From fdf8bdb7a2a8c9a06045d9648ce0ab6bcf117a6d Mon Sep 17 00:00:00 2001
From: bjorn3 <17426603+bjorn3@users.noreply.github.com>
Date: Sun, 20 Jul 2025 09:50:58 +0000
Subject: [PATCH 1/2] Remove the ptr_unique lang item

Miri no longer uses it.
---
 compiler/rustc_hir/src/lang_items.rs | 3 ---
 compiler/rustc_span/src/symbol.rs    | 1 -
 library/core/src/ptr/unique.rs       | 2 --
 3 files changed, 6 deletions(-)

diff --git a/compiler/rustc_hir/src/lang_items.rs b/compiler/rustc_hir/src/lang_items.rs
index 6347f1bfa714d..75c04b23ed6e8 100644
--- a/compiler/rustc_hir/src/lang_items.rs
+++ b/compiler/rustc_hir/src/lang_items.rs
@@ -345,9 +345,6 @@ language_item_table! {
     OwnedBox,                sym::owned_box,           owned_box,                  Target::Struct,         GenericRequirement::Minimum(1);
     GlobalAlloc,             sym::global_alloc_ty,     global_alloc_ty,            Target::Struct,         GenericRequirement::None;
 
-    // Experimental lang item for Miri
-    PtrUnique,               sym::ptr_unique,          ptr_unique,                 Target::Struct,         GenericRequirement::Exact(1);
-
     PhantomData,             sym::phantom_data,        phantom_data,               Target::Struct,         GenericRequirement::Exact(1);
 
     ManuallyDrop,            sym::manually_drop,       manually_drop,              Target::Struct,         GenericRequirement::None;
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index d28a73bc13978..d0d09862ade29 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -1698,7 +1698,6 @@ symbols! {
         ptr_slice_from_raw_parts_mut,
         ptr_swap,
         ptr_swap_nonoverlapping,
-        ptr_unique,
         ptr_write,
         ptr_write_bytes,
         ptr_write_unaligned,
diff --git a/library/core/src/ptr/unique.rs b/library/core/src/ptr/unique.rs
index c069314ff7d23..e9e13f9e97f84 100644
--- a/library/core/src/ptr/unique.rs
+++ b/library/core/src/ptr/unique.rs
@@ -32,8 +32,6 @@ use crate::ptr::NonNull;
 )]
 #[doc(hidden)]
 #[repr(transparent)]
-// Lang item used experimentally by Miri to define the semantics of `Unique`.
-#[lang = "ptr_unique"]
 pub struct Unique<T: PointeeSized> {
     pointer: NonNull<T>,
     // NOTE: this marker has no consequences for variance, but is necessary

From 1fd06975d0ea9d78d0b611ab292df7a121116501 Mon Sep 17 00:00:00 2001
From: bjorn3 <17426603+bjorn3@users.noreply.github.com>
Date: Mon, 21 Jul 2025 07:57:11 +0000
Subject: [PATCH 2/2] Remove Retag for Unique

---
 compiler/rustc_mir_transform/src/add_retag.rs | 2 --
 1 file changed, 2 deletions(-)

diff --git a/compiler/rustc_mir_transform/src/add_retag.rs b/compiler/rustc_mir_transform/src/add_retag.rs
index 3c29d4624b73c..fc08c1df8703a 100644
--- a/compiler/rustc_mir_transform/src/add_retag.rs
+++ b/compiler/rustc_mir_transform/src/add_retag.rs
@@ -4,7 +4,6 @@
 //! of MIR building, and only after this pass we think of the program has having the
 //! normal MIR semantics.
 
-use rustc_hir::LangItem;
 use rustc_middle::mir::*;
 use rustc_middle::ty::{self, Ty, TyCtxt};
 
@@ -28,7 +27,6 @@ fn may_contain_reference<'tcx>(ty: Ty<'tcx>, depth: u32, tcx: TyCtxt<'tcx>) -> b
         // References and Boxes (`noalias` sources)
         ty::Ref(..) => true,
         ty::Adt(..) if ty.is_box() => true,
-        ty::Adt(adt, _) if tcx.is_lang_item(adt.did(), LangItem::PtrUnique) => true,
         // Compound types: recurse
         ty::Array(ty, _) | ty::Slice(ty) => {
             // This does not branch so we keep the depth the same.