3 use self::CombineMapType::*;
7 InferCtxtUndoLogs, MiscVariable, RegionVariableOrigin, Rollback, Snapshot, SubregionOrigin,
10 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
11 use rustc_data_structures::intern::Interned;
12 use rustc_data_structures::sync::Lrc;
13 use rustc_data_structures::undo_log::UndoLogs;
14 use rustc_data_structures::unify as ut;
15 use rustc_index::vec::IndexVec;
16 use rustc_middle::infer::unify_key::{RegionVidKey, UnifiedRegion};
17 use rustc_middle::ty::ReStatic;
18 use rustc_middle::ty::{self, Ty, TyCtxt};
19 use rustc_middle::ty::{ReLateBound, ReVar};
20 use rustc_middle::ty::{Region, RegionVid};
23 use std::collections::BTreeMap;
25 use std::{cmp, fmt, mem};
29 pub use rustc_middle::infer::MemberConstraint;
31 #[derive(Clone, Default)]
32 pub struct RegionConstraintStorage<'tcx> {
33 /// For each `RegionVid`, the corresponding `RegionVariableOrigin`.
34 var_infos: IndexVec<RegionVid, RegionVariableInfo>,
36 data: RegionConstraintData<'tcx>,
38 /// For a given pair of regions (R1, R2), maps to a region R3 that
39 /// is designated as their LUB (edges R1 <= R3 and R2 <= R3
40 /// exist). This prevents us from making many such regions.
41 lubs: CombineMap<'tcx>,
43 /// For a given pair of regions (R1, R2), maps to a region R3 that
44 /// is designated as their GLB (edges R3 <= R1 and R3 <= R2
45 /// exist). This prevents us from making many such regions.
46 glbs: CombineMap<'tcx>,
48 /// When we add a R1 == R2 constraint, we currently add (a) edges
49 /// R1 <= R2 and R2 <= R1 and (b) we unify the two regions in this
50 /// table. You can then call `opportunistic_resolve_var` early
51 /// which will map R1 and R2 to some common region (i.e., either
52 /// R1 or R2). This is important when fulfillment, dropck and other such
53 /// code is iterating to a fixed point, because otherwise we sometimes
54 /// would wind up with a fresh stream of region variables that have been
55 /// equated but appear distinct.
56 pub(super) unification_table: ut::UnificationTableStorage<RegionVidKey<'tcx>>,
58 /// a flag set to true when we perform any unifications; this is used
59 /// to micro-optimize `take_and_reset_data`
60 any_unifications: bool,
63 pub struct RegionConstraintCollector<'a, 'tcx> {
64 storage: &'a mut RegionConstraintStorage<'tcx>,
65 undo_log: &'a mut InferCtxtUndoLogs<'tcx>,
68 impl<'tcx> std::ops::Deref for RegionConstraintCollector<'_, 'tcx> {
69 type Target = RegionConstraintStorage<'tcx>;
71 fn deref(&self) -> &RegionConstraintStorage<'tcx> {
76 impl<'tcx> std::ops::DerefMut for RegionConstraintCollector<'_, 'tcx> {
78 fn deref_mut(&mut self) -> &mut RegionConstraintStorage<'tcx> {
83 pub type VarInfos = IndexVec<RegionVid, RegionVariableInfo>;
85 /// The full set of region constraints gathered up by the collector.
86 /// Describes constraints between the region variables and other
87 /// regions, as well as other conditions that must be verified, or
88 /// assumptions that can be made.
89 #[derive(Debug, Default, Clone)]
90 pub struct RegionConstraintData<'tcx> {
91 /// Constraints of the form `A <= B`, where either `A` or `B` can
92 /// be a region variable (or neither, as it happens).
93 pub constraints: BTreeMap<Constraint<'tcx>, SubregionOrigin<'tcx>>,
95 /// Constraints of the form `R0 member of [R1, ..., Rn]`, meaning that
96 /// `R0` must be equal to one of the regions `R1..Rn`. These occur
97 /// with `impl Trait` quite frequently.
98 pub member_constraints: Vec<MemberConstraint<'tcx>>,
100 /// A "verify" is something that we need to verify after inference
101 /// is done, but which does not directly affect inference in any
104 /// An example is a `A <= B` where neither `A` nor `B` are
105 /// inference variables.
106 pub verifys: Vec<Verify<'tcx>>,
108 /// A "given" is a relationship that is known to hold. In
109 /// particular, we often know from closure fn signatures that a
110 /// particular free region must be a subregion of a region
113 /// foo.iter().filter(<'a> |x: &'a &'b T| ...)
