pub trait Deref {
    type Target: ?Sized;

    // Required method
    fn deref(&self) -> &Self::Target;
}
Available on non-crate feature miri-test-libstd only.
Expand description

Used for immutable dereferencing operations, like *v.

In addition to being used for explicit dereferencing operations with the (unary) * operator in immutable contexts, Deref is also used implicitly by the compiler in many circumstances. This mechanism is called Deref coercion’. In mutable contexts, DerefMut is used.

Implementing Deref for smart pointers makes accessing the data behind them convenient, which is why they implement Deref. On the other hand, the rules regarding Deref and DerefMut were designed specifically to accommodate smart pointers. Because of this, Deref should only be implemented for smart pointers to avoid confusion.

For similar reasons, this trait should never fail. Failure during dereferencing can be extremely confusing when Deref is invoked implicitly.

More on Deref coercion

If T implements Deref<Target = U>, and x is a value of type T, then:

  • In immutable contexts, *x (where T is neither a reference nor a raw pointer) is equivalent to *Deref::deref(&x).
  • Values of type &T are coerced to values of type &U
  • T implicitly implements all the (immutable) methods of the type U.

For more details, visit the chapter in The Rust Programming Language as well as the reference sections on the dereference operator, method resolution and type coercions.

Examples

A struct with a single field which is accessible by dereferencing the struct.

use std::ops::Deref;

struct DerefExample<T> {
    value: T
}

impl<T> Deref for DerefExample<T> {
    type Target = T;

    fn deref(&self) -> &Self::Target {
        &self.value
    }
}

let x = DerefExample { value: 'a' };
assert_eq!('a', *x);

Required Associated Types§

source

type Target: ?Sized

The resulting type after dereferencing.

Required Methods§

source

fn deref(&self) -> &Self::Target

Dereferences the value.

Implementors§

source§

impl Deref for BytesCow

§

type Target = [u8]

§

impl Deref for Bytes

§

type Target = [u8]

§

impl Deref for BytesMut

§

type Target = [u8]

§

impl Deref for CompactString

§

type Target = str

§

impl Deref for Drain<'_>

§

type Target = str

source§

impl Deref for PathBuf

§

type Target = Path

source§

impl Deref for CString

§

type Target = CStr

source§

impl Deref for String

§

type Target = str

source§

impl Deref for OsString

§

impl Deref for ClientConnection

§

type Target = ConnectionCommon<ClientConnectionData>

§

impl Deref for ClientConnection

§

type Target = ConnectionCommon<ClientConnectionData>

§

impl Deref for Connection

§

type Target = CommonState

§

impl Deref for Connection

§

type Target = CommonState

§

impl Deref for ConnectionId

§

type Target = [u8]

§

impl Deref for EnteredSpan

§

type Target = Span

§

impl Deref for FixedBuf

§

type Target = [u8]

§

impl Deref for ServerConnection

§

type Target = ConnectionCommon<ServerConnectionData>

§

impl Deref for ServerConnection

§

type Target = ConnectionCommon<ServerConnectionData>

§

impl Deref for Tls12ClientSessionValue

Available on crate feature tls12 only.
§

type Target = ClientSessionCommon

§

impl Deref for Tls13ClientSessionValue

§

type Target = ClientSessionCommon

§

impl Deref for WakerRef<'_>

1.36.0 · source§

impl<'a> Deref for IoSlice<'a>

§

type Target = [u8]

1.36.0 · source§

impl<'a> Deref for IoSliceMut<'a>

§

type Target = [u8]

source§

impl<'a> Deref for socket2::MaybeUninitSlice<'a>

§

impl<'a> Deref for CRLDistributionPoints<'a>

§

type Target = Vec<CRLDistributionPoint<'a>, Global>

§

impl<'a> Deref for MaybeUninitSlice<'a>

§

impl<'a> Deref for X509Certificate<'a>

§

type Target = TbsCertificate<'a>

source§

impl<'a, 'f> Deref for VaList<'a, 'f>where 'f: 'a,

§

type Target = VaListImpl<'f>

source§

impl<'a, G> Deref for Frozen<'a, G>

Deref allows transparent access to all shared reference (read-only) functionality in the underlying graph.

