Add diagnostic items for <*const _>::cast and <*mut _>::cast_const

Author: Urgau

core/src/ptr/const_ptr.rs

@@ -55,6 +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 _

core/src/ptr/mut_ptr.rs

@@ -112,6 +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 _