Merge #141

141: Fix race::OnceBox<T>: Default to not require T: Default r=matklad a=Arnavion



Co-authored-by: Arnavion <me@arnavion.dev>

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## 1.7.1
+
+- Fix `race::OnceBox<T>` to also impl `Default` even if `T` doesn't impl `Default`.
+
 ## 1.7.0
 
 - Hide the `race` module behind (default) `race` feature.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "once_cell"
-version = "1.7.0"
+version = "1.7.1"
 authors = ["Aleksey Kladov <aleksey.kladov@gmail.com>"]
 license = "MIT OR Apache-2.0"
 edition = "2018"

src/race.rs

@@ -169,12 +169,18 @@ mod once_box {
     use alloc::boxed::Box;
 
     /// A thread-safe cell which can be written to only once.
-    #[derive(Default, Debug)]
+    #[derive(Debug)]
     pub struct OnceBox<T> {
         inner: AtomicPtr<T>,
         ghost: PhantomData<Option<Box<T>>>,
     }
 
+    impl<T> Default for OnceBox<T> {
+        fn default() -> Self {
+            Self::new()
+        }
+    }
+
     impl<T> Drop for OnceBox<T> {
         fn drop(&mut self) {
             let ptr = *self.inner.get_mut();

tests/it.rs

@@ -859,4 +859,12 @@ mod race_once_box {
         });
         assert_eq!(res, "hello");
     }
+
+    #[test]
+    fn once_box_default() {
+        struct Foo;
+
+        let cell: OnceBox<Foo> = Default::default();
+        assert!(cell.get().is_none());
+    }
 }

xtask/src/main.rs

@@ -35,6 +35,10 @@ fn try_main() -> Result<()> {
         cmd!("cargo test --features 'unstable std parking_lot' --no-default-features").run()?;
         cmd!("cargo test --features 'unstable std parking_lot' --no-default-features --release")
             .run()?;
+
+        cmd!("cargo test --features 'unstable alloc' --no-default-features --test it").run()?;
+        cmd!("cargo test --features 'unstable std parking_lot alloc' --no-default-features")
+            .run()?;
     }
 
     {