Enum rustc_middle::traits::Reveal

pub enum Reveal {
    UserFacing,
    All,
}

Depending on the stage of compilation, we want projection to be more or less conservative.

Variants

UserFacing

At type-checking time, we refuse to project any associated type that is marked default. Non-default (“final”) types are always projected. This is necessary in general for soundness of specialization. However, we could allow projections in fully-monomorphic cases. We choose not to, because we prefer for default type to force the type definition to be treated abstractly by any consumers of the impl. Concretely, that means that the following example will fail to compile:

trait Assoc {
    type Output;
}

impl<T> Assoc for T {
    default type Output = bool;
}

fn main() {
    let <() as Assoc>::Output = true;
}

All

At codegen time, all monomorphic projections will succeed. Also, impl Trait is normalized to the concrete type, which has to be already collected by type-checking.

NOTE: as impl Trait’s concrete type should never be observable directly by the user, Reveal::All should not be used by checks which may expose type equality or type contents to the user. There are some exceptions, e.g., around auto traits and transmute-checking, which expose some details, but not the whole concrete type of the impl Trait.

Trait Implementations

impl Clone for Reveal

fn clone(&self) -> Reveal

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for Reveal

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

Formats the value using the given formatter.

impl Hash for Reveal

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, 

Feeds a slice of this type into the given Hasher.

impl<'__ctx> HashStable<StableHashingContext<'__ctx>> for Reveal

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

impl<'tcx> Lift<'tcx> for Reveal

type Lifted = Self

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

impl PartialEq<Reveal> for Reveal

fn eq(&self, other: &Reveal) -> bool

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

#[must_use]

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

This method tests for !=.

impl Tag for Reveal

const BITS: usize

fn into_usize(self) -> usize

unsafe fn from_usize(ptr: usize) -> Self

Safety

impl<'tcx> TypeFoldable<'tcx> for Reveal

fn super_fold_with<F: TypeFolder<'tcx>>(self, _: &mut F) -> Reveal

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

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

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

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 self has any regions that escape binder (and hence are not bound by it).

fn has_escaping_bound_vars(&self) -> bool

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 has_param_types_or_consts(&self) -> bool

fn has_infer_regions(&self) -> bool

fn has_infer_types(&self) -> bool

fn has_infer_types_or_consts(&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 Copy for Reveal

impl Eq for Reveal

impl StructuralEq for Reveal

impl StructuralPartialEq for Reveal