Enum ValTree

pub enum ValTree<'tcx> {
    Leaf(ScalarInt),
    Branch(&'tcx [ValTree<'tcx>]),
}

This datastructure is used to represent the value of constants used in the type system.

We explicitly choose a different datastructure from the way values are processed within CTFE, as in the type system equal values (according to their PartialEq) must also have equal representation (== on the rustc data structure, e.g. ValTree) and vice versa. Since CTFE uses AllocId to represent pointers, it often happens that two different AllocIds point to equal values. So we may end up with different representations for two constants whose value is &42. Furthermore any kind of struct that has padding will have arbitrary values within that padding, even if the values of the struct are the same.

ValTree does not have this problem with representation, as it only contains integers or lists of (nested) ValTree.

Variants

Leaf(ScalarInt)

integers, bool, char are represented as scalars. See the ScalarInt documentation for how ScalarInt guarantees that equal values of these types have the same representation.

Branch(&'tcx [ValTree<'tcx>])

The fields of any kind of aggregate. Structs, tuples and arrays are represented by listing their fields’ values in order.

Enums are represented by storing their discriminant as a field, followed by all the fields of the variant.

ZST types are represented as an empty slice.

Implementations

impl<'tcx> ValTree<'tcx>

pub fn zst() -> Self

pub fn unwrap_leaf(self) -> ScalarInt

pub fn unwrap_branch(self) -> &'tcx [Self]

pub fn from_raw_bytes<'a>(tcx: TyCtxt<'tcx>, bytes: &'a [u8]) -> Self

pub fn from_scalar_int(i: ScalarInt) -> Self

pub fn try_to_scalar(self) -> Option<Scalar>

pub fn try_to_scalar_int(self) -> Option<ScalarInt>

pub fn try_to_target_usize(self, tcx: TyCtxt<'tcx>) -> Option<u64>

pub fn try_to_raw_bytes( self, tcx: TyCtxt<'tcx>, ty: Ty<'tcx>, ) -> Option<&'tcx [u8]>

Get the values inside the ValTree as a slice of bytes. This only works for constants with types &str, &u8, or [u8; _].

Trait Implementations

impl<'tcx> Clone for ValTree<'tcx>

fn clone(&self) -> ValTree<'tcx>

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<'tcx> Debug for ValTree<'tcx>

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

Formats the value using the given formatter.

impl<'tcx, __D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<__D> for ValTree<'tcx>

fn decode(__decoder: &mut __D) -> Self

impl<'tcx, __E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<__E> for ValTree<'tcx>

fn encode(&self, __encoder: &mut __E)

impl<'tcx> EraseType for ValTree<'tcx>

type Result = [u8; 24]

impl<'tcx> Hash for ValTree<'tcx>

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<'tcx, '__ctx> HashStable<StableHashingContext<'__ctx>> for ValTree<'tcx>

fn hash_stable( &self, __hcx: &mut StableHashingContext<'__ctx>, __hasher: &mut StableHasher, )

impl<'tcx> PartialEq for ValTree<'tcx>

fn eq(&self, other: &ValTree<'tcx>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for ValTree<'tcx>

fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>( self, _: &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).

fn fold_with<F: TypeFolder<TyCtxt<'tcx>>>(self, _: &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.

impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for ValTree<'tcx>

fn visit_with<F: TypeVisitor<TyCtxt<'tcx>>>(&self, _: &mut F) -> F::Result

The entry point for visiting. To visit a value t with a visitor v call: t.visit_with(v).

impl<'tcx> Copy for ValTree<'tcx>

impl<'tcx> Eq for ValTree<'tcx>

impl<'tcx> StructuralPartialEq for ValTree<'tcx>

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: 24 bytes

Size for each variant:

• Leaf: 17 bytes
• Branch: 23 bytes