[][src]Enum rustc::mir::FakeReadCause

pub enum FakeReadCause {
    ForMatchGuard,
    ForMatchedPlace,
    ForGuardBinding,
    ForLet,
    ForIndex,
}
⚙️ 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 FakeReadCause describes the type of pattern why a FakeRead statement exists.

Variants

ForMatchGuard
⚙️ 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.

Inject a fake read of the borrowed input at the end of each guards code.

This should ensure that you cannot change the variant for an enum while you are in the midst of matching on it.

ForMatchedPlace
⚙️ 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.

let x: !; match x {} doesn't generate any read of x so we need to generate a read of x to check that it is initialized and safe.

ForGuardBinding
⚙️ 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.

A fake read of the RefWithinGuard version of a bind-by-value variable in a match guard to ensure that it's value hasn't change by the time we create the OutsideGuard version.

ForLet
⚙️ 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.

Officially, the semantics of

let pattern = <expr>;

is that <expr> is evaluated into a temporary and then this temporary is into the pattern.

However, if we see the simple pattern let var = <expr>, we optimize this to evaluate <expr> directly into the variable var. This is mostly unobservable, but in some cases it can affect the borrow checker, as in #53695. Therefore, we insert a "fake read" here to ensure that we get appropriate errors.

ForIndex
⚙️ 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.

If we have an index expression like

(*x)[1][{ x = y; 4}]

then the first bounds check is invalidated when we evaluate the second index expression. Thus we create a fake borrow of x across the second indexer, which will cause a borrow check error.

Trait Implementations

impl Clone for FakeReadCause[src]

impl Copy for FakeReadCause[src]

impl Debug for FakeReadCause[src]

impl Decodable for FakeReadCause[src]

impl Encodable for FakeReadCause[src]

impl<'__ctx> HashStable<StableHashingContext<'__ctx>> for FakeReadCause[src]

impl<'tcx> Lift<'tcx> for FakeReadCause[src]

type Lifted = Self

⚙️ 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 PartialEq<FakeReadCause> for FakeReadCause[src]

impl StructuralPartialEq for FakeReadCause[src]

impl<'tcx> TypeFoldable<'tcx> for FakeReadCause[src]

Auto Trait Implementations

impl RefUnwindSafe for FakeReadCause

impl Send for FakeReadCause

impl Sync for FakeReadCause

impl Unpin for FakeReadCause

impl UnwindSafe for FakeReadCause

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> Decodable for T where
    T: UseSpecializedDecodable
[src]

impl<T> Encodable for T where
    T: UseSpecializedEncodable + ?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<'tcx, T> Subst<'tcx> for T where
    T: TypeFoldable<'tcx>, 
[src]

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

type Owned = T

The resulting type after obtaining ownership.

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.

impl<T> WithConstness for T[src]