rust/src/liballoc/tests/arc.rs

use std::any::Any;
use std::sync::{Arc, Weak};
use std::cell::RefCell;
use std::cmp::PartialEq;

#[test]
fn uninhabited() {
    enum Void {}
    let mut a = Weak::<Void>::new();
    a = a.clone();
    assert!(a.upgrade().is_none());

    let mut a: Weak<dyn Any> = a;  // Unsizing
    a = a.clone();
    assert!(a.upgrade().is_none());
}

#[test]
fn slice() {
    let a: Arc<[u32; 3]> = Arc::new([3, 2, 1]);
    let a: Arc<[u32]> = a;  // Unsizing
    let b: Arc<[u32]> = Arc::from(&[3, 2, 1][..]);  // Conversion
    assert_eq!(a, b);

    // Exercise is_dangling() with a DST
    let mut a = Arc::downgrade(&a);
    a = a.clone();
    assert!(a.upgrade().is_some());
}

#[test]
fn trait_object() {
    let a: Arc<u32> = Arc::new(4);
    let a: Arc<dyn Any> = a;  // Unsizing

    // Exercise is_dangling() with a DST
    let mut a = Arc::downgrade(&a);
    a = a.clone();
    assert!(a.upgrade().is_some());

    let mut b = Weak::<u32>::new();
    b = b.clone();
    assert!(b.upgrade().is_none());
    let mut b: Weak<dyn Any> = b;  // Unsizing
    b = b.clone();
    assert!(b.upgrade().is_none());
}

#[test]
fn float_nan_ne() {
    let x = Arc::new(std::f32::NAN);
    assert!(x != x);
    assert!(!(x == x));
}

#[test]
fn partial_eq() {
    struct TestPEq (RefCell<usize>);
    impl PartialEq for TestPEq {
        fn eq(&self, other: &TestPEq) -> bool {
            *self.0.borrow_mut() += 1;
            *other.0.borrow_mut() += 1;
            true
        }
    }
    let x = Arc::new(TestPEq(RefCell::new(0)));
    assert!(x == x);
    assert!(!(x != x));
    assert_eq!(*x.0.borrow(), 4);
}

#[test]
fn eq() {
    #[derive(Eq)]
    struct TestEq (RefCell<usize>);
    impl PartialEq for TestEq {
        fn eq(&self, other: &TestEq) -> bool {
            *self.0.borrow_mut() += 1;
            *other.0.borrow_mut() += 1;
            true
        }
    }
    let x = Arc::new(TestEq(RefCell::new(0)));
    assert!(x == x);
    assert!(!(x != x));
    assert_eq!(*x.0.borrow(), 0);
}