Enum rustc::traits::Vtable

pub enum Vtable<'tcx, N> {
    VtableImpl(VtableImplData<'tcx, N>),
    VtableAutoImpl(VtableAutoImplData<N>),
    VtableParam(Vec<N>),
    VtableObject(VtableObjectData<'tcx, N>),
    VtableBuiltin(VtableBuiltinData<N>),
    VtableClosure(VtableClosureData<'tcx, N>),
    VtableFnPointer(VtableFnPointerData<'tcx, N>),
    VtableGenerator(VtableGeneratorData<'tcx, N>),
}

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Given the successful resolution of an obligation, the Vtable indicates where the vtable comes from. Note that while we call this a "vtable", it does not necessarily indicate dynamic dispatch at runtime. Vtable instances just tell the compiler where to find methods, but in generic code those methods are typically statically dispatched -- only when an object is constructed is a Vtable instance reified into an actual vtable.

For example, the vtable may be tied to a specific impl (case A), or it may be relative to some bound that is in scope (case B).

impl<T:Clone> Clone<T> for Option<T> { ... } // Impl_1
impl<T:Clone> Clone<T> for Box<T> { ... }    // Impl_2
impl Clone for int { ... }             // Impl_3

fn foo<T:Clone>(concrete: Option<Box<int>>,
                param: T,
                mixed: Option<T>) {

   // Case A: Vtable points at a specific impl. Only possible when
   // type is concretely known. If the impl itself has bounded
   // type parameters, Vtable will carry resolutions for those as well:
   concrete.clone(); // Vtable(Impl_1, [Vtable(Impl_2, [Vtable(Impl_3)])])

   // Case B: Vtable must be provided by caller. This applies when
   // type is a type parameter.
   param.clone();    // VtableParam

   // Case C: A mix of cases A and B.
   mixed.clone();    // Vtable(Impl_1, [VtableParam])
}

The type parameter N

See explanation on VtableImplData.

Variants

VtableImpl(VtableImplData<'tcx, N>)

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Vtable identifying a particular impl.

VtableAutoImpl(VtableAutoImplData<N>)

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Vtable for auto trait implementations This carries the information and nested obligations with regards to an auto implementation for a trait Trait. The nested obligations ensure the trait implementation holds for all the constituent types.

VtableParam(Vec<N>)

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Successful resolution to an obligation provided by the caller for some type parameter. The Vec<N> represents the obligations incurred from normalizing the where-clause (if any).

VtableObject(VtableObjectData<'tcx, N>)

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Virtual calls through an object

VtableBuiltin(VtableBuiltinData<N>)

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Successful resolution for a builtin trait.

VtableClosure(VtableClosureData<'tcx, N>)

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Vtable automatically generated for a closure. The def ID is the ID of the closure expression. This is a VtableImpl in spirit, but the impl is generated by the compiler and does not appear in the source.

VtableFnPointer(VtableFnPointerData<'tcx, N>)

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Same as above, but for a fn pointer type with the given signature.

VtableGenerator(VtableGeneratorData<'tcx, N>)

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Vtable automatically generated for a generator

Methods

impl<'tcx, N> Vtable<'tcx, N>

Important traits for Vec<u8>

impl Write for Vec<u8>

pub fn nested_obligations(self) -> Vec<N>

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pub fn map<M, F>(self, f: F) -> Vtable<'tcx, M> where
    F: FnMut(N) -> M, 

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Trait Implementations

impl<'gcx, N> HashStable<StableHashingContext<'gcx>> for Vtable<'gcx, N> where
    N: HashStable<StableHashingContext<'gcx>>, 

fn hash_stable<W: StableHasherResult>(
    &self,
    hcx: &mut StableHashingContext<'gcx>,
    hasher: &mut StableHasher<W>
)

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impl<'tcx, N: Debug> Debug for Vtable<'tcx, N>

fn fmt(&self, f: &mut Formatter) -> Result

Formats the value using the given formatter.

impl<'a, 'tcx> Lift<'tcx> for Vtable<'a, ()>

type Lifted = Vtable<'tcx, ()>

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fn lift_to_tcx<'b, 'gcx>(
    &self,
    tcx: TyCtxt<'b, 'gcx, 'tcx>
) -> Option<Self::Lifted>

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impl<'tcx, N: TypeFoldable<'tcx>> TypeFoldable<'tcx> for Vtable<'tcx, N>

fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(
    &self,
    folder: &mut F
) -> Self

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fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool

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

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fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool

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fn has_regions_escaping_depth(&self, depth: u32) -> bool

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fn has_escaping_regions(&self) -> bool

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fn has_type_flags(&self, flags: TypeFlags) -> bool

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fn has_projections(&self) -> bool

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fn references_error(&self) -> bool

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fn has_param_types(&self) -> bool

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fn has_self_ty(&self) -> bool

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fn has_infer_types(&self) -> bool

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fn needs_infer(&self) -> bool

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fn needs_subst(&self) -> bool

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fn has_re_skol(&self) -> bool

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fn has_closure_types(&self) -> bool

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fn has_erasable_regions(&self) -> bool

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fn is_normalized_for_trans(&self) -> bool

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fn is_global(&self) -> bool

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Indicates whether this value references only 'global' types/lifetimes that are the same regardless of what fn we are in. This is used for caching. Errs on the side of returning false.

impl<'tcx, N: Clone> Clone for Vtable<'tcx, N>

fn clone(&self) -> Vtable<'tcx, N>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<'tcx, N: Encodable> Encodable for Vtable<'tcx, N>

fn encode<__SN: Encoder>(&self, __arg_0: &mut __SN) -> Result<(), __SN::Error>

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impl<'tcx, N: Decodable> Decodable for Vtable<'tcx, N>

fn decode<__DN: Decoder>(
    __arg_0: &mut __DN
) -> Result<Vtable<'tcx, N>, __DN::Error>

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