Rollup merge of #134797 - spastorino:ergonomic-ref-counting-1, r=nikomatsakis

Ergonomic ref counting

This is an experimental first version of ergonomic ref counting.

This first version implements most of the RFC but doesn't implement any of the optimizations. This was left for following iterations.

RFC: https://github.com/rust-lang/rfcs/pull/3680
Tracking issue: https://github.com/rust-lang/rust/issues/132290
Project goal: https://github.com/rust-lang/rust-project-goals/issues/107

r? ```@nikomatsakis```

3 files changed, 16 insertions, 0 deletions

diff --git a/library/alloc/src/lib.rs b/library/alloc/src/lib.rs
index cb93100f56c..265b68d3b0e 100644
--- a/library/alloc/src/lib.rs
+++ b/library/alloc/src/lib.rs
@@ -56,6 +56,7 @@
 //! [`Rc`]: rc
 //! [`RefCell`]: core::cell
 
+#![allow(incomplete_features)]
 #![allow(unused_attributes)]
 #![stable(feature = "alloc", since = "1.36.0")]
 #![doc(
@@ -113,6 +114,7 @@
 #![feature(deprecated_suggestion)]
 #![feature(deref_pure_trait)]
 #![feature(dispatch_from_dyn)]
+#![feature(ergonomic_clones)]
 #![feature(error_generic_member_access)]
 #![feature(exact_size_is_empty)]
 #![feature(extend_one)]
diff --git a/library/alloc/src/rc.rs b/library/alloc/src/rc.rs
index 09206c2f8b2..5847bd8f281 100644
--- a/library/alloc/src/rc.rs
+++ b/library/alloc/src/rc.rs
@@ -245,6 +245,7 @@ use core::any::Any;
 use core::cell::Cell;
 #[cfg(not(no_global_oom_handling))]
 use core::clone::CloneToUninit;
+use core::clone::UseCloned;
 use core::cmp::Ordering;
 use core::hash::{Hash, Hasher};
 use core::intrinsics::abort;
@@ -2333,6 +2334,9 @@ impl<T: ?Sized, A: Allocator + Clone> Clone for Rc<T, A> {
     }
 }
 
+#[unstable(feature = "ergonomic_clones", issue = "132290")]
+impl<T: ?Sized, A: Allocator + Clone> UseCloned for Rc<T, A> {}
+
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: Default> Default for Rc<T> {
@@ -3496,6 +3500,9 @@ impl<T: ?Sized, A: Allocator + Clone> Clone for Weak<T, A> {
     }
 }
 
+#[unstable(feature = "ergonomic_clones", issue = "132290")]
+impl<T: ?Sized, A: Allocator + Clone> UseCloned for Weak<T, A> {}
+
 #[stable(feature = "rc_weak", since = "1.4.0")]
 impl<T: ?Sized, A: Allocator> fmt::Debug for Weak<T, A> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
diff --git a/library/alloc/src/sync.rs b/library/alloc/src/sync.rs
index 1956dda5388..21ee59cc538 100644
--- a/library/alloc/src/sync.rs
+++ b/library/alloc/src/sync.rs
@@ -11,6 +11,7 @@
 use core::any::Any;
 #[cfg(not(no_global_oom_handling))]
 use core::clone::CloneToUninit;
+use core::clone::UseCloned;
 use core::cmp::Ordering;
 use core::hash::{Hash, Hasher};
 use core::intrinsics::abort;
@@ -2197,6 +2198,9 @@ impl<T: ?Sized, A: Allocator + Clone> Clone for Arc<T, A> {
     }
 }
 
+#[unstable(feature = "ergonomic_clones", issue = "132290")]
+impl<T: ?Sized, A: Allocator + Clone> UseCloned for Arc<T, A> {}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: ?Sized, A: Allocator> Deref for Arc<T, A> {
     type Target = T;
@@ -3158,6 +3162,9 @@ impl<T: ?Sized, A: Allocator + Clone> Clone for Weak<T, A> {
     }
 }
 
+#[unstable(feature = "ergonomic_clones", issue = "132290")]
+impl<T: ?Sized, A: Allocator + Clone> UseCloned for Weak<T, A> {}
+
 #[stable(feature = "downgraded_weak", since = "1.10.0")]
 impl<T> Default for Weak<T> {
     /// Constructs a new `Weak<T>`, without allocating memory.