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

pub struct Steal<T> {
    value: RwLock<Option<T>>,
}
⚙️ This is an internal compiler API. (rustc_private)

This crate is being loaded from the sysroot, a permanently unstable location for private compiler dependencies. It is not intended for general use. Prefer using a public version of this crate from crates.io via Cargo.toml.

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::Body<'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.

Fields

value: RwLock<Option<T>>
⚙️ This is an internal compiler API. (rustc_private)

This crate is being loaded from the sysroot, a permanently unstable location for private compiler dependencies. It is not intended for general use. Prefer using a public version of this crate from crates.io via Cargo.toml.

Methods

impl<T> Steal<T>[src]

pub fn new(value: T) -> Self[src]

⚙️ This is an internal compiler API. (rustc_private)

This crate is being loaded from the sysroot, a permanently unstable location for private compiler dependencies. It is not intended for general use. Prefer using a public version of this crate from crates.io via Cargo.toml.

pub fn borrow(&self) -> MappedReadGuard<T>[src]

⚙️ This is an internal compiler API. (rustc_private)

This crate is being loaded from the sysroot, a permanently unstable location for private compiler dependencies. It is not intended for general use. Prefer using a public version of this crate from crates.io via Cargo.toml.

pub fn steal(&self) -> T[src]

⚙️ This is an internal compiler API. (rustc_private)

This crate is being loaded from the sysroot, a permanently unstable location for private compiler dependencies. It is not intended for general use. Prefer using a public version of this crate from crates.io via Cargo.toml.

Trait Implementations

impl<'tcx> ArenaAllocatable for Steal<BodyAndCache<'tcx>>[src]

impl<'tcx> ArenaAllocatable for Steal<IndexVec<Promoted, BodyAndCache<'tcx>>>[src]

impl<'tcx> ArenaField<'tcx> for Steal<BodyAndCache<'tcx>>[src]

impl<'tcx> ArenaField<'tcx> for Steal<IndexVec<Promoted, BodyAndCache<'tcx>>>[src]

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

Auto Trait Implementations

impl<T> !RefUnwindSafe for Steal<T>

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

impl<T> !Sync for Steal<T>

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

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

Blanket Implementations

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

impl<T> ArenaAllocatable for T where
    T: Copy
[src]

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

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

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

impl<T> Erased for T[src]

impl<T> From<T> for T[src]

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

impl<T> MaybeResult<T> for T[src]

type Error = !

⚙️ This is an internal compiler API. (rustc_private)

This crate is being loaded from the sysroot, a permanently unstable location for private compiler dependencies. It is not intended for general use. Prefer using a public version of this crate from crates.io via Cargo.toml.

impl<E> SpecializationError for E[src]

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

type Error = Infallible

The type returned in the event of a conversion error.

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

type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.