Trait TypeFoldable

pub trait TypeFoldable<I: Interner>: TypeVisitable<I> {
    // Required method
    fn try_fold_with<F: FallibleTypeFolder<I>>(
        self,
        folder: &mut F,
    ) -> Result<Self, F::Error>;

    // Provided method
    fn fold_with<F: TypeFolder<I>>(self, folder: &mut F) -> Self { ... }
}

This trait is implemented for every type that can be folded, providing the skeleton of the traversal.

To implement this conveniently, use the derive macro located in rustc_macros.

This trait is a sub-trait of TypeVisitable. This is because many TypeFolder instances use the methods in TypeVisitableExt while folding, which means in practice almost every foldable type needs to also be visitable. (However, there are some types that are visitable without being foldable.)

Required Methods

fn try_fold_with<F: FallibleTypeFolder<I>>( self, folder: &mut F, ) -> Result<Self, F::Error>

The entry point for folding. To fold a value t with a folder f call: t.try_fold_with(f).

For most types, this just traverses the value, calling try_fold_with on each field/element.

For types of interest (such as Ty), the implementation of this method calls a folder method specifically for that type (such as F::try_fold_ty). This is where control transfers from TypeFoldable to TypeFolder.

Provided Methods

fn fold_with<F: TypeFolder<I>>(self, folder: &mut F) -> Self

A convenient alternative to try_fold_with for use with infallible folders. Do not override this method, to ensure coherence with try_fold_with.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementations on Foreign Types

impl<I: Interner> TypeFoldable<I> for Movability

fn try_fold_with<F: FallibleTypeFolder<I>>( self, _: &mut F, ) -> Result<Self, F::Error>

fn fold_with<F: TypeFolder<I>>(self, _: &mut F) -> Self

impl<I: Interner> TypeFoldable<I> for Mutability

fn try_fold_with<F: FallibleTypeFolder<I>>( self, _: &mut F, ) -> Result<Self, F::Error>

fn fold_with<F: TypeFolder<I>>(self, _: &mut F) -> Self

impl<I: Interner> TypeFoldable<I> for bool

fn try_fold_with<F: FallibleTypeFolder<I>>( self, _: &mut F, ) -> Result<Self, F::Error>

fn fold_with<F: TypeFolder<I>>(self, _: &mut F) -> Self

impl<I: Interner> TypeFoldable<I> for u16

fn try_fold_with<F: FallibleTypeFolder<I>>( self, _: &mut F, ) -> Result<Self, F::Error>

fn fold_with<F: TypeFolder<I>>(self, _: &mut F) -> Self

impl<I: Interner> TypeFoldable<I> for u32

fn try_fold_with<F: FallibleTypeFolder<I>>( self, _: &mut F, ) -> Result<Self, F::Error>

fn fold_with<F: TypeFolder<I>>(self, _: &mut F) -> Self

impl<I: Interner> TypeFoldable<I> for u64

fn try_fold_with<F: FallibleTypeFolder<I>>( self, _: &mut F, ) -> Result<Self, F::Error>

fn fold_with<F: TypeFolder<I>>(self, _: &mut F) -> Self

impl<I: Interner> TypeFoldable<I> for ()

fn try_fold_with<F: FallibleTypeFolder<I>>( self, _: &mut F, ) -> Result<Self, F::Error>

fn fold_with<F: TypeFolder<I>>(self, _: &mut F) -> Self

impl<I: Interner> TypeFoldable<I> for usize

fn try_fold_with<F: FallibleTypeFolder<I>>( self, _: &mut F, ) -> Result<Self, F::Error>

fn fold_with<F: TypeFolder<I>>(self, _: &mut F) -> Self

impl<I: Interner> TypeFoldable<I> for String

fn try_fold_with<F: FallibleTypeFolder<I>>( self, _: &mut F, ) -> Result<Self, F::Error>

fn fold_with<F: TypeFolder<I>>(self, _: &mut F) -> Self

impl<I: Interner, A: TypeFoldable<I>, B: TypeFoldable<I>, C: TypeFoldable<I>> TypeFoldable<I> for (A, B, C)

fn try_fold_with<F: FallibleTypeFolder<I>>( self, folder: &mut F, ) -> Result<(A, B, C), F::Error>

impl<I: Interner, T: TypeFoldable<I>> TypeFoldable<I> for Option<T>

fn try_fold_with<F: FallibleTypeFolder<I>>( self, folder: &mut F, ) -> Result<Self, F::Error>

impl<I: Interner, T: TypeFoldable<I>> TypeFoldable<I> for Box<[T]>

fn try_fold_with<F: FallibleTypeFolder<I>>( self, folder: &mut F, ) -> Result<Self, F::Error>

impl<I: Interner, T: TypeFoldable<I>> TypeFoldable<I> for Box<T>

fn try_fold_with<F: FallibleTypeFolder<I>>( self, folder: &mut F, ) -> Result<Self, F::Error>

impl<I: Interner, T: TypeFoldable<I>> TypeFoldable<I> for Vec<T>

fn try_fold_with<F: FallibleTypeFolder<I>>( self, folder: &mut F, ) -> Result<Self, F::Error>

