library/alloctests/tests/rc.rs

use std::any::Any;
use std::cell::{Cell, RefCell};
use std::iter::TrustedLen;
use std::mem;
use std::rc::{Rc, UniqueRc, Weak};

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

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

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

    // Exercise is_dangling() with a DST
    let mut a = Rc::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 = Rc::new(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 = Rc::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 = Rc::new(TestEq(RefCell::new(0)));
    assert!(x == x);
    assert!(!(x != x));
    assert_eq!(*x.0.borrow(), 0);
}

#[test]
fn eq_unsized() {
    #[derive(Eq)]
    struct TestEq<T: ?Sized>(RefCell<usize>, T);
    impl<T: ?Sized> PartialEq for TestEq<T> {
        fn eq(&self, other: &TestEq<T>) -> bool {
            *self.0.borrow_mut() += 1;
            *other.0.borrow_mut() += 1;
            true
        }
    }
    let x = Rc::<TestEq<[u8; 3]>>::new(TestEq(RefCell::new(0), [0, 1, 2])) as Rc<TestEq<[u8]>>;
    assert!(x == x);
    assert!(!(x != x));
    assert_eq!(*x.0.borrow(), 0);
}

#[test]
fn eq_unsized_slice() {
    let a: Rc<[()]> = Rc::new([(); 3]);
    let ptr: *const () = Rc::into_raw(a.clone()).cast();
    let b: Rc<[()]> = unsafe { Rc::from_raw(ptr.cast_slice(42)) };
    assert!(a == a);
    assert!(!(a != a));
    assert!(a != b);
    assert!(!(a == b));
}

const SHARED_ITER_MAX: u16 = 100;

fn assert_trusted_len<I: TrustedLen>(_: &I) {}

#[test]
fn shared_from_iter_normal() {
    // Exercise the base implementation for non-`TrustedLen` iterators.
    {
        // `Filter` is never `TrustedLen` since we don't
        // know statically how many elements will be kept:
        let iter = (0..SHARED_ITER_MAX).filter(|x| x % 2 == 0).map(Box::new);

        // Collecting into a `Vec<T>` or `Rc<[T]>` should make no difference:
        let vec = iter.clone().collect::<Vec<_>>();
        let rc = iter.collect::<Rc<[_]>>();
        assert_eq!(&*vec, &*rc);

        // Clone a bit and let these get dropped.
        {
            let _rc_2 = rc.clone();
            let _rc_3 = rc.clone();
            let _rc_4 = Rc::downgrade(&_rc_3);
        }
    } // Drop what hasn't been here.
}

#[test]
fn shared_from_iter_trustedlen_normal() {
    // Exercise the `TrustedLen` implementation under normal circumstances
    // where `size_hint()` matches `(_, Some(exact_len))`.
    {
        let iter = (0..SHARED_ITER_MAX).map(Box::new);
        assert_trusted_len(&iter);

        // Collecting into a `Vec<T>` or `Rc<[T]>` should make no difference:
        let vec = iter.clone().collect::<Vec<_>>();
        let rc = iter.collect::<Rc<[_]>>();
        assert_eq!(&*vec, &*rc);
        assert_eq!(size_of::<Box<u16>>() * SHARED_ITER_MAX as usize, size_of_val(&*rc));

        // Clone a bit and let these get dropped.
        {
            let _rc_2 = rc.clone();
            let _rc_3 = rc.clone();
            let _rc_4 = Rc::downgrade(&_rc_3);
        }
    } // Drop what hasn't been here.

