From c155d5149fe49736cfb5b24eaa1c854b836019f3 Mon Sep 17 00:00:00 2001
From: Maybe Waffle <waffle.lapkin@gmail.com>
Date: Thu, 13 Apr 2023 16:45:07 +0000
Subject: [PATCH] Implement `Send`/`Sync` for `CopyTaggedPtr`

---
 .../src/tagged_ptr/copy.rs                    | 20 +++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/compiler/rustc_data_structures/src/tagged_ptr/copy.rs b/compiler/rustc_data_structures/src/tagged_ptr/copy.rs
index 02dcbd389df..68d660f48b4 100644
--- a/compiler/rustc_data_structures/src/tagged_ptr/copy.rs
+++ b/compiler/rustc_data_structures/src/tagged_ptr/copy.rs
@@ -253,6 +253,26 @@ fn hash_stable(&self, hcx: &mut HCX, hasher: &mut StableHasher) {
     }
 }
 
+// Safety:
+// `CopyTaggedPtr<P, T, ..>` is semantically just `{ ptr: P, tag: T }`, as such
+// it's ok to implement `Sync` as long as `P: Sync, T: Sync`
+unsafe impl<P, T, const CP: bool> Sync for CopyTaggedPtr<P, T, CP>
+where
+    P: Sync + Pointer,
+    T: Sync + Tag,
+{
+}
+
+// Safety:
+// `CopyTaggedPtr<P, T, ..>` is semantically just `{ ptr: P, tag: T }`, as such
+// it's ok to implement `Send` as long as `P: Send, T: Send`
+unsafe impl<P, T, const CP: bool> Send for CopyTaggedPtr<P, T, CP>
+where
+    P: Send + Pointer,
+    T: Send + Tag,
+{
+}
+
 /// Test that `new` does not compile if there is not enough alignment for the
 /// tag in the pointer.
 ///