Enum rustc::ty::Region
[−]
[src]
pub enum Region {
ReEarlyBound(EarlyBoundRegion),
ReLateBound(DebruijnIndex, BoundRegion),
ReFree(FreeRegion),
ReScope(CodeExtent),
ReStatic,
ReVar(RegionVid),
ReSkolemized(SkolemizedRegionVid, BoundRegion),
ReEmpty,
}rustc_private)Representation of regions.
Unlike types, most region variants are "fictitious", not concrete,
regions. Among these, ReStatic, ReEmpty and ReScope are the only
ones representing concrete regions.
Bound Regions
These are regions that are stored behind a binder and must be substituted
with some concrete region before being used. There are 2 kind of
bound regions: early-bound, which are bound in a TypeScheme/TraitDef,
and are substituted by a Substs, and late-bound, which are part of
higher-ranked types (e.g. for<'a> fn(&'a ())) and are substituted by
the likes of liberate_late_bound_regions. The distinction exists
because higher-ranked lifetimes aren't supported in all places. See [1][2].
Unlike TyParam-s, bound regions are not supposed to exist "in the wild" outside their binder, e.g. in types passed to type inference, and should first be substituted (by skolemized regions, free regions, or region variables).
Skolemized and Free Regions
One often wants to work with bound regions without knowing their precise identity. For example, when checking a function, the lifetime of a borrow can end up being assigned to some region parameter. In these cases, it must be ensured that bounds on the region can't be accidentally assumed without being checked.
The process of doing that is called "skolemization". The bound regions are replaced by skolemized markers, which don't satisfy any relation not explicity provided.
There are 2 kinds of skolemized regions in rustc: ReFree and
ReSkolemized. When checking an item's body, ReFree is supposed
to be used. These also support explicit bounds: both the internally-stored
scope, which the region is assumed to outlive, as well as other
relations stored in the FreeRegionMap. Note that these relations
aren't checked when you make_subregion (or eq_types), only by
resolve_regions_and_report_errors.
When working with higher-ranked types, some region relations aren't
yet known, so you can't just call resolve_regions_and_report_errors.
ReSkolemized is designed for this purpose. In these contexts,
there's also the risk that some inference variable laying around will
get unified with your skolemized region: if you want to check whether
for<'a> Foo<'_>: 'a, and you substitute your bound region 'a
with a skolemized region '%a, the variable '_ would just be
instantiated to the skolemized region '%a, which is wrong because
the inference variable is supposed to satisfy the relation
for every value of the skolemized region. To ensure that doesn't
happen, you can use leak_check. This is more clearly explained
by infer/higher_ranked/README.md.
[1] http://smallcultfollowing.com/babysteps/blog/2013/10/29/intermingled-parameter-lists/ [2] http://smallcultfollowing.com/babysteps/blog/2013/11/04/intermingled-parameter-lists/
Variants
ReEarlyBound(EarlyBoundRegion)rustc_private)ReLateBound(DebruijnIndex, BoundRegion)rustc_private)ReFree(FreeRegion)rustc_private)When checking a function body, the types of all arguments and so forth that refer to bound region parameters are modified to refer to free region parameters.
ReScope(CodeExtent)rustc_private)A concrete region naming some statically determined extent (e.g. an expression or sequence of statements) within the current function.
ReStaticrustc_private)Static data that has an "infinite" lifetime. Top in the region lattice.
ReVar(RegionVid)rustc_private)A region variable. Should not exist after typeck.
ReSkolemized(SkolemizedRegionVid, BoundRegion)rustc_private)A skolemized region - basically the higher-ranked version of ReFree. Should not exist after typeck.
ReEmptyrustc_private)Empty lifetime is for data that is never accessed. Bottom in the region lattice. We treat ReEmpty somewhat specially; at least right now, we do not generate instances of it during the GLB computations, but rather generate an error instead. This is to improve error messages. The only way to get an instance of ReEmpty is to have a region variable with no constraints.
Methods
impl Region[src]
fn is_bound(&self) -> bool
fn needs_infer(&self) -> bool
fn escapes_depth(&self, depth: u32) -> bool
fn from_depth(&self, depth: u32) -> Region
rustc_private)Returns the depth of self from the (1-based) binding level depth
Trait Implementations
impl<'tcx> Relate<'tcx> for Region[src]
fn relate<'a, 'gcx, R>(relation: &mut R, a: &Region, b: &Region) -> RelateResult<'tcx, Region> where R: TypeRelation<'a, 'gcx, 'tcx>, 'gcx: 'a + 'tcx, 'tcx: 'a
impl<'a, 'tcx> Lift<'tcx> for &'a Region[src]
type Lifted = &'tcx Region
fn lift_to_tcx<'b, 'gcx>(&self, tcx: TyCtxt<'b, 'gcx, 'tcx>) -> Option<&'tcx Region>
impl<'tcx> Lift<'tcx> for Region[src]
type Lifted = Self
fn lift_to_tcx(&self, _: TyCtxt) -> Option<Region>
impl<'tcx> TypeFoldable<'tcx> for Region[src]
fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, _folder: &mut F) -> Self
fn fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, folder: &mut F) -> Self
fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> bool
fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool
fn has_regions_escaping_depth(&self, depth: u32) -> bool
fn has_escaping_regions(&self) -> bool
fn has_type_flags(&self, flags: TypeFlags) -> bool
fn has_projection_types(&self) -> bool
fn references_error(&self) -> bool
fn has_param_types(&self) -> bool
fn has_self_ty(&self) -> bool
fn has_infer_types(&self) -> bool
fn needs_infer(&self) -> bool
fn needs_subst(&self) -> bool
fn has_closure_types(&self) -> bool
fn has_erasable_regions(&self) -> bool
fn is_global(&self) -> bool
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. Read more
impl<'tcx> TypeFoldable<'tcx> for &'tcx Region[src]
fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, _folder: &mut F) -> Self
fn fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, folder: &mut F) -> Self
fn super_visit_with<V: TypeVisitor<'tcx>>(&self, _visitor: &mut V) -> bool
fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool
fn has_regions_escaping_depth(&self, depth: u32) -> bool
fn has_escaping_regions(&self) -> bool
fn has_type_flags(&self, flags: TypeFlags) -> bool
fn has_projection_types(&self) -> bool
fn references_error(&self) -> bool
fn has_param_types(&self) -> bool
fn has_self_ty(&self) -> bool
fn has_infer_types(&self) -> bool
fn needs_infer(&self) -> bool
fn needs_subst(&self) -> bool
fn has_closure_types(&self) -> bool
fn has_erasable_regions(&self) -> bool
fn is_global(&self) -> bool
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. Read more
impl Debug for Region[src]
impl Display for Region[src]
Derived Implementations
impl Decodable for Region[src]
impl Encodable for Region[src]
impl Copy for Region[src]
impl Hash for Region[src]
fn hash<__H: Hasher>(&self, __arg_0: &mut __H)
Feeds this value into the state given, updating the hasher as necessary.
fn hash_slice<H>(data: &[Self], state: &mut H) where H: Hasher1.3.0
Feeds a slice of this type into the state provided.
impl Eq for Region[src]
impl PartialEq for Region[src]
fn eq(&self, __arg_0: &Region) -> bool
This method tests for self and other values to be equal, and is used by ==. Read more
fn ne(&self, __arg_0: &Region) -> bool
This method tests for !=.
impl Clone for Region[src]
fn clone(&self) -> Region
Returns a copy of the value. Read more
fn clone_from(&mut self, source: &Self)1.0.0
Performs copy-assignment from source. Read more