Struct rustc::ty::ParamEnv

pub struct ParamEnv<'tcx> {
    pub caller_bounds: &'tcx List<Predicate<'tcx>>,
    pub reveal: Reveal,
}

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When type checking, we use the ParamEnv to track details about the set of where-clauses that are in scope at this particular point.

Fields

caller_bounds: &'tcx List<Predicate<'tcx>>

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Obligations that the caller must satisfy. This is basically the set of bounds on the in-scope type parameters, translated into Obligations, and elaborated and normalized.

reveal: Reveal

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Typically, this is Reveal::UserFacing, but during codegen we want Reveal::All -- note that this is always paired with an empty environment. To get that, use ParamEnv::reveal().

Methods

impl<'tcx> ParamEnv<'tcx>

pub fn can_type_implement_copy<'a>(     self,     tcx: TyCtxt<'a, 'tcx, 'tcx>,     self_type: Ty<'tcx> ) -> Result<(), CopyImplementationError<'tcx>>

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impl<'tcx> ParamEnv<'tcx>

pub fn empty() -> Self

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Construct a trait environment suitable for contexts where there are no where clauses in scope. Hidden types (like impl Trait) are left hidden, so this is suitable for ordinary type-checking.

pub fn reveal_all() -> Self

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Construct a trait environment with no where clauses in scope where the values of all impl Trait and other hidden types are revealed. This is suitable for monomorphized, post-typeck environments like codegen or doing optimizations.

NB. If you want to have predicates in scope, use ParamEnv::new, or invoke param_env.with_reveal_all().

pub fn new(caller_bounds: &'tcx List<Predicate<'tcx>>, reveal: Reveal) -> Self

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Construct a trait environment with the given set of predicates.

pub fn with_reveal_all(self) -> Self

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Returns a new parameter environment with the same clauses, but which "reveals" the true results of projections in all cases (even for associated types that are specializable). This is the desired behavior during codegen and certain other special contexts; normally though we want to use Reveal::UserFacing, which is the default.

pub fn without_caller_bounds(self) -> Self

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Returns this same environment but with no caller bounds.

pub fn and<T: TypeFoldable<'tcx>>(self, value: T) -> ParamEnvAnd<'tcx, T>

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Creates a suitable environment in which to perform trait queries on the given value. When type-checking, this is simply the pair of the environment plus value. But when reveal is set to All, then if value does not reference any type parameters, we will pair it with the empty environment. This improves caching and is generally invisible.

NB: We preserve the environment when type-checking because it is possible for the user to have wacky where-clauses like where Box<u32>: Copy, which are clearly never satisfiable. We generally want to behave as if they were true, although the surrounding function is never reachable.

Trait Implementations

impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for ParamEnv<'tcx>

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

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impl<'tcx> Key for ParamEnv<'tcx>

fn query_crate(&self) -> CrateNum

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Given an instance of this key, what crate is it referring to? This is used to find the provider.

fn default_span(&self, _: TyCtxt) -> Span

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In the event that a cycle occurs, if no explicit span has been given for a query with key self, what span should we use?

impl<'a, 'tcx> Lift<'tcx> for ParamEnv<'a>

type Lifted = ParamEnv<'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> TypeFoldable<'tcx> for ParamEnv<'tcx>

fn super_fold_with<'gcx: 'tcx, V: TypeFolder<'gcx, 'tcx>>(     &self,     folder: &mut V ) -> 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_bound_at_or_above(&self, binder: DebruijnIndex) -> bool

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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_regions_bound_above(&self, binder: DebruijnIndex) -> bool

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

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 has_skol(&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_free_regions(&self) -> bool

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

fn has_erasable_regions(&self) -> bool

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True if there any any un-erased free regions.

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.

fn has_late_bound_regions(&self) -> bool

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True if there are any late-bound regions

fn visit_tys_shallow(     &self,     visit: impl FnMut(Ty<'tcx>) -> bool ) -> bool

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A visitor that does not recurse into types, works like fn walk_shallow in Ty.

impl<'tcx> Copy for ParamEnv<'tcx>

impl<'tcx> Clone for ParamEnv<'tcx>

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

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<'tcx> Debug for ParamEnv<'tcx>

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

Formats the value using the given formatter.

impl<'tcx> PartialEq for ParamEnv<'tcx>

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

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

fn ne(&self, other: &ParamEnv<'tcx>) -> bool

This method tests for !=.

impl<'tcx> Eq for ParamEnv<'tcx>

fn assert_receiver_is_total_eq(&self)

impl<'tcx> Hash for ParamEnv<'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,

Feeds a slice of this type into the given [Hasher].