1 files changed, 977 insertions, 0 deletions
diff --git a/third_party/rust/once_cell/tests/it.rs b/third_party/rust/once_cell/tests/it.rs
new file mode 100644
index 0000000000..d18f0a1654
--- /dev/null
+++ b/third_party/rust/once_cell/tests/it.rs
@@ -0,0 +1,977 @@
+mod unsync {
+    use core::{
+        cell::Cell,
+        sync::atomic::{AtomicUsize, Ordering::SeqCst},
+    };
+
+    use once_cell::unsync::{Lazy, OnceCell};
+
+    #[test]
+    fn once_cell() {
+        let c = OnceCell::new();
+        assert!(c.get().is_none());
+        c.get_or_init(|| 92);
+        assert_eq!(c.get(), Some(&92));
+
+        c.get_or_init(|| panic!("Kabom!"));
+        assert_eq!(c.get(), Some(&92));
+    }
+
+    #[test]
+    fn once_cell_with_value() {
+        const CELL: OnceCell<i32> = OnceCell::with_value(12);
+        let cell = CELL;
+        assert_eq!(cell.get(), Some(&12));
+    }
+
+    #[test]
+    fn once_cell_get_mut() {
+        let mut c = OnceCell::new();
+        assert!(c.get_mut().is_none());
+        c.set(90).unwrap();
+        *c.get_mut().unwrap() += 2;
+        assert_eq!(c.get_mut(), Some(&mut 92));
+    }
+
+    #[test]
+    fn once_cell_drop() {
+        static DROP_CNT: AtomicUsize = AtomicUsize::new(0);
+        struct Dropper;
+        impl Drop for Dropper {
+            fn drop(&mut self) {
+                DROP_CNT.fetch_add(1, SeqCst);
+            }
+        }
+
+        let x = OnceCell::new();
+        x.get_or_init(|| Dropper);
+        assert_eq!(DROP_CNT.load(SeqCst), 0);
+        drop(x);
+        assert_eq!(DROP_CNT.load(SeqCst), 1);
+    }
+
+    #[test]
+    fn unsync_once_cell_drop_empty() {
+        let x = OnceCell::<String>::new();
+        drop(x);
+    }
+
+    #[test]
+    fn clone() {
+        let s = OnceCell::new();
+        let c = s.clone();
+        assert!(c.get().is_none());
+
+        s.set("hello".to_string()).unwrap();
+        let c = s.clone();
+        assert_eq!(c.get().map(String::as_str), Some("hello"));
+    }
+
+    #[test]
+    fn from_impl() {
+        assert_eq!(OnceCell::from("value").get(), Some(&"value"));
+        assert_ne!(OnceCell::from("foo").get(), Some(&"bar"));
+    }
+
+    #[test]
+    fn partialeq_impl() {
+        assert!(OnceCell::from("value") == OnceCell::from("value"));
+        assert!(OnceCell::from("foo") != OnceCell::from("bar"));
+
+        assert!(OnceCell::<String>::new() == OnceCell::new());
+        assert!(OnceCell::<String>::new() != OnceCell::from("value".to_owned()));
+    }
+
+    #[test]
+    fn into_inner() {
+        let cell: OnceCell<String> = OnceCell::new();
+        assert_eq!(cell.into_inner(), None);
+        let cell = OnceCell::new();
+        cell.set("hello".to_string()).unwrap();
+        assert_eq!(cell.into_inner(), Some("hello".to_string()));
+    }
+
+    #[test]
+    fn debug_impl() {
+        let cell = OnceCell::new();
+        assert_eq!(format!("{:?}", cell), "OnceCell(Uninit)");
+        cell.set("hello".to_string()).unwrap();
+        assert_eq!(format!("{:?}", cell), "OnceCell(\"hello\")");
+    }
+
+    #[test]
+    fn lazy_new() {
+        let called = Cell::new(0);
+        let x = Lazy::new(|| {
+            called.set(called.get() + 1);
+            92
+        });
+
+        assert_eq!(called.get(), 0);
+
+        let y = *x - 30;
+        assert_eq!(y, 62);
+        assert_eq!(called.get(), 1);
+
+        let y = *x - 30;
