Auto merge of rust-lang#106450 - albertlarsan68:fix-arc-ptr-eq, r=Amanieu

Make `{Arc,Rc,Weak}::ptr_eq` ignore pointer metadata

FCP completed in rust-lang#103763 (comment)

Closes rust-lang#103763

Author: bors

alloc/src/rc.rs

@@ -1169,7 +1169,7 @@ impl<T: ?Sized> Rc<T> {
     #[inline]
     #[stable(feature = "ptr_eq", since = "1.17.0")]
     /// Returns `true` if the two `Rc`s point to the same allocation in a vein similar to
-    /// [`ptr::eq`]. See [that function][`ptr::eq`] for caveats when comparing `dyn Trait` pointers.
+    /// [`ptr::eq`]. This function ignores the metadata of  `dyn Trait` pointers.
     ///
     /// # Examples
     ///
@@ -1184,7 +1184,7 @@ impl<T: ?Sized> Rc<T> {
     /// assert!(!Rc::ptr_eq(&five, &other_five));
     /// ```
     pub fn ptr_eq(this: &Self, other: &Self) -> bool {
-        this.ptr.as_ptr() == other.ptr.as_ptr()
+        this.ptr.as_ptr() as *const () == other.ptr.as_ptr() as *const ()
     }
 }
 
@@ -2466,8 +2466,8 @@ impl<T: ?Sized> Weak<T> {
     }
 
     /// Returns `true` if the two `Weak`s point to the same allocation similar to [`ptr::eq`], or if
-    /// both don't point to any allocation (because they were created with `Weak::new()`). See [that
-    /// function][`ptr::eq`] for caveats when comparing `dyn Trait` pointers.
+    /// both don't point to any allocation (because they were created with `Weak::new()`). However,
+    /// this function ignores the metadata of  `dyn Trait` pointers.
     ///
     /// # Notes
     ///
@@ -2508,7 +2508,7 @@ impl<T: ?Sized> Weak<T> {
     #[must_use]
     #[stable(feature = "weak_ptr_eq", since = "1.39.0")]
     pub fn ptr_eq(&self, other: &Self) -> bool {
-        self.ptr.as_ptr() == other.ptr.as_ptr()
+        ptr::eq(self.ptr.as_ptr() as *const (), other.ptr.as_ptr() as *const ())
     }
 }
 

alloc/src/sync.rs

@@ -1267,7 +1267,7 @@ impl<T: ?Sized> Arc<T> {
     }
 
     /// Returns `true` if the two `Arc`s point to the same allocation in a vein similar to
-    /// [`ptr::eq`]. See [that function][`ptr::eq`] for caveats when comparing `dyn Trait` pointers.
+    /// [`ptr::eq`]. This function ignores the metadata of  `dyn Trait` pointers.
     ///
     /// # Examples
     ///
@@ -1287,7 +1287,7 @@ impl<T: ?Sized> Arc<T> {
     #[must_use]
     #[stable(feature = "ptr_eq", since = "1.17.0")]
     pub fn ptr_eq(this: &Self, other: &Self) -> bool {
-        this.ptr.as_ptr() == other.ptr.as_ptr()
+        this.ptr.as_ptr() as *const () == other.ptr.as_ptr() as *const ()
     }
 }
 
@@ -2254,8 +2254,8 @@ impl<T: ?Sized> Weak<T> {
     }
 
     /// Returns `true` if the two `Weak`s point to the same allocation similar to [`ptr::eq`], or if
-    /// both don't point to any allocation (because they were created with `Weak::new()`). See [that
-    /// function][`ptr::eq`] for caveats when comparing `dyn Trait` pointers.
+    /// both don't point to any allocation (because they were created with `Weak::new()`). However,
+    /// this function ignores the metadata of  `dyn Trait` pointers.
     ///
     /// # Notes
     ///
@@ -2298,7 +2298,7 @@ impl<T: ?Sized> Weak<T> {
     #[must_use]
     #[stable(feature = "weak_ptr_eq", since = "1.39.0")]
     pub fn ptr_eq(&self, other: &Self) -> bool {
-        self.ptr.as_ptr() == other.ptr.as_ptr()
+        ptr::eq(self.ptr.as_ptr() as *const (), other.ptr.as_ptr() as *const ())
     }
 }