§

type Target = G

§

impl<'a, K, S> Deref for Ref<'a, K, S>where K: Eq + Hash, S: BuildHasher,

§

type Target = K

§

impl<'a, K, S> Deref for RefMulti<'a, K, S>where K: Eq + Hash, S: BuildHasher,

§

type Target = K

§

impl<'a, K, V, S> Deref for Ref<'a, K, V, S>where K: Eq + Hash, S: BuildHasher,

§

type Target = V

§

impl<'a, K, V, S> Deref for RefMulti<'a, K, V, S>where K: Eq + Hash, S: BuildHasher,

§

type Target = V

§

impl<'a, K, V, S> Deref for RefMut<'a, K, V, S>where K: Eq + Hash, S: BuildHasher,

§

type Target = V

§

impl<'a, K, V, S> Deref for RefMutMulti<'a, K, V, S>where K: Eq + Hash, S: BuildHasher,

§

type Target = V

§

impl<'a, K, V, T, S> Deref for MappedRef<'a, K, V, T, S>where K: Eq + Hash, S: BuildHasher,

§

type Target = T

§

impl<'a, K, V, T, S> Deref for MappedRefMut<'a, K, V, T, S>where K: Eq + Hash, S: BuildHasher,

§

type Target = T

§

impl<'a, R, G, T> Deref for MappedReentrantMutexGuard<'a, R, G, T>where R: RawMutex + 'a, G: GetThreadId + 'a, T: 'a + ?Sized,

§

type Target = T

§

impl<'a, R, G, T> Deref for ReentrantMutexGuard<'a, R, G, T>where R: RawMutex + 'a, G: GetThreadId + 'a, T: 'a + ?Sized,

§

type Target = T

§

impl<'a, R, T> Deref for MappedMutexGuard<'a, R, T>where R: RawMutex + 'a, T: 'a + ?Sized,

§

type Target = T

§

impl<'a, R, T> Deref for MappedRwLockReadGuard<'a, R, T>where R: RawRwLock + 'a, T: 'a + ?Sized,

§

type Target = T

§

impl<'a, R, T> Deref for MappedRwLockWriteGuard<'a, R, T>where R: RawRwLock + 'a, T: 'a + ?Sized,

§

type Target = T

§

impl<'a, R, T> Deref for MutexGuard<'a, R, T>where R: RawMutex + 'a, T: 'a + ?Sized,

§

type Target = T

§

impl<'a, R, T> Deref for RwLockReadGuard<'a, R, T>where R: RawRwLock + 'a, T: 'a + ?Sized,

§

type Target = T

§

impl<'a, R, T> Deref for RwLockUpgradableReadGuard<'a, R, T>where R: RawRwLockUpgrade + 'a, T: 'a + ?Sized,

§

type Target = T

§

impl<'a, R, T> Deref for RwLockWriteGuard<'a, R, T>where R: RawRwLock + 'a, T: 'a + ?Sized,

§

type Target = T

§

impl<'a, T> Deref for AllocatedStackMemory<'a, T>

§

type Target = [T]

§

impl<'a, T> Deref for ArcBorrow<'a, T>

§

type Target = T

§

impl<'a, T> Deref for MappedMutexGuard<'a, T>where T: ?Sized,

§

type Target = T

§

impl<'a, T> Deref for MutexGuard<'a, T>where T: ?Sized,

§

type Target = T

source§

impl<'b, T> Deref for Ptr<'b, T>

§

type Target = T

§

impl<'rwlock, T> Deref for RwLockReadGuard<'rwlock, T>where T: ?Sized,

§

type Target = T

§

impl<'rwlock, T> Deref for RwLockUpgradeableGuard<'rwlock, T>where T: ?Sized,

§

type Target = T

§

impl<'rwlock, T> Deref for RwLockWriteGuard<'rwlock, T>where T: ?Sized,

§

type Target = T

source§

impl<'s> Deref for socket2::sockref::SockRef<'s>

§

impl<'s> Deref for SockRef<'s>

§

type Target = Socket

§

impl<'s, T> Deref for SliceVec<'s, T>

§

type Target = [T]

§

impl<A> Deref for ArrayVec<A>where A: Array,

§

type Target = [<A as Array>::Item]

§

impl<A> Deref for SmallVec<A>where A: Array,

§

type Target = [<A as Array>::Item]

§

impl<A> Deref for TinyVec<A>where A: Array,

§

type Target = [<A as Array>::Item]

const: unstable · source§

impl<B> Deref for Cow<'_, B>where B: ToOwned + ?Sized, <B as ToOwned>::Owned: Borrow<B>,

§

type Target = B

§

impl<Data> Deref for ConnectionCommon<Data>

§

type Target = CommonState

§

impl<H, T> Deref for ThinArc<H, T>

§

type Target = HeaderSlice<HeaderWithLength<H>, [T]>

1.33.0 · source§

impl<P> Deref for Pin<P>where P: Deref,

§

type Target = <P as Deref>::Target

source§

impl<S> Deref for Ascii<S>

§

type Target = S

source§

impl<S> Deref for UniCase<S>

§

type Target = S

§

impl<S> Deref for BlockingStream<S>where S: Stream + Unpin,

§

type Target = S

const: unstable · source§

impl<T> Deref for &Twhere T: ?Sized,

§

type Target = T

const: unstable · source§

impl<T> Deref for &mut Twhere T: ?Sized,

§

type Target = T

source§

impl<T> Deref for kvarn::prelude::compact_str::core::cell::Ref<'_, T>where T: ?Sized,

