sync: add const constructors to RwLock, Notify, and Semaphore (#2833)

* Add const constructors to `RwLock`, `Notify`, and `Semaphore`.

Referring to the types in `tokio::sync`.
Also add `const` to `new` for the remaining atomic integers in `src/loom` and `UnsafeCell`.

Builds upon previous work in #2790
Closes #2756 

4 files changed, 4 insertions, 4 deletions

diff --git a/tokio/src/loom/std/atomic_u16.rs b/tokio/src/loom/std/atomic_u16.rs
index 70390972..c1c53120 100644
--- a/tokio/src/loom/std/atomic_u16.rs
+++ b/tokio/src/loom/std/atomic_u16.rs
@@ -11,7 +11,7 @@ unsafe impl Send for AtomicU16 {}
 unsafe impl Sync for AtomicU16 {}
 
 impl AtomicU16 {
-    pub(crate) fn new(val: u16) -> AtomicU16 {
+    pub(crate) const fn new(val: u16) -> AtomicU16 {
         let inner = UnsafeCell::new(std::sync::atomic::AtomicU16::new(val));
         AtomicU16 { inner }
     }
diff --git a/tokio/src/loom/std/atomic_u32.rs b/tokio/src/loom/std/atomic_u32.rs
index 6f786c51..61f95fb3 100644
--- a/tokio/src/loom/std/atomic_u32.rs
+++ b/tokio/src/loom/std/atomic_u32.rs
@@ -11,7 +11,7 @@ unsafe impl Send for AtomicU32 {}
 unsafe impl Sync for AtomicU32 {}
 
 impl AtomicU32 {
-    pub(crate) fn new(val: u32) -> AtomicU32 {
+    pub(crate) const fn new(val: u32) -> AtomicU32 {
         let inner = UnsafeCell::new(std::sync::atomic::AtomicU32::new(val));
         AtomicU32 { inner }
     }
diff --git a/tokio/src/loom/std/atomic_u8.rs b/tokio/src/loom/std/atomic_u8.rs
index 4fcd0df3..408aea33 100644
--- a/tokio/src/loom/std/atomic_u8.rs
+++ b/tokio/src/loom/std/atomic_u8.rs
@@ -11,7 +11,7 @@ unsafe impl Send for AtomicU8 {}
 unsafe impl Sync for AtomicU8 {}
 
 impl AtomicU8 {
-    pub(crate) fn new(val: u8) -> AtomicU8 {
+    pub(crate) const fn new(val: u8) -> AtomicU8 {
         let inner = UnsafeCell::new(std::sync::atomic::AtomicU8::new(val));
         AtomicU8 { inner }
     }
diff --git a/tokio/src/loom/std/unsafe_cell.rs b/tokio/src/loom/std/unsafe_cell.rs
index f2b03d8d..66c1d794 100644
--- a/tokio/src/loom/std/unsafe_cell.rs
+++ b/tokio/src/loom/std/unsafe_cell.rs
@@ -2,7 +2,7 @@
 pub(crate) struct UnsafeCell<T>(std::cell::UnsafeCell<T>);
 
 impl<T> UnsafeCell<T> {
-    pub(crate) fn new(data: T) -> UnsafeCell<T> {
+    pub(crate) const fn new(data: T) -> UnsafeCell<T> {
         UnsafeCell(std::cell::UnsafeCell::new(data))
     }