pub enum FakeReadCause {
    ForMatchGuard,
    ForMatchedPlace(Option<LocalDefId>),
    ForGuardBinding,
    ForLet(Option<LocalDefId>),
    ForIndex,
}
Expand description

The FakeReadCause describes the type of pattern why a FakeRead statement exists.

Variants§

§

ForMatchGuard

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(Option<LocalDefId>)

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.

If a closure pattern matches a Place starting with an Upvar, then we introduce a FakeRead for that Place outside the closure, in such a case this option would be Some(closure_def_id). Otherwise, the value of the optional LocalDefId will be None.

§

ForGuardBinding

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

§

ForLet(Option<LocalDefId>)

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.

If a closure pattern matches a Place starting with an Upvar, then we introduce a FakeRead for that Place outside the closure, in such a case this option would be Some(closure_def_id). Otherwise, the value of the optional DefId will be None.

§

ForIndex

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§

source§

impl Clone for FakeReadCause

source§

fn clone(&self) -> FakeReadCause

Returns a copy of the value. Read more
1.0.0 · source§

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
source§

impl Debug for FakeReadCause

source§

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
source§

impl<__D: TyDecoder> Decodable<__D> for FakeReadCause

source§

fn decode(__decoder: &mut __D) -> Self

source§

impl<__E: TyEncoder> Encodable<__E> for FakeReadCause

source§

fn encode(&self, __encoder: &mut __E)

source§

impl Hash for FakeReadCause

source§

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher. Read more
1.3.0 · source§

fn hash_slice<H>(data: &[Self], state: &mut H)
where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher. Read more
source§

impl<'__ctx> HashStable<StableHashingContext<'__ctx>> for FakeReadCause

source§

fn hash_stable( &self, __hcx: &mut StableHashingContext<'__ctx>, __hasher: &mut StableHasher )

source§

impl PartialEq for FakeReadCause

source§

fn eq(&self, other: &FakeReadCause) -> bool

This method tests for self and other values to be equal, and is used by ==.
1.0.0 · source§

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
source§

impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for FakeReadCause

source§

fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>( self, _: &mut F ) -> Result<Self, F::Error>

The entry point for folding. To fold a value t with a folder f call: t.try_fold_with(f). Read more
source§

fn fold_with<F: TypeFolder<TyCtxt<'tcx>>>(self, _: &mut F) -> Self

A convenient alternative to try_fold_with for use with infallible folders. Do not override this method, to ensure coherence with try_fold_with.
source§

impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for FakeReadCause

source§

fn visit_with<F: TypeVisitor<TyCtxt<'tcx>>>( &self, _: &mut F ) -> ControlFlow<F::BreakTy>

The entry point for visiting. To visit a value t with a visitor v call: t.visit_with(v). Read more
source§

impl Copy for FakeReadCause

source§

impl StructuralPartialEq for FakeReadCause

Auto Trait Implementations§

Blanket Implementations§

source§

impl<T> Aligned for T

source§

const ALIGN: Alignment = _

Alignment of Self.
source§

impl<T> Any for T
where T: 'static + ?Sized,

source§

fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
§

impl<T> AnyEq for T
where T: Any + PartialEq,

§

fn equals(&self, other: &(dyn Any + 'static)) -> bool

§

fn as_any(&self) -> &(dyn Any + 'static)

source§

impl<'tcx, T> ArenaAllocatable<'tcx, IsCopy> for T
where T: Copy,

source§

fn allocate_on<'a>(self, arena: &'a Arena<'tcx>) -> &'a mut T

source§

fn allocate_from_iter<'a>( arena: &'a Arena<'tcx>, iter: impl IntoIterator<Item = T> ) -> &'a mut [T]

source§

impl<'tcx, T> ArenaAllocatable<'tcx, IsCopy> for T
where T: Copy,

source§

fn allocate_on<'a>(self, arena: &'a Arena<'tcx>) -> &'a mut T

source§

fn allocate_from_iter<'a>( arena: &'a Arena<'tcx>, iter: impl IntoIterator<Item = T> ) -> &'a mut [T]

source§

impl<T> Borrow<T> for T
where T: ?Sized,

source§

fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
source§

impl<T> BorrowMut<T> for T
where T: ?Sized,

source§

fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
source§

impl<T, R> CollectAndApply<T, R> for T

source§

fn collect_and_apply<I, F>(iter: I, f: F) -> R
where I: Iterator<Item = T>, F: FnOnce(&[T]) -> R,

Equivalent to f(&iter.collect::<Vec<_>>()).