    // Try a ZST to make sure it is handled well.
    {
        let iter = (0..SHARED_ITER_MAX).map(drop);
        let vec = iter.clone().collect::<Vec<_>>();
        let rc = iter.collect::<Rc<[_]>>();
        assert_eq!(&*vec, &*rc);
        assert_eq!(0, size_of_val(&*rc));
        {
            let _rc_2 = rc.clone();
            let _rc_3 = rc.clone();
            let _rc_4 = Rc::downgrade(&_rc_3);
        }
    }
}

#[test]
#[should_panic = "I've almost got 99 problems."]
fn shared_from_iter_trustedlen_panic() {
    // Exercise the `TrustedLen` implementation when `size_hint()` matches
    // `(_, Some(exact_len))` but where `.next()` drops before the last iteration.
    let iter = (0..SHARED_ITER_MAX).map(|val| match val {
        98 => panic!("I've almost got 99 problems."),
        _ => Box::new(val),
    });
    assert_trusted_len(&iter);
    let _ = iter.collect::<Rc<[_]>>();

    panic!("I am unreachable.");
}

#[test]
fn shared_from_iter_trustedlen_no_fuse() {
    // Exercise the `TrustedLen` implementation when `size_hint()` matches
    // `(_, Some(exact_len))` but where the iterator does not behave in a fused manner.
    struct Iter(std::vec::IntoIter<Option<Box<u8>>>);

    unsafe impl TrustedLen for Iter {}

    impl Iterator for Iter {
        fn size_hint(&self) -> (usize, Option<usize>) {
            (2, Some(2))
        }

        type Item = Box<u8>;

        fn next(&mut self) -> Option<Self::Item> {
            self.0.next().flatten()
        }
    }

    let vec = vec![Some(Box::new(42)), Some(Box::new(24)), None, Some(Box::new(12))];
    let iter = Iter(vec.into_iter());
    assert_trusted_len(&iter);
    assert_eq!(&[Box::new(42), Box::new(24)], &*iter.collect::<Rc<[_]>>());
}

#[test]
fn weak_may_dangle() {
    fn hmm<'a>(val: &'a mut Weak<&'a str>) -> Weak<&'a str> {
        val.clone()
    }

    // Without #[may_dangle] we get:
    let mut val = Weak::new();
    hmm(&mut val);
    //  ~~~~~~~~ borrowed value does not live long enough
    //
    // `val` dropped here while still borrowed
    // borrow might be used here, when `val` is dropped and runs the `Drop` code for type `std::rc::Weak`
}

/// Test that a panic from a destructor does not leak the allocation.
#[test]
#[cfg_attr(not(panic = "unwind"), ignore = "test requires unwinding support")]
fn panic_no_leak() {
    use std::alloc::{AllocError, Allocator, Global, Layout};
    use std::panic::{AssertUnwindSafe, catch_unwind};
    use std::ptr::NonNull;

    struct AllocCount(Cell<i32>);
    unsafe impl Allocator for AllocCount {
        fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
            self.0.set(self.0.get() + 1);
            Global.allocate(layout)
        }
        unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout) {
            self.0.set(self.0.get() - 1);
            unsafe { Global.deallocate(ptr, layout) }
        }
    }

    struct PanicOnDrop;
    impl Drop for PanicOnDrop {
        fn drop(&mut self) {
            panic!("PanicOnDrop");
        }
    }

    let alloc = AllocCount(Cell::new(0));
    let rc = Rc::new_in(PanicOnDrop, &alloc);
    assert_eq!(alloc.0.get(), 1);

    let panic_message = catch_unwind(AssertUnwindSafe(|| drop(rc))).unwrap_err();
    assert_eq!(*panic_message.downcast_ref::<&'static str>().unwrap(), "PanicOnDrop");
    assert_eq!(alloc.0.get(), 0);
}

#[allow(unused)]
mod pin_coerce_unsized {
    use alloc::rc::{Rc, UniqueRc};
    use core::pin::Pin;

    pub trait MyTrait {}
    impl MyTrait for String {}

    // Pin coercion should work for Rc
    pub fn pin_rc(arg: Pin<Rc<String>>) -> Pin<Rc<dyn MyTrait>> {
        arg
    }
    pub fn pin_unique_rc(arg: Pin<UniqueRc<String>>) -> Pin<UniqueRc<dyn MyTrait>> {
        arg
    }
}

#[test]
fn test_clone() {
    let x = Rc::new(RefCell::new(5));
    let y = x.clone();
    *x.borrow_mut() = 20;
    assert_eq!(*y.borrow(), 20);
}

