1 use crate::infer::InferCtxt;
2 use crate::opaque_types::required_region_bounds;
3 use crate::traits::{self, AssocTypeBoundData};
5 use rustc_hir::def_id::DefId;
6 use rustc_hir::lang_items;
7 use rustc_middle::ty::subst::{GenericArgKind, SubstsRef};
8 use rustc_middle::ty::{self, ToPredicate, Ty, TyCtxt, TypeFoldable, WithConstness};
9 use rustc_span::symbol::{kw, Ident};
12 /// Returns the set of obligations needed to make `ty` well-formed.
13 /// If `ty` contains unresolved inference variables, this may include
14 /// further WF obligations. However, if `ty` IS an unresolved
15 /// inference variable, returns `None`, because we are not able to
16 /// make any progress at all. This is to prevent "livelock" where we
17 /// say "$0 is WF if $0 is WF".
18 pub fn obligations<'a, 'tcx>(
19 infcx: &InferCtxt<'a, 'tcx>,
20 param_env: ty::ParamEnv<'tcx>,
24 ) -> Option<Vec<traits::PredicateObligation<'tcx>>> {
25 let mut wf = WfPredicates { infcx, param_env, body_id, span, out: vec![], item: None };
27 debug!("wf::obligations({:?}, body_id={:?}) = {:?}", ty, body_id, wf.out);
29 let result = wf.normalize();
30 debug!("wf::obligations({:?}, body_id={:?}) ~~> {:?}", ty, body_id, result);
33 None // no progress made, return None
37 /// Returns the obligations that make this trait reference
38 /// well-formed. For example, if there is a trait `Set` defined like
39 /// `trait Set<K:Eq>`, then the trait reference `Foo: Set<Bar>` is WF
41 pub fn trait_obligations<'a, 'tcx>(
42 infcx: &InferCtxt<'a, 'tcx>,
43 param_env: ty::ParamEnv<'tcx>,
45 trait_ref: &ty::TraitRef<'tcx>,
47 item: Option<&'tcx hir::Item<'tcx>>,
48 ) -> Vec<traits::PredicateObligation<'tcx>> {
49 let mut wf = WfPredicates { infcx, param_env, body_id, span, out: vec![], item };
50 wf.compute_trait_ref(trait_ref, Elaborate::All);
54 pub fn predicate_obligations<'a, 'tcx>(
55 infcx: &InferCtxt<'a, 'tcx>,
56 param_env: ty::ParamEnv<'tcx>,
58 predicate: &ty::Predicate<'tcx>,
60 ) -> Vec<traits::PredicateObligation<'tcx>> {
61 let mut wf = WfPredicates { infcx, param_env, body_id, span, out: vec![], item: None };
63 // (*) ok to skip binders, because wf code is prepared for it
65 ty::Predicate::Trait(ref t, _) => {
66 wf.compute_trait_ref(&t.skip_binder().trait_ref, Elaborate::None); // (*)
68 ty::Predicate::RegionOutlives(..) => {}
69 ty::Predicate::TypeOutlives(ref t) => {
70 wf.compute(t.skip_binder().0);
72 ty::Predicate::Projection(ref t) => {
73 let t = t.skip_binder(); // (*)
74 wf.compute_projection(t.projection_ty);
77 ty::Predicate::WellFormed(t) => {
80 ty::Predicate::ObjectSafe(_) => {}
81 ty::Predicate::ClosureKind(..) => {}
82 ty::Predicate::Subtype(ref data) => {
83 wf.compute(data.skip_binder().a); // (*)
84 wf.compute(data.skip_binder().b); // (*)
86 ty::Predicate::ConstEvaluatable(def_id, substs) => {
87 let obligations = wf.nominal_obligations(def_id, substs);
88 wf.out.extend(obligations);
90 for ty in substs.types() {
99 struct WfPredicates<'a, 'tcx> {
100 infcx: &'a InferCtxt<'a, 'tcx>,
101 param_env: ty::ParamEnv<'tcx>,
104 out: Vec<traits::PredicateObligation<'tcx>>,
105 item: Option<&'tcx hir::Item<'tcx>>,
108 /// Controls whether we "elaborate" supertraits and so forth on the WF
109 /// predicates. This is a kind of hack to address #43784. The
110 /// underlying problem in that issue was a trait structure like:
113 /// trait Foo: Copy { }
114 /// trait Bar: Foo { }
115 /// impl<T: Bar> Foo for T { }
116 /// impl<T> Bar for T { }
119 /// Here, in the `Foo` impl, we will check that `T: Copy` holds -- but
120 /// we decide that this is true because `T: Bar` is in the
121 /// where-clauses (and we can elaborate that to include `T:
122 /// Copy`). This wouldn't be a problem, except that when we check the
123 /// `Bar` impl, we decide that `T: Foo` must hold because of the `Foo`
124 /// impl. And so nowhere did we check that `T: Copy` holds!
