[][src]Struct rustc::ty::steal::Steal

pub struct Steal<T> {
    value: RwLock<Option<T>>,
}
🔬 This is a nightly-only experimental API. (rustc_private)

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The Steal struct is intended to used as the value for a query. Specifically, we sometimes have queries (cough MIR cough) where we create a large, complex value that we want to iteratively update (e.g., optimize). We could clone the value for each optimization, but that'd be expensive. And yet we don't just want to mutate it in place, because that would spoil the idea that queries are these pure functions that produce an immutable value (since if you did the query twice, you could observe the mutations). So instead we have the query produce a &'tcx Steal<Mir<'tcx>> (to be very specific). Now we can read from this as much as we want (using borrow()), but you can also steal(). Once you steal, any further attempt to read will panic. Therefore we know that -- assuming no ICE -- nobody is observing the fact that the MIR was updated.

Obviously, whenever you have a query that yields a Steal value, you must treat it with caution, and make sure that you know that -- once the value is stolen -- it will never be read from again.

FIXME(#41710) -- what is the best way to model linear queries?

Fields

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

Methods

impl<T> Steal<T>
[src]

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

Trait Implementations

impl<'a, 'gcx, T> HashStable<StableHashingContext<'a>> for Steal<T> where
    T: HashStable<StableHashingContext<'a>>, 
[src]

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

Auto Trait Implementations

impl<T> Send for Steal<T> where
    T: Send

impl<T> !Sync for Steal<T>

Blanket Implementations

impl<T> MaybeResult for T
[src]

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

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

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]

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

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]

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

The type returned in the event of a conversion error.

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

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]

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

this method will likely be replaced by an associated static

Gets the TypeId of self. Read more

impl<E> SpecializationError for E
[src]

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

this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via Cargo.toml instead?

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