115 /// In situations like this, `'b` is in fact a region variable
116 /// introduced by the call to `iter()`, and `'a` is a bound region
117 /// on the closure (as indicated by the `<'a>` prefix). If we are
118 /// naive, we wind up inferring that `'b` must be `'static`,
119 /// because we require that it be greater than `'a` and we do not
120 /// know what `'a` is precisely.
122 /// This hashmap is used to avoid that naive scenario. Basically
123 /// we record the fact that `'a <= 'b` is implied by the fn
124 /// signature, and then ignore the constraint when solving
125 /// equations. This is a bit of a hack but seems to work.
126 pub givens: FxHashSet<(Region<'tcx>, ty::RegionVid)>,
129 /// Represents a constraint that influences the inference process.
130 #[derive(Clone, Copy, PartialEq, Eq, Debug, PartialOrd, Ord)]
131 pub enum Constraint<'tcx> {
132 /// A region variable is a subregion of another.
133 VarSubVar(RegionVid, RegionVid),
135 /// A concrete region is a subregion of region variable.
136 RegSubVar(Region<'tcx>, RegionVid),
138 /// A region variable is a subregion of a concrete region. This does not
139 /// directly affect inference, but instead is checked after
140 /// inference is complete.
141 VarSubReg(RegionVid, Region<'tcx>),
143 /// A constraint where neither side is a variable. This does not
144 /// directly affect inference, but instead is checked after
145 /// inference is complete.
146 RegSubReg(Region<'tcx>, Region<'tcx>),
149 impl Constraint<'_> {
150 pub fn involves_placeholders(&self) -> bool {
152 Constraint::VarSubVar(_, _) => false,
153 Constraint::VarSubReg(_, r) | Constraint::RegSubVar(r, _) => r.is_placeholder(),
154 Constraint::RegSubReg(r, s) => r.is_placeholder() || s.is_placeholder(),
159 #[derive(Debug, Clone)]
160 pub struct Verify<'tcx> {
161 pub kind: GenericKind<'tcx>,
162 pub origin: SubregionOrigin<'tcx>,
163 pub region: Region<'tcx>,
164 pub bound: VerifyBound<'tcx>,
167 #[derive(Copy, Clone, PartialEq, Eq, Hash, TypeFoldable, TypeVisitable)]
168 pub enum GenericKind<'tcx> {
170 Projection(ty::ProjectionTy<'tcx>),
173 /// Describes the things that some `GenericKind` value `G` is known to
174 /// outlive. Each variant of `VerifyBound` can be thought of as a
176 /// ```ignore (pseudo-rust)
177 /// fn(min: Region) -> bool { .. }
179 /// where `true` means that the region `min` meets that `G: min`.
180 /// (False means nothing.)
182 /// So, for example, if we have the type `T` and we have in scope that
183 /// `T: 'a` and `T: 'b`, then the verify bound might be:
184 /// ```ignore (pseudo-rust)
185 /// fn(min: Region) -> bool {
186 /// ('a: min) || ('b: min)
189 /// This is described with an `AnyRegion('a, 'b)` node.
190 #[derive(Debug, Clone, TypeFoldable, TypeVisitable)]
191 pub enum VerifyBound<'tcx> {
192 /// See [`VerifyIfEq`] docs
193 IfEq(ty::Binder<'tcx, VerifyIfEq<'tcx>>),
195 /// Given a region `R`, expands to the function:
197 /// ```ignore (pseudo-rust)
198 /// fn(min) -> bool {
203 /// This is used when we can establish that `G: R` -- therefore,
204 /// if `R: min`, then by transitivity `G: min`.
205 OutlivedBy(Region<'tcx>),
207 /// Given a region `R`, true if it is `'empty`.
210 /// Given a set of bounds `B`, expands to the function:
212 /// ```ignore (pseudo-rust)
213 /// fn(min) -> bool {
214 /// exists (b in B) { b(min) }
218 /// In other words, if we meet some bound in `B`, that suffices.
219 /// This is used when all the bounds in `B` are known to apply to `G`.
220 AnyBound(Vec<VerifyBound<'tcx>>),
222 /// Given a set of bounds `B`, expands to the function:
224 /// ```ignore (pseudo-rust)
225 /// fn(min) -> bool {
226 /// forall (b in B) { b(min) }
230 /// In other words, if we meet *all* bounds in `B`, that suffices.