126 /// To resolve this, we elaborate the WF requirements that must be
127 /// proven when checking impls. This means that (e.g.) the `impl Bar
128 /// for T` will be forced to prove not only that `T: Foo` but also `T:
129 /// Copy` (which it won't be able to do, because there is no `Copy`
131 #[derive(Debug, PartialEq, Eq, Copy, Clone)]
137 fn extend_cause_with_original_assoc_item_obligation<'tcx>(
139 trait_ref: &ty::TraitRef<'tcx>,
140 item: Option<&hir::Item<'tcx>>,
141 cause: &mut traits::ObligationCause<'tcx>,
142 pred: &ty::Predicate<'_>,
143 mut trait_assoc_items: impl Iterator<Item = ty::AssocItem>,
146 tcx.hir().as_local_hir_id(trait_ref.def_id).and_then(|trait_id| tcx.hir().find(trait_id));
147 let (trait_name, trait_generics) = match trait_item {
148 Some(hir::Node::Item(hir::Item {
150 kind: hir::ItemKind::Trait(.., generics, _, _),
153 | Some(hir::Node::Item(hir::Item {
155 kind: hir::ItemKind::TraitAlias(generics, _),
157 })) => (Some(ident), Some(generics)),
161 let item_span = item.map(|i| tcx.sess.source_map().guess_head_span(i.span));
163 ty::Predicate::Projection(proj) => {
164 // The obligation comes not from the current `impl` nor the `trait` being
165 // implemented, but rather from a "second order" obligation, like in
166 // `src/test/ui/associated-types/point-at-type-on-obligation-failure.rs`:
168 // error[E0271]: type mismatch resolving `<Foo2 as Bar2>::Ok == ()`
169 // --> $DIR/point-at-type-on-obligation-failure.rs:13:5
172 // | -- associated type defined here
174 // LL | impl Bar for Foo {
175 // | ---------------- in this `impl` item
176 // LL | type Ok = ();
177 // | ^^^^^^^^^^^^^ expected `u32`, found `()`
179 // = note: expected type `u32`
182 // FIXME: we would want to point a span to all places that contributed to this
183 // obligation. In the case above, it should be closer to:
185 // error[E0271]: type mismatch resolving `<Foo2 as Bar2>::Ok == ()`
186 // --> $DIR/point-at-type-on-obligation-failure.rs:13:5
189 // | -- associated type defined here
190 // LL | type Sibling: Bar2<Ok=Self::Ok>;
191 // | -------------------------------- obligation set here
193 // LL | impl Bar for Foo {
194 // | ---------------- in this `impl` item
195 // LL | type Ok = ();
196 // | ^^^^^^^^^^^^^ expected `u32`, found `()`
198 // LL | impl Bar2 for Foo2 {
199 // | ---------------- in this `impl` item
200 // LL | type Ok = u32;
201 // | -------------- obligation set here
203 // = note: expected type `u32`
205 if let Some(hir::ItemKind::Impl { items, .. }) = item.map(|i| &i.kind) {
206 let trait_assoc_item = tcx.associated_item(proj.projection_def_id());
207 if let Some(impl_item) =
208 items.iter().find(|item| item.ident == trait_assoc_item.ident)
210 cause.span = impl_item.span;
211 cause.code = traits::AssocTypeBound(Box::new(AssocTypeBoundData {
212 impl_span: item_span,
213 original: trait_assoc_item.ident.span,
219 ty::Predicate::Trait(proj, _) => {
220 // An associated item obligation born out of the `trait` failed to be met.