#[test]
fn test_simple() {
    let x = Rc::new(5);
    assert_eq!(*x, 5);
}

#[test]
fn test_simple_clone() {
    let x = Rc::new(5);
    let y = x.clone();
    assert_eq!(*x, 5);
    assert_eq!(*y, 5);
}

#[test]
fn test_destructor() {
    let x: Rc<Box<_>> = Rc::new(Box::new(5));
    assert_eq!(**x, 5);
}

#[test]
fn test_live() {
    let x = Rc::new(5);
    let y = Rc::downgrade(&x);
    assert!(y.upgrade().is_some());
}

#[test]
fn test_dead() {
    let x = Rc::new(5);
    let y = Rc::downgrade(&x);
    drop(x);
    assert!(y.upgrade().is_none());
}

#[test]
fn weak_self_cyclic() {
    struct Cycle {
        x: RefCell<Option<Weak<Cycle>>>,
    }

    let a = Rc::new(Cycle { x: RefCell::new(None) });
    let b = Rc::downgrade(&a.clone());
    *a.x.borrow_mut() = Some(b);

    // hopefully we don't double-free (or leak)...
}

#[test]
fn is_unique() {
    fn is_unique<T>(this: &Rc<T>) -> bool {
        Rc::weak_count(this) == 0 && Rc::strong_count(this) == 1
    }

    let x = Rc::new(3);
    assert!(is_unique(&x));
    let y = x.clone();
    assert!(!is_unique(&x));
    drop(y);
    assert!(is_unique(&x));
    let w = Rc::downgrade(&x);
    assert!(!is_unique(&x));
    drop(w);
    assert!(is_unique(&x));
}

#[test]
fn test_strong_count() {
    let a = Rc::new(0);
    assert!(Rc::strong_count(&a) == 1);
    let w = Rc::downgrade(&a);
    assert!(Rc::strong_count(&a) == 1);
    let b = w.upgrade().expect("upgrade of live rc failed");
    assert!(Rc::strong_count(&b) == 2);
    assert!(Rc::strong_count(&a) == 2);
    drop(w);
    drop(a);
    assert!(Rc::strong_count(&b) == 1);
    let c = b.clone();
    assert!(Rc::strong_count(&b) == 2);
    assert!(Rc::strong_count(&c) == 2);
}

#[test]
fn test_weak_count() {
    let a = Rc::new(0);
    assert!(Rc::strong_count(&a) == 1);
    assert!(Rc::weak_count(&a) == 0);
    let w = Rc::downgrade(&a);
    assert!(Rc::strong_count(&a) == 1);
    assert!(Rc::weak_count(&a) == 1);
    drop(w);
    assert!(Rc::strong_count(&a) == 1);
    assert!(Rc::weak_count(&a) == 0);
    let c = a.clone();
    assert!(Rc::strong_count(&a) == 2);
    assert!(Rc::weak_count(&a) == 0);
    drop(c);
}

#[test]
fn weak_counts() {
    assert_eq!(Weak::weak_count(&Weak::<u64>::new()), 0);
    assert_eq!(Weak::strong_count(&Weak::<u64>::new()), 0);

    let a = Rc::new(0);
    let w = Rc::downgrade(&a);
    assert_eq!(Weak::strong_count(&w), 1);
    assert_eq!(Weak::weak_count(&w), 1);
    let w2 = w.clone();
    assert_eq!(Weak::strong_count(&w), 1);
    assert_eq!(Weak::weak_count(&w), 2);
    assert_eq!(Weak::strong_count(&w2), 1);
    assert_eq!(Weak::weak_count(&w2), 2);
    drop(w);
    assert_eq!(Weak::strong_count(&w2), 1);
    assert_eq!(Weak::weak_count(&w2), 1);
    let a2 = a.clone();
    assert_eq!(Weak::strong_count(&w2), 2);
    assert_eq!(Weak::weak_count(&w2), 1);
    drop(a2);
    drop(a);
    assert_eq!(Weak::strong_count(&w2), 0);
    assert_eq!(Weak::weak_count(&w2), 0);
    drop(w2);
}