+        assert_eq!(y, 62);
+        assert_eq!(called.get(), 1);
+    }
+
+    #[test]
+    fn lazy_deref_mut() {
+        let called = Cell::new(0);
+        let mut x = Lazy::new(|| {
+            called.set(called.get() + 1);
+            92
+        });
+
+        assert_eq!(called.get(), 0);
+
+        let y = *x - 30;
+        assert_eq!(y, 62);
+        assert_eq!(called.get(), 1);
+
+        *x /= 2;
+        assert_eq!(*x, 46);
+        assert_eq!(called.get(), 1);
+    }
+
+    #[test]
+    fn lazy_force_mut() {
+        let called = Cell::new(0);
+        let mut x = Lazy::new(|| {
+            called.set(called.get() + 1);
+            92
+        });
+        assert_eq!(called.get(), 0);
+        let v = Lazy::force_mut(&mut x);
+        assert_eq!(called.get(), 1);
+
+        *v /= 2;
+        assert_eq!(*x, 46);
+        assert_eq!(called.get(), 1);
+    }
+
+    #[test]
+    fn lazy_get_mut() {
+        let called = Cell::new(0);
+        let mut x: Lazy<u32, _> = Lazy::new(|| {
+            called.set(called.get() + 1);
+            92
+        });
+
+        assert_eq!(called.get(), 0);
+        assert_eq!(*x, 92);
+
+        let mut_ref: &mut u32 = Lazy::get_mut(&mut x).unwrap();
+        assert_eq!(called.get(), 1);
+
+        *mut_ref /= 2;
+        assert_eq!(*x, 46);
+        assert_eq!(called.get(), 1);
+    }
+
+    #[test]
+    fn lazy_default() {
+        static CALLED: AtomicUsize = AtomicUsize::new(0);
+
+        struct Foo(u8);
+        impl Default for Foo {
+            fn default() -> Self {
+                CALLED.fetch_add(1, SeqCst);
+                Foo(42)
+            }
+        }
+
+        let lazy: Lazy<std::sync::Mutex<Foo>> = <_>::default();
+
+        assert_eq!(CALLED.load(SeqCst), 0);
+
+        assert_eq!(lazy.lock().unwrap().0, 42);
+        assert_eq!(CALLED.load(SeqCst), 1);
+
+        lazy.lock().unwrap().0 = 21;
+
+        assert_eq!(lazy.lock().unwrap().0, 21);
+        assert_eq!(CALLED.load(SeqCst), 1);
+    }
+
+    #[test]
+    fn lazy_into_value() {
+        let l: Lazy<i32, _> = Lazy::new(|| panic!());
+        assert!(matches!(Lazy::into_value(l), Err(_)));
+        let l = Lazy::new(|| -> i32 { 92 });
+        Lazy::force(&l);
+        assert!(matches!(Lazy::into_value(l), Ok(92)));
+    }
+
+    #[test]
+    #[cfg(feature = "std")]
+    fn lazy_poisoning() {
+        let x: Lazy<String> = Lazy::new(|| panic!("kaboom"));
+        for _ in 0..2 {
+            let res = std::panic::catch_unwind(|| x.len());
+            assert!(res.is_err());
+        }
+    }
+
+    #[test]
+    fn aliasing_in_get() {
+        let x = OnceCell::new();
+        x.set(42).unwrap();
+        let at_x = x.get().unwrap(); // --- (shared) borrow of inner `Option<T>` --+
+        let _ = x.set(27); // <-- temporary (unique) borrow of inner `Option<T>`   |
+        println!("{}", at_x); // <------- up until here ---------------------------+
+    }
+
+    #[test]
+    #[should_panic(expected = "reentrant init")]
+    fn reentrant_init() {
+        let x: OnceCell<Box<i32>> = OnceCell::new();
+        let dangling_ref: Cell<Option<&i32>> = Cell::new(None);
+        x.get_or_init(|| {
+            let r = x.get_or_init(|| Box::new(92));
+            dangling_ref.set(Some(r));
+            Box::new(62)
+        });
+        eprintln!("use after free: {:?}", dangling_ref.get().unwrap());
+    }
+
+    #[test]
