stabilize unstable rwlock_downgrade feature

Signed-off-by: Connor Tsui <[email protected]>

Author: connortsui20

library/std/src/sync/nonpoison/rwlock.rs

@@ -638,7 +638,6 @@ impl<'rwlock, T: ?Sized> RwLockWriteGuard<'rwlock, T> {
     ///
     /// ```
     /// #![feature(nonpoison_rwlock)]
-    /// #![feature(rwlock_downgrade)]
     ///
     /// use std::sync::nonpoison::{RwLock, RwLockWriteGuard};
     ///
@@ -657,7 +656,6 @@ impl<'rwlock, T: ?Sized> RwLockWriteGuard<'rwlock, T> {
     ///
     /// ```
     /// #![feature(nonpoison_rwlock)]
-    /// #![feature(rwlock_downgrade)]
     ///
     /// use std::sync::Arc;
     /// use std::sync::nonpoison::{RwLock, RwLockWriteGuard};
@@ -690,8 +688,7 @@ impl<'rwlock, T: ?Sized> RwLockWriteGuard<'rwlock, T> {
     /// # let final_check = rw.read();
     /// # assert_eq!(*final_check, 3);
     /// ```
-    #[unstable(feature = "rwlock_downgrade", issue = "128203")]
-    // #[unstable(feature = "nonpoison_rwlock", issue = "134645")]
+    #[unstable(feature = "nonpoison_rwlock", issue = "134645")]
     pub fn downgrade(s: Self) -> RwLockReadGuard<'rwlock, T> {
         let lock = s.lock;
 

library/std/src/sync/poison/rwlock.rs

@@ -813,8 +813,6 @@ impl<'rwlock, T: ?Sized> RwLockWriteGuard<'rwlock, T> {
     /// `downgrade` takes ownership of the `RwLockWriteGuard` and returns a [`RwLockReadGuard`].
     ///
     /// ```
-    /// #![feature(rwlock_downgrade)]
-    ///
     /// use std::sync::{RwLock, RwLockWriteGuard};
     ///
     /// let rw = RwLock::new(0);
@@ -831,8 +829,6 @@ impl<'rwlock, T: ?Sized> RwLockWriteGuard<'rwlock, T> {
     /// thread calling `downgrade` and any reads it performs after downgrading.
     ///
     /// ```
-    /// #![feature(rwlock_downgrade)]
-    ///
     /// use std::sync::{Arc, RwLock, RwLockWriteGuard};
     ///
     /// let rw = Arc::new(RwLock::new(1));
@@ -863,7 +859,7 @@ impl<'rwlock, T: ?Sized> RwLockWriteGuard<'rwlock, T> {
     /// # let final_check = rw.read().unwrap();
     /// # assert_eq!(*final_check, 3);
     /// ```
-    #[unstable(feature = "rwlock_downgrade", issue = "128203")]
+    #[stable(feature = "rwlock_downgrade", since = "CURRENT_RUSTC_VERSION")]
     pub fn downgrade(s: Self) -> RwLockReadGuard<'rwlock, T> {
         let lock = s.lock;
 

library/std/tests/sync/lib.rs

@@ -4,7 +4,6 @@
 #![feature(once_cell_try)]
 #![feature(lock_value_accessors)]
 #![feature(reentrant_lock)]
-#![feature(rwlock_downgrade)]
 #![feature(std_internals)]
 #![feature(sync_nonpoison)]
 #![feature(nonpoison_mutex)]