[][src]Enum rustc::ty::BorrowKind

pub enum BorrowKind {
    ImmBorrow,
    UniqueImmBorrow,
    MutBorrow,
}
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Variants

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Data must be immutable and is aliasable.

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Data must be immutable but not aliasable. This kind of borrow cannot currently be expressed by the user and is used only in implicit closure bindings. It is needed when the closure is borrowing or mutating a mutable referent, e.g.:

let x: &mut isize = ...; let y = || *x += 5;

If we were to try to translate this closure into a more explicit form, we'd encounter an error with the code as written:

struct Env { x: & &mut isize } let x: &mut isize = ...; let y = (&mut Env { &x }, fn_ptr); // Closure is pair of env and fn fn fn_ptr(env: &mut Env) { **env.x += 5; }

This is then illegal because you cannot mutate a &mut found in an aliasable location. To solve, you'd have to translate with an &mut borrow:

struct Env { x: & &mut isize } let x: &mut isize = ...; let y = (&mut Env { &mut x }, fn_ptr); // changed from &x to &mut x fn fn_ptr(env: &mut Env) { **env.x += 5; }

Now the assignment to **env.x is legal, but creating a mutable pointer to x is not because x is not mutable. We could fix this by declaring x as let mut x. This is ok in user code, if awkward, but extra weird for closures, since the borrow is hidden.

So we introduce a "unique imm" borrow -- the referent is immutable, but not aliasable. This solves the problem. For simplicity, we don't give users the way to express this borrow, it's just used when translating closures.

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Data is mutable and not aliasable.

Methods

impl BorrowKind
[src]

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Returns a mutability m such that an &m T pointer could be used to obtain this borrow kind. Because borrow kinds are richer than mutabilities, we sometimes have to pick a mutability that is stronger than necessary so that it at least would permit the borrow in question.

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Trait Implementations

impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for BorrowKind
[src]

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impl Clone for BorrowKind
[src]

Returns a copy of the value. Read more

Performs copy-assignment from source. Read more

impl PartialEq for BorrowKind
[src]

This method tests for self and other values to be equal, and is used by ==. Read more

This method tests for !=.

impl Eq for BorrowKind
[src]

impl Hash for BorrowKind
[src]

Feeds this value into the given [Hasher]. Read more

Feeds a slice of this type into the given [Hasher]. Read more

impl Debug for BorrowKind
[src]

Formats the value using the given formatter. Read more

impl Encodable for BorrowKind
[src]

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impl Decodable for BorrowKind
[src]

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impl Copy for BorrowKind
[src]

Auto Trait Implementations

impl Send for BorrowKind

impl Sync for BorrowKind

Blanket Implementations

impl<T> MaybeResult for T
[src]

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🔬 This is a nightly-only experimental API. (rustc_private)

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impl<'a, T> Captures for T where
    T: ?Sized
[src]

impl<T> ToOwned for T where
    T: Clone
[src]

Creates owned data from borrowed data, usually by cloning. Read more

🔬 This is a nightly-only experimental API. (toowned_clone_into)

recently added

Uses borrowed data to replace owned data, usually by cloning. Read more

impl<T> From for T
[src]

Performs the conversion.

impl<T, U> Into for T where
    U: From<T>, 
[src]

Performs the conversion.

impl<T, U> TryFrom for T where
    T: From<U>, 
[src]

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The type returned in the event of a conversion error.

🔬 This is a nightly-only experimental API. (try_from)

Performs the conversion.

impl<T> Borrow for T where
    T: ?Sized
[src]

Important traits for &'a mut R

Immutably borrows from an owned value. Read more

impl<T, U> TryInto for T where
    U: TryFrom<T>, 
[src]

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The type returned in the event of a conversion error.

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Performs the conversion.

impl<T> BorrowMut for T where
    T: ?Sized
[src]

Important traits for &'a mut R

Mutably borrows from an owned value. Read more

impl<T> Any for T where
    T: 'static + ?Sized
[src]

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this method will likely be replaced by an associated static

Gets the TypeId of self. Read more

impl<T> Encodable for T where
    T: UseSpecializedEncodable + ?Sized
[src]

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impl<T> Decodable for T where
    T: UseSpecializedDecodable
[src]

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impl<E> SpecializationError for E
[src]

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Create an error for a missing method specialization. Defaults to panicking with type, trait & method names. S is the encoder/decoder state type, T is the type being encoded/decoded, and the arguments are the names of the trait and method that should've been overridden. Read more

impl<T> Erased for T
[src]

impl<T> Send for T where
    T: ?Sized
[src]

impl<T> Sync for T where
    T: ?Sized
[src]

impl<T> Erased for T