rust: enable arbitrary_self_types and remove Receiver

The `arbitrary_self_types` RFC [1] is accepted and the feature is being
worked on [2]. As part of the RFC, a new `Receiver` trait is to be added,
and it will be automatically implemented for all types that have `Deref`
implementation. This is different from the existing `Receiver` trait
that we use, which is a custom implementation that opts-in a type into
being used as receiver.

To prepare us for the change, remove the `Receiver` implementation and
the associated feature. To still allow `Arc` and others to be used as
method receivers, turn on `arbitrary_self_types` feature instead.

Cc: Adrian Taylor <ade@hohum.me.uk>
Link: rust-lang/rfcs#3519 [1]
Link: rust-lang/rust#44874 [2]
Signed-off-by: Gary Guo <gary@garyguo.net>

rust/kernel/lib.rs

@@ -12,10 +12,10 @@
 //! do so first instead of bypassing this crate.
 
 #![no_std]
+#![feature(arbitrary_self_types)]
 #![feature(coerce_unsized)]
 #![feature(dispatch_from_dyn)]
 #![feature(new_uninit)]
-#![feature(receiver_trait)]
 #![feature(unsize)]
 
 // Ensure conditional compilation based on the kernel configuration works;

rust/kernel/list/arc.rs

@@ -441,9 +441,6 @@ where
     }
 }
 
-// This is to allow [`ListArc`] (and variants) to be used as the type of `self`.
-impl<T, const ID: u64> core::ops::Receiver for ListArc<T, ID> where T: ListArcSafe<ID> + ?Sized {}
-
 // This is to allow coercion from `ListArc<T>` to `ListArc<U>` if `T` can be converted to the
 // dynamically-sized type (DST) `U`.
 impl<T, U, const ID: u64> core::ops::CoerceUnsized<ListArc<U, ID>> for ListArc<T, ID>

rust/kernel/sync/arc.rs

@@ -171,9 +171,6 @@ impl<T: ?Sized> ArcInner<T> {
     }
 }
 
-// This is to allow [`Arc`] (and variants) to be used as the type of `self`.
-impl<T: ?Sized> core::ops::Receiver 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`.
 impl<T: ?Sized + Unsize<U>, U: ?Sized> core::ops::CoerceUnsized<Arc<U>> for Arc<T> {}
@@ -480,9 +477,6 @@ pub struct ArcBorrow<'a, T: ?Sized + 'a> {
     _p: PhantomData<&'a ()>,
 }
 
-// This is to allow [`ArcBorrow`] (and variants) to be used as the type of `self`.
-impl<T: ?Sized> core::ops::Receiver for ArcBorrow<'_, T> {}
-
 // This is to allow `ArcBorrow<U>` to be dispatched on when `ArcBorrow<T>` can be coerced into
 // `ArcBorrow<U>`.
 impl<T: ?Sized + Unsize<U>, U: ?Sized> core::ops::DispatchFromDyn<ArcBorrow<'_, U>>

scripts/Makefile.build

@@ -263,7 +263,7 @@ $(obj)/%.lst: $(obj)/%.c FORCE
 # Compile Rust sources (.rs)
 # ---------------------------------------------------------------------------
 
-rust_allowed_features := new_uninit
+rust_allowed_features := arbitrary_self_types,new_uninit
 
 # `--out-dir` is required to avoid temporaries being created by `rustc` in the
 # current working directory, which may be not accessible in the out-of-tree