1 //! A visiting traversal mechanism for complex data structures that contain type
4 //! This is a read-only traversal of the data structure.
6 //! This traversal has limited flexibility. Only a small number of "types of
7 //! interest" within the complex data structures can receive custom
8 //! visitation. These are the ones containing the most important type-related
9 //! information, such as `Ty`, `Predicate`, `Region`, and `Const`.
11 //! There are three groups of traits involved in each traversal.
12 //! - `TypeVisitable`. This is implemented once for many types, including:
13 //! - Types of interest, for which the the methods delegate to the
15 //! - All other types, including generic containers like `Vec` and `Option`.
16 //! It defines a "skeleton" of how they should be visited.
17 //! - `TypeSuperVisitable`. This is implemented only for each type of interest,
18 //! and defines the visiting "skeleton" for these types.
19 //! - `TypeVisitor`. This is implemented for each visitor. This defines how
20 //! types of interest are visited.
22 //! This means each visit is a mixture of (a) generic visiting operations, and (b)
23 //! custom visit operations that are specific to the visitor.
24 //! - The `TypeVisitable` impls handle most of the traversal, and call into
25 //! `TypeVisitor` when they encounter a type of interest.
26 //! - A `TypeVisitor` may call into another `TypeVisitable` impl, because some of
27 //! the types of interest are recursive and can contain other types of interest.
28 //! - A `TypeVisitor` may also call into a `TypeSuperVisitable` impl, because each
29 //! visitor might provide custom handling only for some types of interest, or
30 //! only for some variants of each type of interest, and then use default
31 //! traversal for the remaining cases.
33 //! For example, if you have `struct S(Ty, U)` where `S: TypeVisitable` and `U:
34 //! TypeVisitable`, and an instance `s = S(ty, u)`, it would be visited like so:
36 //! s.visit_with(visitor) calls
37 //! - ty.visit_with(visitor) calls
38 //! - visitor.visit_ty(ty) may call
39 //! - ty.super_visit_with(visitor)
40 //! - u.visit_with(visitor)
43 use crate::ty::{self, flags::FlagComputation, Binder, Ty, TyCtxt, TypeFlags};
44 use rustc_errors::ErrorGuaranteed;
46 use rustc_data_structures::fx::FxHashSet;
47 use rustc_data_structures::sso::SsoHashSet;
49 use std::ops::ControlFlow;
51 /// This trait is implemented for every type that can be visited,
52 /// providing the skeleton of the traversal.
54 /// To implement this conveniently, use the derive macro located in
56 pub trait TypeVisitable<'tcx>: fmt::Debug + Clone {
57 /// The entry point for visiting. To visit a value `t` with a visitor `v`
58 /// call: `t.visit_with(v)`.
60 /// For most types, this just traverses the value, calling `visit_with` on
61 /// each field/element.
63 /// For types of interest (such as `Ty`), the implementation of this method
64 /// that calls a visitor method specifically for that type (such as
65 /// `V::visit_ty`). This is where control transfers from `TypeFoldable` to
67 fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy>;
69 /// Returns `true` if `self` has any late-bound regions that are either
70 /// bound by `binder` or bound by some binder outside of `binder`.
71 /// If `binder` is `ty::INNERMOST`, this indicates whether
72 /// there are any late-bound regions that appear free.
73 fn has_vars_bound_at_or_above(&self, binder: ty::DebruijnIndex) -> bool {
74 self.visit_with(&mut HasEscapingVarsVisitor { outer_index: binder }).is_break()
77 /// Returns `true` if this `self` has any regions that escape `binder` (and
78 /// hence are not bound by it).
79 fn has_vars_bound_above(&self, binder: ty::DebruijnIndex) -> bool {
80 self.has_vars_bound_at_or_above(binder.shifted_in(1))
83 fn has_escaping_bound_vars(&self) -> bool {
84 self.has_vars_bound_at_or_above(ty::INNERMOST)
87 #[instrument(level = "trace")]
88 fn has_type_flags(&self, flags: TypeFlags) -> bool {
89 self.visit_with(&mut HasTypeFlagsVisitor { flags }).break_value() == Some(FoundFlags)
91 fn has_projections(&self) -> bool {
92 self.has_type_flags(TypeFlags::HAS_PROJECTION)
94 fn has_opaque_types(&self) -> bool {
95 self.has_type_flags(TypeFlags::HAS_TY_OPAQUE)
97 fn references_error(&self) -> bool {
98 self.has_type_flags(TypeFlags::HAS_ERROR)
100 fn error_reported(&self) -> Option<ErrorGuaranteed> {
101 if self.references_error() {
102 Some(ErrorGuaranteed::unchecked_claim_error_was_emitted())
107 fn has_param_types_or_consts(&self) -> bool {
108 self.has_type_flags(TypeFlags::HAS_TY_PARAM | TypeFlags::HAS_CT_PARAM)
110 fn has_infer_regions(&self) -> bool {
111 self.has_type_flags(TypeFlags::HAS_RE_INFER)
113 fn has_infer_types(&self) -> bool {
114 self.has_type_flags(TypeFlags::HAS_TY_INFER)
116 fn has_infer_types_or_consts(&self) -> bool {
117 self.has_type_flags(TypeFlags::HAS_TY_INFER | TypeFlags::HAS_CT_INFER)
119 fn needs_infer(&self) -> bool {
120 self.has_type_flags(TypeFlags::NEEDS_INFER)
122 fn has_placeholders(&self) -> bool {
124 TypeFlags::HAS_RE_PLACEHOLDER
125 | TypeFlags::HAS_TY_PLACEHOLDER
126 | TypeFlags::HAS_CT_PLACEHOLDER,
129 fn needs_subst(&self) -> bool {
130 self.has_type_flags(TypeFlags::NEEDS_SUBST)
132 /// "Free" regions in this context means that it has any region
133 /// that is not (a) erased or (b) late-bound.