+    // https://github.com/rust-lang/rust/issues/34761#issuecomment-256320669
+    fn arrrrrrrrrrrrrrrrrrrrrr() {
+        let cell = OnceCell::new();
+        {
+            let s = String::new();
+            cell.set(&s).unwrap();
+        }
+    }
+}
+
+#[cfg(any(feature = "std", feature = "critical-section"))]
+mod sync {
+    use std::sync::atomic::{AtomicUsize, Ordering::SeqCst};
+
+    #[cfg(feature = "std")]
+    use std::sync::Barrier;
+
+    #[cfg(not(feature = "std"))]
+    use core::cell::Cell;
+
+    use crossbeam_utils::thread::scope;
+
+    use once_cell::sync::{Lazy, OnceCell};
+
+    #[test]
+    fn once_cell() {
+        let c = OnceCell::new();
+        assert!(c.get().is_none());
+        scope(|s| {
+            s.spawn(|_| {
+                c.get_or_init(|| 92);
+                assert_eq!(c.get(), Some(&92));
+            });
+        })
+        .unwrap();
+        c.get_or_init(|| panic!("Kabom!"));
+        assert_eq!(c.get(), Some(&92));
+    }
+
+    #[test]
+    fn once_cell_with_value() {
+        static CELL: OnceCell<i32> = OnceCell::with_value(12);
+        assert_eq!(CELL.get(), Some(&12));
+    }
+
+    #[test]
+    fn once_cell_get_mut() {
+        let mut c = OnceCell::new();
+        assert!(c.get_mut().is_none());
+        c.set(90).unwrap();
+        *c.get_mut().unwrap() += 2;
+        assert_eq!(c.get_mut(), Some(&mut 92));
+    }
+
+    #[test]
+    fn once_cell_get_unchecked() {
+        let c = OnceCell::new();
+        c.set(92).unwrap();
+        unsafe {
+            assert_eq!(c.get_unchecked(), &92);
+        }
+    }
+
+    #[test]
+    fn once_cell_drop() {
+        static DROP_CNT: AtomicUsize = AtomicUsize::new(0);
+        struct Dropper;
+        impl Drop for Dropper {
+            fn drop(&mut self) {
+                DROP_CNT.fetch_add(1, SeqCst);
+            }
+        }
+
+        let x = OnceCell::new();
+        scope(|s| {
+            s.spawn(|_| {
+                x.get_or_init(|| Dropper);
+                assert_eq!(DROP_CNT.load(SeqCst), 0);
+                drop(x);
+            });
+        })
+        .unwrap();
+        assert_eq!(DROP_CNT.load(SeqCst), 1);
+    }
+
+    #[test]
+    fn once_cell_drop_empty() {
+        let x = OnceCell::<String>::new();
+        drop(x);
+    }
+
+    #[test]
+    fn clone() {
+        let s = OnceCell::new();
+        let c = s.clone();
+        assert!(c.get().is_none());
+
+        s.set("hello".to_string()).unwrap();
+        let c = s.clone();
+        assert_eq!(c.get().map(String::as_str), Some("hello"));
+    }
+
+    #[test]
+    fn get_or_try_init() {
+        let cell: OnceCell<String> = OnceCell::new();
+        assert!(cell.get().is_none());
+
+        let res =
+            std::panic::catch_unwind(|| cell.get_or_try_init(|| -> Result<_, ()> { panic!() }));
+        assert!(res.is_err());
+        assert!(cell.get().is_none());
+
+        assert_eq!(cell.get_or_try_init(|| Err(())), Err(()));
+
+        assert_eq!(
+            cell.get_or_try_init(|| Ok::<_, ()>("hello".to_string())),
+            Ok(&"hello".to_string())
+        );
+        assert_eq!(cell.get(), Some(&"hello".to_string()));
+    }
+
+    #[cfg(feature = "std")]
+    #[test]
+    fn wait() {
+        let cell: OnceCell<String> = OnceCell::new();
+        scope(|s| {
+            s.spawn(|_| cell.set("hello".to_string()));
+            let greeting = cell.wait();
