vec.rs
@@ -33,21 +33,15 @@ enum AllocInit {
     Zeroed,
 }
 
-#[repr(transparent)]
-#[cfg_attr(target_pointer_width = "16", rustc_layout_scalar_valid_range_end(0x7fff))]
-#[cfg_attr(target_pointer_width = "32", rustc_layout_scalar_valid_range_end(0x7fff_ffff))]
-#[cfg_attr(target_pointer_width = "64", rustc_layout_scalar_valid_range_end(0x7fff_ffff_ffff_ffff))]
-struct Cap(usize);
+type Cap = core::num::niche_types::UsizeNoHighBit;
 
-impl Cap {
-    const ZERO: Cap = unsafe { Cap(0) };
+const ZERO_CAP: Cap = unsafe { Cap::new_unchecked(0) };
 
-    /// `Cap(cap)`, except if `T` is a ZST then `Cap::ZERO`.
-    ///
-    /// # Safety: cap must be <= `isize::MAX`.
-    unsafe fn new<T>(cap: usize) -> Self {
-        if T::IS_ZST { Cap::ZERO } else { unsafe { Self(cap) } }
-    }
+/// `Cap(cap)`, except if `T` is a ZST then `Cap::ZERO`.
+///
+/// # Safety: cap must be <= `isize::MAX`.
+unsafe fn new_cap<T>(cap: usize) -> Cap {
+    if T::IS_ZST { ZERO_CAP } else { unsafe { Cap::new_unchecked(cap) } }
 }
 
 /// A low-level utility for more ergonomically allocating, reallocating, and deallocating
@@ -257,7 +251,7 @@ impl<T, A: Allocator> RawVec<T, A> {
         // SAFETY: Precondition passed to the caller
         unsafe {
             let ptr = ptr.cast();
-            let capacity = Cap::new::<T>(capacity);
+            let capacity = new_cap::<T>(capacity);
             Self {
                 inner: RawVecInner::from_raw_parts_in(ptr, capacity, alloc),
                 _marker: PhantomData,
@@ -275,7 +269,7 @@ impl<T, A: Allocator> RawVec<T, A> {
         // SAFETY: Precondition passed to the caller
         unsafe {
             let ptr = ptr.cast();
-            let capacity = Cap::new::<T>(capacity);
+            let capacity = new_cap::<T>(capacity);
             Self { inner: RawVecInner::from_nonnull_in(ptr, capacity, alloc), _marker: PhantomData }
         }
     }
@@ -410,7 +404,7 @@ impl<A: Allocator> RawVecInner<A> {
     const fn new_in(alloc: A, align: usize) -> Self {
         let ptr = unsafe { core::mem::transmute(align) };
         // `cap: 0` means "unallocated". zero-sized types are ignored.
-        Self { ptr, cap: Cap::ZERO, alloc }
+        Self { ptr, cap: ZERO_CAP, alloc }
     }
 
     #[cfg(not(no_global_oom_handling))]
@@ -483,7 +477,11 @@ impl<A: Allocator> RawVecInner<A> {
         // Allocators currently return a `NonNull<[u8]>` whose length
         // matches the size requested. If that ever changes, the capacity
         // here should change to `ptr.len() / mem::size_of::<T>()`.
-        Ok(Self { ptr: Unique::from(ptr.cast()), cap: unsafe { Cap(capacity) }, alloc })
+        Ok(Self {
+            ptr: Unique::from(ptr.cast()),
+            cap: unsafe { Cap::new_unchecked(capacity) },
+            alloc,
+        })
     }
 
     #[inline]
@@ -508,7 +506,7 @@ impl<A: Allocator> RawVecInner<A> {
 
     #[inline]
     const fn capacity(&self, elem_size: usize) -> usize {
-        if elem_size == 0 { usize::MAX } else { self.cap.0 }
+        if elem_size == 0 { usize::MAX } else { self.cap.as_inner() }
     }
 