134 fn has_free_regions(&self) -> bool {
135 self.has_type_flags(TypeFlags::HAS_FREE_REGIONS)
138 fn has_erased_regions(&self) -> bool {
139 self.has_type_flags(TypeFlags::HAS_RE_ERASED)
142 /// True if there are any un-erased free regions.
143 fn has_erasable_regions(&self) -> bool {
144 self.has_type_flags(TypeFlags::HAS_FREE_REGIONS)
147 /// Indicates whether this value references only 'global'
148 /// generic parameters that are the same regardless of what fn we are
149 /// in. This is used for caching.
150 fn is_global(&self) -> bool {
151 !self.has_type_flags(TypeFlags::HAS_FREE_LOCAL_NAMES)
154 /// True if there are any late-bound regions
155 fn has_late_bound_regions(&self) -> bool {
156 self.has_type_flags(TypeFlags::HAS_RE_LATE_BOUND)
159 /// Indicates whether this value still has parameters/placeholders/inference variables
160 /// which could be replaced later, in a way that would change the results of `impl`
162 fn still_further_specializable(&self) -> bool {
163 self.has_type_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE)
167 pub trait TypeSuperVisitable<'tcx>: TypeVisitable<'tcx> {
168 /// Provides a default visit for a type of interest. This should only be
169 /// called within `TypeVisitor` methods, when a non-custom traversal is
170 /// desired for the value of the type of interest passed to that method.
171 /// For example, in `MyVisitor::visit_ty(ty)`, it is valid to call
172 /// `ty.super_visit_with(self)`, but any other visiting should be done
173 /// with `xyz.visit_with(self)`.
174 fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy>;
177 /// This trait is implemented for every visiting traversal. There is a visit
178 /// method defined for every type of interest. Each such method has a default
179 /// that recurses into the type's fields in a non-custom fashion.
180 pub trait TypeVisitor<'tcx>: Sized {
183 fn visit_binder<T: TypeVisitable<'tcx>>(
186 ) -> ControlFlow<Self::BreakTy> {
187 t.super_visit_with(self)
190 fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
191 t.super_visit_with(self)
194 fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
195 r.super_visit_with(self)
198 fn visit_const(&mut self, c: ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> {
199 c.super_visit_with(self)
202 fn visit_unevaluated(&mut self, uv: ty::Unevaluated<'tcx>) -> ControlFlow<Self::BreakTy> {
203 uv.super_visit_with(self)
206 fn visit_predicate(&mut self, p: ty::Predicate<'tcx>) -> ControlFlow<Self::BreakTy> {
207 p.super_visit_with(self)
210 fn visit_mir_const(&mut self, c: mir::ConstantKind<'tcx>) -> ControlFlow<Self::BreakTy> {
211 c.super_visit_with(self)
215 ///////////////////////////////////////////////////////////////////////////
218 impl<'tcx> TyCtxt<'tcx> {
219 /// Invoke `callback` on every region appearing free in `value`.
220 pub fn for_each_free_region(
222 value: &impl TypeVisitable<'tcx>,
223 mut callback: impl FnMut(ty::Region<'tcx>),
225 self.any_free_region_meets(value, |r| {
231 /// Returns `true` if `callback` returns true for every region appearing free in `value`.
232 pub fn all_free_regions_meet(
234 value: &impl TypeVisitable<'tcx>,
235 mut callback: impl FnMut(ty::Region<'tcx>) -> bool,
237 !self.any_free_region_meets(value, |r| !callback(r))
240 /// Returns `true` if `callback` returns true for some region appearing free in `value`.
