Enum rustc_infer::infer::region_constraints::VerifyBound[][src]

pub enum VerifyBound<'tcx> {
    IfEq(Ty<'tcx>, Box<VerifyBound<'tcx>>),
    OutlivedBy(Region<'tcx>),
    IsEmpty,
    AnyBound(Vec<VerifyBound<'tcx>>),
    AllBounds(Vec<VerifyBound<'tcx>>),
}

Describes the things that some GenericKind value G is known to outlive. Each variant of VerifyBound can be thought of as a function:

fn(min: Region) -> bool { .. }

where true means that the region min meets that G: min. (False means nothing.)

So, for example, if we have the type T and we have in scope that T: 'a and T: 'b, then the verify bound might be:

fn(min: Region) -> bool {
   ('a: min) || ('b: min)
}

This is described with a AnyRegion('a, 'b) node.

Variants

IfEq(Ty<'tcx>, Box<VerifyBound<'tcx>>)

Given a kind K and a bound B, expands to a function like the following, where G is the generic for which this verify bound was created:

fn(min) -> bool {
    if G == K {
        B(min)
    } else {
        false
    }
}

In other words, if the generic G that we are checking is equal to K, then check the associated verify bound (otherwise, false).

This is used when we have something in the environment that may or may not be relevant, depending on the region inference results. For example, we may have where <T as Trait<'a>>::Item: 'b in our where-clauses. If we are generating the verify-bound for <T as Trait<'0>>::Item, then this where-clause is only relevant if '0 winds up inferred to 'a.

So we would compile to a verify-bound like

IfEq(<T as Trait<'a>>::Item, AnyRegion('a))

meaning, if the subject G is equal to <T as Trait<'a>>::Item (after inference), and 'a: min, then G: min.

OutlivedBy(Region<'tcx>)

Given a region R, expands to the function:

fn(min) -> bool {
    R: min
}

This is used when we can establish that G: R – therefore, if R: min, then by transitivity G: min.

IsEmpty

Given a region R, true if it is 'empty.

AnyBound(Vec<VerifyBound<'tcx>>)

Given a set of bounds B, expands to the function:

fn(min) -> bool {
    exists (b in B) { b(min) }
}

In other words, if we meet some bound in B, that suffices. This is used when all the bounds in B are known to apply to G.

AllBounds(Vec<VerifyBound<'tcx>>)

Given a set of bounds B, expands to the function:

fn(min) -> bool {
    forall (b in B) { b(min) }
}

In other words, if we meet all bounds in B, that suffices. This is used when some bound in B is known to suffice, but we don’t know which.

Implementations

impl<'tcx> VerifyBound<'tcx>[src]

pub fn must_hold(&self) -> bool[src]

pub fn cannot_hold(&self) -> bool[src]

pub fn or(self, vb: VerifyBound<'tcx>) -> VerifyBound<'tcx>[src]

pub fn and(self, vb: VerifyBound<'tcx>) -> VerifyBound<'tcx>[src]

Trait Implementations

impl<'tcx> Clone for VerifyBound<'tcx>[src]

impl<'tcx> Debug for VerifyBound<'tcx>[src]

Auto Trait Implementations

impl<'tcx> !RefUnwindSafe for VerifyBound<'tcx>

impl<'tcx> !Send for VerifyBound<'tcx>

impl<'tcx> !Sync for VerifyBound<'tcx>

impl<'tcx> Unpin for VerifyBound<'tcx>

impl<'tcx> !UnwindSafe for VerifyBound<'tcx>

Blanket Implementations

impl<T> Any for T where
    T: 'static + ?Sized
[src]

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

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

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

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

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

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

type Owned = T

The resulting type after obtaining ownership.

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.

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.

impl<T> WithConstness for T[src]