Enum rustc_middle::ty::BorrowKind
source · pub enum BorrowKind {
ImmBorrow,
UniqueImmBorrow,
MutBorrow,
}
Variants§
ImmBorrow
Data must be immutable and is aliasable.
UniqueImmBorrow
Data must be immutable but not aliasable. This kind of borrow cannot currently be expressed by the user and is used only in implicit closure bindings. It is needed when the closure is borrowing or mutating a mutable referent, e.g.:
let mut z = 3;
let x: &mut isize = &mut z;
let y = || *x += 5;
If we were to try to translate this closure into a more explicit form, we’d encounter an error with the code as written:
struct Env<'a> { x: &'a &'a mut isize }
let mut z = 3;
let x: &mut isize = &mut z;
let y = (&mut Env { x: &x }, fn_ptr); // Closure is pair of env and fn
fn fn_ptr(env: &mut Env) { **env.x += 5; }
This is then illegal because you cannot mutate a &mut
found
in an aliasable location. To solve, you’d have to translate with
an &mut
borrow:
struct Env<'a> { x: &'a mut &'a mut isize }
let mut z = 3;
let x: &mut isize = &mut z;
let y = (&mut Env { x: &mut x }, fn_ptr); // changed from &x to &mut x
fn fn_ptr(env: &mut Env) { **env.x += 5; }
Now the assignment to **env.x
is legal, but creating a
mutable pointer to x
is not because x
is not mutable. We
could fix this by declaring x
as let mut x
. This is ok in
user code, if awkward, but extra weird for closures, since the
borrow is hidden.
So we introduce a “unique imm” borrow – the referent is immutable, but not aliasable. This solves the problem. For simplicity, we don’t give users the way to express this borrow, it’s just used when translating closures.
FIXME: Rename this to indicate the borrow is actually not immutable.
MutBorrow
Data is mutable and not aliasable.
Implementations§
source§impl BorrowKind
impl BorrowKind
pub fn from_mutbl(m: Mutability) -> BorrowKind
sourcepub fn to_mutbl_lossy(self) -> Mutability
pub fn to_mutbl_lossy(self) -> Mutability
Returns a mutability m
such that an &m T
pointer could be used to obtain this borrow
kind. Because borrow kinds are richer than mutabilities, we sometimes have to pick a
mutability that is stronger than necessary so that it at least would permit the borrow in
question.
Trait Implementations§
source§impl Clone for BorrowKind
impl Clone for BorrowKind
source§fn clone(&self) -> BorrowKind
fn clone(&self) -> BorrowKind
1.0.0 · source§fn clone_from(&mut self, source: &Self)
fn clone_from(&mut self, source: &Self)
source
. Read moresource§impl Debug for BorrowKind
impl Debug for BorrowKind
source§impl<'__ctx> HashStable<StableHashingContext<'__ctx>> for BorrowKind
impl<'__ctx> HashStable<StableHashingContext<'__ctx>> for BorrowKind
fn hash_stable( &self, __hcx: &mut StableHashingContext<'__ctx>, __hasher: &mut StableHasher )
source§impl PartialEq<BorrowKind> for BorrowKind
impl PartialEq<BorrowKind> for BorrowKind
source§fn eq(&self, other: &BorrowKind) -> bool
fn eq(&self, other: &BorrowKind) -> bool
self
and other
values to be equal, and is used
by ==
.source§impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for BorrowKind
impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for BorrowKind
source§fn try_fold_with<__F: FallibleTypeFolder<TyCtxt<'tcx>>>(
self,
__folder: &mut __F
) -> Result<Self, __F::Error>
fn try_fold_with<__F: FallibleTypeFolder<TyCtxt<'tcx>>>( self, __folder: &mut __F ) -> Result<Self, __F::Error>
source§fn fold_with<F>(self, folder: &mut F) -> Selfwhere
F: TypeFolder<I>,
fn fold_with<F>(self, folder: &mut F) -> Selfwhere F: TypeFolder<I>,
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 BorrowKind
impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for BorrowKind
source§fn visit_with<__V: TypeVisitor<TyCtxt<'tcx>>>(
&self,
__visitor: &mut __V
) -> ControlFlow<__V::BreakTy>
fn visit_with<__V: TypeVisitor<TyCtxt<'tcx>>>( &self, __visitor: &mut __V ) -> ControlFlow<__V::BreakTy>
impl Copy for BorrowKind
impl StructuralPartialEq for BorrowKind
Auto Trait Implementations§
impl RefUnwindSafe for BorrowKind
impl Send for BorrowKind