+            assert_eq!(greeting, "hello")
+        })
+        .unwrap();
+    }
+
+    #[cfg(feature = "std")]
+    #[test]
+    fn get_or_init_stress() {
+        let n_threads = if cfg!(miri) { 30 } else { 1_000 };
+        let n_cells = if cfg!(miri) { 30 } else { 1_000 };
+        let cells: Vec<_> = std::iter::repeat_with(|| (Barrier::new(n_threads), OnceCell::new()))
+            .take(n_cells)
+            .collect();
+        scope(|s| {
+            for t in 0..n_threads {
+                let cells = &cells;
+                s.spawn(move |_| {
+                    for (i, (b, s)) in cells.iter().enumerate() {
+                        b.wait();
+                        let j = if t % 2 == 0 { s.wait() } else { s.get_or_init(|| i) };
+                        assert_eq!(*j, i);
+                    }
+                });
+            }
+        })
+        .unwrap();
+    }
+
+    #[test]
+    fn from_impl() {
+        assert_eq!(OnceCell::from("value").get(), Some(&"value"));
+        assert_ne!(OnceCell::from("foo").get(), Some(&"bar"));
+    }
+
+    #[test]
+    fn partialeq_impl() {
+        assert!(OnceCell::from("value") == OnceCell::from("value"));
+        assert!(OnceCell::from("foo") != OnceCell::from("bar"));
+
+        assert!(OnceCell::<String>::new() == OnceCell::new());
+        assert!(OnceCell::<String>::new() != OnceCell::from("value".to_owned()));
+    }
+
+    #[test]
+    fn into_inner() {
+        let cell: OnceCell<String> = OnceCell::new();
+        assert_eq!(cell.into_inner(), None);
+        let cell = OnceCell::new();
+        cell.set("hello".to_string()).unwrap();
+        assert_eq!(cell.into_inner(), Some("hello".to_string()));
+    }
+
+    #[test]
+    fn debug_impl() {
+        let cell = OnceCell::new();
+        assert_eq!(format!("{:#?}", cell), "OnceCell(Uninit)");
+        cell.set(vec!["hello", "world"]).unwrap();
+        assert_eq!(
+            format!("{:#?}", cell),
+            r#"OnceCell(
+    [
+        "hello",
+        "world",
+    ],
+)"#
+        );
+    }
+
+    #[test]
+    #[cfg_attr(miri, ignore)] // miri doesn't support processes
+    #[cfg(feature = "std")]
+    fn reentrant_init() {
+        let examples_dir = {
+            let mut exe = std::env::current_exe().unwrap();
+            exe.pop();
+            exe.pop();
+            exe.push("examples");
+            exe
+        };
+        let bin = examples_dir
+            .join("reentrant_init_deadlocks")
+            .with_extension(std::env::consts::EXE_EXTENSION);
+        let mut guard = Guard { child: std::process::Command::new(bin).spawn().unwrap() };
+        std::thread::sleep(std::time::Duration::from_secs(2));
+        let status = guard.child.try_wait().unwrap();
+        assert!(status.is_none());
+
+        struct Guard {
+            child: std::process::Child,
+        }
+
+        impl Drop for Guard {
+            fn drop(&mut self) {
+                let _ = self.child.kill();
+            }
+        }
+    }
+
+    #[cfg(not(feature = "std"))]
+    #[test]
+    #[should_panic(expected = "reentrant init")]
+    fn reentrant_init() {
+        let x: OnceCell<Box<i32>> = OnceCell::new();
+        let dangling_ref: Cell<Option<&i32>> = Cell::new(None);
+        x.get_or_init(|| {
+            let r = x.get_or_init(|| Box::new(92));
+            dangling_ref.set(Some(r));
+            Box::new(62)
+        });
