Make {Mutex, Condvar, RwLock}::new() const.

library/std/src/sync/condvar.rs

@@ -122,6 +122,7 @@ impl Condvar {
     /// let condvar = Condvar::new();
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[rustc_const_stable(feature = "const_locks", since = "1.63.0")]
     #[must_use]
     #[inline]
     pub const fn new() -> Condvar {

library/std/src/sync/mutex.rs

@@ -214,6 +214,7 @@ impl<T> Mutex<T> {
     /// let mutex = Mutex::new(0);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[rustc_const_stable(feature = "const_locks", since = "1.63.0")]
     #[inline]
     pub const fn new(t: T) -> Mutex<T> {
         Mutex {

library/std/src/sync/rwlock.rs

@@ -146,6 +146,7 @@ impl<T> RwLock<T> {
     /// let lock = RwLock::new(5);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[rustc_const_stable(feature = "const_locks", since = "1.63.0")]
     #[inline]
     pub const fn new(t: T) -> RwLock<T> {
         RwLock {

library/std/src/sys_common/mutex.rs

@@ -62,7 +62,7 @@ unsafe impl Sync for MovableMutex {}
 impl MovableMutex {
     /// Creates a new mutex.
     #[inline]
-    pub fn new() -> Self {
+    pub const fn new() -> Self {
         Self(imp::MovableMutex::new())
     }
 

library/std/src/sys_common/rwlock.rs

@@ -75,7 +75,7 @@ fn drop(&mut self) {
 impl MovableRwLock {
     /// Creates a new reader-writer lock for use.
     #[inline]
-    pub fn new() -> Self {
+    pub const fn new() -> Self {
         Self(imp::MovableRwLock::new())
     }