mirror of https://github.com/rust-lang/rust
43 lines
1.4 KiB
Rust
43 lines
1.4 KiB
Rust
//@ run-pass
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// Check that trait objects without a principal codegen properly.
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use std::sync::atomic::{AtomicUsize, Ordering};
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use std::mem;
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// Array is to make sure the size is not exactly pointer-size, so
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// we can be sure we are measuring the right size in the
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// `size_of_val` test.
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struct SetOnDrop<'a>(&'a AtomicUsize, #[allow(dead_code)] [u8; 64]);
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impl<'a> Drop for SetOnDrop<'a> {
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fn drop(&mut self) {
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self.0.store(self.0.load(Ordering::Relaxed) + 1, Ordering::Relaxed);
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}
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}
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trait TypeEq<V: ?Sized> {}
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impl<T: ?Sized> TypeEq<T> for T {}
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fn assert_types_eq<U: ?Sized, V: ?Sized>() where U: TypeEq<V> {}
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fn main() {
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// Check that different ways of writing the same type are equal.
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assert_types_eq::<dyn Sync, dyn Sync + Sync>();
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assert_types_eq::<dyn Sync + Send, dyn Send + Sync>();
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assert_types_eq::<dyn Sync + Send + Sync, dyn Send + Sync>();
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// Check that codegen works.
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//
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// Using `AtomicUsize` here because `Cell<u32>` is not `Sync`, and
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// so can't be made into a `Box<dyn Sync>`.
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let c = AtomicUsize::new(0);
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{
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let d: Box<dyn Sync> = Box::new(SetOnDrop(&c, [0; 64]));
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assert_eq!(mem::size_of_val(&*d),
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mem::size_of::<SetOnDrop>());
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assert_eq!(mem::align_of_val(&*d),
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mem::align_of::<SetOnDrop>());
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assert_eq!(c.load(Ordering::Relaxed), 0);
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}
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assert_eq!(c.load(Ordering::Relaxed), 1);
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}
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