+        eprintln!("use after free: {:?}", dangling_ref.get().unwrap());
+    }
+
+    #[test]
+    fn lazy_new() {
+        let called = AtomicUsize::new(0);
+        let x = Lazy::new(|| {
+            called.fetch_add(1, SeqCst);
+            92
+        });
+
+        assert_eq!(called.load(SeqCst), 0);
+
+        scope(|s| {
+            s.spawn(|_| {
+                let y = *x - 30;
+                assert_eq!(y, 62);
+                assert_eq!(called.load(SeqCst), 1);
+            });
+        })
+        .unwrap();
+
+        let y = *x - 30;
+        assert_eq!(y, 62);
+        assert_eq!(called.load(SeqCst), 1);
+    }
+
+    #[test]
+    fn lazy_deref_mut() {
+        let called = AtomicUsize::new(0);
+        let mut x = Lazy::new(|| {
+            called.fetch_add(1, SeqCst);
+            92
+        });
+
+        assert_eq!(called.load(SeqCst), 0);
+
+        let y = *x - 30;
+        assert_eq!(y, 62);
+        assert_eq!(called.load(SeqCst), 1);
+
+        *x /= 2;
+        assert_eq!(*x, 46);
+        assert_eq!(called.load(SeqCst), 1);
+    }
+
+    #[test]
+    fn lazy_default() {
+        static CALLED: AtomicUsize = AtomicUsize::new(0);
+
+        struct Foo(u8);
+        impl Default for Foo {
+            fn default() -> Self {
+                CALLED.fetch_add(1, SeqCst);
+                Foo(42)
+            }
+        }
+
+        let lazy: Lazy<std::sync::Mutex<Foo>> = <_>::default();
+
+        assert_eq!(CALLED.load(SeqCst), 0);
+
+        assert_eq!(lazy.lock().unwrap().0, 42);
+        assert_eq!(CALLED.load(SeqCst), 1);
+
+        lazy.lock().unwrap().0 = 21;
+
+        assert_eq!(lazy.lock().unwrap().0, 21);
+        assert_eq!(CALLED.load(SeqCst), 1);
+    }
+
+    #[test]
+    fn static_lazy() {
+        static XS: Lazy<Vec<i32>> = Lazy::new(|| {
+            let mut xs = Vec::new();
+            xs.push(1);
+            xs.push(2);
+            xs.push(3);
+            xs
+        });
+        scope(|s| {
+            s.spawn(|_| {
+                assert_eq!(&*XS, &vec![1, 2, 3]);
+            });
+        })
+        .unwrap();
+        assert_eq!(&*XS, &vec![1, 2, 3]);
+    }
+
+    #[test]
+    fn static_lazy_via_fn() {
+        fn xs() -> &'static Vec<i32> {
+            static XS: OnceCell<Vec<i32>> = OnceCell::new();
+            XS.get_or_init(|| {
+                let mut xs = Vec::new();
+                xs.push(1);
+                xs.push(2);
+                xs.push(3);
+                xs
+            })
+        }
+        assert_eq!(xs(), &vec![1, 2, 3]);
+    }
+
+    #[test]
+    fn lazy_into_value() {
+        let l: Lazy<i32, _> = Lazy::new(|| panic!());
+        assert!(matches!(Lazy::into_value(l), Err(_)));
+        let l = Lazy::new(|| -> i32 { 92 });
+        Lazy::force(&l);
+        assert!(matches!(Lazy::into_value(l), Ok(92)));
+    }
+
+    #[test]
+    fn lazy_poisoning() {
+        let x: Lazy<String> = Lazy::new(|| panic!("kaboom"));
+        for _ in 0..2 {
+            let res = std::panic::catch_unwind(|| x.len());
+            assert!(res.is_err());
+        }
+    }
+
+    #[test]
+    fn once_cell_is_sync_send() {
+        fn assert_traits<T: Send + Sync>() {}
+        assert_traits::<OnceCell<String>>();
+        assert_traits::<Lazy<String>>();
+    }
+
+    #[test]
+    fn eval_once_macro() {
+        macro_rules! eval_once {
+            (|| -> $ty:ty {
+                $($body:tt)*