impl Sync for BorrowKind
impl Unpin for BorrowKind
impl UnwindSafe for BorrowKind
Blanket Implementations§
source§impl<'tcx, T> ArenaAllocatable<'tcx, IsCopy> for Twhere
T: Copy,
impl<'tcx, T> ArenaAllocatable<'tcx, IsCopy> for Twhere T: Copy,
fn allocate_on<'a>(self, arena: &'a Arena<'tcx>) -> &'a mut T
fn allocate_from_iter<'a>( arena: &'a Arena<'tcx>, iter: impl IntoIterator<Item = T> ) -> &'a mut [T]
source§impl<T> BorrowMut<T> for Twhere
T: ?Sized,
impl<T> BorrowMut<T> for Twhere T: ?Sized,
source§fn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
source§impl<T, R> CollectAndApply<T, R> for T
impl<T, R> CollectAndApply<T, R> for T
source§impl<Tcx, T> DepNodeParams<Tcx> for Twhere
Tcx: DepContext,
T: for<'a> HashStable<StableHashingContext<'a>> + Debug,
impl<Tcx, T> DepNodeParams<Tcx> for Twhere Tcx: DepContext, T: for<'a> HashStable<StableHashingContext<'a>> + Debug,
default fn fingerprint_style() -> FingerprintStyle
source§default fn to_fingerprint(&self, tcx: Tcx) -> Fingerprint
default fn to_fingerprint(&self, tcx: Tcx) -> Fingerprint
default fn to_debug_str(&self, _: Tcx) -> String
source§default fn recover(_: Tcx, _: &DepNode) -> Option<T>
default fn recover(_: Tcx, _: &DepNode) -> Option<T>
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.source§impl<P> IntoQueryParam<P> for P
impl<P> IntoQueryParam<P> for P
fn into_query_param(self) -> P
source§impl<'tcx, T> IsSuggestable<'tcx> for Twhere
T: TypeVisitable<TyCtxt<'tcx>> + TypeFoldable<TyCtxt<'tcx>>,
impl<'tcx, T> IsSuggestable<'tcx> for Twhere T: TypeVisitable<TyCtxt<'tcx>> + TypeFoldable<TyCtxt<'tcx>>,
source§impl<T> MaybeResult<T> for T
impl<T> MaybeResult<T> for T
source§impl<'tcx, T> ToPredicate<'tcx, T> for T
impl<'tcx, T> ToPredicate<'tcx, T> for T
fn to_predicate(self, _tcx: TyCtxt<'tcx>) -> T
source§impl<'tcx, T> TypeVisitableExt<'tcx> for Twhere
T: TypeVisitable<TyCtxt<'tcx>>,
impl<'tcx, T> TypeVisitableExt<'tcx> for Twhere T: TypeVisitable<TyCtxt<'tcx>>,
source§fn has_vars_bound_at_or_above(&self, binder: DebruijnIndex) -> bool
fn has_vars_bound_at_or_above(&self, binder: DebruijnIndex) -> bool
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 has_vars_bound_above(&self, binder: DebruijnIndex) -> bool
fn has_vars_bound_above(&self, binder: DebruijnIndex) -> bool
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
fn has_escaping_bound_vars(&self) -> bool
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 morefn has_type_flags(&self, flags: TypeFlags) -> bool
fn has_projections(&self) -> bool
fn has_inherent_projections(&self) -> bool
fn has_opaque_types(&self) -> bool
fn has_generators(&self) -> bool
fn references_error(&self) -> bool
fn error_reported(&self) -> Result<(), ErrorGuaranteed>
fn has_non_region_param(&self) -> bool
fn has_infer_regions(&self) -> bool
fn has_infer_types(&self) -> bool
fn has_non_region_infer(&self) -> bool
fn has_infer(&self) -> bool
fn has_placeholders(&self) -> bool
fn has_non_region_placeholders(&self) -> bool
fn has_param(&self) -> bool
source§fn has_free_regions(&self) -> bool
fn has_free_regions(&self) -> bool
fn has_erased_regions(&self) -> bool
source§fn has_erasable_regions(&self) -> bool
fn has_erasable_regions(&self) -> bool
source§fn is_global(&self) -> bool
fn is_global(&self) -> bool
source§fn has_late_bound_regions(&self) -> bool
fn has_late_bound_regions(&self) -> bool
source§fn has_non_region_late_bound(&self) -> bool
fn has_non_region_late_bound(&self) -> bool
source§fn has_late_bound_vars(&self) -> bool
fn has_late_bound_vars(&self) -> bool
source§fn still_further_specializable(&self) -> bool
fn still_further_specializable(&self) -> bool
impl
specialization.source§impl<Tcx, T> Value<Tcx> for Twhere
Tcx: DepContext,
impl<Tcx, T> Value<Tcx> for Twhere Tcx: DepContext,
default fn from_cycle_error( tcx: Tcx, cycle: &[QueryInfo], _guar: ErrorGuaranteed ) -> T
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: 1 byte
Size for each variant:
ImmBorrow
: 0 bytesUniqueImmBorrow
: 0 bytesMutBorrow
: 0 bytes