Trait hacspec_lib::prelude::Deref

1.0.0 · source · [−]
pub trait Deref {
    type Target: ?Sized;

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

The resulting type after dereferencing.

Required Methods

Dereferences the value.

Implementors

impl<'a, S: 'a + ToOwned + ?Sized> Deref for ANSIGenericString<'a, S> where
    <S as ToOwned>::Owned: Debug, 

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

impl Deref for Underscore

impl Deref for Add

impl Deref for And

impl Deref for At

impl Deref for Bang

impl Deref for Caret

impl Deref for Colon

impl Deref for Comma

impl Deref for Div

impl Deref for Dollar

impl Deref for Dot

impl Deref for Eq

impl Deref for Gt

impl Deref for Lt

impl Deref for Or

impl Deref for Pound

impl Deref for Question

impl Deref for Rem

impl Deref for Semi

impl Deref for Star

impl Deref for Sub

impl Deref for Tilde

impl<'c, 'a> Deref for StepCursor<'c, 'a>