+            }) => {{
+                static ONCE_CELL: OnceCell<$ty> = OnceCell::new();
+                fn init() -> $ty {
+                    $($body)*
+                }
+                ONCE_CELL.get_or_init(init)
+            }};
+        }
+
+        let fib: &'static Vec<i32> = eval_once! {
+            || -> Vec<i32> {
+                let mut res = vec![1, 1];
+                for i in 0..10 {
+                    let next = res[i] + res[i + 1];
+                    res.push(next);
+                }
+                res
+            }
+        };
+        assert_eq!(fib[5], 8)
+    }
+
+    #[test]
+    fn once_cell_does_not_leak_partially_constructed_boxes() {
+        let n_tries = if cfg!(miri) { 10 } else { 100 };
+        let n_readers = 10;
+        let n_writers = 3;
+        const MSG: &str = "Hello, World";
+
+        for _ in 0..n_tries {
+            let cell: OnceCell<String> = OnceCell::new();
+            scope(|scope| {
+                for _ in 0..n_readers {
+                    scope.spawn(|_| loop {
+                        if let Some(msg) = cell.get() {
+                            assert_eq!(msg, MSG);
+                            break;
+                        }
+                    });
+                }
+                for _ in 0..n_writers {
+                    let _ = scope.spawn(|_| cell.set(MSG.to_owned()));
+                }
+            })
+            .unwrap()
+        }
+    }
+
+    #[cfg(feature = "std")]
+    #[test]
+    fn get_does_not_block() {
+        let cell = OnceCell::new();
+        let barrier = Barrier::new(2);
+        scope(|scope| {
+            scope.spawn(|_| {
+                cell.get_or_init(|| {
+                    barrier.wait();
+                    barrier.wait();
+                    "hello".to_string()
+                });
+            });
+            barrier.wait();
+            assert_eq!(cell.get(), None);
+            barrier.wait();
+        })
+        .unwrap();
+        assert_eq!(cell.get(), Some(&"hello".to_string()));
+    }
+
+    #[test]
+    // https://github.com/rust-lang/rust/issues/34761#issuecomment-256320669
+    fn arrrrrrrrrrrrrrrrrrrrrr() {
+        let cell = OnceCell::new();
+        {
+            let s = String::new();
+            cell.set(&s).unwrap();
+        }
+    }
+}
+
+#[cfg(feature = "race")]
+mod race {
+    #[cfg(feature = "std")]
+    use std::sync::Barrier;
+    use std::{
+        num::NonZeroUsize,
+        sync::atomic::{AtomicUsize, Ordering::SeqCst},
+    };
+
+    use crossbeam_utils::thread::scope;
+
+    use once_cell::race::{OnceBool, OnceNonZeroUsize};
+
+    #[test]
+    fn once_non_zero_usize_smoke_test() {
+        let cnt = AtomicUsize::new(0);
+        let cell = OnceNonZeroUsize::new();
+        let val = NonZeroUsize::new(92).unwrap();
+        scope(|s| {
+            s.spawn(|_| {
+                assert_eq!(
+                    cell.get_or_init(|| {
+                        cnt.fetch_add(1, SeqCst);
+                        val
+                    }),
+                    val
+                );
+                assert_eq!(cnt.load(SeqCst), 1);
+
+                assert_eq!(
+                    cell.get_or_init(|| {
+                        cnt.fetch_add(1, SeqCst);
+                        val
+                    }),
+                    val
+                );
+                assert_eq!(cnt.load(SeqCst), 1);
