Auto merge of #133223 - zachs18:uniquerc-impls, r=Noratrieb

`UniqueRc` trait impls

UniqueRc tracking Issue: #112566

Stable traits: (i.e. impls behind only the `unique_rc_arc` feature gate)

* Support the same formatting as `Rc`:
  * `fmt::Debug` and `fmt::Display` delegate to the pointee.
  * `fmt::Pointer` prints the address of the pointee.
* Add explicit `!Send` and `!Sync` impls, to mirror `Rc`.
* Borrowing traits: `Borrow`, `BorrowMut`, `AsRef`, `AsMut`
  * `Rc` does not implement `BorrowMut` and `AsMut`, but `UniqueRc` can.
* Unconditional `Unpin`, like other heap-allocated types.
* Comparison traits `(Partial)Ord` and `(Partial)Eq` delegate to the pointees.
  * `PartialEq for UniqueRc` does not do `Rc`'s specialization shortcut for pointer equality when `T: Eq`, since by definition two `UniqueRc`s cannot share an allocation.
* `Hash` delegates to the pointee.
* `AsRawFd`, `AsFd`, `AsHandle`, `AsSocket` delegate to the pointee like `Rc`.
  * Sidenote: The bounds on `T` for the existing `Pointer<T>` impls for specifically `AsRawFd` and `AsSocket` do not allow `T: ?Sized`. For the added `UniqueRc` impls I allowed `T: ?Sized` for all four traits, but I did not change the existing (stable) impls.

Unstable traits:
* `DispatchFromDyn`, allows using `UniqueRc<Self>` as a method receiver under `feature(arbitrary_self_types)`.
* Existing `PinCoerceUnsized for UniqueRc` is generalized to allow non-`Global` allocators, like `Rc`.
* `DerefPure`, allows using `UniqueRc` in deref-patterns under `feature(deref_patterns)`, like `Rc`.

For documentation, `Rc` only has documentation on the comparison traits' methods, so I copied/adapted the documentation for those, and left the rest without impl-specific docs.

~~Edit: Marked as draft while I figure out `UnwindSafe`.~~
Edit: Ignoring `UnwindSafe` for this PR

1 files changed, 249 insertions, 4 deletions

diff --git a/library/alloc/src/rc.rs b/library/alloc/src/rc.rs
index 7aa1457b1df..bb27fe3c62d 100644
--- a/library/alloc/src/rc.rs
+++ b/library/alloc/src/rc.rs
@@ -2232,12 +2232,20 @@ impl<T: ?Sized, A: Allocator> Deref for Rc<T, A> {
 #[unstable(feature = "pin_coerce_unsized_trait", issue = "123430")]
 unsafe impl<T: ?Sized, A: Allocator> PinCoerceUnsized for Rc<T, A> {}
 
+//#[unstable(feature = "unique_rc_arc", issue = "112566")]
+#[unstable(feature = "pin_coerce_unsized_trait", issue = "123430")]
+unsafe impl<T: ?Sized, A: Allocator> PinCoerceUnsized for UniqueRc<T, A> {}
+
 #[unstable(feature = "pin_coerce_unsized_trait", issue = "123430")]
 unsafe impl<T: ?Sized, A: Allocator> PinCoerceUnsized for Weak<T, A> {}
 
 #[unstable(feature = "deref_pure_trait", issue = "87121")]
 unsafe impl<T: ?Sized, A: Allocator> DerefPure for Rc<T, A> {}
 
+//#[unstable(feature = "unique_rc_arc", issue = "112566")]
+#[unstable(feature = "deref_pure_trait", issue = "87121")]
+unsafe impl<T: ?Sized, A: Allocator> DerefPure for UniqueRc<T, A> {}
+
 #[unstable(feature = "legacy_receiver_trait", issue = "none")]
 impl<T: ?Sized> LegacyReceiver for Rc<T> {}
 
@@ -3684,7 +3692,6 @@ fn data_offset_align(align: usize) -> usize {
 /// previous example, `UniqueRc` allows for more flexibility in the construction of cyclic data,
 /// including fallible or async constructors.
 #[unstable(feature = "unique_rc_arc", issue = "112566")]
-#[derive(Debug)]
 pub struct UniqueRc<
     T: ?Sized,
     #[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
@@ -3694,12 +3701,253 @@ pub struct UniqueRc<
     alloc: A,
 }
 