§

type Target = T

source§

impl<T> Deref for kvarn::prelude::compact_str::core::cell::RefMut<'_, T>where T: ?Sized,

§

type Target = T

1.20.0 (const: unstable) · source§

impl<T> Deref for ManuallyDrop<T>where T: ?Sized,

§

type Target = T

1.9.0 · source§

impl<T> Deref for AssertUnwindSafe<T>

§

type Target = T

source§

impl<T> Deref for kvarn::prelude::Arc<T>where T: ?Sized,

§

type Target = T

source§

impl<T> Deref for ThinBox<T>where T: ?Sized,

§

type Target = T

1.12.0 · source§

impl<T> Deref for PeekMut<'_, T>where T: Ord,

§

type Target = T

source§

impl<T> Deref for Rc<T>where T: ?Sized,

§

type Target = T

source§

impl<T> Deref for std::sync::mutex::MutexGuard<'_, T>where T: ?Sized,

§

type Target = T

source§

impl<T> Deref for std::sync::rwlock::RwLockReadGuard<'_, T>where T: ?Sized,

§

type Target = T

source§

impl<T> Deref for std::sync::rwlock::RwLockWriteGuard<'_, T>where T: ?Sized,

§

type Target = T

§

impl<T> Deref for Arc<T>where T: ?Sized,

§

type Target = T

§

impl<T> Deref for CachePadded<T>

§

type Target = T

§

impl<T> Deref for ConnectionCommon<T>

§

type Target = CommonState

§

impl<T> Deref for MutexGuard<'_, T>where T: ?Sized,

§

type Target = T

§

impl<T> Deref for MutexGuard<'_, T>where T: ?Sized,

§

type Target = T

§

impl<T> Deref for OffsetArc<T>

§

type Target = T

§

impl<T> Deref for Owned<T>where T: Pointable + ?Sized,

§

type Target = T

§

impl<T> Deref for OwnedMutexGuard<T>where T: ?Sized,

§

type Target = T

§

impl<T> Deref for OwnedMutexGuard<T>where T: ?Sized,

§

type Target = T

§

impl<T> Deref for OwnedRwLockWriteGuard<T>where T: ?Sized,

§

type Target = T

§

impl<T> Deref for Ref<'_, T>

§

type Target = T

§

impl<T> Deref for Retrieved<T>

§

type Target = T

§

impl<T> Deref for RwLockMappedWriteGuard<'_, T>where T: ?Sized,

§

type Target = T

§

impl<T> Deref for RwLockReadGuard<'_, T>where T: ?Sized,

§

type Target = T

§

impl<T> Deref for RwLockWriteGuard<'_, T>where T: ?Sized,

§

type Target = T

§

impl<T> Deref for ShardedLockReadGuard<'_, T>where T: ?Sized,

§

type Target = T

§

impl<T> Deref for ShardedLockWriteGuard<'_, T>where T: ?Sized,

§

type Target = T

§

impl<T> Deref for Slice<T>where T: IoBuf,

§

type Target = [u8]

§

impl<T> Deref for UniqueArc<T>where T: ?Sized,

§

type Target = T

const: unstable · source§

impl<T, A> Deref for Box<T, A>where A: Allocator, T: ?Sized,

§

type Target = T

source§

impl<T, A> Deref for Vec<T, A>where A: Allocator,

§

type Target = [T]

source§

impl<T, F> Deref for LazyCell<T, F>where F: FnOnce() -> T,

§

type Target = T

source§

impl<T, F> Deref for LazyLock<T, F>where F: FnOnce() -> T,

§

type Target = T

§

impl<T, F> Deref for Lazy<T, F>where F: FnOnce() -> T,

§

type Target = T

§

impl<T, F> Deref for Lazy<T, F>where F: FnOnce() -> T,

§

type Target = T

source§

impl<T, F, S> Deref for ScopeGuard<T, F, S>where F: FnOnce(T), S: Strategy,

§

type Target = T

§

impl<T, N> Deref for GenericArray<T, N>where N: ArrayLength<T>,

§

type Target = [T]

§

impl<T, U> Deref for MappedMutexGuard<'_, T, U>where T: ?Sized, U: ?Sized,

§

type Target = U

§

impl<T, U> Deref for OwnedMappedMutexGuard<T, U>where T: ?Sized, U: ?Sized,

§

type Target = U

§

impl<T, U> Deref for OwnedRwLockMappedWriteGuard<T, U>where T: ?Sized, U: ?Sized,

§

type Target = U

§

impl<T, U> Deref for OwnedRwLockReadGuard<T, U>where T: ?Sized, U: ?Sized,

§

type Target = U