Merging upstream version 1.73.0+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

6 files changed, 59 insertions, 10 deletions

diff --git a/library/core/src/ptr/const_ptr.rs b/library/core/src/ptr/const_ptr.rs
index 926189a17..ee69d89a4 100644
--- a/library/core/src/ptr/const_ptr.rs
+++ b/library/core/src/ptr/const_ptr.rs
@@ -1,7 +1,7 @@
 use super::*;
 use crate::cmp::Ordering::{self, Equal, Greater, Less};
 use crate::intrinsics::{self, const_eval_select};
-use crate::mem;
+use crate::mem::{self, SizedTypeProperties};
 use crate::slice::{self, SliceIndex};
 
 impl<T: ?Sized> *const T {
@@ -30,6 +30,7 @@ impl<T: ?Sized> *const T {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_const_unstable(feature = "const_ptr_is_null", issue = "74939")]
+    #[rustc_diagnostic_item = "ptr_const_is_null"]
     #[inline]
     pub const fn is_null(self) -> bool {
         #[inline]
@@ -54,6 +55,7 @@ impl<T: ?Sized> *const T {
     /// Casts to a pointer of another type.
     #[stable(feature = "ptr_cast", since = "1.38.0")]
     #[rustc_const_stable(feature = "const_ptr_cast", since = "1.38.0")]
+    #[rustc_diagnostic_item = "const_ptr_cast"]
     #[inline(always)]
     pub const fn cast<U>(self) -> *const U {
         self as _
@@ -994,14 +996,23 @@ impl<T: ?Sized> *const T {
     #[stable(feature = "pointer_methods", since = "1.26.0")]
     #[must_use = "returns a new pointer rather than modifying its argument"]
     #[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
+    // We could always go back to wrapping if unchecked becomes unacceptable
+    #[rustc_allow_const_fn_unstable(const_int_unchecked_arith)]
     #[inline(always)]
     #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     pub const unsafe fn sub(self, count: usize) -> Self
     where
         T: Sized,
     {
-        // SAFETY: the caller must uphold the safety contract for `offset`.
-        unsafe { self.offset((count as isize).wrapping_neg()) }
+        if T::IS_ZST {
+            // Pointer arithmetic does nothing when the pointee is a ZST.
+            self
+        } else {
+            // SAFETY: the caller must uphold the safety contract for `offset`.
+            // Because the pointee is *not* a ZST, that means that `count` is
+            // at most `isize::MAX`, and thus the negation cannot overflow.
+            unsafe { self.offset(intrinsics::unchecked_sub(0, count as isize)) }
+        }
     }
 
     /// Calculates the offset from a pointer in bytes (convenience for
diff --git a/library/core/src/ptr/metadata.rs b/library/core/src/ptr/metadata.rs
index daaa44b1d..040aa0697 100644
--- a/library/core/src/ptr/metadata.rs
+++ b/library/core/src/ptr/metadata.rs
@@ -50,8 +50,7 @@ use crate::hash::{Hash, Hasher};
 ///
 /// [`to_raw_parts`]: *const::to_raw_parts
 #[lang = "pointee_trait"]
-#[cfg_attr(not(bootstrap), rustc_deny_explicit_impl(implement_via_object = false))]
-#[cfg_attr(bootstrap, rustc_deny_explicit_impl)]
+#[rustc_deny_explicit_impl(implement_via_object = false)]
 pub trait Pointee {
     /// The type for metadata in pointers and references to `Self`.
     #[lang = "metadata_type"]
diff --git a/library/core/src/ptr/mod.rs b/library/core/src/ptr/mod.rs
index acc9ca29d..5f094ac4e 100644
--- a/library/core/src/ptr/mod.rs
+++ b/library/core/src/ptr/mod.rs
@@ -710,6 +710,7 @@ pub const fn from_ref<T: ?Sized>(r: &T) -> *const T {
 #[inline(always)]
 #[must_use]
 #[unstable(feature = "ptr_from_ref", issue = "106116")]
+#[rustc_diagnostic_item = "ptr_from_mut"]
 pub const fn from_mut<T: ?Sized>(r: &mut T) -> *mut T {
     r
 }
diff --git a/library/core/src/ptr/mut_ptr.rs b/library/core/src/ptr/mut_ptr.rs
index c6f438578..9dbb3f9d3 100644
--- a/library/core/src/ptr/mut_ptr.rs
+++ b/library/core/src/ptr/mut_ptr.rs
@@ -1,6 +1,7 @@
 use super::*;
 use crate::cmp::Ordering::{self, Equal, Greater, Less};
 use crate::intrinsics::{self, const_eval_select};
+use crate::mem::SizedTypeProperties;
 use crate::slice::{self, SliceIndex};
 