+// Not necessary for correctness since `UniqueRc` contains `NonNull`,
+// but having an explicit negative impl is nice for documentation purposes
+// and results in nicer error messages.
+#[unstable(feature = "unique_rc_arc", issue = "112566")]
+impl<T: ?Sized, A: Allocator> !Send for UniqueRc<T, A> {}
+
+// Not necessary for correctness since `UniqueRc` contains `NonNull`,
+// but having an explicit negative impl is nice for documentation purposes
+// and results in nicer error messages.
+#[unstable(feature = "unique_rc_arc", issue = "112566")]
+impl<T: ?Sized, A: Allocator> !Sync for UniqueRc<T, A> {}
+
 #[unstable(feature = "unique_rc_arc", issue = "112566")]
 impl<T: ?Sized + Unsize<U>, U: ?Sized, A: Allocator> CoerceUnsized<UniqueRc<U, A>>
     for UniqueRc<T, A>
 {
 }
 
+//#[unstable(feature = "unique_rc_arc", issue = "112566")]
+#[unstable(feature = "dispatch_from_dyn", issue = "none")]
+impl<T: ?Sized + Unsize<U>, U: ?Sized> DispatchFromDyn<UniqueRc<U>> for UniqueRc<T> {}
+
+#[unstable(feature = "unique_rc_arc", issue = "112566")]
+impl<T: ?Sized + fmt::Display, A: Allocator> fmt::Display for UniqueRc<T, A> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Display::fmt(&**self, f)
+    }
+}
+
+#[unstable(feature = "unique_rc_arc", issue = "112566")]
+impl<T: ?Sized + fmt::Debug, A: Allocator> fmt::Debug for UniqueRc<T, A> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Debug::fmt(&**self, f)
+    }
+}
+
+#[unstable(feature = "unique_rc_arc", issue = "112566")]
+impl<T: ?Sized, A: Allocator> fmt::Pointer for UniqueRc<T, A> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Pointer::fmt(&(&raw const **self), f)
+    }
+}
+
+#[unstable(feature = "unique_rc_arc", issue = "112566")]
+impl<T: ?Sized, A: Allocator> borrow::Borrow<T> for UniqueRc<T, A> {
+    fn borrow(&self) -> &T {
+        &**self
+    }
+}
+
+#[unstable(feature = "unique_rc_arc", issue = "112566")]
+impl<T: ?Sized, A: Allocator> borrow::BorrowMut<T> for UniqueRc<T, A> {
+    fn borrow_mut(&mut self) -> &mut T {
+        &mut **self
+    }
+}
+
+#[unstable(feature = "unique_rc_arc", issue = "112566")]
+impl<T: ?Sized, A: Allocator> AsRef<T> for UniqueRc<T, A> {
+    fn as_ref(&self) -> &T {
+        &**self
+    }
+}
+
+#[unstable(feature = "unique_rc_arc", issue = "112566")]
+impl<T: ?Sized, A: Allocator> AsMut<T> for UniqueRc<T, A> {
+    fn as_mut(&mut self) -> &mut T {
+        &mut **self
+    }
+}
+
+#[unstable(feature = "unique_rc_arc", issue = "112566")]
+impl<T: ?Sized, A: Allocator> Unpin for UniqueRc<T, A> {}
+
+#[unstable(feature = "unique_rc_arc", issue = "112566")]
+impl<T: ?Sized + PartialEq, A: Allocator> PartialEq for UniqueRc<T, A> {
+    /// Equality for two `UniqueRc`s.
+    ///
+    /// Two `UniqueRc`s are equal if their inner values are equal.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(unique_rc_arc)]
+    /// use std::rc::UniqueRc;
+    ///
+    /// let five = UniqueRc::new(5);
+    ///
+    /// assert!(five == UniqueRc::new(5));
+    /// ```
+    #[inline]
+    fn eq(&self, other: &Self) -> bool {
+        PartialEq::eq(&**self, &**other)
+    }
+
+    /// Inequality for two `UniqueRc`s.
+    ///
+    /// Two `UniqueRc`s are not equal if their inner values are not equal.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(unique_rc_arc)]
+    /// use std::rc::UniqueRc;
+    ///
+    /// let five = UniqueRc::new(5);
+    ///
+    /// assert!(five != UniqueRc::new(6));
+    /// ```
+    #[inline]
+    fn ne(&self, other: &Self) -> bool {
+        PartialEq::ne(&**self, &**other)
+    }
+}
+
+#[unstable(feature = "unique_rc_arc", issue = "112566")]
+impl<T: ?Sized + PartialOrd, A: Allocator> PartialOrd for UniqueRc<T, A> {
+    /// Partial comparison for two `UniqueRc`s.
+    ///