§

type Output = R

source§

impl<Tcx, T> DepNodeParams<Tcx> for T
where Tcx: DepContext, T: for<'a> HashStable<StableHashingContext<'a>> + Debug,

source§

default fn fingerprint_style() -> FingerprintStyle

source§

default fn to_fingerprint(&self, tcx: Tcx) -> Fingerprint

This method turns the parameters of a DepNodeConstructor into an opaque Fingerprint to be used in DepNode. Not all DepNodeParams support being turned into a Fingerprint (they don’t need to if the corresponding DepNode is anonymous).
source§

default fn to_debug_str(&self, _: Tcx) -> String

source§

default fn recover(_: Tcx, _: &DepNode) -> Option<T>

This method tries to recover the query key from the given DepNode, something which is needed when forcing DepNodes during red-green evaluation. The query system will only call this method if fingerprint_style() is not FingerprintStyle::Opaque. It is always valid to return None here, in which case incremental compilation will treat the query as having changed instead of forcing it.
§

impl<T> Filterable for T

§

fn filterable( self, filter_name: &'static str ) -> RequestFilterDataProvider<T, fn(_: DataRequest<'_>) -> bool>

Creates a filterable data provider with the given name for debugging. Read more
source§

impl<T> From<T> for T

source§

fn from(t: T) -> T

Returns the argument unchanged.

source§

impl<T> Instrument for T

source§

fn instrument(self, span: Span) -> Instrumented<Self>

Instruments this type with the provided Span, returning an Instrumented wrapper. Read more
source§

fn in_current_span(self) -> Instrumented<Self>

Instruments this type with the current Span, returning an Instrumented wrapper. Read more
source§

impl<T, U> Into<U> for T
where U: From<T>,

source§

fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

source§

impl<P> IntoQueryParam<P> for P

source§

impl<'tcx, T> IsSuggestable<'tcx> for T
where T: TypeVisitable<TyCtxt<'tcx>> + TypeFoldable<TyCtxt<'tcx>>,

source§

fn is_suggestable(self, tcx: TyCtxt<'tcx>, infer_suggestable: bool) -> bool

Whether this makes sense to suggest in a diagnostic. Read more
source§

fn make_suggestable( self, tcx: TyCtxt<'tcx>, infer_suggestable: bool ) -> Option<T>

source§

impl<T> MaybeResult<T> for T

§

type Error = !

source§

fn from(_: Result<T, <T as MaybeResult<T>>::Error>) -> T

source§

fn to_result(self) -> Result<T, <T as MaybeResult<T>>::Error>

§

impl<T> Pointable for T

§

const ALIGN: usize = _

The alignment of pointer.
§

type Init = T

The type for initializers.
§

unsafe fn init(init: <T as Pointable>::Init) -> usize

Initializes a with the given initializer. Read more
§

unsafe fn deref<'a>(ptr: usize) -> &'a T

Dereferences the given pointer. Read more
§

unsafe fn deref_mut<'a>(ptr: usize) -> &'a mut T

Mutably dereferences the given pointer. Read more
§

unsafe fn drop(ptr: usize)

Drops the object pointed to by the given pointer. Read more
source§

impl<T> Same for T

§

type Output = T

Should always be Self
source§

impl<T> ToOwned for T
where T: Clone,

§

type Owned = T

The resulting type after obtaining ownership.
source§

fn to_owned(&self) -> T

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

fn clone_into(&self, target: &mut T)

