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Rollup merge of #152646 - zachs18:unsafeunpin-marker-impls-pointee, r=Mark-Simulacrum

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Update `UnsafeUnpin` impls involving extern types.

`UnsafeUnpin` tracking issue: https://github.com/rust-lang/rust/issues/125735

Relaxes from `T: ?Sized` (i.e. `T: MetaSized`) to `T: PointeeSized` for the `UnsafeUnpin` impls for pointers, references, and `PhantomData<T>`, and for the negative `UnsafeUnpin` impl for `UnsafePinned<T>`. (Compare to the impls for `Freeze` on lines 911-921.)

Both `UnsafeUnpin` and `extern type`s (the only way to have a `!MetaSized` type) are unstable, so this should have no effect on stable code.

Also updates the marker_impls macro docs to use PointeeSized bound, as most uses of the macro now do.

Concretely, this change means that the following types will newly implement `UnsafeUnpin`:

* pointers and references to `T` where `T` is an `extern type`
* `PhantomData<T>` where `T` is an extern type
* either of the above where `T` is a `struct` or tuple with `extern type` tail

Additionally, the negative `UnsafeUnpin` impl for `UnsafePinned<T>` is also relaxed to `T: PointeeSized` to align with the analogous negative `Freeze` impl for `UnsafeCell<T>`, even though both structs have `T: ?Sized` in their declaration (which probably should be relaxed, but that is a separate issue), so this part of the change doesn't actually *do* anything currently, but if `UnsafeCell` and `UnsafePinned` are later relaxed to `T: PointeeSized`, then the negative impl will apply to the newly possible instantiations. Also cc https://github.com/rust-lang/rust/issues/152645 that these impls compile at all.
This commit is contained in:
Jonathan Brouwer
2026-03-08 22:51:51 +01:00
committed by GitHub
parent 1ef29e7af6 ca1defc40b
commit e21a5df27e
1 changed files with 8 additions and 8 deletions
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library/core/src/marker.rs
+8 -8
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@@ -46,8 +46,8 @@
/// marker_impls! {
/// MarkerTrait for
/// u8, i8,
/// {T: ?Sized} *const T,
/// {T: ?Sized} *mut T,
/// {T: PointeeSized} *const T,
/// {T: PointeeSized} *mut T,
/// {T: MarkerTrait} PhantomData<T>,
/// u32,
/// }
@@ -931,15 +931,15 @@ impl<T: PointeeSized> !Freeze for UnsafeCell<T> {}
pub unsafe auto trait UnsafeUnpin {}
#[unstable(feature = "unsafe_unpin", issue = "125735")]
impl<T: ?Sized> !UnsafeUnpin for UnsafePinned<T> {}
impl<T: PointeeSized> !UnsafeUnpin for UnsafePinned<T> {}
marker_impls! {
#[unstable(feature = "unsafe_unpin", issue = "125735")]
unsafe UnsafeUnpin for
{T: ?Sized} PhantomData<T>,
{T: ?Sized} *const T,
{T: ?Sized} *mut T,
{T: ?Sized} &T,
{T: ?Sized} &mut T,
{T: PointeeSized} PhantomData<T>,
{T: PointeeSized} *const T,
{T: PointeeSized} *mut T,
{T: PointeeSized} &T,
{T: PointeeSized} &mut T,
}
/// Types that do not require any pinning guarantees.