+    /// The two are compared by calling `partial_cmp()` on their inner values.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(unique_rc_arc)]
+    /// use std::rc::UniqueRc;
+    /// use std::cmp::Ordering;
+    ///
+    /// let five = UniqueRc::new(5);
+    ///
+    /// assert_eq!(Some(Ordering::Less), five.partial_cmp(&UniqueRc::new(6)));
+    /// ```
+    #[inline(always)]
+    fn partial_cmp(&self, other: &UniqueRc<T, A>) -> Option<Ordering> {
+        (**self).partial_cmp(&**other)
+    }
+
+    /// Less-than comparison for two `UniqueRc`s.
+    ///
+    /// The two are compared by calling `<` on their inner values.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(unique_rc_arc)]
+    /// use std::rc::UniqueRc;
+    ///
+    /// let five = UniqueRc::new(5);
+    ///
+    /// assert!(five < UniqueRc::new(6));
+    /// ```
+    #[inline(always)]
+    fn lt(&self, other: &UniqueRc<T, A>) -> bool {
+        **self < **other
+    }
+
+    /// 'Less than or equal to' comparison for two `UniqueRc`s.
+    ///
+    /// The two are compared by calling `<=` on their inner values.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(unique_rc_arc)]
+    /// use std::rc::UniqueRc;
+    ///
+    /// let five = UniqueRc::new(5);
+    ///
+    /// assert!(five <= UniqueRc::new(5));
+    /// ```
+    #[inline(always)]
+    fn le(&self, other: &UniqueRc<T, A>) -> bool {
+        **self <= **other
+    }
+
+    /// Greater-than comparison for two `UniqueRc`s.
+    ///
+    /// The two are compared by calling `>` on their inner values.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(unique_rc_arc)]
+    /// use std::rc::UniqueRc;
+    ///
+    /// let five = UniqueRc::new(5);
+    ///
+    /// assert!(five > UniqueRc::new(4));
+    /// ```
+    #[inline(always)]
+    fn gt(&self, other: &UniqueRc<T, A>) -> bool {
+        **self > **other
+    }
+
+    /// 'Greater than or equal to' comparison for two `UniqueRc`s.
+    ///
+    /// The two are compared by calling `>=` on their inner values.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(unique_rc_arc)]
+    /// use std::rc::UniqueRc;
+    ///
+    /// let five = UniqueRc::new(5);
+    ///
+    /// assert!(five >= UniqueRc::new(5));
+    /// ```
+    #[inline(always)]
+    fn ge(&self, other: &UniqueRc<T, A>) -> bool {
+        **self >= **other
+    }
+}
+
+#[unstable(feature = "unique_rc_arc", issue = "112566")]
+impl<T: ?Sized + Ord, A: Allocator> Ord for UniqueRc<T, A> {
+    /// Comparison for two `UniqueRc`s.
+    ///
+    /// The two are compared by calling `cmp()` on their inner values.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(unique_rc_arc)]
+    /// use std::rc::UniqueRc;
+    /// use std::cmp::Ordering;
+    ///
+    /// let five = UniqueRc::new(5);
+    ///
+    /// assert_eq!(Ordering::Less, five.cmp(&UniqueRc::new(6)));
+    /// ```
+    #[inline]
+    fn cmp(&self, other: &UniqueRc<T, A>) -> Ordering {
+        (**self).cmp(&**other)
+    }
+}
+
+#[unstable(feature = "unique_rc_arc", issue = "112566")]
+impl<T: ?Sized + Eq, A: Allocator> Eq for UniqueRc<T, A> {}
+
+#[unstable(feature = "unique_rc_arc", issue = "112566")]
+impl<T: ?Sized + Hash, A: Allocator> Hash for UniqueRc<T, A> {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        (**self).hash(state);
+    }
+}
+
 // Depends on A = Global
 impl<T> UniqueRc<T> {
     /// Creates a new `UniqueRc`.
@@ -3791,9 +4039,6 @@ impl<T: ?Sized, A: Allocator> Deref for UniqueRc<T, A> {
     }
 }
 
-#[unstable(feature = "pin_coerce_unsized_trait", issue = "123430")]
-unsafe impl<T: ?Sized> PinCoerceUnsized for UniqueRc<T> {}
-
 #[unstable(feature = "unique_rc_arc", issue = "112566")]
 impl<T: ?Sized, A: Allocator> DerefMut for UniqueRc<T, A> {
     fn deref_mut(&mut self) -> &mut T {