231 /// This is used when *some* bound in `B` is known to suffice, but
232 /// we don't know which.
233 AllBounds(Vec<VerifyBound<'tcx>>),
236 /// This is a "conditional bound" that checks the result of inference
237 /// and supplies a bound if it ended up being relevant. It's used in situations
241 /// fn foo<'a, 'b, T: SomeTrait<'a>>
243 /// <T as SomeTrait<'a>>::Item: 'b
246 /// If we have an obligation like `<T as SomeTrait<'?x>>::Item: 'c`, then
247 /// we don't know yet whether it suffices to show that `'b: 'c`. If `'?x` winds
248 /// up being equal to `'a`, then the where-clauses on function applies, and
249 /// in that case we can show `'b: 'c`. But if `'?x` winds up being something
250 /// else, the bound isn't relevant.
252 /// In the [`VerifyBound`], this struct is enclosed in `Binder to account
256 /// where for<'a> <T as SomeTrait<'a>::Item: 'a
259 /// The idea is that we have to find some instantiation of `'a` that can
260 /// make `<T as SomeTrait<'a>>::Item` equal to the final value of `G`,
261 /// the generic we are checking.
263 /// ```ignore (pseudo-rust)
264 /// fn(min) -> bool {
274 #[derive(Debug, Copy, Clone, TypeFoldable, TypeVisitable)]
275 pub struct VerifyIfEq<'tcx> {
276 /// Type which must match the generic `G`
279 /// Bound that applies if `ty` is equal.
280 pub bound: Region<'tcx>,
283 #[derive(Copy, Clone, PartialEq, Eq, Hash)]
284 pub(crate) struct TwoRegions<'tcx> {
289 #[derive(Copy, Clone, PartialEq)]
290 pub(crate) enum UndoLog<'tcx> {
291 /// We added `RegionVid`.
294 /// We added the given `constraint`.
295 AddConstraint(Constraint<'tcx>),
297 /// We added the given `verify`.
300 /// We added the given `given`.
301 AddGiven(Region<'tcx>, ty::RegionVid),
303 /// We added a GLB/LUB "combination variable".
304 AddCombination(CombineMapType, TwoRegions<'tcx>),
307 #[derive(Copy, Clone, PartialEq)]
308 pub(crate) enum CombineMapType {
313 type CombineMap<'tcx> = FxHashMap<TwoRegions<'tcx>, RegionVid>;
315 #[derive(Debug, Clone, Copy)]
316 pub struct RegionVariableInfo {
317 pub origin: RegionVariableOrigin,
318 pub universe: ty::UniverseIndex,
321 pub struct RegionSnapshot {
322 any_unifications: bool,
325 impl<'tcx> RegionConstraintStorage<'tcx> {
326 pub fn new() -> Self {
331 pub(crate) fn with_log<'a>(
333 undo_log: &'a mut InferCtxtUndoLogs<'tcx>,
334 ) -> RegionConstraintCollector<'a, 'tcx> {
335 RegionConstraintCollector { storage: self, undo_log }
338 fn rollback_undo_entry(&mut self, undo_entry: UndoLog<'tcx>) {
341 self.var_infos.pop().unwrap();
342 assert_eq!(self.var_infos.len(), vid.index() as usize);
344 AddConstraint(ref constraint) => {
345 self.data.constraints.remove(constraint);
347 AddVerify(index) => {
348 self.data.verifys.pop();
349 assert_eq!(self.data.verifys.len(), index);
351 AddGiven(sub, sup) => {
352 self.data.givens.remove(&(sub, sup));
354 AddCombination(Glb, ref regions) => {
355 self.glbs.remove(regions);
357 AddCombination(Lub, ref regions) => {
358 self.lubs.remove(regions);
364 impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
365 pub fn num_region_vars(&self) -> usize {
369 pub fn region_constraint_data(&self) -> &RegionConstraintData<'tcx> {
373 /// Once all the constraints have been gathered, extract out the final data.
375 /// Not legal during a snapshot.
376 pub fn into_infos_and_data(self) -> (VarInfos, RegionConstraintData<'tcx>) {
377 assert!(!UndoLogs::<super::UndoLog<'_>>::in_snapshot(&self.undo_log));
378 (mem::take(&mut self.storage.var_infos), mem::take(&mut self.storage.data))
381 /// Takes (and clears) the current set of constraints. Note that
382 /// the set of variables remains intact, but all relationships
383 /// between them are reset. This is used during NLL checking to
384 /// grab the set of constraints that arose from a particular
387 /// We don't want to leak relationships between variables between
388 /// points because just because (say) `r1 == r2` was true at some
389 /// point P in the graph doesn't imply that it will be true at
390 /// some other point Q, in NLL.
