pub struct Ascription<'tcx> {
pub annotation: CanonicalUserTypeAnnotation<'tcx>,
pub variance: Variance,
}
Fields§
§annotation: CanonicalUserTypeAnnotation<'tcx>
§variance: Variance
Variance to use when relating the user_ty
to the type of the value being
matched. Typically, this is Variance::Covariant
, since the value being matched must
have a type that is some subtype of the ascribed type.
Note that this variance does not apply for any bindings within subpatterns. The type
assigned to those bindings must be exactly equal to the user_ty
given here.
The only place where this field is not Covariant
is when matching constants, where
we currently use Contravariant
– this is because the constant type just needs to
be “comparable” to the type of the input value. So, for example:
match x { "foo" => .. }
requires that &'static str <: T_x
, where T_x
is the type of x
. Really, we should
probably be checking for a PartialEq
impl instead, but this preserves the behavior
of the old type-check for now. See #57280 for details.
Trait Implementations§
Source§impl<'tcx> Clone for Ascription<'tcx>
impl<'tcx> Clone for Ascription<'tcx>
Source§fn clone(&self) -> Ascription<'tcx>
fn clone(&self) -> Ascription<'tcx>
1.0.0 · Source§fn clone_from(&mut self, source: &Self)
fn clone_from(&mut self, source: &Self)
source
. Read moreSource§impl<'tcx> Debug for Ascription<'tcx>
impl<'tcx> Debug for Ascription<'tcx>
Source§impl<'tcx, '__ctx> HashStable<StableHashingContext<'__ctx>> for Ascription<'tcx>
impl<'tcx, '__ctx> HashStable<StableHashingContext<'__ctx>> for Ascription<'tcx>
fn hash_stable( &self, __hcx: &mut StableHashingContext<'__ctx>, __hasher: &mut StableHasher, )
Source§impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for Ascription<'tcx>
impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for Ascription<'tcx>
Source§fn visit_with<__V: TypeVisitor<TyCtxt<'tcx>>>(
&self,
__visitor: &mut __V,
) -> __V::Result
fn visit_with<__V: TypeVisitor<TyCtxt<'tcx>>>( &self, __visitor: &mut __V, ) -> __V::Result
Auto Trait Implementations§
impl<'tcx> DynSend for Ascription<'tcx>
impl<'tcx> DynSync for Ascription<'tcx>
impl<'tcx> Freeze for Ascription<'tcx>
impl<'tcx> !RefUnwindSafe for Ascription<'tcx>
impl<'tcx> Send for Ascription<'tcx>
impl<'tcx> Sync for Ascription<'tcx>
impl<'tcx> Unpin for Ascription<'tcx>
impl<'tcx> !UnwindSafe for Ascription<'tcx>
Blanket Implementations§
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> CloneToUninit for Twhere
T: Clone,
impl<T> CloneToUninit for Twhere
T: Clone,
Source§unsafe fn clone_to_uninit(&self, dst: *mut T)
unsafe fn clone_to_uninit(&self, dst: *mut T)
clone_to_uninit
)Source§impl<T, R> CollectAndApply<T, R> for T
impl<T, R> CollectAndApply<T, R> for T
Source§impl<Tcx, T> DepNodeParams<Tcx> for T
impl<Tcx, T> DepNodeParams<Tcx> for T
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<T> Filterable for T
impl<T> Filterable for T
Source§fn filterable(
self,
filter_name: &'static str,
) -> RequestFilterDataProvider<T, fn(_: DataRequest<'_>) -> bool>
fn filterable( self, filter_name: &'static str, ) -> RequestFilterDataProvider<T, fn(_: DataRequest<'_>) -> bool>
Source§impl<T> Instrument for T
impl<T> Instrument for T
Source§fn instrument(self, span: Span) -> Instrumented<Self>
fn instrument(self, span: Span) -> Instrumented<Self>
Source§fn in_current_span(self) -> Instrumented<Self>
fn in_current_span(self) -> Instrumented<Self>
Source§impl<T> IntoEither for T
impl<T> IntoEither for T
Source§fn into_either(self, into_left: bool) -> Either<Self, Self>
fn into_either(self, into_left: bool) -> Either<Self, Self>
self
into a Left
variant of Either<Self, Self>
if into_left
is true
.
Converts self
into a Right
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otherwise. Read moreSource§fn into_either_with<F>(self, into_left: F) -> Either<Self, Self>
fn into_either_with<F>(self, into_left: F) -> Either<Self, Self>
self
into a Left
variant of Either<Self, Self>
if into_left(&self)
returns true
.
Converts self
into a Right
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impl<P> IntoQueryParam<P> for P
fn into_query_param(self) -> P
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I: Interner,
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I: Interner,
T: TypeVisitable<I>,
fn has_type_flags(&self, flags: TypeFlags) -> bool
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
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, this indicates whether
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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
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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_aliases(&self) -> bool
fn has_opaque_types(&self) -> bool
fn has_coroutines(&self) -> bool
fn references_error(&self) -> bool
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_bound_regions(&self) -> bool
fn has_bound_regions(&self) -> bool
Source§fn has_non_region_bound_vars(&self) -> bool
fn has_non_region_bound_vars(&self) -> bool
Source§fn has_bound_vars(&self) -> bool
fn has_bound_vars(&self) -> bool
Source§fn still_further_specializable(&self) -> bool
fn still_further_specializable(&self) -> bool
impl
specialization.Source§impl<I, T, U> Upcast<I, U> for Twhere
U: UpcastFrom<I, T>,
impl<I, T, U> Upcast<I, U> for Twhere
U: UpcastFrom<I, T>,
Source§impl<I, T> UpcastFrom<I, T> for T
impl<I, T> UpcastFrom<I, T> for T
fn upcast_from(from: T, _tcx: I) -> T
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_error: &CycleError, _guar: ErrorGuaranteed, ) -> T
Source§impl<T> WithSubscriber for T
impl<T> WithSubscriber for T
Source§fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>
fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>
Source§fn with_current_subscriber(self) -> WithDispatch<Self>
fn with_current_subscriber(self) -> WithDispatch<Self>
impl<'a, T> Captures<'a> for Twhere
T: ?Sized,
impl<T> ErasedDestructor for Twhere
T: 'static,
impl<T> MaybeSendSync for 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: 32 bytes