 impl<T: ?Sized> *mut T {
@@ -29,6 +30,7 @@ impl<T: ?Sized> *mut T {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_const_unstable(feature = "const_ptr_is_null", issue = "74939")]
+    #[rustc_diagnostic_item = "ptr_is_null"]
     #[inline]
     pub const fn is_null(self) -> bool {
         #[inline]
@@ -53,6 +55,7 @@ impl<T: ?Sized> *mut T {
     /// Casts to a pointer of another type.
     #[stable(feature = "ptr_cast", since = "1.38.0")]
     #[rustc_const_stable(feature = "const_ptr_cast", since = "1.38.0")]
+    #[rustc_diagnostic_item = "ptr_cast"]
     #[inline(always)]
     pub const fn cast<U>(self) -> *mut U {
         self as _
@@ -109,6 +112,7 @@ impl<T: ?Sized> *mut T {
     /// [`cast_mut`]: #method.cast_mut
     #[stable(feature = "ptr_const_cast", since = "1.65.0")]
     #[rustc_const_stable(feature = "ptr_const_cast", since = "1.65.0")]
+    #[rustc_diagnostic_item = "ptr_cast_const"]
     #[inline(always)]
     pub const fn cast_const(self) -> *const T {
         self as _
@@ -1093,14 +1097,23 @@ impl<T: ?Sized> *mut T {
     #[stable(feature = "pointer_methods", since = "1.26.0")]
     #[must_use = "returns a new pointer rather than modifying its argument"]
     #[rustc_const_stable(feature = "const_ptr_offset", since = "1.61.0")]
+    // We could always go back to wrapping if unchecked becomes unacceptable
+    #[rustc_allow_const_fn_unstable(const_int_unchecked_arith)]
     #[inline(always)]
     #[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
     pub const unsafe fn sub(self, count: usize) -> Self
     where
         T: Sized,
     {
-        // SAFETY: the caller must uphold the safety contract for `offset`.
-        unsafe { self.offset((count as isize).wrapping_neg()) }
+        if T::IS_ZST {
+            // Pointer arithmetic does nothing when the pointee is a ZST.
+            self
+        } else {
+            // SAFETY: the caller must uphold the safety contract for `offset`.
+            // Because the pointee is *not* a ZST, that means that `count` is
+            // at most `isize::MAX`, and thus the negation cannot overflow.
+            unsafe { self.offset(intrinsics::unchecked_sub(0, count as isize)) }
+        }
     }
 
     /// Calculates the offset from a pointer in bytes (convenience for
diff --git a/library/core/src/ptr/non_null.rs b/library/core/src/ptr/non_null.rs
index b492d2f07..e0fd347a0 100644
--- a/library/core/src/ptr/non_null.rs
+++ b/library/core/src/ptr/non_null.rs
@@ -367,13 +367,14 @@ impl<T: ?Sized> NonNull<T> {
     ///
     /// [the module documentation]: crate::ptr#safety
     #[stable(feature = "nonnull", since = "1.25.0")]
-    #[rustc_const_unstable(feature = "const_ptr_as_ref", issue = "91822")]
+    #[rustc_const_stable(feature = "const_nonnull_as_ref", since = "1.73.0")]
     #[must_use]
     #[inline(always)]
     pub const unsafe fn as_ref<'a>(&self) -> &'a T {
         // SAFETY: the caller must guarantee that `self` meets all the
         // requirements for a reference.
-        unsafe { &*self.as_ptr() }
+        // `cast_const` avoids a mutable raw pointer deref.
+        unsafe { &*self.as_ptr().cast_const() }
     }
 
     /// Returns a unique reference to the value. If the value may be uninitialized, [`as_uninit_mut`]
@@ -462,6 +463,30 @@ impl<T: ?Sized> NonNull<T> {
         // And the caller promised the `delta` is sound to add.
         unsafe { NonNull { pointer: self.pointer.add(delta) } }
     }
+
+    /// See [`pointer::sub`] for semantics and safety requirements.
+    #[inline]
+    pub(crate) const unsafe fn sub(self, delta: usize) -> Self
+    where
+        T: Sized,
+    {
+        // SAFETY: We require that the delta stays in-bounds of the object, and
+        // thus it cannot become null, as no legal objects can be allocated
+        // in such as way that the null address is part of them.
+        // And the caller promised the `delta` is sound to subtract.
+        unsafe { NonNull { pointer: self.pointer.sub(delta) } }
+    }
+
+    /// See [`pointer::sub_ptr`] for semantics and safety requirements.
+    #[inline]
+    pub(crate) const unsafe fn sub_ptr(self, subtrahend: Self) -> usize
+    where
+        T: Sized,
+    {
+        // SAFETY: The caller promised that this is safe to do, and
+        // the non-nullness is irrelevant to the operation.
+        unsafe { self.pointer.sub_ptr(subtrahend.pointer) }
+    }
 }
 
 impl<T> NonNull<[T]> {
diff --git a/library/core/src/ptr/unique.rs b/library/core/src/ptr/unique.rs
index ff7e91d3e..bf8b86677 100644
--- a/library/core/src/ptr/unique.rs
+++ b/library/core/src/ptr/unique.rs
@@ -33,7 +33,7 @@ use crate::ptr::NonNull;
 #[doc(hidden)]
 #[repr(transparent)]
 // Lang item used experimentally by Miri to define the semantics of `Unique`.
-#[cfg_attr(not(bootstrap), lang = "ptr_unique")]
+#[lang = "ptr_unique"]
 pub struct Unique<T: ?Sized> {
     pointer: NonNull<T>,
     // NOTE: this marker has no consequences for variance, but is necessary