392 /// Not legal during a snapshot.
393 pub fn take_and_reset_data(&mut self) -> RegionConstraintData<'tcx> {
394 assert!(!UndoLogs::<super::UndoLog<'_>>::in_snapshot(&self.undo_log));
396 // If you add a new field to `RegionConstraintCollector`, you
397 // should think carefully about whether it needs to be cleared
398 // or updated in some way.
399 let RegionConstraintStorage {
404 unification_table: _,
408 // Clear the tables of (lubs, glbs), so that we will create
409 // fresh regions if we do a LUB operation. As it happens,
410 // LUB/GLB are not performed by the MIR type-checker, which is
411 // the one that uses this method, but it's good to be correct.
415 let data = mem::take(data);
417 // Clear all unifications and recreate the variables a "now
418 // un-unified" state. Note that when we unify `a` and `b`, we
419 // also insert `a <= b` and a `b <= a` edges, so the
420 // `RegionConstraintData` contains the relationship here.
421 if *any_unifications {
422 *any_unifications = false;
423 self.unification_table().reset_unifications(|_| UnifiedRegion(None));
429 pub fn data(&self) -> &RegionConstraintData<'tcx> {
433 pub fn start_snapshot(&mut self) -> RegionSnapshot {
434 debug!("RegionConstraintCollector: start_snapshot");
435 RegionSnapshot { any_unifications: self.any_unifications }
438 pub fn rollback_to(&mut self, snapshot: RegionSnapshot) {
439 debug!("RegionConstraintCollector: rollback_to({:?})", snapshot);
440 self.any_unifications = snapshot.any_unifications;
443 pub fn new_region_var(
445 universe: ty::UniverseIndex,
446 origin: RegionVariableOrigin,
448 let vid = self.var_infos.push(RegionVariableInfo { origin, universe });
450 let u_vid = self.unification_table().new_key(UnifiedRegion(None));
451 assert_eq!(vid, u_vid.vid);
452 self.undo_log.push(AddVar(vid));
453 debug!("created new region variable {:?} in {:?} with origin {:?}", vid, universe, origin);
457 /// Returns the universe for the given variable.
458 pub fn var_universe(&self, vid: RegionVid) -> ty::UniverseIndex {
459 self.var_infos[vid].universe
462 /// Returns the origin for the given variable.
463 pub fn var_origin(&self, vid: RegionVid) -> RegionVariableOrigin {
464 self.var_infos[vid].origin
467 fn add_constraint(&mut self, constraint: Constraint<'tcx>, origin: SubregionOrigin<'tcx>) {
468 // cannot add constraints once regions are resolved
469 debug!("RegionConstraintCollector: add_constraint({:?})", constraint);
471 // never overwrite an existing (constraint, origin) - only insert one if it isn't
472 // present in the map yet. This prevents origins from outside the snapshot being
473 // replaced with "less informative" origins e.g., during calls to `can_eq`
474 let undo_log = &mut self.undo_log;
475 self.storage.data.constraints.entry(constraint).or_insert_with(|| {
476 undo_log.push(AddConstraint(constraint));
481 fn add_verify(&mut self, verify: Verify<'tcx>) {
482 // cannot add verifys once regions are resolved
483 debug!("RegionConstraintCollector: add_verify({:?})", verify);
485 // skip no-op cases known to be satisfied
486 if let VerifyBound::AllBounds(ref bs) = verify.bound && bs.is_empty() {
490 let index = self.data.verifys.len();
491 self.data.verifys.push(verify);
492 self.undo_log.push(AddVerify(index));
495 pub fn add_given(&mut self, sub: Region<'tcx>, sup: ty::RegionVid) {
