pub 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.

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§tcx: TyCtxt<'tcx>

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impl<'tcx> MatchAgainstFreshVars<'tcx>

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

Trait Implementations§

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

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

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

Switch variance for the purpose of relating a and b.
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fn regions( &mut self, a: Region<'tcx>, _b: Region<'tcx>, ) -> RelateResult<'tcx, Region<'tcx>>

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

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

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

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

Generic relation routine suitable for most anything.
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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>>

Relate the two args for the given item. The default is to look up the variance for the item and proceed accordingly.

Auto Trait Implementations§

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

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

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

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

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

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

Blanket Implementations§

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impl<T> Aligned for T

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const ALIGN: Alignment = _

Alignment of Self.
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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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

Mutably borrows from an owned value. Read more
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impl<T, R> CollectAndApply<T, R> for T

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

Equivalent to f(&iter.collect::<Vec<_>>()).

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type Output = R

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impl<T> Filterable for T

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

Creates a filterable data provider with the given name for debugging. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T> Instrument for T

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

Instruments this type with the provided Span, returning an Instrumented wrapper. Read more
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fn in_current_span(self) -> Instrumented<Self>

Instruments this type with the current Span, returning an Instrumented wrapper. Read more
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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T> IntoEither for T

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

Converts self into a Left variant of Either<Self, Self> if into_left is true. Converts self into a Right variant of Either<Self, Self> otherwise. Read more
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fn into_either_with<F>(self, into_left: F) -> Either<Self, Self>
where F: FnOnce(&Self) -> bool,

Converts self into a Left variant of Either<Self, Self> if into_left(&self) returns true. Converts self into a Right variant of Either<Self, Self> otherwise. Read more
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impl<P> IntoQueryParam<P> for P

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impl<T> MaybeResult<T> for T

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type Error = !

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

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

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impl<T> Same for T

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type Output = T

Should always be Self
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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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impl<I, T, U> Upcast<I, U> for T
where U: UpcastFrom<I, T>,

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

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

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

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

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fn vzip(self) -> V

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

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

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impl<T> WithSubscriber for T

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

Attaches the provided Subscriber to this type, returning a WithDispatch wrapper. Read more
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fn with_current_subscriber(self) -> WithDispatch<Self>

Attaches the current default Subscriber to this type, returning a WithDispatch wrapper. Read more
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impl<'a, T> Captures<'a> for T
where T: ?Sized,

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

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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: 8 bytes