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Rollup merge of #125048 - dingxiangfei2009:stable-deref, r=amanieu

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PinCoerceUnsized trait into core

cc ``@Darksonn`` ``@wedsonaf`` ``@ojeda``

This is a PR to introduce a `PinCoerceUnsized` trait in order to make trait impls generated by the proc-macro `#[derive(SmartPointer)]`, proposed by [RFC](e17e19ac7a/text/3621-derive-smart-pointer.md (pincoerceunsized-1)), sound. There you may find explanation, justification and discussion about the alternatives.

Note that we do not seek stabilization of this `PinCoerceUnsized` trait in the near future. The stabilisation of this trait does not block the eventual stabilization process of the `#[derive(SmartPointer)]` macro. Ideally, use of `DerefPure` is more preferrable except this will actually constitute a breaking change. `PinCoerceUnsized` emerges as a solution to the said soundness hole while avoiding the breaking change. More details on the `DerefPure` option have been described in this [section](e17e19ac7a/text/3621-derive-smart-pointer.md (derefpure)) of the RFC linked above.

Earlier discussion can be found in this [Zulip stream](https://rust-lang.zulipchat.com/#narrow/stream/136281-t-opsem/topic/Pin.20and.20soundness.20of.20unsizing.20coercions) and [rust-for-linux thread](https://rust-lang.zulipchat.com/#narrow/stream/425075-rust-for-linux/topic/.23.5Bderive.28SmartPointer.29.5D.20and.20pin.20unsoundness.20rfc.233621).

try-job: dist-various-2
This commit is contained in:
Matthias Krüger
2024-08-07 00:34:11 +02:00
committed by GitHub
parent 38e631ee04 d495b84a9a
commit 16b251be10
16 changed files with 218 additions and 4 deletions
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10
library/alloc/src/rc.rs
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@@ -256,6 +256,7 @@ use core::ops::{CoerceUnsized, Deref, DerefMut, DerefPure, DispatchFromDyn, Rece
use core::panic::{RefUnwindSafe, UnwindSafe};
#[cfg(not(no_global_oom_handling))]
use core::pin::Pin;
use core::pin::PinCoerceUnsized;
use core::ptr::{self, drop_in_place, NonNull};
#[cfg(not(no_global_oom_handling))]
use core::slice::from_raw_parts_mut;
@@ -2177,6 +2178,12 @@ impl<T: ?Sized, A: Allocator> Deref for Rc<T, A> {
}
}
#[unstable(feature = "pin_coerce_unsized_trait", issue = "123430")]
unsafe impl<T: ?Sized, A: Allocator> PinCoerceUnsized for Rc<T, A> {}
#[unstable(feature = "pin_coerce_unsized_trait", issue = "123430")]
unsafe impl<T: ?Sized, A: Allocator> PinCoerceUnsized for Weak<T, A> {}
#[unstable(feature = "deref_pure_trait", issue = "87121")]
unsafe impl<T: ?Sized, A: Allocator> DerefPure for Rc<T, A> {}
@@ -3691,6 +3698,9 @@ impl<T: ?Sized, A: Allocator> Deref for UniqueRc<T, A> {
}
}
#[unstable(feature = "pin_coerce_unsized_trait", issue = "123430")]
unsafe impl<T: ?Sized> PinCoerceUnsized for UniqueRc<T> {}
#[unstable(feature = "unique_rc_arc", issue = "112566")]
impl<T: ?Sized, A: Allocator> DerefMut for UniqueRc<T, A> {
fn deref_mut(&mut self) -> &mut T {