#[test]
fn try_unwrap() {
    let x = Rc::new(3);
    assert_eq!(Rc::try_unwrap(x), Ok(3));
    let x = Rc::new(4);
    let _y = x.clone();
    assert_eq!(Rc::try_unwrap(x), Err(Rc::new(4)));
    let x = Rc::new(5);
    let _w = Rc::downgrade(&x);
    assert_eq!(Rc::try_unwrap(x), Ok(5));
}

#[test]
fn into_inner() {
    let x = Rc::new(3);
    assert_eq!(Rc::into_inner(x), Some(3));

    let x = Rc::new(4);
    let y = Rc::clone(&x);
    assert_eq!(Rc::into_inner(x), None);
    assert_eq!(Rc::into_inner(y), Some(4));

    let x = Rc::new(5);
    let _w = Rc::downgrade(&x);
    assert_eq!(Rc::into_inner(x), Some(5));
}

#[test]
fn into_from_raw() {
    let x = Rc::new(Box::new("hello"));
    let y = x.clone();

    let x_ptr = Rc::into_raw(x);
    drop(y);
    unsafe {
        assert_eq!(**x_ptr, "hello");

        let x = Rc::from_raw(x_ptr);
        assert_eq!(**x, "hello");

        assert_eq!(Rc::try_unwrap(x).map(|x| *x), Ok("hello"));
    }
}

#[test]
fn test_into_from_raw_unsized() {
    use std::fmt::Display;
    use std::string::ToString;

    let rc: Rc<str> = Rc::from("foo");

    let ptr = Rc::into_raw(rc.clone());
    let rc2 = unsafe { Rc::from_raw(ptr) };

    assert_eq!(unsafe { &*ptr }, "foo");
    assert_eq!(rc, rc2);

    let rc: Rc<dyn Display> = Rc::new(123);

    let ptr = Rc::into_raw(rc.clone());
    let rc2 = unsafe { Rc::from_raw(ptr) };

    assert_eq!(unsafe { &*ptr }.to_string(), "123");
    assert_eq!(rc2.to_string(), "123");
}

#[test]
fn into_from_weak_raw() {
    let x = Rc::new(Box::new("hello"));
    let y = Rc::downgrade(&x);

    let y_ptr = Weak::into_raw(y);
    unsafe {
        assert_eq!(**y_ptr, "hello");

        let y = Weak::from_raw(y_ptr);
        let y_up = Weak::upgrade(&y).unwrap();
        assert_eq!(**y_up, "hello");
        drop(y_up);

        assert_eq!(Rc::try_unwrap(x).map(|x| *x), Ok("hello"));
    }
}

#[test]
fn test_into_from_weak_raw_unsized() {
    use std::fmt::Display;
    use std::string::ToString;

    let arc: Rc<str> = Rc::from("foo");
    let weak: Weak<str> = Rc::downgrade(&arc);

    let ptr = Weak::into_raw(weak.clone());
    let weak2 = unsafe { Weak::from_raw(ptr) };

    assert_eq!(unsafe { &*ptr }, "foo");
    assert!(weak.ptr_eq(&weak2));

    let arc: Rc<dyn Display> = Rc::new(123);
    let weak: Weak<dyn Display> = Rc::downgrade(&arc);

    let ptr = Weak::into_raw(weak.clone());
    let weak2 = unsafe { Weak::from_raw(ptr) };

    assert_eq!(unsafe { &*ptr }.to_string(), "123");
    assert!(weak.ptr_eq(&weak2));
}

#[test]
fn get_mut() {
    let mut x = Rc::new(3);
    *Rc::get_mut(&mut x).unwrap() = 4;
    assert_eq!(*x, 4);
    let y = x.clone();
    assert!(Rc::get_mut(&mut x).is_none());
    drop(y);
    assert!(Rc::get_mut(&mut x).is_some());
    let _w = Rc::downgrade(&x);
    assert!(Rc::get_mut(&mut x).is_none());
}

#[test]
fn test_cowrc_clone_make_unique() {
    let mut cow0 = Rc::new(75);
    let mut cow1 = cow0.clone();
    let mut cow2 = cow1.clone();

    assert!(75 == *Rc::make_mut(&mut cow0));
    assert!(75 == *Rc::make_mut(&mut cow1));
    assert!(75 == *Rc::make_mut(&mut cow2));