     #[inline]
@@ -518,7 +516,7 @@ impl<A: Allocator> RawVecInner<A> {
 
     #[inline]
     fn current_memory(&self, elem_layout: Layout) -> Option<(NonNull<u8>, Layout)> {
-        if elem_layout.size() == 0 || self.cap.0 == 0 {
+        if elem_layout.size() == 0 || self.cap.as_inner() == 0 {
             None
         } else {
             // We could use Layout::array here which ensures the absence of isize and usize overflows
@@ -526,7 +524,7 @@ impl<A: Allocator> RawVecInner<A> {
             // has already been allocated so we know it can't overflow and currently Rust does not
             // support such types. So we can do better by skipping some checks and avoid an unwrap.
             unsafe {
-                let alloc_size = elem_layout.size().unchecked_mul(self.cap.0);
+                let alloc_size = elem_layout.size().unchecked_mul(self.cap.as_inner());
                 let layout = Layout::from_size_align_unchecked(alloc_size, elem_layout.align());
                 Some((self.ptr.into(), layout))
             }
@@ -562,7 +560,7 @@ impl<A: Allocator> RawVecInner<A> {
     #[inline]
     #[track_caller]
     fn grow_one(&mut self, elem_layout: Layout) {
-        if let Err(err) = self.grow_amortized(self.cap.0, 1, elem_layout) {
+        if let Err(err) = self.grow_amortized(self.cap.as_inner(), 1, elem_layout) {
             handle_error(err);
         }
     }
@@ -627,7 +625,7 @@ impl<A: Allocator> RawVecInner<A> {
         // the size requested. If that ever changes, the capacity here should
         // change to `ptr.len() / mem::size_of::<T>()`.
         self.ptr = Unique::from(ptr.cast());
-        self.cap = unsafe { Cap(cap) };
+        self.cap = unsafe { Cap::new_unchecked(cap) };
     }
 
     fn grow_amortized(
@@ -650,7 +648,7 @@ impl<A: Allocator> RawVecInner<A> {
 
         // This guarantees exponential growth. The doubling cannot overflow
         // because `cap <= isize::MAX` and the type of `cap` is `usize`.
-        let cap = cmp::max(self.cap.0 * 2, required_cap);
+        let cap = cmp::max(self.cap.as_inner() * 2, required_cap);
         let cap = cmp::max(min_non_zero_cap(elem_layout.size()), cap);
 
         let new_layout = layout_array(cap, elem_layout)?;
@@ -719,7 +717,7 @@ impl<A: Allocator> RawVecInner<A> {
             unsafe { self.alloc.deallocate(ptr, layout) };
             self.ptr =
                 unsafe { Unique::new_unchecked(ptr::without_provenance_mut(elem_layout.align())) };
-            self.cap = Cap::ZERO;
+            self.cap = ZERO_CAP;
         } else {
             let ptr = unsafe {
                 // Layout cannot overflow here because it would have
diff --git a/library/alloc/src/rc.rs b/library/alloc/src/rc.rs
index e014404eff3..ae3318b839d 100644
--- a/library/alloc/src/rc.rs
+++ b/library/alloc/src/rc.rs
@@ -252,6 +252,7 @@ use core::intrinsics::abort;
 use core::iter;
 use core::marker::{PhantomData, Unsize};
 use core::mem::{self, ManuallyDrop, align_of_val_raw};
+use core::num::NonZeroUsize;
 use core::ops::{CoerceUnsized, Deref, DerefMut, DerefPure, DispatchFromDyn, LegacyReceiver};
 use core::panic::{RefUnwindSafe, UnwindSafe};
 #[cfg(not(no_global_oom_handling))]
@@ -1789,7 +1790,7 @@ impl<T: ?Sized, A: Allocator> Rc<T, A> {
     /// let x: Rc<&str> = Rc::new("Hello, world!");
     /// {
     ///     let s = String::from("Oh, no!");
-    ///     let mut y: Rc<&str> = x.clone().into();
+    ///     let mut y: Rc<&str> = x.clone();
     ///     unsafe {
     ///         // this is Undefined Behavior, because x's inner type
     ///         // is &'long str, not &'short str
@@ -3027,12 +3028,7 @@ impl<T> Weak<T> {
     #[rustc_const_stable(feature = "const_weak_new", since = "1.73.0")]
     #[must_use]
     pub const fn new() -> Weak<T> {
-        Weak {
-            ptr: unsafe {
-                NonNull::new_unchecked(ptr::without_provenance_mut::<RcInner<T>>(usize::MAX))
-            },
-            alloc: Global,
-        }
+        Weak { ptr: NonNull::without_provenance(NonZeroUsize::MAX), alloc: Global }
     }
 }
 
