rust: kernel: {arc, kbox}: use pin_coerce_unsized_trait

Required by the asahi driver for its driver data.

Signed-off-by: Janne Grunau <j@jannau.net>

Author: jannau

rust/kernel/alloc/kbox.rs

@@ -65,7 +65,8 @@ use crate::types::ForeignOwnable;
 /// `self.0` is always properly aligned and either points to memory allocated with `A` or, for
 /// zero-sized types, is a dangling, well aligned pointer.
 #[repr(transparent)]
-pub struct Box<T: ?Sized, A: Allocator>(NonNull<T>, PhantomData<A>);
+#[cfg_attr(CONFIG_RUSTC_HAS_COERCE_POINTEE, derive(core::marker::CoercePointee))]
+pub struct Box<#[pointee] T: ?Sized, A: Allocator>(NonNull<T>, PhantomData<A>);
 
 /// Type alias for [`Box`] with a [`Kmalloc`] allocator.
 ///

rust/kernel/lib.rs

@@ -15,6 +15,7 @@
 #![feature(arbitrary_self_types)]
 #![feature(associated_type_defaults)]
 #![cfg_attr(CONFIG_RUSTC_HAS_COERCE_POINTEE, feature(derive_coerce_pointee))]
+#![cfg_attr(CONFIG_RUSTC_HAS_COERCE_POINTEE, feature(pin_coerce_unsized_trait))]
 #![cfg_attr(not(CONFIG_RUSTC_HAS_COERCE_POINTEE), feature(coerce_unsized))]
 #![cfg_attr(not(CONFIG_RUSTC_HAS_COERCE_POINTEE), feature(dispatch_from_dyn))]
 #![cfg_attr(not(CONFIG_RUSTC_HAS_COERCE_POINTEE), feature(unsize))]

rust/kernel/sync/arc.rs

@@ -199,6 +199,11 @@ impl<T: ?Sized> ArcInner<T> {
 #[cfg(not(CONFIG_RUSTC_HAS_COERCE_POINTEE))]
 impl<T: ?Sized + core::marker::Unsize<U>, U: ?Sized> core::ops::CoerceUnsized<Arc<U>> for Arc<T> {}
 
+// This is to allow coercion from `Arc<T>` to `Arc<U>` if `T` can be converted to the
+// dynamically-sized type (DST) `U`.
+#[cfg(CONFIG_RUSTC_HAS_COERCE_POINTEE)]
+unsafe impl<T: ?Sized> core::pin::PinCoerceUnsized for Arc<T> {}
+
 // This is to allow `Arc<U>` to be dispatched on when `Arc<T>` can be coerced into `Arc<U>`.
 #[cfg(not(CONFIG_RUSTC_HAS_COERCE_POINTEE))]
 impl<T: ?Sized + core::marker::Unsize<U>, U: ?Sized> core::ops::DispatchFromDyn<Arc<U>> for Arc<T> {}