Struct rustc_middle::ty::UniverseIndex [−][src]
“Universes” are used during type- and trait-checking in the
presence of for<..>
binders to control what sets of names are
visible. Universes are arranged into a tree: the root universe
contains names that are always visible. Each child then adds a new
set of names that are visible, in addition to those of its parent.
We say that the child universe “extends” the parent universe with
new names.
To make this more concrete, consider this program:
struct Foo { } fn bar<T>(x: T) { let y: for<'a> fn(&'a u8, Foo) = ...; }
The struct name Foo
is in the root universe U0. But the type
parameter T
, introduced on bar
, is in an extended universe U1
– i.e., within bar
, we can name both T
and Foo
, but outside
of bar
, we cannot name T
. Then, within the type of y
, the
region 'a
is in a universe U2 that extends U1, because we can
name it inside the fn type but not outside.
Universes are used to do type- and trait-checking around these
“forall” binders (also called universal quantification). The
idea is that when, in the body of bar
, we refer to T
as a
type, we aren’t referring to any type in particular, but rather a
kind of “fresh” type that is distinct from all other types we have
actually declared. This is called a placeholder type, and we
use universes to talk about this. In other words, a type name in
universe 0 always corresponds to some “ground” type that the user
declared, but a type name in a non-zero universe is a placeholder
type – an idealized representative of “types in general” that we
use for checking generic functions.
Fields
private: u32
Implementations
impl UniverseIndex
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pub const MAX_AS_U32: u32
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pub const MAX: Self
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pub const fn from_usize(value: usize) -> Self
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pub const fn from_u32(value: u32) -> Self
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pub const unsafe fn from_u32_unchecked(value: u32) -> Self
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pub const fn index(self) -> usize
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Extracts the value of this index as an integer.
pub const fn as_u32(self) -> u32
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Extracts the value of this index as a u32
.
pub const fn as_usize(self) -> usize
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Extracts the value of this index as a usize
.
impl UniverseIndex
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pub const ROOT: UniverseIndex
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pub fn next_universe(self) -> UniverseIndex
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Returns the “next” universe index in order – this new index
is considered to extend all previous universes. This
corresponds to entering a forall
quantifier. So, for
example, suppose we have this type in universe U
:
for<'a> fn(&'a u32)
Once we “enter” into this for<'a>
quantifier, we are in a
new universe that extends U
– in this new universe, we can
name the region 'a
, but that region was not nameable from
U
because it was not in scope there.
pub fn can_name(self, other: UniverseIndex) -> bool
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Returns true
if self
can name a name from other
– in other words,
if the set of names in self
is a superset of those in
other
(self >= other
).
pub fn cannot_name(self, other: UniverseIndex) -> bool
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Returns true
if self
cannot name some names from other
– in other
words, if the set of names in self
is a strict subset of
those in other
(self < other
).
Trait Implementations
impl Add<usize> for UniverseIndex
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type Output = Self
The resulting type after applying the +
operator.
fn add(self, other: usize) -> Self
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impl Clone for UniverseIndex
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fn clone(&self) -> Self
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pub fn clone_from(&mut self, source: &Self)
1.0.0[src]
impl Copy for UniverseIndex
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impl Debug for UniverseIndex
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impl<D: Decoder> Decodable<D> for UniverseIndex
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impl<E: Encoder> Encodable<E> for UniverseIndex
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impl Eq for UniverseIndex
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impl From<u32> for UniverseIndex
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impl From<usize> for UniverseIndex
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impl Hash for UniverseIndex
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fn hash<__H: Hasher>(&self, state: &mut __H)
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pub fn hash_slice<H>(data: &[Self], state: &mut H) where
H: Hasher,
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H: Hasher,
impl<'__ctx> HashStable<StableHashingContext<'__ctx>> for UniverseIndex
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fn hash_stable(
&self,
__hcx: &mut StableHashingContext<'__ctx>,
__hasher: &mut StableHasher
)
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&self,
__hcx: &mut StableHashingContext<'__ctx>,
__hasher: &mut StableHasher
)
impl Idx for UniverseIndex
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fn new(value: usize) -> Self
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fn index(self) -> usize
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pub fn increment_by(&mut self, amount: usize)
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pub fn plus(self, amount: usize) -> Self
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impl<'tcx> Lift<'tcx> for UniverseIndex
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type Lifted = Self
fn lift_to_tcx(self, _: TyCtxt<'tcx>) -> Option<Self>
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impl Ord for UniverseIndex
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fn cmp(&self, other: &UniverseIndex) -> Ordering
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#[must_use]pub fn max(self, other: Self) -> Self
1.21.0[src]
#[must_use]pub fn min(self, other: Self) -> Self
1.21.0[src]
#[must_use]pub fn clamp(self, min: Self, max: Self) -> Self
1.50.0[src]
impl PartialEq<UniverseIndex> for UniverseIndex
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fn eq(&self, other: &UniverseIndex) -> bool
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fn ne(&self, other: &UniverseIndex) -> bool
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impl PartialOrd<UniverseIndex> for UniverseIndex
