Enum rustc_middle::ty::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<AllocId>>

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

pub fn try_to_machine_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> From<ValTree<'tcx>> for ConstKind<'tcx>

fn from(original: ValTree<'tcx>) -> ConstKind<'tcx>

Converts to this type from the input type.

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> Lift<'tcx> for ValTree<'tcx>

type Lifted = ValTree<'tcx>

fn lift_to_tcx(self, _: TyCtxt<'tcx>) -> Option<Self>

impl<'tcx> Ord for ValTree<'tcx>

fn cmp(&self, other: &ValTree<'tcx>) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Selfwhere
    Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Selfwhere
    Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Selfwhere
    Self: Sized + PartialOrd<Self>,

Restrict a value to a certain interval.

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

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

This method tests for self and other values to be equal, and is used by ==.

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

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

impl<'tcx> PartialOrd<ValTree<'tcx>> for ValTree<'tcx>

fn partial_cmp(&self, other: &ValTree<'tcx>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

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

This method tests less than (for self and other) and is used by the < operator.

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

This method tests less than or equal to (for self and other) and is used by the <= operator.

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

This method tests greater than (for self and other) and is used by the > operator.

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

This method tests greater than or equal to (for self and other) and is used by the >= operator.

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

fn try_fold_with<F: FallibleTypeFolder<'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<'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<'tcx> for ValTree<'tcx>

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

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

fn has_vars_bound_at_or_above(&self, binder: DebruijnIndex) -> bool

Returns true if self has any late-bound regions that are either bound by binder or bound by some binder outside of binder. If binder is ty::INNERMOST, this indicates whether there are any late-bound regions that appear free.

fn has_vars_bound_above(&self, binder: DebruijnIndex) -> bool

Returns true if this type has any regions that escape binder (and hence are not bound by it).

fn has_escaping_bound_vars(&self) -> bool

Return true if this type has regions that are not a part of the type. For example, for<'a> fn(&'a i32) return false, while fn(&'a i32) would return true. The latter can occur when traversing through the former.

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

fn has_projections(&self) -> bool

fn has_opaque_types(&self) -> bool

fn references_error(&self) -> bool

fn error_reported(&self) -> Result<(), ErrorGuaranteed>

fn has_non_region_param(&self) -> bool

fn has_infer_regions(&self) -> bool

fn has_infer_types(&self) -> bool

fn has_non_region_infer(&self) -> bool

fn needs_infer(&self) -> bool

fn has_placeholders(&self) -> bool

fn needs_subst(&self) -> bool

fn has_free_regions(&self) -> bool

“Free” regions in this context means that it has any region that is not (a) erased or (b) late-bound.

fn has_erased_regions(&self) -> bool

fn has_erasable_regions(&self) -> bool

True if there are any un-erased free regions.

fn is_global(&self) -> bool

Indicates whether this value references only ‘global’ generic parameters that are the same regardless of what fn we are in. This is used for caching.

fn has_late_bound_regions(&self) -> bool

True if there are any late-bound regions

fn still_further_specializable(&self) -> bool

Indicates whether this value still has parameters/placeholders/inference variables which could be replaced later, in a way that would change the results of impl specialization.

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

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

impl<'tcx> StructuralEq 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