Struct rustc_middle::ty::UniverseIndex[][src]

pub struct UniverseIndex {
    private: u32,
}
Expand description

“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[src]

pub const MAX_AS_U32: u32[src]

pub const MAX: Self[src]

pub const fn from_usize(value: usize) -> Self[src]

pub const fn from_u32(value: u32) -> Self[src]

pub const unsafe fn from_u32_unchecked(value: u32) -> Self[src]

pub const fn index(self) -> usize[src]

Extracts the value of this index as an integer.

pub const fn as_u32(self) -> u32[src]

Extracts the value of this index as a u32.

pub const fn as_usize(self) -> usize[src]

Extracts the value of this index as a usize.

impl UniverseIndex[src]

pub const ROOT: UniverseIndex[src]

pub fn next_universe(self) -> UniverseIndex[src]

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[src]

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[src]

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[src]

type Output = Self

The resulting type after applying the + operator.

fn add(self, other: usize) -> Self[src]

Performs the + operation. Read more

impl Clone for UniverseIndex[src]

fn clone(&self) -> Self[src]

Returns a copy of the value. Read more

fn clone_from(&mut self, source: &Self)1.0.0[src]

Performs copy-assignment from source. Read more

impl Debug for UniverseIndex[src]

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

Formats the value using the given formatter. Read more

impl<D: Decoder> Decodable<D> for UniverseIndex[src]

fn decode(d: &mut D) -> Result<Self, D::Error>[src]

impl<E: Encoder> Encodable<E> for UniverseIndex[src]

fn encode(&self, e: &mut E) -> Result<(), E::Error>[src]

impl From<u32> for UniverseIndex[src]

fn from(value: u32) -> Self[src]

Performs the conversion.

impl From<usize> for UniverseIndex[src]

fn from(value: usize) -> Self[src]

Performs the conversion.

impl Hash for UniverseIndex[src]

fn hash<__H: Hasher>(&self, state: &mut __H)[src]

Feeds this value into the given Hasher. Read more

fn hash_slice<H>(data: &[Self], state: &mut H) where
    H: Hasher
1.3.0[src]

Feeds a slice of this type into the given Hasher. Read more

impl<'__ctx> HashStable<StableHashingContext<'__ctx>> for UniverseIndex[src]

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

impl Idx for UniverseIndex[src]

fn new(value: usize) -> Self[src]

fn index(self) -> usize[src]

fn increment_by(&mut self, amount: usize)[src]

fn plus(self, amount: usize) -> Self[src]

impl<'tcx> Lift<'tcx> for UniverseIndex[src]

type Lifted = Self

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

impl Ord for UniverseIndex[src]

fn cmp(&self, other: &UniverseIndex) -> Ordering[src]

This method returns an Ordering between self and other. Read more

#[must_use]
fn max(self, other: Self) -> Self
1.21.0[src]

Compares and returns the maximum of two values. Read more

#[must_use]
fn min(self, other: Self) -> Self
1.21.0[src]

Compares and returns the minimum of two values. Read more

#[must_use]
fn clamp(self, min: Self, max: Self) -> Self
1.50.0[src]

Restrict a value to a certain interval. Read more

impl PartialEq<UniverseIndex> for UniverseIndex[src]

fn eq(&self, other: &UniverseIndex) -> bool[src]

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

fn ne(&self, other: &UniverseIndex) -> bool[src]

This method tests for !=.

impl PartialOrd<UniverseIndex> for UniverseIndex[src]

fn partial_cmp(&self, other: &UniverseIndex) -> Option<Ordering>[src]

This method returns an ordering between self and other values if one exists. Read more

#[must_use]
fn lt(&self, other: &Rhs) -> bool
1.0.0[src]

This method tests less than (for self and other) and is used by the < operator. Read more

#[must_use]
fn le(&self, other: &Rhs) -> bool
1.0.0[src]

This method tests less than or equal to (for self and other) and is used by the <= operator. Read more

#[must_use]
fn gt(&self, other: &Rhs) -> bool
1.0.0[src]

This method tests greater than (for self and other) and is used by the > operator. Read more

#[must_use]
fn ge(&self, other: &Rhs) -> bool
1.0.0[src]

This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more

impl Step for UniverseIndex[src]

fn steps_between(start: &Self, end: &Self) -> Option<usize>[src]

🔬 This is a nightly-only experimental API. (step_trait)

recently redesigned

Returns the number of successor steps required to get from start to end. Read more

fn forward_checked(start: Self, u: usize) -> Option<Self>[src]

🔬 This is a nightly-only experimental API. (step_trait_ext)

recently added

Returns the value that would be obtained by taking the successor of self count times. Read more

fn backward_checked(start: Self, u: usize) -> Option<Self>[src]

🔬 This is a nightly-only experimental API. (step_trait_ext)

recently added

Returns the value that would be obtained by taking the predecessor of self count times. Read more

fn forward(start: Self, count: usize) -> Self[src]

🔬 This is a nightly-only experimental API. (step_trait_ext)

recently added

Returns the value that would be obtained by taking the successor of self count times. Read more

unsafe fn forward_unchecked(start: Self, count: usize) -> Self[src]

🔬 This is a nightly-only experimental API. (step_trait_ext)

recently added

Returns the value that would be obtained by taking the successor of self count times. Read more

fn backward(start: Self, count: usize) -> Self[src]

