28 lines · 987 B · Rust
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// SPDX-License-Identifier: Apache-2.0 OR MIT //! The contents of this file come from the Rust standard library, hosted in//! the <https://github.com/rust-lang/rust> repository, licensed under//! "Apache-2.0 OR MIT" and adapted for kernel use. For copyright details,//! see <https://github.com/rust-lang/rust/blob/master/COPYRIGHT>. use crate::sync::{arc::ArcInner, Arc};use core::any::Any; impl Arc<dyn Any + Send + Sync> {    /// Attempt to downcast the `Arc<dyn Any + Send + Sync>` to a concrete type.    pub fn downcast<T>(self) -> core::result::Result<Arc<T>, Self>    where        T: Any + Send + Sync,    {        if (*self).is::<T>() {            // SAFETY: We have just checked that the type is correct, so we can cast the pointer.            unsafe {                let ptr = self.ptr.cast::<ArcInner<T>>();                core::mem::forget(self);                Ok(Arc::from_inner(ptr))            }        } else {            Err(self)        }    }}