      1
      2
      3
      4
      5
      6
      7
      8
      9
     10
     11
     12
     13
     14
     15
     16
     17
     18
     19
     20
     21
     22
     23
     24
     25
     26
     27
     28
     29
     30
     31
     32
     33
     34
     35
     36
     37
     38
     39
     40
     41
     42
     43
     44
     45
     46
     47
     48
     49
     50
     51
     52
     53
     54
     55
     56
     57
     58
     59
     60
     61
     62
     63
     64
     65
     66
     67
     68
     69
     70
     71
     72
     73
     74
     75
     76
     77
     78
     79
     80
     81
     82
     83
     84
     85
     86
     87
     88
     89
     90
     91
     92
     93
     94
     95
     96
     97
     98
     99
    100
    101
    102
    103
    104
    105
    106
    107
    108
    109
    110
    111
    112
    113
    114
    115
    116
    117
    118
    119
    120
    121
    122
    123
    124
    125
    126
    127
    128
    129
    130
    131
    132
    133
    134
    135
    136
    137
    138
    139
    140
    141
    142
    143
    144
    145
    146
    147
    148
    149
    150
    151
    152
    153
    154
    155
    156
    157
    158
    159
    160
    161
    162
    163
    164
    165
    166
    167
    168
    169
    170
    171
    172
    173
    174
    175
    176
    177
    178
    179
    180
    181
    182
    183
    184
    185
    186
    187
    188
    189
    190
    191
    192
    193
    194

    /// 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'][more]. 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*][book]
    /// as well as the reference sections on [the dereference operator][ref-deref-op],
    /// [method resolution] and [type coercions].
    ///
    /// [book]: ../../book/ch15-02-deref.html
    /// [`DerefMut`]: trait.DerefMut.html
    /// [more]: #more-on-deref-coercion
    /// [ref-deref-op]: ../../reference/expressions/operator-expr.html#the-dereference-operator
    /// [method resolution]: ../../reference/expressions/method-call-expr.html
    /// [type coercions]: ../../reference/type-coercions.html
    ///
    /// # 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);
    /// ```
    #[lang = "deref"]
    #[doc(alias = "*")]
    #[doc(alias = "&*")]
    #[stable(feature = "rust1", since = "1.0.0")]
    pub trait Deref {
        /// The resulting type after dereferencing.
        #[stable(feature = "rust1", since = "1.0.0")]
        type Target: ?Sized;

        /// Dereferences the value.
        #[must_use]
        #[stable(feature = "rust1", since = "1.0.0")]
        fn deref(&self) -> &Self::Target;
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    impl<T: ?Sized> Deref for &T {
        type Target = T;

        fn deref(&self) -> &T {
            *self
        }
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    impl<T: ?Sized> !DerefMut for &T {}

    #[stable(feature = "rust1", since = "1.0.0")]
    impl<T: ?Sized> Deref for &mut T {
        type Target = T;

        fn deref(&self) -> &T {
            *self
        }
    }

    /// 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
    /// ['`Deref` coercion'][more]. In immutable contexts, [`Deref`] is used.
    ///
    /// Implementing `DerefMut` for smart pointers makes mutating the data behind
    /// them convenient, which is why they implement `DerefMut`. On the other hand,
    /// the rules regarding [`Deref`] and `DerefMut` were designed specifically to
    /// accommodate smart pointers. Because of this, **`DerefMut` 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 `DerefMut` is invoked
    /// implicitly.
    ///
    /// # More on `Deref` coercion
    ///
    /// If `T` implements `DerefMut<Target = U>`, and `x` is a value of type `T`,
    /// then:
    ///
    /// * In mutable contexts, `*x` (where `T` is neither a reference nor a raw pointer)
    ///   is equivalent to `*DerefMut::deref_mut(&mut x)`.
    /// * 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*][book]
    /// as well as the reference sections on [the dereference operator][ref-deref-op],
    /// [method resolution] and [type coercions].
    ///
    /// [book]: ../../book/ch15-02-deref.html
    /// [`Deref`]: trait.Deref.html
    /// [more]: #more-on-deref-coercion
    /// [ref-deref-op]: ../../reference/expressions/operator-expr.html#the-dereference-operator
    /// [method resolution]: ../../reference/expressions/method-call-expr.html
    /// [type coercions]: ../../reference/type-coercions.html
    ///
    /// # 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);
    /// ```
    #[lang = "deref_mut"]
    #[doc(alias = "*")]
    #[stable(feature = "rust1", since = "1.0.0")]
    pub trait DerefMut: Deref {
        /// Mutably dereferences the value.
        #[stable(feature = "rust1", since = "1.0.0")]
        fn deref_mut(&mut self) -> &mut Self::Target;
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    impl<T: ?Sized> DerefMut for &mut T {
        fn deref_mut(&mut self) -> &mut T {
            *self
        }
    }

    /// Indicates that a struct can be used as a method receiver, without the
    /// `arbitrary_self_types` feature. This is implemented by stdlib pointer types like `Box<T>`,
    /// `Rc<T>`, `&T`, and `Pin<P>`.
    #[lang = "receiver"]
    #[unstable(feature = "receiver_trait", issue = "none")]
    #[doc(hidden)]
    pub trait Receiver {
        // Empty.
    }

    #[unstable(feature = "receiver_trait", issue = "none")]
    impl<T: ?Sized> Receiver for &T {}

    #[unstable(feature = "receiver_trait", issue = "none")]
    impl<T: ?Sized> Receiver for &mut T {}