rustc_trait_selection::traits::select::_match

Struct MatchAgainstFreshVars

pub(crate) struct MatchAgainstFreshVars<'tcx> {
    tcx: TyCtxt<'tcx>,
}

Expand description

A type “A” matches “B” if the fresh types in B could be instantiated with values so as to make it equal to A. Matching is intended to be used only on freshened types, and it basically indicates if the non-freshened versions of A and B could have been unified.

It is only an approximation. If it yields false, unification would definitely fail, but a true result doesn’t mean unification would succeed. This is because we don’t track the “side-constraints” on type variables, nor do we track if the same freshened type appears more than once. To some extent these approximations could be fixed, given effort.

Like subtyping, matching is really a binary relation, so the only important thing about the result is Ok/Err. Also, matching never affects any type variables or unification state.

Fields§

§tcx: TyCtxt<'tcx>

Struct MatchAgainstFreshVarsCopy item path

Fields§

Implementations§

impl<'tcx> MatchAgainstFreshVars<'tcx>

pub(crate) fn new(tcx: TyCtxt<'tcx>) -> MatchAgainstFreshVars<'tcx>

Trait Implementations§

impl<'tcx> TypeRelation<TyCtxt<'tcx>> for MatchAgainstFreshVars<'tcx>

fn cx(&self) -> TyCtxt<'tcx>

fn relate_with_variance<T: Relate<TyCtxt<'tcx>>>( &mut self, _: Variance, _: VarianceDiagInfo<TyCtxt<'tcx>>, a: T, b: T, ) -> RelateResult<'tcx, T>

fn regions( &mut self, a: Region<'tcx>, _b: Region<'tcx>, ) -> RelateResult<'tcx, Region<'tcx>>

fn tys(&mut self, a: Ty<'tcx>, b: Ty<'tcx>) -> RelateResult<'tcx, Ty<'tcx>>

fn consts( &mut self, a: Const<'tcx>, b: Const<'tcx>, ) -> RelateResult<'tcx, Const<'tcx>>

fn binders<T>( &mut self, a: Binder<'tcx, T>, b: Binder<'tcx, T>, ) -> RelateResult<'tcx, Binder<'tcx, T>>where T: Relate<TyCtxt<'tcx>>,

fn relate<T>(&mut self, a: T, b: T) -> Result<T, TypeError<I>>where T: Relate<I>,

fn relate_item_args( &mut self, item_def_id: <I as Interner>::DefId, a_arg: <I as Interner>::GenericArgs, b_arg: <I as Interner>::GenericArgs, ) -> Result<<I as Interner>::GenericArgs, TypeError<I>>

Auto Trait Implementations§

impl<'tcx> DynSend for MatchAgainstFreshVars<'tcx>

impl<'tcx> DynSync for MatchAgainstFreshVars<'tcx>

impl<'tcx> Freeze for MatchAgainstFreshVars<'tcx>

impl<'tcx> !RefUnwindSafe for MatchAgainstFreshVars<'tcx>

impl<'tcx> !Send for MatchAgainstFreshVars<'tcx>

impl<'tcx> !Sync for MatchAgainstFreshVars<'tcx>

impl<'tcx> Unpin for MatchAgainstFreshVars<'tcx>

impl<'tcx> !UnwindSafe for MatchAgainstFreshVars<'tcx>

Blanket Implementations§

impl<T> Aligned for T

const ALIGN: Alignment = _

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

fn type_id(&self) -> TypeId

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

fn borrow(&self) -> &T

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

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

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

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

type Output = R

impl<T> Filterable for T

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

impl<T> From<T> for T

fn from(t: T) -> T

impl<T> Instrument for T

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

fn in_current_span(self) -> Instrumented<Self>

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

fn into(self) -> U

impl<T> IntoEither for T

fn into_either(self, into_left: bool) -> Either<Self, Self>

fn into_either_with<F>(self, into_left: F) -> Either<Self, Self>where F: FnOnce(&Self) -> bool,

impl<P> IntoQueryParam<P> for P

fn into_query_param(self) -> P

impl<T> MaybeResult<T> for T

type Error = !

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

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

impl<T> Pointable for T

const ALIGN: usize = _

type Init = T

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

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

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

unsafe fn drop(ptr: usize)

impl<T> Same for T

type Output = T

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

type Error = Infallible

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

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

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

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

impl<I, T, U> Upcast<I, U> for Twhere U: UpcastFrom<I, T>,

fn upcast(self, interner: I) -> U

impl<I, T> UpcastFrom<I, T> for T

fn upcast_from(from: T, _tcx: I) -> T

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

fn vzip(self) -> V

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

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

impl<T> WithSubscriber for T

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

fn with_current_subscriber(self) -> WithDispatch<Self>

Struct MatchAgainstFreshVars

fn binders<T>( &mut self, a: Binder<'tcx, T>, b: Binder<'tcx, T>, ) -> RelateResult<'tcx, Binder<'tcx, T>>
where T: Relate<TyCtxt<'tcx>>,

fn relate<T>(&mut self, a: T, b: T) -> Result<T, TypeError<I>>
where T: Relate<I>,

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

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

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

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

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

fn into_either_with<F>(self, into_left: F) -> Either<Self, Self>
where F: FnOnce(&Self) -> bool,

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

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

impl<I, T, U> Upcast<I, U> for T
where U: UpcastFrom<I, T>,

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

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

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

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

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