Rollup merge of #102721 - nbdd0121:panic, r=Amanieu

[rust.git] / library / core / src / ptr / mut_ptr.rs

diff --git a/library/core/src/ptr/mut_ptr.rs b/library/core/src/ptr/mut_ptr.rs
index bbcc7c699e03612e8874e0f3172d80712874b964..6764002bcd434e525fe8cc30d8f3a0f177107462 100644 (file)
--- a/library/core/src/ptr/mut_ptr.rs
+++ b/library/core/src/ptr/mut_ptr.rs
@@ -80,10 +80,14 @@ pub const fn cast<U>(self) -> *mut U {
     #[unstable(feature = "set_ptr_value", issue = "75091")]
     #[must_use = "returns a new pointer rather than modifying its argument"]
     #[inline]
-    pub fn with_metadata_of<U>(self, mut val: *mut U) -> *mut U
+    pub fn with_metadata_of<U>(self, val: *const U) -> *mut U
     where
         U: ?Sized,
     {
+        // Prepare in the type system that we will replace the pointer value with a mutable
+        // pointer, taking the mutable provenance from the `self` pointer.
+        let mut val = val as *mut U;
+        // Pointer to the pointer value within the value.
         let target = &mut val as *mut *mut U as *mut *mut u8;
         // SAFETY: In case of a thin pointer, this operations is identical
         // to a simple assignment. In case of a fat pointer, with the current
@@ -726,7 +730,7 @@ pub const fn guaranteed_eq(self, other: *mut T) -> Option<bool>
 
     /// Returns whether two pointers are guaranteed to be inequal.
     ///
-    /// At runtime this function behaves like `Some(self == other)`.
+    /// At runtime this function behaves like `Some(self != other)`.
     /// However, in some contexts (e.g., compile-time evaluation),
     /// it is not always possible to determine inequality of two pointers, so this function may
     /// spuriously return `None` for pointers that later actually turn out to have its inequality known.