UnsafePinned in std::pin - Rust
Description: This type provides a way to entirely opt-out of typical aliasing rules; specifically, `&mut UnsafePinned<T>` is not guaranteed to be a unique pointer. This also subsumes the effects of `UnsafeCell`, i.e., `&UnsafePinned<T>` may point to data that is being mutated.

## UnsafePinned

# Struct UnsafePinned

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    pub struct UnsafePinned<T>where
        T: ?Sized,{ /* private fields */ }

🔬This is a nightly-only experimental API. (`unsafe_pinned` #125735)
Expand description

This type provides a way to entirely opt-out of typical aliasing rules; specifically, `&mut UnsafePinned<T>` is not guaranteed to be a unique pointer. This also subsumes the effects of `UnsafeCell`, i.e., `&UnsafePinned<T>` may point to data that is being mutated.

However, even if you define your type like `pub struct Wrapper(UnsafePinned<...>)`, it is still very risky to have an `&mut Wrapper` that aliases anything else. Many functions that work generically on `&mut T` assume that the memory that stores `T` is uniquely owned (such as `mem::swap`). In other words, while having aliasing with `&mut Wrapper` is not immediate Undefined Behavior, it is still unsound to expose such a mutable reference to code you do not control! Techniques such as pinning via `Pin` are needed to ensure soundness.

Similar to `UnsafeCell`, `UnsafePinned` will not usually show up in the public API of a library. It is an internal implementation detail of libraries that need to support aliasing mutable references.

This type blocks niches the same way `UnsafeCell` does.

## Implementations§

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### impl<T> UnsafePinned<T>

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#### pub const fn new(value: T) -> UnsafePinned<T>

🔬This is a nightly-only experimental API. (`unsafe_pinned` #125735)

Constructs a new instance of `UnsafePinned` which will wrap the specified value.

All access to the inner value through `&UnsafePinned<T>` or `&mut UnsafePinned<T>` or `Pin<&mut UnsafePinned<T>>` requires `unsafe` code.

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#### pub const fn into_inner(self) -> T

🔬This is a nightly-only experimental API. (`unsafe_pinned` #125735)

Unwraps the value, consuming this `UnsafePinned`.

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### impl<T> UnsafePinned<T>
where T: ?Sized,

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#### pub const fn get_mut_pinned(self: Pin<&mut UnsafePinned<T>>) -> *mut T

🔬This is a nightly-only experimental API. (`unsafe_pinned` #125735)

Get read-write access to the contents of a pinned `UnsafePinned`.

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#### pub const fn get_mut_unchecked(&mut self) -> *mut T

🔬This is a nightly-only experimental API. (`unsafe_pinned` #125735)

Get read-write access to the contents of an `UnsafePinned`.

You should usually be using `get_mut_pinned` instead to explicitly track the fact that this memory is “pinned” due to there being aliases.

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#### pub const fn get(&self) -> *mut T

🔬This is a nightly-only experimental API. (`unsafe_pinned` #125735)

Get mutable access to the contents of a shared `UnsafePinned`.

This can be cast to a pointer of any kind. When creating references, you must uphold the aliasing rules; see `UnsafeCell` for more discussion and caveats.

    #![feature(unsafe_pinned)]
    use std::pin::UnsafePinned;

    unsafe {
        let mut x = UnsafePinned::new(0);
        let ptr = x.get();
        x.get_mut_unchecked().write(1);
        assert_eq!(ptr.read(), 1);
    }

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#### pub const fn raw_get(this: *const UnsafePinned<T>) -> *mut T

🔬This is a nightly-only experimental API. (`unsafe_pinned` #125735)

Gets an immutable pointer to the wrapped value.

The difference from `get` is that this function accepts a raw pointer, which is useful to avoid the creation of temporary references.

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#### pub const fn raw_get_mut(this: *mut UnsafePinned<T>) -> *mut T

🔬This is a nightly-only experimental API. (`unsafe_pinned` #125735)

Gets a mutable pointer to the wrapped value.

The difference from `get_mut_pinned` and `get_mut_unchecked` is that this function accepts a raw pointer, which is useful to avoid the creation of temporary references.

## Trait Implementations§

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### impl<T> Debug for UnsafePinned<T>
where T: ?Sized,

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#### fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter. Read more
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### impl<T> Default for UnsafePinned<T>
where T: Default,

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#### fn default() -> UnsafePinned<T>

Creates an `UnsafePinned`, with the `Default` value for T.

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### impl<T> From<T> for UnsafePinned<T>

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#### fn from(value: T) -> UnsafePinned<T>

Creates a new `UnsafePinned<T>` containing the given value.

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### impl<T, U> CoerceUnsized<UnsafePinned<U>> for UnsafePinned<T>
where T: CoerceUnsized<U>,

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### impl<T, U> DispatchFromDyn<UnsafePinned<U>> for UnsafePinned<T>
where T: DispatchFromDyn<U>,

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### impl<T> Sync for UnsafePinned<T>
where T: Sync + ?Sized,

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### impl<T> !Unpin for UnsafePinned<T>
where T: ?Sized,

When this type is used, that almost certainly means safe APIs need to use pinning to avoid the aliases from becoming invalidated. Therefore let’s mark this as `!Unpin`. You can always opt back in to `Unpin` with an `impl` block, provided your API is still sound while unpinned.

## Auto Trait Implementations§

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### impl<T> !Freeze for UnsafePinned<T>

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### impl<T> !RefUnwindSafe for UnsafePinned<T>

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### impl<T> Send for UnsafePinned<T>
where T: Send + ?Sized,

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### impl<T> UnwindSafe for UnsafePinned<T>
where T: UnwindSafe + ?Sized,

## Blanket Implementations§

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### impl<T> Any for T
where T: 'static + ?Sized,

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more
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### impl<T> Borrow<T> for T
where T: ?Sized,

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#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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### impl<T> BorrowMut<T> for T
where T: ?Sized,

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#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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### impl<T> From<!> for T

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#### fn from(t: !) -> T

Converts to this type from the input type.
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### impl<T> From<T> for T

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#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T, U> Into<U> for T
where U: From<T>,

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#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

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### impl<T, U> TryFrom<U> for T
where U: Into<T>,

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#### type Error = Infallible

The type returned in the event of a conversion error.
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#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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### impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.