Introduce Reborrow lang item and trait

5 files changed, 14 insertions, 1 deletions

diff --git a/compiler/rustc_feature/src/unstable.rs b/compiler/rustc_feature/src/unstable.rs
index 6a7370c2472..d70d15b6815 100644
--- a/compiler/rustc_feature/src/unstable.rs
+++ b/compiler/rustc_feature/src/unstable.rs
@@ -614,7 +614,7 @@ declare_features! (
     (unstable, proc_macro_hygiene, "1.30.0", Some(54727)),
     /// Allows the use of raw-dylibs on ELF platforms
     (incomplete, raw_dylib_elf, "1.87.0", Some(135694)),
-    (unstable, reborrow, "CURRENT_RUSTC_VERSION", None),
+    (unstable, reborrow, "CURRENT_RUSTC_VERSION", Some(145612)),
     /// Makes `&` and `&mut` patterns eat only one layer of references in Rust 2024.
     (incomplete, ref_pat_eat_one_layer_2024, "1.79.0", Some(123076)),
     /// Makes `&` and `&mut` patterns eat only one layer of references in Rust 2024—structural variant
diff --git a/compiler/rustc_hir/src/lang_items.rs b/compiler/rustc_hir/src/lang_items.rs
index 905b84a8cbe..0464665b41f 100644
--- a/compiler/rustc_hir/src/lang_items.rs
+++ b/compiler/rustc_hir/src/lang_items.rs
@@ -437,6 +437,9 @@ language_item_table! {
     DefaultTrait1,           sym::default_trait1,      default_trait1_trait,       Target::Trait,          GenericRequirement::None;
 
     ContractCheckEnsures,     sym::contract_check_ensures,      contract_check_ensures_fn,      Target::Fn, GenericRequirement::None;
+
+    // Reborrowing related lang-items
+    Reborrow,                sym::reborrow,            reborrow,                   Target::Trait,          GenericRequirement::Exact(0);
 }
 
 /// The requirement imposed on the generics of a lang item
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index dcb1becc957..8465845d792 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -1754,6 +1754,7 @@ symbols! {
         readonly,
         realloc,
         reason,
+        reborrow,
         receiver,
         receiver_target,
         recursion_limit,
diff --git a/library/core/src/lib.rs b/library/core/src/lib.rs
index 71abd707374..f69d6a98592 100644
--- a/library/core/src/lib.rs
+++ b/library/core/src/lib.rs
@@ -172,6 +172,7 @@
 #![feature(no_core)]
 #![feature(optimize_attribute)]
 #![feature(prelude_import)]
+#![feature(reborrow)]
 #![feature(repr_simd)]
 #![feature(rustc_allow_const_fn_unstable)]
 #![feature(rustc_attrs)]
diff --git a/library/core/src/marker.rs b/library/core/src/marker.rs
index ba00ee17b65..8ad58599c68 100644
--- a/library/core/src/marker.rs
+++ b/library/core/src/marker.rs
@@ -1365,3 +1365,11 @@ pub macro CoercePointee($item:item) {
 pub trait CoercePointeeValidated {
     /* compiler built-in */
 }
+
+/// Allows value to be reborrowed as exclusive, creating a copy of the value
+/// that disables the source for reads and writes for the lifetime of the copy.
+#[lang = "reborrow"]
+#[unstable(feature = "reborrow", issue = "145612")]
+pub trait Reborrow {
+    // Empty.
+}