    *Rc::make_mut(&mut cow0) += 1;
    *Rc::make_mut(&mut cow1) += 2;
    *Rc::make_mut(&mut cow2) += 3;

    assert!(76 == *cow0);
    assert!(77 == *cow1);
    assert!(78 == *cow2);

    // none should point to the same backing memory
    assert!(*cow0 != *cow1);
    assert!(*cow0 != *cow2);
    assert!(*cow1 != *cow2);
}

#[test]
fn test_cowrc_clone_unique2() {
    let mut cow0 = Rc::new(75);
    let cow1 = cow0.clone();
    let cow2 = cow1.clone();

    assert!(75 == *cow0);
    assert!(75 == *cow1);
    assert!(75 == *cow2);

    *Rc::make_mut(&mut cow0) += 1;

    assert!(76 == *cow0);
    assert!(75 == *cow1);
    assert!(75 == *cow2);

    // cow1 and cow2 should share the same contents
    // cow0 should have a unique reference
    assert!(*cow0 != *cow1);
    assert!(*cow0 != *cow2);
    assert!(*cow1 == *cow2);
}

#[test]
fn test_cowrc_clone_weak() {
    let mut cow0 = Rc::new(75);
    let cow1_weak = Rc::downgrade(&cow0);

    assert!(75 == *cow0);
    assert!(75 == *cow1_weak.upgrade().unwrap());

    *Rc::make_mut(&mut cow0) += 1;

    assert!(76 == *cow0);
    assert!(cow1_weak.upgrade().is_none());
}

/// This is similar to the doc-test for `Rc::make_mut()`, but on an unsized type (slice).
#[test]
fn test_cowrc_unsized() {
    use std::rc::Rc;

    let mut data: Rc<[i32]> = Rc::new([10, 20, 30]);

    Rc::make_mut(&mut data)[0] += 1; // Won't clone anything
    let mut other_data = Rc::clone(&data); // Won't clone inner data
    Rc::make_mut(&mut data)[1] += 1; // Clones inner data
    Rc::make_mut(&mut data)[2] += 1; // Won't clone anything
    Rc::make_mut(&mut other_data)[0] *= 10; // Won't clone anything

    // Now `data` and `other_data` point to different allocations.
    assert_eq!(*data, [11, 21, 31]);
    assert_eq!(*other_data, [110, 20, 30]);
}

#[test]
fn test_show() {
    let foo = Rc::new(75);
    assert_eq!(format!("{foo:?}"), "75");
}

#[test]
fn test_unsized() {
    let foo: Rc<[i32]> = Rc::new([1, 2, 3]);
    assert_eq!(foo, foo.clone());
}

#[test]
fn test_maybe_thin_unsized() {
    // If/when custom thin DSTs exist, this test should be updated to use one
    use std::ffi::CStr;

    let x: Rc<CStr> = Rc::from(c"swordfish");
    assert_eq!(format!("{x:?}"), "\"swordfish\"");
    let y: Weak<CStr> = Rc::downgrade(&x);
    drop(x);

    // At this point, the weak points to a dropped DST
    assert!(y.upgrade().is_none());
    // But we still need to be able to get the alloc layout to drop.
    // CStr has no drop glue, but custom DSTs might, and need to work.
    drop(y);
}

#[test]
fn test_from_owned() {
    let foo = 123;
    let foo_rc = Rc::from(foo);
    assert!(123 == *foo_rc);
}

#[test]
fn test_new_weak() {
    let foo: Weak<usize> = Weak::new();
    assert!(foo.upgrade().is_none());
}

#[test]
fn test_ptr_eq() {
    let five = Rc::new(5);
    let same_five = five.clone();
    let other_five = Rc::new(5);

    assert!(Rc::ptr_eq(&five, &same_five));
    assert!(!Rc::ptr_eq(&five, &other_five));
}