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fn partial_cmp(&self, other: &UniverseIndex) -> Option<Ordering>
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#[must_use]pub fn lt(&self, other: &Rhs) -> bool
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#[must_use]pub fn le(&self, other: &Rhs) -> bool
1.0.0[src]
#[must_use]pub fn gt(&self, other: &Rhs) -> bool
1.0.0[src]
#[must_use]pub fn ge(&self, other: &Rhs) -> bool
1.0.0[src]
impl Step for UniverseIndex
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fn steps_between(start: &Self, end: &Self) -> Option<usize>
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fn forward_checked(start: Self, u: usize) -> Option<Self>
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fn backward_checked(start: Self, u: usize) -> Option<Self>
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pub fn forward(start: Self, count: usize) -> Self
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pub unsafe fn forward_unchecked(start: Self, count: usize) -> Self
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pub fn backward(start: Self, count: usize) -> Self
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pub unsafe fn backward_unchecked(start: Self, count: usize) -> Self
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impl StructuralEq for UniverseIndex
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impl StructuralPartialEq for UniverseIndex
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impl<'tcx> TypeFoldable<'tcx> for UniverseIndex
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fn super_fold_with<F: TypeFolder<'tcx>>(self, _: &mut F) -> UniverseIndex
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fn super_visit_with<F: TypeVisitor<'tcx>>(
&self,
_: &mut F
) -> ControlFlow<F::BreakTy>
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&self,
_: &mut F
) -> ControlFlow<F::BreakTy>
fn fold_with<F: TypeFolder<'tcx>>(self, folder: &mut F) -> Self
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fn visit_with<V: TypeVisitor<'tcx>>(
&self,
visitor: &mut V
) -> ControlFlow<V::BreakTy>
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&self,
visitor: &mut V
) -> ControlFlow<V::BreakTy>
fn has_vars_bound_at_or_above(&self, binder: DebruijnIndex) -> bool
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fn has_vars_bound_above(&self, binder: DebruijnIndex) -> bool
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fn has_escaping_bound_vars(&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 has_opaque_types(&self) -> bool
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fn references_error(&self) -> bool
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fn has_param_types_or_consts(&self) -> bool
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fn has_infer_regions(&self) -> bool
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fn has_infer_types(&self) -> bool
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fn has_infer_types_or_consts(&self) -> bool
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fn needs_infer(&self) -> bool
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fn has_placeholders(&self) -> bool
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fn needs_subst(&self) -> bool
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fn has_free_regions(&self) -> bool
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fn has_erased_regions(&self) -> bool
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fn has_erasable_regions(&self) -> bool
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fn is_global(&self) -> bool
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fn has_late_bound_regions(&self) -> bool
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fn still_further_specializable(&self) -> bool
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Auto Trait Implementations
impl RefUnwindSafe for UniverseIndex
impl Send for UniverseIndex
impl Sync for UniverseIndex
impl Unpin for UniverseIndex
impl UnwindSafe for UniverseIndex
Blanket Implementations
impl<T> Any for T where
T: 'static + ?Sized,
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T: 'static + ?Sized,
impl<'tcx, T> ArenaAllocatable<'tcx, ()> for T where
T: Copy,
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T: Copy,
pub fn allocate_on(Self, &'a Arena<'tcx>) -> &'a mut T
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pub fn allocate_from_iter(
&'a Arena<'tcx>,
impl IntoIterator<Item = T>
) -> &'a mut [T]ⓘ
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&'a Arena<'tcx>,
impl IntoIterator<Item = T>
) -> &'a mut [T]ⓘ
impl<T> Borrow<T> for T where
T: ?Sized,
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T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
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T: ?Sized,
pub fn borrow_mut(&mut self) -> &mut T
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impl<'a, T> Captures<'a> for T where
T: ?Sized,
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T: ?Sized,
impl<T> From<T> for T
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impl<T, U> Into<U> for T where
U: From<T>,
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U: From<T>,
impl<T> MaybeResult<T> for T
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type Error = !
pub fn from(Result<T, <T as MaybeResult<T>>::Error>) -> T
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pub fn to_result(self) -> Result<T, <T as MaybeResult<T>>::Error>
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impl<'tcx, T> Subst<'tcx> for T where
T: TypeFoldable<'tcx>,
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T: TypeFoldable<'tcx>,
pub fn subst_spanned(Self, TyCtxt<'tcx>, &[GenericArg<'tcx>], Option<Span>) -> T
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fn subst(self, tcx: TyCtxt<'tcx>, substs: &[GenericArg<'tcx>]) -> Self
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impl<T> ToOwned for T where
T: Clone,
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T: Clone,
type Owned = T
The resulting type after obtaining ownership.
pub fn to_owned(&self) -> T
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pub fn clone_into(&self, target: &mut T)
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impl<T, U> TryFrom<U> for T where
U: Into<T>,
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U: Into<T>,
type Error = Infallible
The type returned in the event of a conversion error.
pub fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
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impl<T, U> TryInto<U> for T where
U: TryFrom<T>,
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U: TryFrom<T>,
type Error = <U as TryFrom<T>>::Error
The type returned in the event of a conversion error.