impl<I: Interner, T: TypeFoldable<I>> TypeFoldable<I> for ThinVec<T>

fn try_fold_with<F: FallibleTypeFolder<I>>( self, folder: &mut F, ) -> Result<Self, F::Error>

impl<I: Interner, T: TypeFoldable<I>, E: TypeFoldable<I>> TypeFoldable<I> for Result<T, E>

fn try_fold_with<F: FallibleTypeFolder<I>>( self, folder: &mut F, ) -> Result<Self, F::Error>

impl<I: Interner, T: TypeFoldable<I>, Ix: Idx> TypeFoldable<I> for IndexVec<Ix, T>

fn try_fold_with<F: FallibleTypeFolder<I>>( self, folder: &mut F, ) -> Result<Self, F::Error>

impl<I: Interner, T: TypeFoldable<I>, U: TypeFoldable<I>> TypeFoldable<I> for (T, U)

fn try_fold_with<F: FallibleTypeFolder<I>>( self, folder: &mut F, ) -> Result<(T, U), F::Error>

Implementors

impl<I> TypeFoldable<I> for CanonicalTyVarKind

where I: Interner,

impl<I> TypeFoldable<I> for CanonicalVarKind<I>

where I: Interner, I::PlaceholderTy: TypeFoldable<I>, I::PlaceholderRegion: TypeFoldable<I>, I::PlaceholderConst: TypeFoldable<I>,

impl<I> TypeFoldable<I> for ExistentialPredicate<I>

where I: Interner, ExistentialTraitRef<I>: TypeFoldable<I>, ExistentialProjection<I>: TypeFoldable<I>, I::DefId: TypeFoldable<I>,

impl<I> TypeFoldable<I> for ClauseKind<I>

where I: Interner, TraitPredicate<I>: TypeFoldable<I>, OutlivesPredicate<I, I::Region>: TypeFoldable<I>, OutlivesPredicate<I, I::Ty>: TypeFoldable<I>, ProjectionPredicate<I>: TypeFoldable<I>, I::Const: TypeFoldable<I>, I::Ty: TypeFoldable<I>, I::GenericArg: TypeFoldable<I>, HostEffectPredicate<I>: TypeFoldable<I>,

impl<I> TypeFoldable<I> for PredicateKind<I>

where I: Interner, ClauseKind<I>: TypeFoldable<I>, I::DefId: TypeFoldable<I>, SubtypePredicate<I>: TypeFoldable<I>, CoercePredicate<I>: TypeFoldable<I>, I::Const: TypeFoldable<I>, NormalizesTo<I>: TypeFoldable<I>, I::Term: TypeFoldable<I>,

impl<I> TypeFoldable<I> for ProbeKind<I>

where I: Interner, QueryResult<I>: TypeFoldable<I>, CandidateSource<I>: TypeFoldable<I>,

impl<I> TypeFoldable<I> for CanonicalVarInfo<I>

where I: Interner, CanonicalVarKind<I>: TypeFoldable<I>,

impl<I> TypeFoldable<I> for CanonicalVarValues<I>

where I: Interner, I::GenericArgs: TypeFoldable<I>,

impl<I> TypeFoldable<I> for UnevaluatedConst<I>

where I: Interner, I::DefId: TypeFoldable<I>, I::GenericArgs: TypeFoldable<I>,

impl<I> TypeFoldable<I> for OpaqueTypeKey<I>

where I: Interner, I::LocalDefId: TypeFoldable<I>, I::GenericArgs: TypeFoldable<I>,

impl<I> TypeFoldable<I> for AliasTerm<I>

where I: Interner, I::GenericArgs: TypeFoldable<I>, I::DefId: TypeFoldable<I>,

impl<I> TypeFoldable<I> for CoercePredicate<I>

where I: Interner, I::Ty: TypeFoldable<I>,

impl<I> TypeFoldable<I> for ExistentialProjection<I>

where I: Interner, I::DefId: TypeFoldable<I>, I::GenericArgs: TypeFoldable<I>, I::Term: TypeFoldable<I>,

impl<I> TypeFoldable<I> for ExistentialTraitRef<I>

where I: Interner, I::DefId: TypeFoldable<I>, I::GenericArgs: TypeFoldable<I>,

impl<I> TypeFoldable<I> for HostEffectPredicate<I>

where I: Interner, TraitRef<I>: TypeFoldable<I>,

impl<I> TypeFoldable<I> for NormalizesTo<I>

where I: Interner, AliasTerm<I>: TypeFoldable<I>, I::Term: TypeFoldable<I>,

impl<I> TypeFoldable<I> for ProjectionPredicate<I>

where I: Interner, AliasTerm<I>: TypeFoldable<I>, I::Term: TypeFoldable<I>,

impl<I> TypeFoldable<I> for SubtypePredicate<I>

where I: Interner, I::Ty: TypeFoldable<I>,

impl<I> TypeFoldable<I> for TraitPredicate<I>

where I: Interner, TraitRef<I>: TypeFoldable<I>,

impl<I> TypeFoldable<I> for TraitRef<I>

where I: Interner, I::DefId: TypeFoldable<I>, I::GenericArgs: TypeFoldable<I>,

impl<I> TypeFoldable<I> for ExternalConstraintsData<I>

where I: Interner, Vec<OutlivesPredicate<I, I::GenericArg>>: TypeFoldable<I>, Vec<(OpaqueTypeKey<I>, I::Ty)>: TypeFoldable<I>, NestedNormalizationGoals<I>: TypeFoldable<I>,