@@ -3054,12 +3050,7 @@ impl<T, A: Allocator> Weak<T, A> {
     #[inline]
     #[unstable(feature = "allocator_api", issue = "32838")]
     pub fn new_in(alloc: A) -> Weak<T, A> {
-        Weak {
-            ptr: unsafe {
-                NonNull::new_unchecked(ptr::without_provenance_mut::<RcInner<T>>(usize::MAX))
-            },
-            alloc,
-        }
+        Weak { ptr: NonNull::without_provenance(NonZeroUsize::MAX), alloc }
     }
 }
 
@@ -3717,7 +3708,11 @@ pub struct UniqueRc<
     #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
 > {
     ptr: NonNull<RcInner<T>>,
-    phantom: PhantomData<RcInner<T>>,
+    // Define the ownership of `RcInner<T>` for drop-check
+    _marker: PhantomData<RcInner<T>>,
+    // Invariance is necessary for soundness: once other `Weak`
+    // references exist, we already have a form of shared mutability!
+    _marker2: PhantomData<*mut T>,
     alloc: A,
 }
 
@@ -4003,7 +3998,7 @@ impl<T, A: Allocator> UniqueRc<T, A> {
             },
             alloc,
         ));
-        Self { ptr: ptr.into(), phantom: PhantomData, alloc }
+        Self { ptr: ptr.into(), _marker: PhantomData, _marker2: PhantomData, alloc }
     }
 }
 
diff --git a/library/alloc/src/sync.rs b/library/alloc/src/sync.rs
index b34a6d3f660..8eee7cff208 100644
--- a/library/alloc/src/sync.rs
+++ b/library/alloc/src/sync.rs
@@ -18,6 +18,7 @@ use core::intrinsics::abort;
 use core::iter;
 use core::marker::{PhantomData, Unsize};
 use core::mem::{self, ManuallyDrop, align_of_val_raw};
+use core::num::NonZeroUsize;
 use core::ops::{CoerceUnsized, Deref, DerefPure, DispatchFromDyn, LegacyReceiver};
 use core::panic::{RefUnwindSafe, UnwindSafe};
 use core::pin::{Pin, PinCoerceUnsized};
@@ -1396,6 +1397,8 @@ impl<T: ?Sized> Arc<T> {
     /// different types. See [`mem::transmute`][transmute] for more information
     /// on what restrictions apply in this case.
     ///
+    /// The raw pointer must point to a block of memory allocated by the global allocator.
+    ///
     /// The user of `from_raw` has to make sure a specific value of `T` is only
     /// dropped once.
     ///
@@ -1451,7 +1454,8 @@ impl<T: ?Sized> Arc<T> {
     ///
     /// The pointer must have been obtained through `Arc::into_raw`, and the
     /// associated `Arc` instance must be valid (i.e. the strong count must be at
-    /// least 1) for the duration of this method.
+    /// least 1) for the duration of this method, and `ptr` must point to a block of memory
+    /// allocated by the global allocator.
     ///
     /// # Examples
     ///
@@ -1485,7 +1489,8 @@ impl<T: ?Sized> Arc<T> {
     ///
     /// The pointer must have been obtained through `Arc::into_raw`, and the
     /// associated `Arc` instance must be valid (i.e. the strong count must be at
-    /// least 1) when invoking this method. This method can be used to release the final
+    /// least 1) when invoking this method, and `ptr` must point to a block of memory
+    /// allocated by the global allocator. This method can be used to release the final
     /// `Arc` and backing storage, but **should not** be called after the final `Arc` has been
     /// released.
     ///
@@ -2468,7 +2473,7 @@ impl<T: ?Sized, A: Allocator> Arc<T, A> {
     /// let x: Arc<&str> = Arc::new("Hello, world!");
     /// {
     ///     let s = String::from("Oh, no!");
-    ///     let mut y: Arc<&str> = x.clone().into();
+    ///     let mut y: Arc<&str> = x.clone();
     ///     unsafe {
     ///         // this is Undefined Behavior, because x's inner type
     ///         // is &'long str, not &'short str
@@ -2687,12 +2692,7 @@ impl<T> Weak<T> {
     #[rustc_const_stable(feature = "const_weak_new", since = "1.73.0")]
     #[must_use]
     pub const fn new() -> Weak<T> {
-        Weak {
-            ptr: unsafe {
-                NonNull::new_unchecked(ptr::without_provenance_mut::<ArcInner<T>>(usize::MAX))
-            },
-            alloc: Global,
-        }
+        Weak { ptr: NonNull::without_provenance(NonZeroUsize::MAX), alloc: Global }
     }
 }
 