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

impl<'tcx, T> ToPredicate<'tcx, T> for T

source§

fn to_predicate(self, _tcx: TyCtxt<'tcx>) -> T

source§

impl<T, U> TryFrom<U> for T
where U: Into<T>,

§

type Error = Infallible

The type returned in the event of a conversion error.
source§

fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
source§

impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

§

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

The type returned in the event of a conversion error.
source§

fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
source§

impl<I, T> TypeVisitableExt<I> for T
where I: Interner, T: TypeVisitable<I>,

source§

fn has_type_flags(&self, flags: TypeFlags) -> bool

source§

fn has_vars_bound_at_or_above(&self, binder: DebruijnIndex) -> bool

Returns true if self has any late-bound regions that are either bound by binder or bound by some binder outside of binder. If binder is ty::INNERMOST, this indicates whether there are any late-bound regions that appear free.
source§

fn error_reported(&self) -> Result<(), <I as Interner>::ErrorGuaranteed>

source§

fn has_vars_bound_above(&self, binder: DebruijnIndex) -> bool

Returns true if this type has any regions that escape binder (and hence are not bound by it).
source§

fn has_escaping_bound_vars(&self) -> bool

Return true if this type has regions that are not a part of the type. For example, for<'a> fn(&'a i32) return false, while fn(&'a i32) would return true. The latter can occur when traversing through the former. Read more
source§

fn has_projections(&self) -> bool

source§

fn has_inherent_projections(&self) -> bool

source§

fn has_opaque_types(&self) -> bool

source§

fn has_coroutines(&self) -> bool

source§

fn references_error(&self) -> bool

source§

fn has_non_region_param(&self) -> bool

source§

fn has_infer_regions(&self) -> bool

source§

fn has_infer_types(&self) -> bool

source§

fn has_non_region_infer(&self) -> bool

source§

fn has_infer(&self) -> bool

source§

fn has_placeholders(&self) -> bool

source§

fn has_non_region_placeholders(&self) -> bool

source§

fn has_param(&self) -> bool

source§

fn has_free_regions(&self) -> bool

“Free” regions in this context means that it has any region that is not (a) erased or (b) late-bound.
source§

fn has_erased_regions(&self) -> bool

source§

fn has_erasable_regions(&self) -> bool

True if there are any un-erased free regions.
source§

fn is_global(&self) -> bool

Indicates whether this value references only ‘global’ generic parameters that are the same regardless of what fn we are in. This is used for caching.
source§

fn has_bound_regions(&self) -> bool

True if there are any late-bound regions
source§

fn has_non_region_bound_vars(&self) -> bool

True if there are any late-bound non-region variables
source§

fn has_bound_vars(&self) -> bool

True if there are any bound variables
source§

fn still_further_specializable(&self) -> bool

Indicates whether this value still has parameters/placeholders/inference variables which could be replaced later, in a way that would change the results of impl specialization.
§

impl<V, T> VZip<V> for T
where V: MultiLane<T>,

§

fn vzip(self) -> V

source§

impl<Tcx, T> Value<Tcx> for T
where Tcx: DepContext,

source§

default fn from_cycle_error( tcx: Tcx, cycle_error: &CycleError, _guar: ErrorGuaranteed ) -> T

source§

impl<T> WithSubscriber for T

source§

fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>
where S: Into<Dispatch>,

Attaches the provided Subscriber to this type, returning a WithDispatch wrapper. Read more
source§

fn with_current_subscriber(self) -> WithDispatch<Self>

Attaches the current default Subscriber to this type, returning a WithDispatch wrapper. Read more
source§

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

§

impl<T> ErasedDestructor for T
where T: 'static,

§

impl<T> MaybeSendSync for T
where T: Send + Sync,

Layout§

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 8 bytes

Size for each variant:

  • ForMatchGuard: 0 bytes
  • ForMatchedPlace: 4 bytes
  • ForGuardBinding: 0 bytes
  • ForLet: 4 bytes
  • ForIndex: 0 bytes