impl<I> TypeFoldable<I> for NestedNormalizationGoals<I>

where I: Interner, Vec<(GoalSource, Goal<I, I::Predicate>)>: TypeFoldable<I>,

impl<I> TypeFoldable<I> for PredefinedOpaquesData<I>

where I: Interner, Vec<(OpaqueTypeKey<I>, I::Ty)>: TypeFoldable<I>,

impl<I> TypeFoldable<I> for Response<I>

where I: Interner, CanonicalVarValues<I>: TypeFoldable<I>, I::ExternalConstraints: TypeFoldable<I>,

impl<I> TypeFoldable<I> for ClosureArgs<I>

where I: Interner, I::GenericArgs: TypeFoldable<I>,

impl<I> TypeFoldable<I> for CoroutineArgs<I>

where I: Interner, I::GenericArgs: TypeFoldable<I>,

impl<I> TypeFoldable<I> for CoroutineClosureArgs<I>

where I: Interner, I::GenericArgs: TypeFoldable<I>,

impl<I> TypeFoldable<I> for CoroutineClosureSignature<I>

where I: Interner, I::Ty: TypeFoldable<I>,

impl<I> TypeFoldable<I> for GenSig<I>

where I: Interner, I::Ty: TypeFoldable<I>,

impl<I> TypeFoldable<I> for AliasTy<I>

where I: Interner, I::GenericArgs: TypeFoldable<I>, I::DefId: TypeFoldable<I>,

impl<I> TypeFoldable<I> for FnHeader<I>

where I: Interner, I::Safety: TypeFoldable<I>, I::Abi: TypeFoldable<I>,

impl<I> TypeFoldable<I> for FnSig<I>

where I: Interner, I::Tys: TypeFoldable<I>,

impl<I> TypeFoldable<I> for FnSigTys<I>

where I: Interner, I::Tys: TypeFoldable<I>,

impl<I> TypeFoldable<I> for TypeAndMut<I>

where I: Interner, I::Ty: TypeFoldable<I>,

impl<I, A> TypeFoldable<I> for OutlivesPredicate<I, A>

where I: Interner, A: TypeFoldable<I>, I::Region: TypeFoldable<I>,

impl<I, P> TypeFoldable<I> for Goal<I, P>

where I: Interner, I::ParamEnv: TypeFoldable<I>, P: TypeFoldable<I>,

impl<I, P> TypeFoldable<I> for QueryInput<I, P>

where I: Interner, Goal<I, P>: TypeFoldable<I>, I::PredefinedOpaques: TypeFoldable<I>,

impl<I, T> TypeFoldable<I> for State<I, T>

where I: Interner, CanonicalVarValues<I>: TypeFoldable<I>, T: TypeFoldable<I>,

impl<I, V> TypeFoldable<I> for Canonical<I, V>

where I: Interner, V: TypeFoldable<I>, I::CanonicalVars: TypeFoldable<I>,

impl<I: Interner> TypeFoldable<I> for Variance

impl<I: Interner> TypeFoldable<I> for BoundConstness

impl<I: Interner> TypeFoldable<I> for PredicatePolarity

impl<I: Interner> TypeFoldable<I> for AliasRelationDirection

impl<I: Interner> TypeFoldable<I> for BuiltinImplSource

impl<I: Interner> TypeFoldable<I> for Certainty

impl<I: Interner> TypeFoldable<I> for GoalSource

impl<I: Interner> TypeFoldable<I> for MaybeCause

impl<I: Interner> TypeFoldable<I> for AliasTyKind

impl<I: Interner> TypeFoldable<I> for FloatTy

impl<I: Interner> TypeFoldable<I> for InferTy

impl<I: Interner> TypeFoldable<I> for IntVarValue

impl<I: Interner> TypeFoldable<I> for RegionVid

impl<I: Interner> TypeFoldable<I> for NoSolution

impl<I: Interner> TypeFoldable<I> for DebruijnIndex

impl<I: Interner> TypeFoldable<I> for UniverseIndex

impl<I: Interner, T> !TypeFoldable<I> for EarlyBinder<I, T>

For early binders, you should first call instantiate before using any visitors.

impl<I: Interner, T: TypeFoldable<I>> TypeFoldable<I> for Binder<I, T>

impl<I: Interner, T: TypeFoldable<I>> TypeFoldable<I> for Lrc<T>

impl<T, I> TypeFoldable<I> for ExpectedFound<T>

where I: Interner, T: TypeFoldable<I>,