+            });
+        })
+        .unwrap();
+        assert_eq!(cell.get(), Some(val));
+        assert_eq!(cnt.load(SeqCst), 1);
+    }
+
+    #[test]
+    fn once_non_zero_usize_set() {
+        let val1 = NonZeroUsize::new(92).unwrap();
+        let val2 = NonZeroUsize::new(62).unwrap();
+
+        let cell = OnceNonZeroUsize::new();
+
+        assert!(cell.set(val1).is_ok());
+        assert_eq!(cell.get(), Some(val1));
+
+        assert!(cell.set(val2).is_err());
+        assert_eq!(cell.get(), Some(val1));
+    }
+
+    #[cfg(feature = "std")]
+    #[test]
+    fn once_non_zero_usize_first_wins() {
+        let val1 = NonZeroUsize::new(92).unwrap();
+        let val2 = NonZeroUsize::new(62).unwrap();
+
+        let cell = OnceNonZeroUsize::new();
+
+        let b1 = Barrier::new(2);
+        let b2 = Barrier::new(2);
+        let b3 = Barrier::new(2);
+        scope(|s| {
+            s.spawn(|_| {
+                let r1 = cell.get_or_init(|| {
+                    b1.wait();
+                    b2.wait();
+                    val1
+                });
+                assert_eq!(r1, val1);
+                b3.wait();
+            });
+            b1.wait();
+            s.spawn(|_| {
+                let r2 = cell.get_or_init(|| {
+                    b2.wait();
+                    b3.wait();
+                    val2
+                });
+                assert_eq!(r2, val1);
+            });
+        })
+        .unwrap();
+
+        assert_eq!(cell.get(), Some(val1));
+    }
+
+    #[test]
+    fn once_bool_smoke_test() {
+        let cnt = AtomicUsize::new(0);
+        let cell = OnceBool::new();
+        scope(|s| {
+            s.spawn(|_| {
+                assert_eq!(
+                    cell.get_or_init(|| {
+                        cnt.fetch_add(1, SeqCst);
+                        false
+                    }),
+                    false
+                );
+                assert_eq!(cnt.load(SeqCst), 1);
+
+                assert_eq!(
+                    cell.get_or_init(|| {
+                        cnt.fetch_add(1, SeqCst);
+                        false
+                    }),
+                    false
+                );
+                assert_eq!(cnt.load(SeqCst), 1);
+            });
+        })
+        .unwrap();
+        assert_eq!(cell.get(), Some(false));
+        assert_eq!(cnt.load(SeqCst), 1);
+    }
+
+    #[test]
+    fn once_bool_set() {
+        let cell = OnceBool::new();
+
+        assert!(cell.set(false).is_ok());
+        assert_eq!(cell.get(), Some(false));
+
+        assert!(cell.set(true).is_err());
+        assert_eq!(cell.get(), Some(false));
+    }
+}
+
+#[cfg(all(feature = "race", feature = "alloc"))]
+mod race_once_box {
+    #[cfg(feature = "std")]
+    use std::sync::Barrier;
+    use std::sync::{
+        atomic::{AtomicUsize, Ordering::SeqCst},
+        Arc,
+    };
+
+    #[cfg(feature = "std")]
+    use crossbeam_utils::thread::scope;
+
+    use once_cell::race::OnceBox;
+
+    #[derive(Default)]
+    struct Heap {
+        total: Arc<AtomicUsize>,
+    }
+
+    #[derive(Debug)]
+    struct Pebble<T> {
+        val: T,
+        total: Arc<AtomicUsize>,
+    }
+
+    impl<T> Drop for Pebble<T> {
+        fn drop(&mut self) {
+            self.total.fetch_sub(1, SeqCst);
+        }
+    }
+
+    impl Heap {
+        fn total(&self) -> usize {
+            self.total.load(SeqCst)
