Enum rustc_middle::mir::FakeReadCause
source · [−]pub enum FakeReadCause {
ForMatchGuard,
ForMatchedPlace(Option<DefId>),
ForGuardBinding,
ForLet(Option<DefId>),
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<DefId>)
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 DefId 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<DefId>)
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
sourceimpl Clone for FakeReadCause
impl Clone for FakeReadCause
sourcefn clone(&self) -> FakeReadCause
fn clone(&self) -> FakeReadCause
Returns a copy of the value. Read more
1.0.0 · sourcefn clone_from(&mut self, source: &Self)
fn clone_from(&mut self, source: &Self)
Performs copy-assignment from source
. Read more
sourceimpl Debug for FakeReadCause
impl Debug for FakeReadCause
sourceimpl<'tcx, __D: TyDecoder<'tcx>> Decodable<__D> for FakeReadCause
impl<'tcx, __D: TyDecoder<'tcx>> Decodable<__D> for FakeReadCause
sourceimpl<'tcx, __E: TyEncoder<'tcx>> Encodable<__E> for FakeReadCause
impl<'tcx, __E: TyEncoder<'tcx>> Encodable<__E> for FakeReadCause
sourceimpl Hash for FakeReadCause
impl Hash for FakeReadCause
sourceimpl<'__ctx> HashStable<StableHashingContext<'__ctx>> for FakeReadCause
impl<'__ctx> HashStable<StableHashingContext<'__ctx>> for FakeReadCause
fn hash_stable(
&self,
__hcx: &mut StableHashingContext<'__ctx>,
__hasher: &mut StableHasher
)
sourceimpl<'tcx> Lift<'tcx> for FakeReadCause
impl<'tcx> Lift<'tcx> for FakeReadCause
type Lifted = FakeReadCause
fn lift_to_tcx(self, _: TyCtxt<'tcx>) -> Option<Self>
sourceimpl PartialEq<FakeReadCause> for FakeReadCause
impl PartialEq<FakeReadCause> for FakeReadCause
sourcefn eq(&self, other: &FakeReadCause) -> bool
fn eq(&self, other: &FakeReadCause) -> bool
This method tests for self
and other
values to be equal, and is used
by ==
. Read more
sourcefn ne(&self, other: &FakeReadCause) -> bool
fn ne(&self, other: &FakeReadCause) -> bool
This method tests for !=
.
sourceimpl<'tcx> TypeFoldable<'tcx> for FakeReadCause
impl<'tcx> TypeFoldable<'tcx> for FakeReadCause
sourcefn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
self,
_: &mut F
) -> Result<FakeReadCause, F::Error>
fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
self,
_: &mut F
) -> Result<FakeReadCause, F::Error>
Traverses the type in question, typically by calling try_fold_with
on
each field/element. This is true even for types of interest such as
Ty
. This should only be called within TypeFolder
methods, when
non-custom traversals are desired for types of interest. Read more
sourcefn super_visit_with<F: TypeVisitor<'tcx>>(
&self,
_: &mut F
) -> ControlFlow<F::BreakTy>
fn super_visit_with<F: TypeVisitor<'tcx>>(
&self,
_: &mut F
) -> ControlFlow<F::BreakTy>
Traverses the type in question, typically by calling visit_with
on
each field/element. This is true even for types of interest such as
Ty
. This should only be called within TypeVisitor
methods, when
non-custom traversals are desired for types of interest. Read more
sourcefn try_fold_with<F: FallibleTypeFolder<'tcx>>(
self,
folder: &mut F
) -> Result<Self, F::Error>
fn try_fold_with<F: FallibleTypeFolder<'tcx>>(
self,
folder: &mut F
) -> Result<Self, F::Error>
The main entry point for folding. To fold a value t
with a folder f
call: t.try_fold_with(f)
. Read more
sourcefn fold_with<F: TypeFolder<'tcx, Error = !>>(self, folder: &mut F) -> Self
fn fold_with<F: TypeFolder<'tcx, Error = !>>(self, folder: &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
. Read more
sourcefn super_fold_with<F: TypeFolder<'tcx, Error = !>>(self, folder: &mut F) -> Self
fn super_fold_with<F: TypeFolder<'tcx, Error = !>>(self, folder: &mut F) -> Self
A convenient alternative to try_super_fold_with
for use with
infallible folders. Do not override this method, to ensure coherence
with try_super_fold_with
. Read more
sourcefn visit_with<V: TypeVisitor<'tcx>>(
&self,
visitor: &mut V