🔬 This is a nightly-only experimental API. (step_trait_ext)

recently added

Returns the value that would be obtained by taking the predecessor of self count times. Read more

unsafe fn backward_unchecked(start: Self, count: usize) -> Self[src]

🔬 This is a nightly-only experimental API. (step_trait_ext)

recently added

Returns the value that would be obtained by taking the predecessor of self count times. Read more

impl<'tcx> TypeFoldable<'tcx> for UniverseIndex[src]

fn super_fold_with<F: TypeFolder<'tcx>>(self, _: &mut F) -> UniverseIndex[src]

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

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

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

fn has_vars_bound_at_or_above(&self, binder: DebruijnIndex) -> bool[src]

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. Read more

fn has_vars_bound_above(&self, binder: DebruijnIndex) -> bool[src]

Returns true if this self has any regions that escape binder (and hence are not bound by it). Read more

fn has_escaping_bound_vars(&self) -> bool[src]

fn has_type_flags(&self, flags: TypeFlags) -> bool[src]

fn has_projections(&self) -> bool[src]

fn has_opaque_types(&self) -> bool[src]

fn references_error(&self) -> bool[src]

fn has_param_types_or_consts(&self) -> bool[src]

fn has_infer_regions(&self) -> bool[src]

fn has_infer_types(&self) -> bool[src]

fn has_infer_types_or_consts(&self) -> bool[src]

fn needs_infer(&self) -> bool[src]

fn has_placeholders(&self) -> bool[src]

fn needs_subst(&self) -> bool[src]

fn has_free_regions(&self) -> bool[src]

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

fn has_erased_regions(&self) -> bool[src]

fn has_erasable_regions(&self) -> bool[src]

True if there are any un-erased free regions.

fn is_global(&self) -> bool[src]

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. Read more

fn has_late_bound_regions(&self) -> bool[src]

True if there are any late-bound regions

fn still_further_specializable(&self) -> bool[src]

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. Read more

impl Copy for UniverseIndex[src]

impl Eq for UniverseIndex[src]

impl StructuralEq for UniverseIndex[src]

impl StructuralPartialEq for UniverseIndex[src]

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
[src]

pub fn type_id(&self) -> TypeId[src]

Gets the TypeId of self. Read more

impl<'tcx, T> ArenaAllocatable<'tcx, ()> for T where
    T: Copy
[src]

pub fn allocate_on(Self, &'a Arena<'tcx>) -> &'a mut T[src]

pub fn allocate_from_iter(
    &'a Arena<'tcx>,
    impl IntoIterator<Item = T>
) -> &'a mut [T]

Notable traits for &'_ [u8]

impl<'_> Read for &'_ [u8]impl<'_> Write for &'_ mut [u8]
[src]

impl<T> Borrow<T> for T where
    T: ?Sized
[src]

pub fn borrow(&self) -> &T[src]

Immutably borrows from an owned value. Read more

impl<T> BorrowMut<T> for T where
    T: ?Sized
[src]

pub fn borrow_mut(&mut self) -> &mut T[src]

Mutably borrows from an owned value. Read more

impl<T> From<T> for T[src]

pub fn from(t: T) -> T[src]

Performs the conversion.

impl<T, U> Into<U> for T where
    U: From<T>, 
[src]

pub fn into(self) -> U[src]

Performs the conversion.

impl<T> MaybeResult<T> for T[src]

type Error = !

pub fn from(Result<T, <T as MaybeResult<T>>::Error>) -> T[src]

pub fn to_result(self) -> Result<T, <T as MaybeResult<T>>::Error>[src]

impl<'tcx, T> Subst<'tcx> for T where
    T: TypeFoldable<'tcx>, 
[src]

pub fn subst_spanned(Self, TyCtxt<'tcx>, &[GenericArg<'tcx>], Option<Span>) -> T[src]

fn subst(self, tcx: TyCtxt<'tcx>, substs: &[GenericArg<'tcx>]) -> Self[src]

impl<T> ToOwned for T where
    T: Clone
[src]

type Owned = T

The resulting type after obtaining ownership.

pub fn to_owned(&self) -> T[src]

Creates owned data from borrowed data, usually by cloning. Read more

pub fn clone_into(&self, target: &mut T)[src]

🔬 This is a nightly-only experimental API. (toowned_clone_into)

recently added

Uses borrowed data to replace owned data, usually by cloning. Read more

impl<T, U> TryFrom<U> for T where
    U: Into<T>, 
[src]

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>[src]

Performs the conversion.

impl<T, U> TryInto<U> for T where
    U: TryFrom<T>, 
[src]

type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.

pub fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>[src]

Performs the conversion.

impl<T> WithConstness for T[src]

fn with_constness(self, constness: Constness) -> ConstnessAnd<Self>[src]

fn with_const(self) -> ConstnessAnd<Self>[src]

fn without_const(self) -> ConstnessAnd<Self>[src]

impl<'a, T> Captures<'a> for T where
    T: ?Sized
[src]

Layout

Note: Most layout information is completely unstable and may be different between compiler versions and platforms. The only exception is types with certain repr(...) attributes. Please see the Rust Reference’s “Type Layout” chapter for details on type layout guarantees.

Size: 4 bytes