Trait tor_hsservice::internal_prelude::DerefMut

1.0.0 · source ·

pub(crate) trait DerefMut: Deref {
    // Required method
    fn deref_mut(&mut self) -> &mut Self::Target;
}

Expand description

Used for mutable dereferencing operations, like in *v = 1;.

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

Warning: Deref coercion is a powerful language feature which has far-reaching implications for every type that implements DerefMut. The compiler will silently insert calls to DerefMut::deref_mut. For this reason, one should be careful about implementing DerefMut and only do so when mutable deref coercion is desirable. See the Deref docs for advice on when this is typically desirable or undesirable.

Types that implement DerefMut or Deref are often called “smart pointers” and the mechanism of deref coercion has been specifically designed to facilitate the pointer-like behaviour that name suggests. Often, the purpose of a “smart pointer” type is to change the ownership semantics of a contained value (for example, Rc or Cow) or the storage semantics of a contained value (for example, Box).

§Mutable deref coercion

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

In mutable contexts, *v (where T is neither a reference nor a raw pointer) is equivalent to *DerefMut::deref_mut(&mut v).
Values of type &mut T are coerced to values of type &mut U
T implicitly implements all the (mutable) 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.

§Fallibility

This trait’s method should never unexpectedly fail. Deref coercion means the compiler will often insert calls to DerefMut::deref_mut implicitly. Failure during dereferencing can be extremely confusing when DerefMut is invoked implicitly. In the majority of uses it should be infallible, though it may be acceptable to panic if the type is misused through programmer error, for example.

However, infallibility is not enforced and therefore not guaranteed. As such, unsafe code should not rely on infallibility in general for soundness.

§Examples

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

use std::ops::{Deref, DerefMut};

struct DerefMutExample<T> {
    value: T
}

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

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

impl<T> DerefMut for DerefMutExample<T> {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.value
    }
}

let mut x = DerefMutExample { value: 'a' };
*x = 'b';
assert_eq!('b', x.value);

Required Methods§

1.0.0 · source

fn deref_mut(&mut self) -> &mut Self::Target

Mutably dereferences the value.

Trait tor_hsservice::internal_prelude::DerefMutCopy item path

§Mutable deref coercion

§Fallibility

§Examples

Required Methods§

fn deref_mut(&mut self) -> &mut Self::Target

Implementors§

impl DerefMut for CTorPath

impl DerefMut for String

impl DerefMut for OsString

impl DerefMut for Asn1BitString

impl DerefMut for Asn1Enumerated

impl DerefMut for Asn1GeneralizedTime

impl DerefMut for Asn1Integer

impl DerefMut for Asn1Object

impl DerefMut for Asn1OctetString

impl DerefMut for Asn1String

impl DerefMut for Asn1Time

impl DerefMut for BigNum

impl DerefMut for BigNumContext

impl DerefMut for Cipher

impl DerefMut for CipherCtx

impl DerefMut for CmsContentInfo

impl DerefMut for Conf

impl DerefMut for DsaSig

impl DerefMut for EcGroup

impl DerefMut for EcPoint

impl DerefMut for EcdsaSig

impl DerefMut for DigestBytes

impl DerefMut for LibCtx

impl DerefMut for Md

impl DerefMut for MdCtx

impl DerefMut for OcspBasicResponse

impl DerefMut for OcspCertId

impl DerefMut for OcspOneReq

impl DerefMut for OcspRequest

impl DerefMut for OcspResponse

impl DerefMut for Pkcs7

impl DerefMut for Pkcs7Signed

impl DerefMut for Pkcs7SignerInfo

impl DerefMut for Pkcs12

impl DerefMut for Provider

impl DerefMut for SrtpProtectionProfile

impl DerefMut for ConnectConfiguration

impl DerefMut for SslAcceptorBuilder

impl DerefMut for SslConnectorBuilder

impl DerefMut for Ssl

impl DerefMut for SslCipher

impl DerefMut for SslContext

impl DerefMut for SslSession

impl DerefMut for OpensslString

impl DerefMut for X509Store

impl DerefMut for X509StoreBuilder

impl DerefMut for AccessDescription

impl DerefMut for DistPoint

impl DerefMut for DistPointName

impl DerefMut for GeneralName

impl DerefMut for X509

impl DerefMut for X509Algorithm

impl DerefMut for X509Crl

impl DerefMut for X509Extension

impl DerefMut for X509Name

impl DerefMut for X509NameEntry

impl DerefMut for X509Object

impl DerefMut for X509Req

impl DerefMut for X509Revoked

impl DerefMut for X509StoreContext

impl DerefMut for X509VerifyParam

impl DerefMut for ByteBuf

impl DerefMut for Bytes

impl DerefMut for PathBuf

impl DerefMut for AsciiString

impl DerefMut for BytesMut

impl DerefMut for ClientConnection

impl DerefMut for ClientConnection

impl DerefMut for Connection

impl DerefMut for Connection

impl DerefMut for DocumentMut

impl DerefMut for OptionsMap

impl DerefMut for ServerConnection

Trait tor_hsservice::internal_prelude::DerefMut

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

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

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

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

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

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

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

impl<'a, T, F> DerefMut for PoolGuard<'a, T, F>
where T: Send, F: Fn() -> T,

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

impl<'v, R: SleepProvider> DerefMut for NotifyingBorrow<'v, R>
where MutexGuard<'v, PublishIptSet>: DerefMut,

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

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

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

impl<A, O> DerefMut for BitArray<A, O>
where A: BitViewSized, O: BitOrder,

impl<B, T> DerefMut for Ref<B, [T]>
where B: ByteSliceMut, T: FromBytes + AsBytes,

impl<B, T> DerefMut for Ref<B, T>
where B: ByteSliceMut, T: FromBytes + AsBytes,

impl<L, R> DerefMut for Either<L, R>
where L: DerefMut, R: DerefMut<Target = <L as Deref>::Target>,

impl<Ptr> DerefMut for Pin<Ptr>
where Ptr: DerefMut, <Ptr as Deref>::Target: Unpin,

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

impl<T> !DerefMut for &T
where T: ?Sized,

impl<T> DerefMut for &mut T
where T: ?Sized,

impl<T> DerefMut for Redacted<T>
where T: Redactable,

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

impl<T> DerefMut for core::cell::RefMut<'_, T>
where T: ?Sized,

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

impl<T> DerefMut for std::sync::mutex::MappedMutexGuard<'_, T>
where T: ?Sized,

impl<T> DerefMut for std::sync::rwlock::MappedRwLockWriteGuard<'_, T>
where T: ?Sized,

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

impl<T> DerefMut for Stack<T>
where T: Stackable,

impl<T> DerefMut for DropNotifyWatchSender<T>
where T: DropNotifyEofSignallable,

impl<T> DerefMut for tor_hsservice::internal_prelude::MutexGuard<'_, T>
where T: ?Sized,

impl<T> DerefMut for ByAddress<T>
where T: Deref + ?Sized,

impl<T> DerefMut for ByThinAddress<T>
where T: Deref + ?Sized,

impl<T> DerefMut for FmtBinary<T>
where T: Binary,

impl<T> DerefMut for FmtDisplay<T>
where T: Display,

impl<T> DerefMut for FmtList<T>
where &'a T: for<'a> IntoIterator,

impl<T> DerefMut for FmtLowerExp<T>
where T: LowerExp,

impl<T> DerefMut for FmtLowerHex<T>
where T: LowerHex,

impl<T> DerefMut for FmtOctal<T>
where T: Octal,

impl<T> DerefMut for FmtPointer<T>
where T: Pointer,