+        }
+        fn new_pebble<T>(&self, val: T) -> Pebble<T> {
+            self.total.fetch_add(1, SeqCst);
+            Pebble { val, total: Arc::clone(&self.total) }
+        }
+    }
+
+    #[cfg(feature = "std")]
+    #[test]
+    fn once_box_smoke_test() {
+        let heap = Heap::default();
+        let global_cnt = AtomicUsize::new(0);
+        let cell = OnceBox::new();
+        let b = Barrier::new(128);
+        scope(|s| {
+            for _ in 0..128 {
+                s.spawn(|_| {
+                    let local_cnt = AtomicUsize::new(0);
+                    cell.get_or_init(|| {
+                        global_cnt.fetch_add(1, SeqCst);
+                        local_cnt.fetch_add(1, SeqCst);
+                        b.wait();
+                        Box::new(heap.new_pebble(()))
+                    });
+                    assert_eq!(local_cnt.load(SeqCst), 1);
+
+                    cell.get_or_init(|| {
+                        global_cnt.fetch_add(1, SeqCst);
+                        local_cnt.fetch_add(1, SeqCst);
+                        Box::new(heap.new_pebble(()))
+                    });
+                    assert_eq!(local_cnt.load(SeqCst), 1);
+                });
+            }
+        })
+        .unwrap();
+        assert!(cell.get().is_some());
+        assert!(global_cnt.load(SeqCst) > 10);
+
+        assert_eq!(heap.total(), 1);
+        drop(cell);
+        assert_eq!(heap.total(), 0);
+    }
+
+    #[test]
+    fn once_box_set() {
+        let heap = Heap::default();
+        let cell = OnceBox::new();
+        assert!(cell.get().is_none());
+
+        assert!(cell.set(Box::new(heap.new_pebble("hello"))).is_ok());
+        assert_eq!(cell.get().unwrap().val, "hello");
+        assert_eq!(heap.total(), 1);
+
+        assert!(cell.set(Box::new(heap.new_pebble("world"))).is_err());
+        assert_eq!(cell.get().unwrap().val, "hello");
+        assert_eq!(heap.total(), 1);
+
+        drop(cell);
+        assert_eq!(heap.total(), 0);
+    }
+
+    #[cfg(feature = "std")]
+    #[test]
+    fn once_box_first_wins() {
+        let cell = OnceBox::new();
+        let val1 = 92;
+        let val2 = 62;
+
+        let b1 = Barrier::new(2);
+        let b2 = Barrier::new(2);
+        let b3 = Barrier::new(2);
+        scope(|s| {
+            s.spawn(|_| {
+                let r1 = cell.get_or_init(|| {
+                    b1.wait();
+                    b2.wait();
+                    Box::new(val1)
+                });
+                assert_eq!(*r1, val1);
+                b3.wait();
+            });
+            b1.wait();
+            s.spawn(|_| {
+                let r2 = cell.get_or_init(|| {
+                    b2.wait();
+                    b3.wait();
+                    Box::new(val2)
+                });
+                assert_eq!(*r2, val1);
+            });
+        })
+        .unwrap();
+
+        assert_eq!(cell.get(), Some(&val1));
+    }
+
+    #[test]
+    fn once_box_reentrant() {
+        let cell = OnceBox::new();
+        let res = cell.get_or_init(|| {
+            cell.get_or_init(|| Box::new("hello".to_string()));
+            Box::new("world".to_string())
+        });
+        assert_eq!(res, "hello");
+    }
+
+    #[test]
+    fn once_box_default() {
+        struct Foo;
+
+        let cell: OnceBox<Foo> = Default::default();
+        assert!(cell.get().is_none());
+    }
+}