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Rollup merge of #123480 - Nadrieril:impl-all-derefpures, r=compiler-errors

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deref patterns: impl `DerefPure` for more std types

Context: [deref patterns](https://github.com/rust-lang/rust/issues/87121). The requirements of `DerefPure` aren't precise yet, but these types unambiguously satisfy them.

Interestingly, a hypothetical `impl DerefMut for Cow` that does a `Clone` would *not* be eligible for `DerefPure` if we allow mixing deref patterns with normal patterns. If the following is exhaustive then the `DerefMut` would cause UB:
```rust
match &mut Cow::Borrowed(&()) {
    Cow::Owned(_) => ..., // Doesn't match
    deref!(_x) if false => ..., // Causes the variant to switch to `Owned`
    Cow::Borrowed(_) => ..., // Doesn't match
    // We reach unreachable
}
```
This commit is contained in:
Matthias Krüger 2024-05-03 06:04:19 +02:00 committed by GitHub
commit e17a222a0a
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4 changed files with 19 additions and 4 deletions
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5
library/alloc/src/borrow.rs
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@ -4,9 +4,9 @@
use core::cmp::Ordering;
use core::hash::{Hash, Hasher};
use core::ops::Deref;
#[cfg(not(no_global_oom_handling))]
use core::ops::{Add, AddAssign};
use core::ops::{Deref, DerefPure};
#[stable(feature = "rust1", since = "1.0.0")]
pub use core::borrow::{Borrow, BorrowMut};
@ -343,6 +343,9 @@ where
}
}
#[unstable(feature = "deref_pure_trait", issue = "87121")]
unsafe impl<B: ?Sized + ToOwned> DerefPure for Cow<'_, B> where B::Owned: Borrow<B> {}
#[stable(feature = "rust1", since = "1.0.0")]
impl<B: ?Sized> Eq for Cow<'_, B> where B: Eq + ToOwned {}

8
library/core/src/cell.rs
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@ -239,7 +239,7 @@ use crate::cmp::Ordering;
use crate::fmt::{self, Debug, Display};
use crate::marker::{PhantomData, Unsize};
use crate::mem::{self, size_of};
use crate::ops::{CoerceUnsized, Deref, DerefMut, DispatchFromDyn};
use crate::ops::{CoerceUnsized, Deref, DerefMut, DerefPure, DispatchFromDyn};
use crate::ptr::{self, NonNull};
mod lazy;
@ -1452,6 +1452,9 @@ impl<T: ?Sized> Deref for Ref<'_, T> {
}
}
#[unstable(feature = "deref_pure_trait", issue = "87121")]
unsafe impl<T: ?Sized> DerefPure for Ref<'_, T> {}
impl<'b, T: ?Sized> Ref<'b, T> {
/// Copies a `Ref`.
///
@ -1844,6 +1847,9 @@ impl<T: ?Sized> DerefMut for RefMut<'_, T> {
}
}
#[unstable(feature = "deref_pure_trait", issue = "87121")]
unsafe impl<T: ?Sized> DerefPure for RefMut<'_, T> {}
#[unstable(feature = "coerce_unsized", issue = "18598")]
impl<'b, T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<RefMut<'b, U>> for RefMut<'b, T> {}

5
library/core/src/mem/manually_drop.rs
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@ -1,4 +1,4 @@
use crate::ops::{Deref, DerefMut};
use crate::ops::{Deref, DerefMut, DerefPure};
use crate::ptr;
/// A wrapper to inhibit compiler from automatically calling `T`’s destructor.
@ -161,3 +161,6 @@ impl<T: ?Sized> DerefMut for ManuallyDrop<T> {
&mut self.value
}
}
#[unstable(feature = "deref_pure_trait", issue = "87121")]
unsafe impl<T: ?Sized> DerefPure for ManuallyDrop<T> {}

5
library/core/src/pin.rs
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@ -923,7 +923,7 @@
use crate::cmp;
use crate::fmt;
use crate::hash::{Hash, Hasher};
use crate::ops::{CoerceUnsized, Deref, DerefMut, DispatchFromDyn, Receiver};
use crate::ops::{CoerceUnsized, Deref, DerefMut, DerefPure, DispatchFromDyn, Receiver};
#[allow(unused_imports)]
use crate::{
@ -1684,6 +1684,9 @@ impl<Ptr: DerefMut<Target: Unpin>> DerefMut for Pin<Ptr> {
}
}
#[unstable(feature = "deref_pure_trait", issue = "87121")]
unsafe impl<Ptr: DerefPure> DerefPure for Pin<Ptr> {}
#[unstable(feature = "receiver_trait", issue = "none")]
impl<Ptr: Receiver> Receiver for Pin<Ptr> {}