) -> ControlFlow<V::BreakTy>
fn visit_with<V: TypeVisitor<'tcx>>(
&self,
visitor: &mut V
) -> ControlFlow<V::BreakTy>
The entry point for visiting. To visit a value t
with a visitor v
call: t.visit_with(v)
. Read more
sourcefn has_vars_bound_at_or_above(&self, binder: DebruijnIndex) -> bool
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. Read more
sourcefn has_vars_bound_above(&self, binder: DebruijnIndex) -> bool
fn has_vars_bound_above(&self, binder: DebruijnIndex) -> bool
Returns true
if this self
has any regions that escape binder
(and
hence are not bound by it). Read more
fn has_escaping_bound_vars(&self) -> bool
fn has_type_flags(&self, flags: TypeFlags) -> bool
fn has_projections(&self) -> bool
fn has_opaque_types(&self) -> bool
fn references_error(&self) -> bool
fn error_reported(&self) -> Option<ErrorGuaranteed>
fn has_param_types_or_consts(&self) -> bool
fn has_infer_regions(&self) -> bool
fn has_infer_types(&self) -> bool
fn has_infer_types_or_consts(&self) -> bool
fn needs_infer(&self) -> bool
fn has_placeholders(&self) -> bool
fn needs_subst(&self) -> bool
sourcefn has_free_regions(&self) -> bool
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. Read more
fn has_erased_regions(&self) -> bool
sourcefn has_erasable_regions(&self) -> bool
fn has_erasable_regions(&self) -> bool
True if there are any un-erased free regions.
sourcefn is_global(&self) -> bool
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. Read more
sourcefn has_late_bound_regions(&self) -> bool
fn has_late_bound_regions(&self) -> bool
True if there are any late-bound regions
sourcefn still_further_specializable(&self) -> bool
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. Read more
impl Copy for FakeReadCause
impl StructuralPartialEq for FakeReadCause
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
sourceimpl<'tcx, T> ArenaAllocatable<'tcx, IsCopy> for T where
T: Copy,
impl<'tcx, T> ArenaAllocatable<'tcx, IsCopy> for T where
T: Copy,
fn allocate_on(self, arena: &'a Arena<'tcx>) -> &'a mut T
fn allocate_from_iter(
arena: &'a Arena<'tcx>,
iter: impl IntoIterator<Item = T>
) -> &'a mut [T]ⓘNotable traits for &'_ [u8]impl<'_> Read for &'_ [u8]impl<'_> Write for &'_ mut [u8]
sourceimpl<T> BorrowMut<T> for T where
T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
const: unstable · sourcefn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more
sourceimpl<Ctxt, T> DepNodeParams<Ctxt> for T where
Ctxt: DepContext,
T: for<'a> HashStable<StableHashingContext<'a>> + Debug,
impl<Ctxt, T> DepNodeParams<Ctxt> for T where
Ctxt: DepContext,
T: for<'a> HashStable<StableHashingContext<'a>> + Debug,
default fn fingerprint_style() -> FingerprintStyle
sourcedefault fn to_fingerprint(&self, tcx: Ctxt) -> Fingerprint
default fn to_fingerprint(&self, tcx: Ctxt) -> 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). Read more
default fn to_debug_str(&self, Ctxt) -> String
sourcedefault fn recover(Ctxt, &DepNode<<Ctxt as DepContext>::DepKind>) -> Option<T>
default fn recover(Ctxt, &DepNode<<Ctxt as DepContext>::DepKind>) -> Option<T>
This method tries to recover the query key from the given DepNode
,
something which is needed when forcing DepNode
s 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. Read more
sourceimpl<T> MaybeResult<T> for T
impl<T> MaybeResult<T> for T
sourceimpl<T> ToOwned for T where
T: Clone,
impl<T> ToOwned for T where
T: Clone,
type Owned = T
type Owned = T
The resulting type after obtaining ownership.
sourcefn clone_into(&self, target: &mut T)
fn clone_into(&self, target: &mut T)
toowned_clone_into
)Uses borrowed data to replace owned data, usually by cloning. Read more
impl<'a, T> Captures<'a> for T where
T: ?Sized,
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: 12 bytes
Size for each variant:
ForMatchGuard
: 0 bytesForMatchedPlace
: 8 bytesForGuardBinding
: 0 bytesForLet
: 8 bytesForIndex
: 0 bytes