496 // cannot add givens once regions are resolved
497 if self.data.givens.insert((sub, sup)) {
498 debug!("add_given({:?} <= {:?})", sub, sup);
500 self.undo_log.push(AddGiven(sub, sup));
504 pub fn make_eqregion(
506 origin: SubregionOrigin<'tcx>,
511 // Eventually, it would be nice to add direct support for
513 self.make_subregion(origin.clone(), sub, sup);
514 self.make_subregion(origin, sup, sub);
517 (Region(Interned(ReVar(sub), _)), Region(Interned(ReVar(sup), _))) => {
518 debug!("make_eqregion: unifying {:?} with {:?}", sub, sup);
519 self.unification_table().union(*sub, *sup);
520 self.any_unifications = true;
522 (Region(Interned(ReVar(vid), _)), value)
523 | (value, Region(Interned(ReVar(vid), _))) => {
524 debug!("make_eqregion: unifying {:?} with {:?}", vid, value);
525 self.unification_table().union_value(*vid, UnifiedRegion(Some(value)));
526 self.any_unifications = true;
533 pub fn member_constraint(
535 key: ty::OpaqueTypeKey<'tcx>,
536 definition_span: Span,
538 member_region: ty::Region<'tcx>,
539 choice_regions: &Lrc<Vec<ty::Region<'tcx>>>,
541 debug!("member_constraint({:?} in {:#?})", member_region, choice_regions);
543 if choice_regions.iter().any(|&r| r == member_region) {
547 self.data.member_constraints.push(MemberConstraint {
552 choice_regions: choice_regions.clone(),
556 #[instrument(skip(self, origin), level = "debug")]
557 pub fn make_subregion(
559 origin: SubregionOrigin<'tcx>,
563 // cannot add constraints once regions are resolved
564 debug!("origin = {:#?}", origin);
567 (ReLateBound(..), _) | (_, ReLateBound(..)) => {
568 span_bug!(origin.span(), "cannot relate bound region: {:?} <= {:?}", sub, sup);
571 // all regions are subregions of static, so we can ignore this
573 (ReVar(sub_id), ReVar(sup_id)) => {
574 self.add_constraint(Constraint::VarSubVar(sub_id, sup_id), origin);
576 (_, ReVar(sup_id)) => {
577 self.add_constraint(Constraint::RegSubVar(sub, sup_id), origin);
579 (ReVar(sub_id), _) => {
580 self.add_constraint(Constraint::VarSubReg(sub_id, sup), origin);
583 self.add_constraint(Constraint::RegSubReg(sub, sup), origin);
588 pub fn verify_generic_bound(
590 origin: SubregionOrigin<'tcx>,
591 kind: GenericKind<'tcx>,
593 bound: VerifyBound<'tcx>,
595 self.add_verify(Verify { kind, origin, region: sub, bound });
601 origin: SubregionOrigin<'tcx>,
605 // cannot add constraints once regions are resolved
606 debug!("RegionConstraintCollector: lub_regions({:?}, {:?})", a, b);
607 if a.is_static() || b.is_static() {
608 a // nothing lives longer than static
612 self.combine_vars(tcx, Lub, a, b, origin)
619 origin: SubregionOrigin<'tcx>,
623 // cannot add constraints once regions are resolved
624 debug!("RegionConstraintCollector: glb_regions({:?}, {:?})", a, b);
626 b // static lives longer than everything else
627 } else if b.is_static() {
628 a // static lives longer than everything else
632 self.combine_vars(tcx, Glb, a, b, origin)
636 /// Resolves the passed RegionVid to the root RegionVid in the unification table
637 pub fn opportunistic_resolve_var(&mut self, rid: ty::RegionVid) -> ty::RegionVid {
638 self.unification_table().find(rid).vid
641 /// If the Region is a `ReVar`, then resolves it either to the root value in
642 /// the unification table, if it exists, or to the root `ReVar` in the table.
643 /// If the Region is not a `ReVar`, just returns the Region itself.
