Enum Const

pub enum Const<'tcx> {
    Ty(Ty<'tcx>, Const<'tcx>),
    Unevaluated(UnevaluatedConst<'tcx>, Ty<'tcx>),
    Val(ConstValue<'tcx>, Ty<'tcx>),
}

Constants

Variants

Ty(Ty<'tcx>, Const<'tcx>)

This constant came from the type system.

Any way of turning ty::Const into ConstValue should go through valtree_to_const_val; this ensures that we consistently produce “clean” values without data in the padding or anything like that.

FIXME(BoxyUwU): We should remove this Ty and look up the type for params via ParamEnv

Unevaluated(UnevaluatedConst<'tcx>, Ty<'tcx>)

An unevaluated mir constant which is not part of the type system.

Note that Ty(ty::ConstKind::Unevaluated) and this variant are not identical! Ty will always flow through a valtree, so all data not captured in the valtree is lost. This variant directly uses the evaluated result of the given constant, including e.g. data stored in padding.

Val(ConstValue<'tcx>, Ty<'tcx>)

This constant cannot go back into the type system, as it represents something the type system cannot handle (e.g. pointers).

Implementations

impl<'tcx> Const<'tcx>

pub fn from_unevaluated( tcx: TyCtxt<'tcx>, def_id: DefId, ) -> EarlyBinder<'tcx, Const<'tcx>>

Creates an unevaluated const from a DefId for a const item. The binders of the const item still need to be instantiated.

pub fn ty(&self) -> Ty<'tcx>

pub fn is_required_const(&self) -> bool

Determines whether we need to add this const to required_consts. This is the case if and only if evaluating it may error.

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

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

pub fn try_to_bits(self, size: Size) -> Option<u128>

pub fn try_to_bool(self) -> Option<bool>

pub fn eval( self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>, span: Span, ) -> Result<ConstValue<'tcx>, ErrorHandled>

pub fn try_eval_scalar( self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>, ) -> Option<Scalar>

pub fn try_eval_scalar_int( self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>, ) -> Option<ScalarInt>

pub fn try_eval_bits( &self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>, ) -> Option<u128>

pub fn eval_bits(self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>) -> u128

Panics if the value cannot be evaluated or doesn’t contain a valid integer of the given type.

pub fn try_eval_target_usize( self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>, ) -> Option<u64>

pub fn eval_target_usize( self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>, ) -> u64

Panics if the value cannot be evaluated or doesn’t contain a valid usize.

pub fn try_eval_bool( self, tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>, ) -> Option<bool>

pub fn from_value(val: ConstValue<'tcx>, ty: Ty<'tcx>) -> Self

pub fn from_bits( tcx: TyCtxt<'tcx>, bits: u128, param_env_ty: ParamEnvAnd<'tcx, Ty<'tcx>>, ) -> Self

pub fn from_bool(tcx: TyCtxt<'tcx>, v: bool) -> Self

pub fn zero_sized(ty: Ty<'tcx>) -> Self

pub fn from_usize(tcx: TyCtxt<'tcx>, n: u64) -> Self

pub fn from_scalar(_tcx: TyCtxt<'tcx>, s: Scalar, ty: Ty<'tcx>) -> Self

pub fn from_ty_const(c: Const<'tcx>, ty: Ty<'tcx>, tcx: TyCtxt<'tcx>) -> Self

pub fn is_deterministic(&self) -> bool

Return true if any evaluation of this constant always returns the same value, taking into account even pointer identity tests.

Trait Implementations

impl<'tcx> Clone for Const<'tcx>

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

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<'tcx> Debug for Const<'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 Const<'tcx>

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

impl<'tcx> Display for Const<'tcx>

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

Formats the value using the given formatter.

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

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

impl<'tcx> EraseType for Const<'tcx>

type Result = [u8; 40]

impl<'tcx> Hash for Const<'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 Const<'tcx>

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

impl<'tcx, '__lifted> Lift<TyCtxt<'__lifted>> for Const<'tcx>

type Lifted = Const<'__lifted>

fn lift_to_interner(self, __tcx: TyCtxt<'__lifted>) -> Option<Const<'__lifted>>

impl<'tcx> PartialEq for Const<'tcx>

fn eq(&self, other: &Const<'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 Const<'tcx>

fn try_fold_with<__F: FallibleTypeFolder<TyCtxt<'tcx>>>( 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).

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

where F: TypeFolder<I>,

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 Const<'tcx>

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

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

impl<'tcx> Copy for Const<'tcx>

impl<'tcx> Eq for Const<'tcx>

impl<'tcx> StructuralPartialEq for Const<'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: 40 bytes

Size for each variant:

• Ty: 16 bytes
• Unevaluated: 32 bytes
• Val: 32 bytes