struct ArgFolder<'a, 'tcx> {
    tcx: TyCtxt<'tcx>,
    args: &'a [GenericArg<'tcx>],
    binders_passed: u32,
}

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§tcx: TyCtxt<'tcx>§args: &'a [GenericArg<'tcx>]§binders_passed: u32

Number of region binders we have passed through while doing the instantiation

Implementations§

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impl<'a, 'tcx> ArgFolder<'a, 'tcx>

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fn ty_for_param(&self, p: ParamTy, source_ty: Ty<'tcx>) -> Ty<'tcx>

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fn type_param_expected( &self, p: ParamTy, ty: Ty<'tcx>, kind: GenericArgKind<'tcx> ) -> !

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fn type_param_out_of_range(&self, p: ParamTy, ty: Ty<'tcx>) -> !

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fn const_for_param(&self, p: ParamConst, source_ct: Const<'tcx>) -> Const<'tcx>

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fn const_param_expected( &self, p: ParamConst, ct: Const<'tcx>, kind: GenericArgKind<'tcx> ) -> !

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fn const_param_out_of_range(&self, p: ParamConst, ct: Const<'tcx>) -> !

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fn shift_vars_through_binders<T: TypeFoldable<TyCtxt<'tcx>>>(&self, val: T) -> T

It is sometimes necessary to adjust the De Bruijn indices during instantiation. This occurs when we are instantating a type with escaping bound vars into a context where we have passed through binders. That’s quite a mouthful. Let’s see an example:

type Func<A> = fn(A);
type MetaFunc = for<'a> fn(Func<&'a i32>);

The type MetaFunc, when fully expanded, will be

for<'a> fn(fn(&'a i32))
//      ^~ ^~ ^~~
//      |  |  |
//      |  |  DebruijnIndex of 2
//      Binders

Here the 'a lifetime is bound in the outer function, but appears as an argument of the inner one. Therefore, that appearance will have a DebruijnIndex of 2, because we must skip over the inner binder (remember that we count De Bruijn indices from 1). However, in the definition of MetaFunc, the binder is not visible, so the type &'a i32 will have a De Bruijn index of 1. It’s only during the instantiation that we can see we must increase the depth by 1 to account for the binder that we passed through.

As a second example, consider this twist:

type FuncTuple<A> = (A,fn(A));
type MetaFuncTuple = for<'a> fn(FuncTuple<&'a i32>);

Here the final type will be:

for<'a> fn((&'a i32, fn(&'a i32)))
//          ^~~         ^~~
//          |           |
//   DebruijnIndex of 1 |
//               DebruijnIndex of 2

As indicated in the diagram, here the same type &'a i32 is instantiated once, but in the first case we do not increase the De Bruijn index and in the second case we do. The reason is that only in the second case have we passed through a fn binder.

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fn shift_region_through_binders(&self, region: Region<'tcx>) -> Region<'tcx>

Trait Implementations§

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impl<'a, 'tcx> TypeFolder<TyCtxt<'tcx>> for ArgFolder<'a, 'tcx>

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

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fn fold_binder<T: TypeFoldable<TyCtxt<'tcx>>>( &mut self, t: Binder<'tcx, T> ) -> Binder<'tcx, T>

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fn fold_region(&mut self, r: Region<'tcx>) -> Region<'tcx>

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fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx>

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fn fold_const(&mut self, c: Const<'tcx>) -> Const<'tcx>

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impl<'a, 'tcx> DynSend for ArgFolder<'a, 'tcx>

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impl<'a, 'tcx> DynSync for ArgFolder<'a, 'tcx>

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impl<'a, 'tcx> !RefUnwindSafe for ArgFolder<'a, 'tcx>

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impl<'a, 'tcx> !Send for ArgFolder<'a, 'tcx>

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impl<'a, 'tcx> !Sync for ArgFolder<'a, 'tcx>

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impl<'a, 'tcx> Unpin for ArgFolder<'a, 'tcx>

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impl<'a, 'tcx> !UnwindSafe for ArgFolder<'a, '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<I, F> FallibleTypeFolder<I> for F
where I: Interner, F: TypeFolder<I>,

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type Error = !

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fn interner(&self) -> I

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fn try_fold_binder<T>( &mut self, t: <I as Interner>::Binder<T> ) -> Result<<I as Interner>::Binder<T>, !>
where T: TypeFoldable<I>, <I as Interner>::Binder<T>: TypeSuperFoldable<I>,

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fn try_fold_ty( &mut self, t: <I as Interner>::Ty ) -> Result<<I as Interner>::Ty, !>
where <I as Interner>::Ty: TypeSuperFoldable<I>,

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fn try_fold_region( &mut self, r: <I as Interner>::Region ) -> Result<<I as Interner>::Region, !>

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fn try_fold_const( &mut self, c: <I as Interner>::Const ) -> Result<<I as Interner>::Const, !>
where <I as Interner>::Const: TypeSuperFoldable<I>,

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fn try_fold_predicate( &mut self, p: <I as Interner>::Predicate ) -> Result<<I as Interner>::Predicate, !>

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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<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> Pointable for T

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const ALIGN: usize = _

The alignment of pointer.
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type Init = T

The type for initializers.
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unsafe fn init(init: <T as Pointable>::Init) -> usize

Initializes a with the given initializer. Read more
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unsafe fn deref<'a>(ptr: usize) -> &'a T

Dereferences the given pointer. Read more
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unsafe fn deref_mut<'a>(ptr: usize) -> &'a mut T

Mutably dereferences the given pointer. Read more
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unsafe fn drop(ptr: usize)

Drops the object pointed to by the given pointer. Read more
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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<'tcx, T> ToPredicate<'tcx, T> for T

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fn to_predicate(self, _tcx: TyCtxt<'tcx>) -> T

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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<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,

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