221 // Point at the `impl` that failed the obligation, the associated item that
222 // needed to meet the obligation, and the definition of that associated item,
223 // which should hold the obligation in most cases. An example can be seen in
224 // `src/test/ui/associated-types/point-at-type-on-obligation-failure-2.rs`:
226 // error[E0277]: the trait bound `bool: Bar` is not satisfied
227 // --> $DIR/point-at-type-on-obligation-failure-2.rs:8:5
229 // LL | type Assoc: Bar;
230 // | ----- associated type defined here
232 // LL | impl Foo for () {
233 // | --------------- in this `impl` item
234 // LL | type Assoc = bool;
235 // | ^^^^^^^^^^^^^^^^^^ the trait `Bar` is not implemented for `bool`
237 // If the obligation comes from the where clause in the `trait`, we point at it:
239 // error[E0277]: the trait bound `bool: Bar` is not satisfied
240 // --> $DIR/point-at-type-on-obligation-failure-2.rs:8:5
242 // | trait Foo where <Self as Foo>>::Assoc: Bar {
243 // | -------------------------- restricted in this bound
245 // | ----- associated type defined here
247 // LL | impl Foo for () {
248 // | --------------- in this `impl` item
249 // LL | type Assoc = bool;
250 // | ^^^^^^^^^^^^^^^^^^ the trait `Bar` is not implemented for `bool`
252 ty::Projection(ty::ProjectionTy { item_def_id, .. }),
253 Some(hir::ItemKind::Impl { items, .. }),
254 ) = (&proj.skip_binder().self_ty().kind, item.map(|i| &i.kind))
256 if let Some((impl_item, trait_assoc_item)) = trait_assoc_items
257 .find(|i| i.def_id == *item_def_id)
258 .and_then(|trait_assoc_item| {
261 .find(|i| i.ident == trait_assoc_item.ident)
262 .map(|impl_item| (impl_item, trait_assoc_item))
265 let bounds = trait_generics
267 get_generic_bound_spans(&generics, trait_name, trait_assoc_item.ident)
269 .unwrap_or_else(Vec::new);
270 cause.span = impl_item.span;
271 cause.code = traits::AssocTypeBound(Box::new(AssocTypeBoundData {
272 impl_span: item_span,
273 original: trait_assoc_item.ident.span,
283 impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
284 fn cause(&mut self, code: traits::ObligationCauseCode<'tcx>) -> traits::ObligationCause<'tcx> {
285 traits::ObligationCause::new(self.span, self.body_id, code)
288 fn normalize(&mut self) -> Vec<traits::PredicateObligation<'tcx>> {
289 let cause = self.cause(traits::MiscObligation);
290 let infcx = &mut self.infcx;
291 let param_env = self.param_env;
292 let mut obligations = Vec::with_capacity(self.out.len());
293 for pred in &self.out {
294 assert!(!pred.has_escaping_bound_vars());
295 let mut selcx = traits::SelectionContext::new(infcx);
296 let i = obligations.len();
298 traits::normalize_to(&mut selcx, param_env, cause.clone(), pred, &mut obligations);
299 obligations.insert(i, value);
304 /// Pushes the obligations required for `trait_ref` to be WF into `self.out`.
305 fn compute_trait_ref(&mut self, trait_ref: &ty::TraitRef<'tcx>, elaborate: Elaborate) {
306 let tcx = self.infcx.tcx;
307 let obligations = self.nominal_obligations(trait_ref.def_id, trait_ref.substs);
309 let cause = self.cause(traits::MiscObligation);
310 let param_env = self.param_env;
312 let item = self.item;
314 if let Elaborate::All = elaborate {
315 let implied_obligations = traits::util::elaborate_obligations(tcx, obligations.clone());
316 let implied_obligations = implied_obligations.map(|obligation| {
317 let mut cause = cause.clone();
318 extend_cause_with_original_assoc_item_obligation(
323 &obligation.predicate,
324 tcx.associated_items(trait_ref.def_id).in_definition_order().copied(),
326 traits::Obligation::new(cause, param_env, obligation.predicate)
328 self.out.extend(implied_obligations);
331 self.out.extend(obligations);
333 self.out.extend(trait_ref.substs.types().filter(|ty| !ty.has_escaping_bound_vars()).map(
334 |ty| traits::Obligation::new(cause.clone(), param_env, ty::Predicate::WellFormed(ty)),
338 /// Pushes the obligations required for `trait_ref::Item` to be WF
340 fn compute_projection(&mut self, data: ty::ProjectionTy<'tcx>) {
341 // A projection is well-formed if (a) the trait ref itself is
342 // WF and (b) the trait-ref holds. (It may also be
343 // normalizable and be WF that way.)
