Struct rustc_middle::thir::Ascription
source · 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
sourceimpl<'tcx> Clone for Ascription<'tcx>
impl<'tcx> Clone for Ascription<'tcx>
sourcefn clone(&self) -> Ascription<'tcx>
fn clone(&self) -> Ascription<'tcx>
1.0.0 · sourcefn clone_from(&mut self, source: &Self)
fn clone_from(&mut self, source: &Self)
source
. Read moresourceimpl<'tcx> Debug for Ascription<'tcx>
impl<'tcx> Debug for Ascription<'tcx>
sourceimpl<'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
)
Auto Trait Implementations
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
sourceimpl<T> BorrowMut<T> for Twhere
T: ?Sized,
impl<T> BorrowMut<T> for Twhere
T: ?Sized,
const: unstable · sourcefn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
sourceimpl<Ctxt, T> DepNodeParams<Ctxt> for Twhere
Ctxt: DepContext,
T: for<'a> HashStable<StableHashingContext<'a>> + Debug,
impl<Ctxt, T> DepNodeParams<Ctxt> for Twhere
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
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>
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 moresourceimpl<T, R> InternIteratorElement<T, R> for T
impl<T, R> InternIteratorElement<T, R> for T
type Output = R
fn intern_with<I, F>(iter: I, f: F) -> <T as InternIteratorElement<T, R>>::Outputwhere
I: Iterator<Item = T>,
F: FnOnce(&[T]) -> R,
sourceimpl<T> MaybeResult<T> for T
impl<T> MaybeResult<T> for T
sourceimpl<CTX, T> Value<CTX> for Twhere
CTX: DepContext,
impl<CTX, T> Value<CTX> for Twhere
CTX: DepContext,
default fn from_cycle_error(tcx: CTX) -> T
impl<'a, T> Captures<'a> for Twhere
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: 32 bytes