1// SPDX-License-Identifier: Apache-2.0 OR MIT
 2
 3//! The contents of this file come from the Rust standard library, hosted in
 4//! the <https://github.com/rust-lang/rust> repository, licensed under
 5//! "Apache-2.0 OR MIT" and adapted for kernel use. For copyright details,
 6//! see <https://github.com/rust-lang/rust/blob/master/COPYRIGHT>.
 7
 8use crate::sync::{arc::ArcInner, Arc};
 9use core::any::Any;
10
11impl Arc<dyn Any + Send + Sync> {
12    /// Attempt to downcast the `Arc<dyn Any + Send + Sync>` to a concrete type.
13    pub fn downcast<T>(self) -> core::result::Result<Arc<T>, Self>
14    where
15        T: Any + Send + Sync,
16    {
17        if (*self).is::<T>() {
18            // SAFETY: We have just checked that the type is correct, so we can cast the pointer.
19            unsafe {
20                let ptr = self.ptr.cast::<ArcInner<T>>();
21                core::mem::forget(self);
22                Ok(Arc::from_inner(ptr))
23            }
24        } else {
25            Err(self)
26        }
27    }
28}