new way

crates/std/src/arena/ptr.rs

@@ -1,5 +1,32 @@
 use std::{hash::Hash, num::NonZeroU32};
 
+#[macro_export]
+#[doc(hidden)]
+macro_rules! _tags {
+    ($(
+        $(#[$outer:meta])*
+        $vis:vis enum $name:ident {
+            $($tag:ident),*
+            $(,)?
+        }
+    )*) => {$(
+        #[derive(
+            Debug,
+            Clone,
+            Copy,
+            PartialEq,
+            Eq,
+            PartialOrd,
+            Ord,
+            Hash,
+        )]
+        $(#[$outer])*
+        $vis enum $name {
+            $($tag),*
+        }
+    )*};
+}
+
 #[macro_export]
 #[doc(hidden)]
 macro_rules! _ptrs {
@@ -57,3 +84,4 @@ pub trait Ptr: Copy + Eq + Into<NonZeroU32> + From<NonZeroU32> + Hash {
 }
 
 pub use crate::_ptrs as define;
+pub use crate::_tags as tags;