344 let trait_ref = data.trait_ref(self.infcx.tcx);
345 self.compute_trait_ref(&trait_ref, Elaborate::None);
347 if !data.has_escaping_bound_vars() {
348 let predicate = trait_ref.without_const().to_predicate();
349 let cause = self.cause(traits::ProjectionWf(data));
350 self.out.push(traits::Obligation::new(cause, self.param_env, predicate));
354 /// Pushes the obligations required for an array length to be WF
356 fn compute_array_len(&mut self, constant: ty::Const<'tcx>) {
357 if let ty::ConstKind::Unevaluated(def_id, substs, promoted) = constant.val {
358 assert!(promoted.is_none());
360 let obligations = self.nominal_obligations(def_id, substs);
361 self.out.extend(obligations);
363 let predicate = ty::Predicate::ConstEvaluatable(def_id, substs);
364 let cause = self.cause(traits::MiscObligation);
365 self.out.push(traits::Obligation::new(cause, self.param_env, predicate));
369 fn require_sized(&mut self, subty: Ty<'tcx>, cause: traits::ObligationCauseCode<'tcx>) {
370 if !subty.has_escaping_bound_vars() {
371 let cause = self.cause(cause);
372 let trait_ref = ty::TraitRef {
373 def_id: self.infcx.tcx.require_lang_item(lang_items::SizedTraitLangItem, None),
374 substs: self.infcx.tcx.mk_substs_trait(subty, &[]),
376 self.out.push(traits::Obligation::new(
379 trait_ref.without_const().to_predicate(),
384 /// Pushes new obligations into `out`. Returns `true` if it was able
385 /// to generate all the predicates needed to validate that `ty0`
386 /// is WF. Returns false if `ty0` is an unresolved type variable,
387 /// in which case we are not able to simplify at all.
388 fn compute(&mut self, ty0: Ty<'tcx>) -> bool {
389 let mut walker = ty0.walk();
390 let param_env = self.param_env;
391 while let Some(arg) = walker.next() {
392 let ty = match arg.unpack() {
393 GenericArgKind::Type(ty) => ty,
395 // No WF constraints for lifetimes being present, any outlives
396 // obligations are handled by the parent (e.g. `ty::Ref`).
397 GenericArgKind::Lifetime(_) => continue,
399 // FIXME(eddyb) this is wrong and needs to be replaced
400 // (see https://github.com/rust-lang/rust/pull/70107).
401 GenericArgKind::Const(_) => continue,
412 | ty::GeneratorWitness(..)
416 | ty::Placeholder(..)
417 | ty::Foreign(..) => {
418 // WfScalar, WfParameter, etc
421 ty::Slice(subty) => {
422 self.require_sized(subty, traits::SliceOrArrayElem);
425 ty::Array(subty, len) => {
426 self.require_sized(subty, traits::SliceOrArrayElem);
427 // FIXME(eddyb) handle `GenericArgKind::Const` above instead.
428 self.compute_array_len(*len);
431 ty::Tuple(ref tys) => {
432 if let Some((_last, rest)) = tys.split_last() {
434 self.require_sized(elem.expect_ty(), traits::TupleElem);
440 // simple cases that are WF if their type args are WF
443 ty::Projection(data) => {
444 walker.skip_current_subtree(); // subtree handled by compute_projection
445 self.compute_projection(data);
448 ty::UnnormalizedProjection(..) => bug!("only used with chalk-engine"),
450 ty::Adt(def, substs) => {
452 let obligations = self.nominal_obligations(def.did, substs);
453 self.out.extend(obligations);
456 ty::FnDef(did, substs) => {
457 let obligations = self.nominal_obligations(did, substs);
458 self.out.extend(obligations);
461 ty::Ref(r, rty, _) => {
463 if !r.has_escaping_bound_vars() && !rty.has_escaping_bound_vars() {
464 let cause = self.cause(traits::ReferenceOutlivesReferent(ty));
465 self.out.push(traits::Obligation::new(
468 ty::Predicate::TypeOutlives(ty::Binder::dummy(ty::OutlivesPredicate(
475 ty::Generator(..) => {
476 // Walk ALL the types in the generator: this will
477 // include the upvar types as well as the yield
478 // type. Note that this is mildly distinct from
479 // the closure case, where we have to be careful
480 // about the signature of the closure. We don't
481 // have the problem of implied bounds here since
482 // generators don't take arguments.