#[test]
fn test_from_str() {
    let r: Rc<str> = Rc::from("foo");

    assert_eq!(&r[..], "foo");
}

#[test]
fn test_copy_from_slice() {
    let s: &[u32] = &[1, 2, 3];
    let r: Rc<[u32]> = Rc::from(s);

    assert_eq!(&r[..], [1, 2, 3]);
}

#[test]
fn test_clone_from_slice() {
    #[derive(Clone, Debug, Eq, PartialEq)]
    struct X(u32);

    let s: &[X] = &[X(1), X(2), X(3)];
    let r: Rc<[X]> = Rc::from(s);

    assert_eq!(&r[..], s);
}

#[test]
#[should_panic]
fn test_clone_from_slice_panic() {
    use std::string::{String, ToString};

    struct Fail(u32, String);

    impl Clone for Fail {
        fn clone(&self) -> Fail {
            if self.0 == 2 {
                panic!();
            }
            Fail(self.0, self.1.clone())
        }
    }

    let s: &[Fail] =
        &[Fail(0, "foo".to_string()), Fail(1, "bar".to_string()), Fail(2, "baz".to_string())];

    // Should panic, but not cause memory corruption
    let _r: Rc<[Fail]> = Rc::from(s);
}

#[test]
fn test_from_box() {
    let b: Box<u32> = Box::new(123);
    let r: Rc<u32> = Rc::from(b);

    assert_eq!(*r, 123);
}

#[test]
fn test_from_box_str() {
    use std::string::String;

    let s = String::from("foo").into_boxed_str();
    assert_eq!((&&&s).as_str(), "foo");

    let r: Rc<str> = Rc::from(s);
    assert_eq!((&r).as_str(), "foo");
    assert_eq!(r.as_str(), "foo");

    assert_eq!(&r[..], "foo");
}

#[test]
fn test_from_box_slice() {
    let s = vec![1, 2, 3].into_boxed_slice();
    let r: Rc<[u32]> = Rc::from(s);

    assert_eq!(&r[..], [1, 2, 3]);
}

#[test]
fn test_from_box_trait() {
    use std::fmt::Display;
    use std::string::ToString;

    let b: Box<dyn Display> = Box::new(123);
    let r: Rc<dyn Display> = Rc::from(b);

    assert_eq!(r.to_string(), "123");
}

#[test]
fn test_from_box_trait_zero_sized() {
    use std::fmt::Debug;

    let b: Box<dyn Debug> = Box::new(());
    let r: Rc<dyn Debug> = Rc::from(b);

    assert_eq!(format!("{r:?}"), "()");
}

#[test]
fn test_from_vec() {
    let v = vec![1, 2, 3];
    let r: Rc<[u32]> = Rc::from(v);

    assert_eq!(&r[..], [1, 2, 3]);
}

#[test]
fn test_downcast() {
    use std::any::Any;

    let r1: Rc<dyn Any> = Rc::new(i32::MAX);
    let r2: Rc<dyn Any> = Rc::new("abc");

    assert!(r1.clone().downcast::<u32>().is_err());

    let r1i32 = r1.downcast::<i32>();
    assert!(r1i32.is_ok());
    assert_eq!(r1i32.unwrap(), Rc::new(i32::MAX));

    assert!(r2.clone().downcast::<i32>().is_err());

    let r2str = r2.downcast::<&'static str>();
    assert!(r2str.is_ok());
    assert_eq!(r2str.unwrap(), Rc::new("abc"));
}

#[test]
fn test_array_from_slice() {
    let v = vec![1, 2, 3];
    let r: Rc<[u32]> = Rc::from(v);

    let a: Result<Rc<[u32; 3]>, _> = r.clone().try_into();
    assert!(a.is_ok());

    let a: Result<Rc<[u32; 2]>, _> = r.clone().try_into();
    assert!(a.is_err());
}

#[test]
fn test_rc_cyclic_with_zero_refs() {
    struct ZeroRefs {
        inner: Weak<ZeroRefs>,
    }

    let zero_refs = Rc::new_cyclic(|inner| {
        assert_eq!(inner.strong_count(), 0);
        assert!(inner.upgrade().is_none());
        ZeroRefs { inner: Weak::new() }
    });

    assert_eq!(Rc::strong_count(&zero_refs), 1);
    assert_eq!(Rc::weak_count(&zero_refs), 0);
    assert_eq!(zero_refs.inner.strong_count(), 0);
    assert_eq!(zero_refs.inner.weak_count(), 0);
}