@@ -2717,12 +2717,7 @@ impl<T, A: Allocator> Weak<T, A> {
     #[inline]
     #[unstable(feature = "allocator_api", issue = "32838")]
     pub fn new_in(alloc: A) -> Weak<T, A> {
-        Weak {
-            ptr: unsafe {
-                NonNull::new_unchecked(ptr::without_provenance_mut::<ArcInner<T>>(usize::MAX))
-            },
-            alloc,
-        }
+        Weak { ptr: NonNull::without_provenance(NonZeroUsize::MAX), alloc }
     }
 }
 
diff --git a/library/alloc/src/vec/is_zero.rs b/library/alloc/src/vec/is_zero.rs
index ba57d940d8c..a3ddd6f6e23 100644
--- a/library/alloc/src/vec/is_zero.rs
+++ b/library/alloc/src/vec/is_zero.rs
@@ -40,19 +40,8 @@ impl_is_zero!(char, |x| x == '\0');
 impl_is_zero!(f32, |x: f32| x.to_bits() == 0);
 impl_is_zero!(f64, |x: f64| x.to_bits() == 0);
 
-unsafe impl<T> IsZero for *const T {
-    #[inline]
-    fn is_zero(&self) -> bool {
-        (*self).is_null()
-    }
-}
-
-unsafe impl<T> IsZero for *mut T {
-    #[inline]
-    fn is_zero(&self) -> bool {
-        (*self).is_null()
-    }
-}
+// `IsZero` cannot be soundly implemented for pointers because of provenance
+// (see #135338).
 
 unsafe impl<T: IsZero, const N: usize> IsZero for [T; N] {
     #[inline]
diff --git a/library/alloc/src/vec/mod.rs b/library/alloc/src/vec/mod.rs
index 3a706d5f36b..cd2afd7a473 100644
--- a/library/alloc/src/vec/mod.rs
+++ b/library/alloc/src/vec/mod.rs
@@ -3587,7 +3587,7 @@ impl<T, A: Allocator> Vec<T, A> {
     /// with the given `replace_with` iterator and yields the removed items.
     /// `replace_with` does not need to be the same length as `range`.
     ///
-    /// `range` is removed even if the iterator is not consumed until the end.
+    /// `range` is removed even if the `Splice` iterator is not consumed before it is dropped.
     ///
     /// It is unspecified how many elements are removed from the vector
     /// if the `Splice` value is leaked.
@@ -3613,8 +3613,18 @@ impl<T, A: Allocator> Vec<T, A> {
     /// let mut v = vec![1, 2, 3, 4];
     /// let new = [7, 8, 9];
     /// let u: Vec<_> = v.splice(1..3, new).collect();
-    /// assert_eq!(v, &[1, 7, 8, 9, 4]);
-    /// assert_eq!(u, &[2, 3]);
+    /// assert_eq!(v, [1, 7, 8, 9, 4]);
+    /// assert_eq!(u, [2, 3]);
+    /// ```
+    ///
+    /// Using `splice` to insert new items into a vector efficiently at a specific position
+    /// indicated by an empty range:
+    ///
+    /// ```
+    /// let mut v = vec![1, 5];
+    /// let new = [2, 3, 4];
+    /// v.splice(1..1, new);
+    /// assert_eq!(v, [1, 2, 3, 4, 5]);
     /// ```
     #[cfg(not(no_global_oom_handling))]
     #[inline]
diff --git a/library/alloc/tests/vec.rs b/library/alloc/tests/vec.rs
index 2e654d3d1ff..b24daec2968 100644
--- a/library/alloc/tests/vec.rs
+++ b/library/alloc/tests/vec.rs
@@ -2742,3 +2742,13 @@ fn max_swap_remove() {
     let mut v = vec![0];
     v.swap_remove(usize::MAX);
 }
+
+// Regression test for #135338
+#[test]
+fn vec_null_ptr_roundtrip() {
+    let ptr = std::ptr::from_ref(&42);
+    let zero = ptr.with_addr(0);
+    let roundtripped = vec![zero; 1].pop().unwrap();
+    let new = roundtripped.with_addr(ptr.addr());
+    unsafe { new.read() };
+}