Enum rustc_trait_selection::infer::region_constraints::VerifyBound

pub enum VerifyBound<'tcx> {
    IfEq(Binder<'tcx, VerifyIfEq<'tcx>>),
    OutlivedBy(Region<'tcx>),
    IsEmpty,
    AnyBound(Vec<VerifyBound<'tcx>, Global>),
    AllBounds(Vec<VerifyBound<'tcx>, Global>),
}

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 an AnyRegion('a, 'b) node.

Variants

IfEq(Binder<'tcx, VerifyIfEq<'tcx>>)

See VerifyIfEq docs

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>, Global>)

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>, Global>)

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.

Layout

Note: Most layout information is completely unstable and may even differ between compilations. 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: 32 bytes

Size for each variant:

• IfEq: 24 bytes
• OutlivedBy: 8 bytes
• IsEmpty: 0 bytes
• AnyBound: 24 bytes
• AllBounds: 24 bytes