Struct rustc_mir::borrow_check::nll::type_check::free_region_relations::UniversalRegionRelations

pub(crate) struct UniversalRegionRelations<'tcx> {
    universal_regions: Rc<UniversalRegions<'tcx>>,
    outlives: TransitiveRelation<RegionVid>,
    inverse_outlives: TransitiveRelation<RegionVid>,
}

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Fields

universal_regions: Rc<UniversalRegions<'tcx>>

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outlives: TransitiveRelation<RegionVid>

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

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Stores the outlives relations that are known to hold from the implied bounds, in-scope where clauses, and that sort of thing.

inverse_outlives: TransitiveRelation<RegionVid>

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

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This is the <= relation; that is, if a: b, then b <= a, and we store that here. This is useful when figuring out how to express some local region in terms of external regions our caller will understand.

Methods

impl<'tcx> UniversalRegionRelations<'tcx>

fn relate_universal_regions(&mut self, fr_a: RegionVid, fr_b: RegionVid)

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Records in the outlives_relation (and inverse_outlives_relation) that fr_a: fr_b. Invoked by the builder below.

pub(crate) fn postdom_upper_bound(     &self,     fr1: RegionVid,     fr2: RegionVid ) -> RegionVid

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Given two universal regions, returns the postdominating upper-bound (effectively the least upper bound).

(See TransitiveRelation::postdom_upper_bound for details on the postdominating upper bound in general.)

pub(crate) fn non_local_upper_bound(&self, fr: RegionVid) -> RegionVid

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Finds an "upper bound" for fr that is not local. In other words, returns the smallest (*) known region fr1 that (a) outlives fr and (b) is not local. This cannot fail, because we will always find 'static at worst.

(*) If there are multiple competing choices, we pick the "postdominating" one. See TransitiveRelation::postdom_upper_bound for details.

pub(crate) fn non_local_lower_bound(&self, fr: RegionVid) -> Option<RegionVid>

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Finds a "lower bound" for fr that is not local. In other words, returns the largest (*) known region fr1 that (a) is outlived by fr and (b) is not local. This cannot fail, because we will always find 'static at worst.

(*) If there are multiple competing choices, we pick the "postdominating" one. See TransitiveRelation::postdom_upper_bound for details.

fn non_local_bound(     &self,     relation: &TransitiveRelation<RegionVid>,     fr0: RegionVid ) -> Option<RegionVid>

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Helper for non_local_upper_bound and non_local_lower_bound. Repeatedly invokes postdom_parent until we find something that is not local. Returns None if we never do so.

pub(crate) fn outlives(&self, fr1: RegionVid, fr2: RegionVid) -> bool

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True if fr1 is known to outlive fr2.

This will only ever be true for universally quantified regions.

Important traits for Vec<u8>

impl Write for Vec<u8>

pub(crate) fn regions_outlived_by(&self, fr1: RegionVid) -> Vec<&RegionVid>

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Returns a vector of free regions x such that fr1: x is known to hold.

Trait Implementations

impl<'tcx> Debug for UniversalRegionRelations<'tcx>

fn fmt(&self, f: &mut Formatter) -> Result

Formats the value using the given formatter.

impl<'tcx> FreeRegionRelations<'tcx> for UniversalRegionRelations<'tcx>

This trait is used by the impl-trait constraint code to abstract over the FreeRegionMap from lexical regions and UniversalRegions (from NLL)`.

fn sub_free_regions(&self, shorter: Region<'tcx>, longer: Region<'tcx>) -> bool

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

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Tests whether r_a <= r_b. Both must be free regions or 'static.