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impl DispatchFromDyn for Cell and UnsafeCell
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@ -196,7 +196,7 @@
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use crate::fmt::{self, Debug, Display};
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use crate::marker::{PhantomData, Unsize};
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use crate::mem;
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use crate::ops::{CoerceUnsized, Deref, DerefMut};
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use crate::ops::{CoerceUnsized, Deref, DerefMut, DispatchFromDyn};
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use crate::ptr::{self, NonNull};
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mod lazy;
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@ -571,6 +571,16 @@ pub fn take(&self) -> T {
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#[unstable(feature = "coerce_unsized", issue = "18598")]
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impl<T: CoerceUnsized<U>, U> CoerceUnsized<Cell<U>> for Cell<T> {}
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// Allow types that wrap `Cell` to also implement `DispatchFromDyn`
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// and become object safe method receivers.
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// Note that currently `Cell` itself cannot be a method receiver
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// because it does not implement Deref.
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// In other words:
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// `self: Cell<&Self>` won't work
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// `self: CellWrapper<Self>` becomes possible
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#[unstable(feature = "dispatch_from_dyn", issue = "none")]
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impl<T: DispatchFromDyn<U>, U> DispatchFromDyn<Cell<U>> for Cell<T> {}
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impl<T> Cell<[T]> {
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/// Returns a `&[Cell<T>]` from a `&Cell<[T]>`
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///
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@ -2078,6 +2088,16 @@ fn from(t: T) -> UnsafeCell<T> {
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#[unstable(feature = "coerce_unsized", issue = "18598")]
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impl<T: CoerceUnsized<U>, U> CoerceUnsized<UnsafeCell<U>> for UnsafeCell<T> {}
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// Allow types that wrap `UnsafeCell` to also implement `DispatchFromDyn`
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// and become object safe method receivers.
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// Note that currently `UnsafeCell` itself cannot be a method receiver
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// because it does not implement Deref.
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// In other words:
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// `self: UnsafeCell<&Self>` won't work
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// `self: UnsafeCellWrapper<Self>` becomes possible
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#[unstable(feature = "dispatch_from_dyn", issue = "none")]
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impl<T: DispatchFromDyn<U>, U> DispatchFromDyn<UnsafeCell<U>> for UnsafeCell<T> {}
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/// [`UnsafeCell`], but [`Sync`].
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///
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/// This is just an `UnsafeCell`, except it implements `Sync`
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@ -2169,6 +2189,17 @@ fn from(t: T) -> SyncUnsafeCell<T> {
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//#[unstable(feature = "sync_unsafe_cell", issue = "95439")]
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impl<T: CoerceUnsized<U>, U> CoerceUnsized<SyncUnsafeCell<U>> for SyncUnsafeCell<T> {}
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// Allow types that wrap `SyncUnsafeCell` to also implement `DispatchFromDyn`
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// and become object safe method receivers.
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// Note that currently `SyncUnsafeCell` itself cannot be a method receiver
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// because it does not implement Deref.
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// In other words:
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// `self: SyncUnsafeCell<&Self>` won't work
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// `self: SyncUnsafeCellWrapper<Self>` becomes possible
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#[unstable(feature = "dispatch_from_dyn", issue = "none")]
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//#[unstable(feature = "sync_unsafe_cell", issue = "95439")]
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impl<T: DispatchFromDyn<U>, U> DispatchFromDyn<SyncUnsafeCell<U>> for SyncUnsafeCell<T> {}
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#[allow(unused)]
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fn assert_coerce_unsized(
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a: UnsafeCell<&i32>,
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@ -3,6 +3,7 @@
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#![feature(rustc_attrs)]
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use std::{
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cell::Cell,
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ops::{Deref, CoerceUnsized, DispatchFromDyn},
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marker::Unsize,
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};
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@ -20,6 +21,20 @@ fn deref(&self) -> &T {
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impl<T: Unsize<U> + ?Sized, U: ?Sized> CoerceUnsized<Ptr<U>> for Ptr<T> {}
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impl<T: Unsize<U> + ?Sized, U: ?Sized> DispatchFromDyn<Ptr<U>> for Ptr<T> {}
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struct CellPtr<'a, T: ?Sized>(Cell<&'a T>);
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impl<'a, T: ?Sized> Deref for CellPtr<'a, T> {
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type Target = T;
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fn deref(&self) -> &T {
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self.0.get()
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}
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}
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impl<'a, T: Unsize<U> + ?Sized, U: ?Sized> CoerceUnsized<CellPtr<'a, U>> for CellPtr<'a, T> {}
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impl<'a, T: Unsize<U> + ?Sized, U: ?Sized> DispatchFromDyn<CellPtr<'a, U>> for CellPtr<'a, T> {}
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struct Wrapper<T: ?Sized>(T);
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impl<T: ?Sized> Deref for Wrapper<T> {
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@ -42,6 +57,7 @@ trait Trait {
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fn ptr_wrapper(self: Ptr<Wrapper<Self>>) -> i32;
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fn wrapper_ptr(self: Wrapper<Ptr<Self>>) -> i32;
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fn wrapper_ptr_wrapper(self: Wrapper<Ptr<Wrapper<Self>>>) -> i32;
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fn cell(self: CellPtr<Self>) -> i32;
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}
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impl Trait for i32 {
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@ -54,6 +70,9 @@ fn wrapper_ptr(self: Wrapper<Ptr<Self>>) -> i32 {
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fn wrapper_ptr_wrapper(self: Wrapper<Ptr<Wrapper<Self>>>) -> i32 {
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***self
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}
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fn cell(self: CellPtr<Self>) -> i32 {
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*self
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}
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}
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fn main() {
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@ -65,4 +84,7 @@ fn main() {
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let wpw = Wrapper(Ptr(Box::new(Wrapper(7)))) as Wrapper<Ptr<Wrapper<dyn Trait>>>;
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assert_eq!(wpw.wrapper_ptr_wrapper(), 7);
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let c = CellPtr(Cell::new(&8)) as CellPtr<dyn Trait>;
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assert_eq!(c.cell(), 8);
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}
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