Enum rustc::mir::BorrowKind [] [src]

pub enum BorrowKind {
    Shared,
    Unique,
    Mut,
}
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Variants

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Data must be immutable and is aliasable.

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

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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 you 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.

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

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Data is mutable and not aliasable.

Methods

impl BorrowKind
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Trait Implementations

impl<'tcx> HashStable<StableHashingContext<'tcx>> for BorrowKind
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impl Copy for BorrowKind
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impl Clone for BorrowKind
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Returns a copy of the value. Read more

1.0.0
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Performs copy-assignment from source. Read more

impl Debug for BorrowKind
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Formats the value using the given formatter.

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

1.0.0
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This method tests for !=.

impl Eq for BorrowKind
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impl Encodable for BorrowKind
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impl Decodable for BorrowKind
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[src]

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

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