#[test]
fn test_rc_cyclic_with_one_ref() {
    struct OneRef {
        inner: Weak<OneRef>,
    }

    let one_ref = Rc::new_cyclic(|inner| {
        assert_eq!(inner.strong_count(), 0);
        assert!(inner.upgrade().is_none());
        OneRef { inner: inner.clone() }
    });

    assert_eq!(Rc::strong_count(&one_ref), 1);
    assert_eq!(Rc::weak_count(&one_ref), 1);

    let one_ref2 = Weak::upgrade(&one_ref.inner).unwrap();
    assert!(Rc::ptr_eq(&one_ref, &one_ref2));

    assert_eq!(one_ref.inner.strong_count(), 2);
    assert_eq!(one_ref.inner.weak_count(), 1);
}

#[test]
fn test_rc_cyclic_with_two_ref() {
    struct TwoRefs {
        inner: Weak<TwoRefs>,
        inner1: Weak<TwoRefs>,
    }

    let two_refs = Rc::new_cyclic(|inner| {
        assert_eq!(inner.strong_count(), 0);
        assert!(inner.upgrade().is_none());
        TwoRefs { inner: inner.clone(), inner1: inner.clone() }
    });

    assert_eq!(Rc::strong_count(&two_refs), 1);
    assert_eq!(Rc::weak_count(&two_refs), 2);

    let two_ref3 = Weak::upgrade(&two_refs.inner).unwrap();
    assert!(Rc::ptr_eq(&two_refs, &two_ref3));

    let two_ref2 = Weak::upgrade(&two_refs.inner1).unwrap();
    assert!(Rc::ptr_eq(&two_refs, &two_ref2));

    assert_eq!(Rc::strong_count(&two_refs), 3);
    assert_eq!(Rc::weak_count(&two_refs), 2);
}

#[test]
fn test_unique_rc_weak() {
    let rc = UniqueRc::new(42);
    let weak = UniqueRc::downgrade(&rc);
    assert!(weak.upgrade().is_none());

    let _rc = UniqueRc::into_rc(rc);
    assert_eq!(*weak.upgrade().unwrap(), 42);
}

#[test]
fn test_unique_rc_drop_weak() {
    let rc = UniqueRc::new(42);
    let weak = UniqueRc::downgrade(&rc);
    mem::drop(weak);

    let rc = UniqueRc::into_rc(rc);
    assert_eq!(*rc, 42);
}

#[test]
fn test_unique_rc_drops_contents() {
    let mut dropped = false;
    struct DropMe<'a>(&'a mut bool);
    impl Drop for DropMe<'_> {
        fn drop(&mut self) {
            *self.0 = true;
        }
    }
    {
        let rc = UniqueRc::new(DropMe(&mut dropped));
        drop(rc);
    }
    assert!(dropped);
}

/// Exercise the non-default allocator usage.
#[test]
fn test_unique_rc_with_alloc_drops_contents() {
    let mut dropped = false;
    struct DropMe<'a>(&'a mut bool);
    impl Drop for DropMe<'_> {
        fn drop(&mut self) {
            *self.0 = true;
        }
    }
    {
        let rc = UniqueRc::new_in(DropMe(&mut dropped), std::alloc::System);
        drop(rc);
    }
    assert!(dropped);
}

#[test]
fn test_unique_rc_weak_clone_holding_ref() {
    let mut v = UniqueRc::new(0u8);
    let w = UniqueRc::downgrade(&v);
    let r = &mut *v;
    let _ = w.clone(); // touch weak count
    *r = 123;
}

#[test]
fn test_unique_rc_unsizing_coercion() {
    let mut rc: UniqueRc<[u8]> = UniqueRc::new([0u8; 3]);
    assert_eq!(rc.len(), 3);
    rc[0] = 123;
    let rc: Rc<[u8]> = UniqueRc::into_rc(rc);
    assert_eq!(*rc, [123, 0, 0]);
}