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[XXX] MORE XXX / XXX @brodycj loose ends from PR 195 - for future consideration - XXX DO NOT MERGE #5

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[XXX] MORE XXX / XXX @brodycj loose ends from PR 195 - for future consideration - XXX DO NOT MERGE #5

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26 changes: 23 additions & 3 deletions portable-atomic-util/src/arc.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -115,6 +115,16 @@ impl<T: ?Sized + core::panic::RefUnwindSafe> core::panic::UnwindSafe for Arc<T>
#[cfg(all(portable_atomic_no_core_unwind_safe, feature = "std"))]
impl<T: ?Sized + std::panic::RefUnwindSafe> std::panic::UnwindSafe for Arc<T> {}

// XXX TODO RAISE ISSUE TO IMPROVE FEATURE PARITY WITH RUST STD ARC

// XXX TBD PROPOSED IN PR 195:
// #[cfg(portable_atomic_unstable_coerce_unsized)]
// impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<Arc<U>> for Arc<T> {}

// XXX TBD UNSTABLE FEATURE with DispatchFromDyn support - ???
// #[unstable(feature = "dispatch_from_dyn", issue = "none")]
// impl<T: ?Sized + Unsize<U>, U: ?Sized> DispatchFromDyn<Arc<U>> for Arc<T> {}

impl<T: ?Sized> Arc<T> {
#[inline]
fn into_inner_non_null(this: Self) -> NonNull<ArcInner<T>> {
Expand Down Expand Up @@ -174,6 +184,14 @@ pub struct Weak<T: ?Sized> {
unsafe impl<T: ?Sized + Sync + Send> Send for Weak<T> {}
unsafe impl<T: ?Sized + Sync + Send> Sync for Weak<T> {}

// XXX TBD PROPOSED IN PR 195:
// #[cfg(portable_atomic_unstable_coerce_unsized)]
// impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<Weak<U>> for Weak<T> {}

// XXX TBD UNSTABLE FEATURE with DispatchFromDyn support - ???
// #[unstable(feature = "dispatch_from_dyn", issue = "none")]
// impl<T: ?Sized + Unsize<U>, U: ?Sized> DispatchFromDyn<Weak<U>> for Weak<T> {}

impl<T: ?Sized> fmt::Debug for Weak<T> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.write_str("(Weak)")
Expand Down Expand Up @@ -1186,6 +1204,8 @@ impl<T: ?Sized> Deref for Arc<T> {
}
}

// XXX TODO support PinCoerceUnsized for Arc & Weak (if possible)

impl<T: ?Sized + CloneToUninit> Arc<T> {
/// Makes a mutable reference into the given `Arc`.
///
Expand Down Expand Up @@ -1508,11 +1528,11 @@ impl Arc<dyn Any + Send + Sync> {
/// }
///
/// let my_string = "Hello World".to_string();
// TODO: CoerceUnsized is needed to cast Arc<String> -> Arc<dyn Any + Send + Sync> directly.
// /// print_if_string(Arc::new(my_string));
// /// print_if_string(Arc::new(0i8));
/// print_if_string(Arc::from(Box::new(my_string) as Box<dyn Any + Send + Sync>));
/// print_if_string(Arc::from(Box::new(0i8) as Box<dyn Any + Send + Sync>));
/// // or with XXX portable_atomic_no_core_unwind_safe CFG FEATURE ENABLED WITH RUST NIGHTLY:
/// // print_if_string(Arc::new(my_string));
/// // print_if_string(Arc::new(0i8));
/// ```
#[inline]
pub fn downcast<T>(self) -> Result<Arc<T>, Self>
Expand Down