485 ty::Closure(_, substs) => {
486 // Only check the upvar types for WF, not the rest
487 // of the types within. This is needed because we
488 // capture the signature and it may not be WF
489 // without the implied bounds. Consider a closure
490 // like `|x: &'a T|` -- it may be that `T: 'a` is
491 // not known to hold in the creator's context (and
492 // indeed the closure may not be invoked by its
493 // creator, but rather turned to someone who *can*
496 // The special treatment of closures here really
497 // ought not to be necessary either; the problem
498 // is related to #25860 -- there is no way for us
499 // to express a fn type complete with the implied
500 // bounds that it is assuming. I think in reality
501 // the WF rules around fn are a bit messed up, and
502 // that is the rot problem: `fn(&'a T)` should
503 // probably always be WF, because it should be
504 // shorthand for something like `where(T: 'a) {
505 // fn(&'a T) }`, as discussed in #25860.
507 // Note that we are also skipping the generic
508 // types. This is consistent with the `outlives`
509 // code, but anyway doesn't matter: within the fn
510 // body where they are created, the generics will
511 // always be WF, and outside of that fn body we
512 // are not directly inspecting closure types
513 // anyway, except via auto trait matching (which
514 // only inspects the upvar types).
515 walker.skip_current_subtree(); // subtree handled by compute_projection
516 for upvar_ty in substs.as_closure().upvar_tys() {
517 self.compute(upvar_ty);
522 // let the loop iterate into the argument/return
523 // types appearing in the fn signature
526 ty::Opaque(did, substs) => {
527 // all of the requirements on type parameters
528 // should've been checked by the instantiation
529 // of whatever returned this exact `impl Trait`.
531 // for named opaque `impl Trait` types we still need to check them
532 if ty::is_impl_trait_defn(self.infcx.tcx, did).is_none() {
533 let obligations = self.nominal_obligations(did, substs);
534 self.out.extend(obligations);
538 ty::Dynamic(data, r) => {
541 // Here, we defer WF checking due to higher-ranked
542 // regions. This is perhaps not ideal.
543 self.from_object_ty(ty, data, r);
545 // FIXME(#27579) RFC also considers adding trait
546 // obligations that don't refer to Self and
549 let defer_to_coercion = self.infcx.tcx.features().object_safe_for_dispatch;
551 if !defer_to_coercion {
552 let cause = self.cause(traits::MiscObligation);
553 let component_traits = data.auto_traits().chain(data.principal_def_id());
554 self.out.extend(component_traits.map(|did| {
555 traits::Obligation::new(
558 ty::Predicate::ObjectSafe(did),
564 // Inference variables are the complicated case, since we don't
565 // know what type they are. We do two things:
567 // 1. Check if they have been resolved, and if so proceed with
569 // 2. If not, check whether this is the type that we
570 // started with (ty0). In that case, we've made no
571 // progress at all, so return false. Otherwise,
572 // we've at least simplified things (i.e., we went
573 // from `Vec<$0>: WF` to `$0: WF`, so we can
574 // register a pending obligation and keep
575 // moving. (Goal is that an "inductive hypothesis"
576 // is satisfied to ensure termination.)
578 let ty = self.infcx.shallow_resolve(ty);
579 if let ty::Infer(_) = ty.kind {
580 // not yet resolved...
582 // ...this is the type we started from! no progress.
586 let cause = self.cause(traits::MiscObligation);
588 // ...not the type we started from, so we made progress.
589 traits::Obligation::new(
592 ty::Predicate::WellFormed(ty),
596 // Yes, resolved, proceed with the
597 // result. Should never return false because
598 // `ty` is not a Infer.
599 assert!(self.compute(ty));
605 // if we made it through that loop above, we made progress!