644 pub fn opportunistic_resolve_region(
647 region: ty::Region<'tcx>,
648 ) -> ty::Region<'tcx> {
651 let unified_region = self.unification_table().probe_value(rid);
652 unified_region.0.unwrap_or_else(|| {
653 let root = self.unification_table().find(rid).vid;
654 tcx.reuse_or_mk_region(region, ty::ReVar(root))
661 fn combine_map(&mut self, t: CombineMapType) -> &mut CombineMap<'tcx> {
663 Glb => &mut self.glbs,
664 Lub => &mut self.lubs,
674 origin: SubregionOrigin<'tcx>,
676 let vars = TwoRegions { a, b };
677 if let Some(&c) = self.combine_map(t).get(&vars) {
678 return tcx.mk_region(ReVar(c));
680 let a_universe = self.universe(a);
681 let b_universe = self.universe(b);
682 let c_universe = cmp::max(a_universe, b_universe);
683 let c = self.new_region_var(c_universe, MiscVariable(origin.span()));
684 self.combine_map(t).insert(vars, c);
685 self.undo_log.push(AddCombination(t, vars));
686 let new_r = tcx.mk_region(ReVar(c));
687 for old_r in [a, b] {
689 Glb => self.make_subregion(origin.clone(), new_r, old_r),
690 Lub => self.make_subregion(origin.clone(), old_r, new_r),
693 debug!("combine_vars() c={:?}", c);
697 pub fn universe(&self, region: Region<'tcx>) -> ty::UniverseIndex {
699 ty::ReStatic | ty::ReErased | ty::ReFree(..) | ty::ReEarlyBound(..) => {
700 ty::UniverseIndex::ROOT
702 ty::ReEmpty(ui) => ui,
703 ty::RePlaceholder(placeholder) => placeholder.universe,
704 ty::ReVar(vid) => self.var_universe(vid),
705 ty::ReLateBound(..) => bug!("universe(): encountered bound region {:?}", region),
709 pub fn vars_since_snapshot(
712 ) -> (Range<RegionVid>, Vec<RegionVariableOrigin>) {
713 let range = RegionVid::from(value_count)..RegionVid::from(self.unification_table.len());
716 (range.start.index()..range.end.index())
717 .map(|index| self.var_infos[ty::RegionVid::from(index)].origin)
722 /// See `InferCtxt::region_constraints_added_in_snapshot`.
723 pub fn region_constraints_added_in_snapshot(&self, mark: &Snapshot<'tcx>) -> Option<bool> {
725 .region_constraints_in_snapshot(mark)
726 .map(|&elt| match elt {
727 AddConstraint(constraint) => Some(constraint.involves_placeholders()),
735 fn unification_table(&mut self) -> super::UnificationTable<'_, 'tcx, RegionVidKey<'tcx>> {
736 ut::UnificationTable::with_log(&mut self.storage.unification_table, self.undo_log)
740 impl fmt::Debug for RegionSnapshot {
741 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
742 write!(f, "RegionSnapshot")
746 impl<'tcx> fmt::Debug for GenericKind<'tcx> {
747 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
749 GenericKind::Param(ref p) => write!(f, "{:?}", p),
750 GenericKind::Projection(ref p) => write!(f, "{:?}", p),
755 impl<'tcx> fmt::Display for GenericKind<'tcx> {
756 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
758 GenericKind::Param(ref p) => write!(f, "{}", p),
759 GenericKind::Projection(ref p) => write!(f, "{}", p),
764 impl<'tcx> GenericKind<'tcx> {
765 pub fn to_ty(&self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
767 GenericKind::Param(ref p) => p.to_ty(tcx),
768 GenericKind::Projection(ref p) => tcx.mk_projection(p.item_def_id, p.substs),
773 impl<'tcx> VerifyBound<'tcx> {
774 pub fn must_hold(&self) -> bool {
776 VerifyBound::IfEq(..) => false,
777 VerifyBound::OutlivedBy(re) => re.is_static(),
778 VerifyBound::IsEmpty => false,
779 VerifyBound::AnyBound(bs) => bs.iter().any(|b| b.must_hold()),
780 VerifyBound::AllBounds(bs) => bs.iter().all(|b| b.must_hold()),
784 pub fn cannot_hold(&self) -> bool {
786 VerifyBound::IfEq(..) => false,
787 VerifyBound::IsEmpty => false,
788 VerifyBound::OutlivedBy(_) => false,
789 VerifyBound::AnyBound(bs) => bs.iter().all(|b| b.cannot_hold()),
790 VerifyBound::AllBounds(bs) => bs.iter().any(|b| b.cannot_hold()),
794 pub fn or(self, vb: VerifyBound<'tcx>) -> VerifyBound<'tcx> {
795 if self.must_hold() || vb.cannot_hold() {
797 } else if self.cannot_hold() || vb.must_hold() {
800 VerifyBound::AnyBound(vec![self, vb])
805 impl<'tcx> RegionConstraintData<'tcx> {
806 /// Returns `true` if this region constraint data contains no constraints, and `false`
808 pub fn is_empty(&self) -> bool {
809 let RegionConstraintData { constraints, member_constraints, verifys, givens } = self;
810 constraints.is_empty()
811 && member_constraints.is_empty()
812 && verifys.is_empty()
817 impl<'tcx> Rollback<UndoLog<'tcx>> for RegionConstraintStorage<'tcx> {
818 fn reverse(&mut self, undo: UndoLog<'tcx>) {
819 self.rollback_undo_entry(undo)