2 // Check that trait objects without a principal codegen properly.
4 use std::sync::atomic::{AtomicUsize, Ordering};
7 // Array is to make sure the size is not exactly pointer-size, so
8 // we can be sure we are measuring the right size in the
10 struct SetOnDrop<'a>(&'a AtomicUsize, [u8; 64]);
11 impl<'a> Drop for SetOnDrop<'a> {
13 self.0.store(self.0.load(Ordering::Relaxed) + 1, Ordering::Relaxed);
17 trait TypeEq<V: ?Sized> {}
18 impl<T: ?Sized> TypeEq<T> for T {}
19 fn assert_types_eq<U: ?Sized, V: ?Sized>() where U: TypeEq<V> {}
22 // Check that different ways of writing the same type are equal.
23 assert_types_eq::<dyn Sync, dyn Sync + Sync>();
24 assert_types_eq::<dyn Sync + Send, dyn Send + Sync>();
25 assert_types_eq::<dyn Sync + Send + Sync, dyn Send + Sync>();
27 // Check that codegen works.
29 // Using `AtomicUsize` here because `Cell<u32>` is not `Sync`, and
30 // so can't be made into a `Box<dyn Sync>`.
31 let c = AtomicUsize::new(0);
33 let d: Box<dyn Sync> = Box::new(SetOnDrop(&c, [0; 64]));
35 assert_eq!(mem::size_of_val(&*d),
36 mem::size_of::<SetOnDrop>());
37 assert_eq!(mem::align_of_val(&*d),
38 mem::align_of::<SetOnDrop>());
39 assert_eq!(c.load(Ordering::Relaxed), 0);
41 assert_eq!(c.load(Ordering::Relaxed), 1);