Struct rustc_type_ir::binder::ArgFolder

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struct ArgFolder<'a, I: Interner> {
    cx: I,
    args: &'a [I::GenericArg],
    binders_passed: u32,
}

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§cx: I§args: &'a [I::GenericArg]§binders_passed: u32

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

Implementations§

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impl<'a, I: Interner> ArgFolder<'a, I>

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fn ty_for_param(&self, p: I::ParamTy, source_ty: I::Ty) -> I::Ty

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

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fn type_param_out_of_range(&self, p: I::ParamTy, ty: I::Ty) -> !

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fn const_for_param(&self, p: I::ParamConst, source_ct: I::Const) -> I::Const

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

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fn const_param_out_of_range(&self, p: I::ParamConst, ct: I::Const) -> !

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fn region_param_expected( &self, ebr: I::EarlyParamRegion, r: I::Region, kind: GenericArgKind<I>, ) -> !

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fn region_param_out_of_range(&self, ebr: I::EarlyParamRegion, r: I::Region) -> !

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fn shift_vars_through_binders<T: TypeFoldable<I>>(&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: I::Region) -> I::Region

Trait Implementations§

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impl<'a, I: Interner> TypeFolder<I> for ArgFolder<'a, I>

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fn cx(&self) -> I

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fn fold_binder<T: TypeFoldable<I>>(&mut self, t: Binder<I, T>) -> Binder<I, T>

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fn fold_region(&mut self, r: I::Region) -> I::Region

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fn fold_ty(&mut self, t: I::Ty) -> I::Ty

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fn fold_const(&mut self, c: I::Const) -> I::Const

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fn fold_predicate(&mut self, p: I::Predicate) -> I::Predicate

Auto Trait Implementations§

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impl<'a, I> Freeze for ArgFolder<'a, I>
where I: Freeze,

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impl<'a, I> RefUnwindSafe for ArgFolder<'a, I>

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impl<'a, I> Send for ArgFolder<'a, I>
where I: Send, <I as Interner>::GenericArg: Sync,

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impl<'a, I> Sync for ArgFolder<'a, I>
where I: Sync, <I as Interner>::GenericArg: Sync,

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impl<'a, I> Unpin for ArgFolder<'a, I>
where I: Unpin,

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impl<'a, I> UnwindSafe for ArgFolder<'a, I>

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 cx(&self) -> I

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

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

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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, !>

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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> 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<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<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,

Layout§

Note: Unable to compute type layout, possibly due to this type having generic parameters. Layout can only be computed for concrete, fully-instantiated types.