rust: sync: arc: Implement Arc<dyn Any + Send + Sync>::downcast()

This mirrors the standard library's alloc::sync::Arc::downcast().

Based on the Rust standard library implementation, ver 1.62.0,
licensed under "Apache-2.0 OR MIT", from:

    https://github.com/rust-lang/rust/tree/1.62.0/library/alloc/src

For copyright details, please see:

    https://github.com/rust-lang/rust/blob/1.62.0/COPYRIGHT

Reviewed-by: Martin Rodriguez Reboredo <[email protected]>
Reviewed-by: Andreas Hindborg <[email protected]>
Reviewed-by: Vincenzo Palazzo <[email protected]>
Reviewed-by: Gary Guo <[email protected]>
Signed-off-by: Asahi Lina <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
[ Moved `mod std_vendor;` up. ]
Signed-off-by: Miguel Ojeda <[email protected]>

0 files changed, 0 insertions, 0 deletions