609 fn nominal_obligations(
612 substs: SubstsRef<'tcx>,
613 ) -> Vec<traits::PredicateObligation<'tcx>> {
614 let predicates = self.infcx.tcx.predicates_of(def_id).instantiate(self.infcx.tcx, substs);
618 .zip(predicates.spans.into_iter())
619 .map(|(pred, span)| {
620 let cause = self.cause(traits::BindingObligation(def_id, span));
621 traits::Obligation::new(cause, self.param_env, pred)
623 .filter(|pred| !pred.has_escaping_bound_vars())
630 data: ty::Binder<&'tcx ty::List<ty::ExistentialPredicate<'tcx>>>,
631 region: ty::Region<'tcx>,
633 // Imagine a type like this:
636 // trait Bar<'c> : 'c { }
638 // &'b (Foo+'c+Bar<'d>)
641 // In this case, the following relationships must hold:
646 // The first conditions is due to the normal region pointer
647 // rules, which say that a reference cannot outlive its
650 // The final condition may be a bit surprising. In particular,
651 // you may expect that it would have been `'c <= 'd`, since
652 // usually lifetimes of outer things are conservative
653 // approximations for inner things. However, it works somewhat
654 // differently with trait objects: here the idea is that if the
655 // user specifies a region bound (`'c`, in this case) it is the
656 // "master bound" that *implies* that bounds from other traits are
657 // all met. (Remember that *all bounds* in a type like
658 // `Foo+Bar+Zed` must be met, not just one, hence if we write
659 // `Foo<'x>+Bar<'y>`, we know that the type outlives *both* 'x and
662 // Note: in fact we only permit builtin traits, not `Bar<'d>`, I
663 // am looking forward to the future here.
664 if !data.has_escaping_bound_vars() && !region.has_escaping_bound_vars() {
665 let implicit_bounds = object_region_bounds(self.infcx.tcx, data);
667 let explicit_bound = region;
669 self.out.reserve(implicit_bounds.len());
670 for implicit_bound in implicit_bounds {
671 let cause = self.cause(traits::ObjectTypeBound(ty, explicit_bound));
673 ty::Binder::dummy(ty::OutlivesPredicate(explicit_bound, implicit_bound));
674 self.out.push(traits::Obligation::new(
677 outlives.to_predicate(),
684 /// Given an object type like `SomeTrait + Send`, computes the lifetime
685 /// bounds that must hold on the elided self type. These are derived
686 /// from the declarations of `SomeTrait`, `Send`, and friends -- if
687 /// they declare `trait SomeTrait : 'static`, for example, then
688 /// `'static` would appear in the list. The hard work is done by
689 /// `infer::required_region_bounds`, see that for more information.
690 pub fn object_region_bounds<'tcx>(
692 existential_predicates: ty::Binder<&'tcx ty::List<ty::ExistentialPredicate<'tcx>>>,
693 ) -> Vec<ty::Region<'tcx>> {
694 // Since we don't actually *know* the self type for an object,
695 // this "open(err)" serves as a kind of dummy standin -- basically
696 // a placeholder type.
697 let open_ty = tcx.mk_ty_infer(ty::FreshTy(0));
699 let predicates = existential_predicates
701 .filter_map(|predicate| {
702 if let ty::ExistentialPredicate::Projection(_) = *predicate.skip_binder() {
705 Some(predicate.with_self_ty(tcx, open_ty))
710 required_region_bounds(tcx, open_ty, predicates)
713 /// Find the span of a generic bound affecting an associated type.
714 fn get_generic_bound_spans(
715 generics: &hir::Generics<'_>,
716 trait_name: Option<&Ident>,
717 assoc_item_name: Ident,
719 let mut bounds = vec![];
720 for clause in generics.where_clause.predicates.iter() {
721 if let hir::WherePredicate::BoundPredicate(pred) = clause {
722 match &pred.bounded_ty.kind {
723 hir::TyKind::Path(hir::QPath::Resolved(Some(ty), path)) => {
724 let mut s = path.segments.iter();
725 if let (a, Some(b), None) = (s.next(), s.next(), s.next()) {
726 if a.map(|s| &s.ident) == trait_name
727 && b.ident == assoc_item_name
728 && is_self_path(&ty.kind)
730 // `<Self as Foo>::Bar`
731 bounds.push(pred.span);
735 hir::TyKind::Path(hir::QPath::TypeRelative(ty, segment)) => {
736 if segment.ident == assoc_item_name {
737 if is_self_path(&ty.kind) {
739 bounds.push(pred.span);
750 fn is_self_path(kind: &hir::TyKind<'_>) -> bool {
751 if let hir::TyKind::Path(hir::QPath::Resolved(None, path)) = kind {
752 let mut s = path.segments.iter();
753 if let (Some(segment), None) = (s.next(), s.next()) {
754 if segment.ident.name == kw::SelfUpper {