Add diagnostic items for ptr::cast_mut and ptr::from_ref

library/core/src/ptr/mod.rs

@@ -698,6 +698,7 @@ where
 #[inline(always)]
 #[must_use]
 #[unstable(feature = "ptr_from_ref", issue = "106116")]
+#[rustc_diagnostic_item = "ptr_from_ref"]
 pub const fn from_ref<T: ?Sized>(r: &T) -> *const T {
     r
 }