fn drop(&mut self) {
        // Because `fetch_sub` is already atomic, we do not need to synchronize
        // with other threads unless we are going to delete the object. This
        // same logic applies to the below `fetch_sub` to the `weak` count.
        if self.inner().strong.fetch_sub(1, Release) != 1 {
            return;
        }

        // This fence is needed to prevent reordering of use of the data and
        // deletion of the data.  Because it is marked `Release`, the decreasing
        // of the reference count synchronizes with this `Acquire` fence. This
        // means that use of the data happens before decreasing the reference
        // count, which happens before this fence, which happens before the
        // deletion of the data.
        //
        // As explained in the [Boost documentation][1],
        //
        // > It is important to enforce any possible access to the object in one
        // > thread (through an existing reference) to *happen before* deleting
        // > the object in a different thread. This is achieved by a "release"
        // > operation after dropping a reference (any access to the object
        // > through this reference must obviously happened before), and an
        // > "acquire" operation before deleting the object.
        //
        // In particular, while the contents of an Arc are usually immutable, it's
        // possible to have interior writes to something like a Mutex<T>. Since a
        // Mutex is not acquired when it is deleted, we can't rely on its
        // synchronization logic to make writes in thread A visible to a destructor
        // running in thread B.
        //
        // Also note that the Acquire fence here could probably be replaced with an
        // Acquire load, which could improve performance in highly-contended
        // situations. See [2].
        //
        // [1]: (www.boost.org/doc/libs/1_55_0/doc/html/atomic/usage_examples.html)
        // [2]: (https://github.com/rust-lang/rust/pull/41714)
        acquire!(self.inner().strong);

        unsafe {
            self.drop_slow();
        }
    }
Attempt to downcast the `Arc<dyn Any + Send + Sync>` to a concrete type.

# Examples

```
use std::any::Any;
use std::sync::Arc;

fn print_if_string(value: Arc<dyn Any + Send + Sync>) {
if let Ok(string) = value.downcast::<String>() {
println!("String ({}): {}", string.len(), string);
}
}

let my_string = "Hello World".to_string();
print_if_string(Arc::new(my_string));
print_if_string(Arc::new(0i8));
benchmarks/haystacks/code/rust-library.rs