Struct rustc::ty::ParamEnv

pub struct ParamEnv<'tcx> {
    pub caller_bounds: &'tcx Slice<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 Slice<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 trans 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 empty(reveal: Reveal) -> Self

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Construct a trait environment suitable for contexts where there are no where clauses in scope.

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

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Construct a trait environment with the given set of predicates.

pub fn 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 trans and certain other special contexts; normally though we want to use Reveal::UserFacing, which is the default.

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

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impl<'tcx> ParamEnv<'tcx>

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. This will either be self or the empty environment, depending on whether value references type parameters that are in scope. (If it doesn't, then any judgements should be completely independent of the context, and hence we can safely use the empty environment so as to enable more sharing across functions.)

NB: This is a mildly dubious thing to do, in that a function (or other environment) might have wacky where-clauses like where Box<u32>: Copy, which are clearly never satisfiable. The code will at present ignore these, effectively, when type-checking the body of said function. This preserves existing behavior in any case. --nmatsakis

Trait Implementations

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

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

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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_escaping_depth(&self, depth: u32) -> bool

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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 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_erasable_regions(&self) -> bool

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fn is_normalized_for_trans(&self) -> bool

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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. Errs on the side of returning false.

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, __arg_0: &mut Formatter) -> Result

Formats the value using the given formatter.

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

fn eq(&self, __arg_0: &ParamEnv<'tcx>) -> bool

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

fn ne(&self, __arg_0: &ParamEnv<'tcx>) -> bool

This method tests for !=.

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

impl<'tcx> Hash for ParamEnv<'tcx>

fn hash<__H: Hasher>(&self, __arg_0: &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].