241 pub fn any_free_region_meets(
243 value: &impl TypeVisitable<'tcx>,
244 callback: impl FnMut(ty::Region<'tcx>) -> bool,
246 struct RegionVisitor<F> {
247 /// The index of a binder *just outside* the things we have
248 /// traversed. If we encounter a bound region bound by this
249 /// binder or one outer to it, it appears free. Example:
251 /// ```ignore (illustrative)
252 /// for<'a> fn(for<'b> fn(), T)
254 /// // | | | | here, would be shifted in 1
255 /// // | | | here, would be shifted in 2
256 /// // | | here, would be `INNERMOST` shifted in by 1
257 /// // | here, initially, binder would be `INNERMOST`
260 /// You see that, initially, *any* bound value is free,
261 /// because we've not traversed any binders. As we pass
262 /// through a binder, we shift the `outer_index` by 1 to
263 /// account for the new binder that encloses us.
264 outer_index: ty::DebruijnIndex,
268 impl<'tcx, F> TypeVisitor<'tcx> for RegionVisitor<F>
270 F: FnMut(ty::Region<'tcx>) -> bool,
274 fn visit_binder<T: TypeVisitable<'tcx>>(
277 ) -> ControlFlow<Self::BreakTy> {
278 self.outer_index.shift_in(1);
279 let result = t.super_visit_with(self);
280 self.outer_index.shift_out(1);
284 fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
286 ty::ReLateBound(debruijn, _) if debruijn < self.outer_index => {
287 ControlFlow::CONTINUE
290 if (self.callback)(r) {
293 ControlFlow::CONTINUE
299 fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
300 // We're only interested in types involving regions
301 if ty.flags().intersects(TypeFlags::HAS_FREE_REGIONS) {
302 ty.super_visit_with(self)
304 ControlFlow::CONTINUE
309 value.visit_with(&mut RegionVisitor { outer_index: ty::INNERMOST, callback }).is_break()
312 /// Returns a set of all late-bound regions that are constrained
313 /// by `value`, meaning that if we instantiate those LBR with
314 /// variables and equate `value` with something else, those
315 /// variables will also be equated.
316 pub fn collect_constrained_late_bound_regions<T>(
318 value: &Binder<'tcx, T>,
319 ) -> FxHashSet<ty::BoundRegionKind>
321 T: TypeVisitable<'tcx>,
323 self.collect_late_bound_regions(value, true)
326 /// Returns a set of all late-bound regions that appear in `value` anywhere.
327 pub fn collect_referenced_late_bound_regions<T>(
329 value: &Binder<'tcx, T>,
330 ) -> FxHashSet<ty::BoundRegionKind>
332 T: TypeVisitable<'tcx>,
334 self.collect_late_bound_regions(value, false)
337 fn collect_late_bound_regions<T>(
339 value: &Binder<'tcx, T>,
340 just_constraint: bool,
341 ) -> FxHashSet<ty::BoundRegionKind>
343 T: TypeVisitable<'tcx>,
345 let mut collector = LateBoundRegionsCollector::new(just_constraint);
346 let result = value.as_ref().skip_binder().visit_with(&mut collector);
347 assert!(result.is_continue()); // should never have stopped early
352 pub struct ValidateBoundVars<'tcx> {
353 bound_vars: &'tcx ty::List<ty::BoundVariableKind>,
354 binder_index: ty::DebruijnIndex,
355 // We may encounter the same variable at different levels of binding, so
356 // this can't just be `Ty`
357 visited: SsoHashSet<(ty::DebruijnIndex, Ty<'tcx>)>,
360 impl<'tcx> ValidateBoundVars<'tcx> {
361 pub fn new(bound_vars: &'tcx ty::List<ty::BoundVariableKind>) -> Self {
364 binder_index: ty::INNERMOST,
365 visited: SsoHashSet::default(),
370 impl<'tcx> TypeVisitor<'tcx> for ValidateBoundVars<'tcx> {
373 fn visit_binder<T: TypeVisitable<'tcx>>(
376 ) -> ControlFlow<Self::BreakTy> {
377 self.binder_index.shift_in(1);
378 let result = t.super_visit_with(self);
379 self.binder_index.shift_out(1);
383 fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
384 if t.outer_exclusive_binder() < self.binder_index
385 || !self.visited.insert((self.binder_index, t))
387 return ControlFlow::BREAK;
390 ty::Bound(debruijn, bound_ty) if debruijn == self.binder_index => {
391 if self.bound_vars.len() <= bound_ty.var.as_usize() {
392 bug!("Not enough bound vars: {:?} not found in {:?}", t, self.bound_vars);
394 let list_var = self.bound_vars[bound_ty.var.as_usize()];
396 ty::BoundVariableKind::Ty(kind) => {
397 if kind != bound_ty.kind {
399 "Mismatched type kinds: {:?} doesn't var in list {:?}",
406 bug!("Mismatched bound variable kinds! Expected type, found {:?}", list_var)
414 t.super_visit_with(self)
417 fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
419 ty::ReLateBound(index, br) if index == self.binder_index => {
420 if self.bound_vars.len() <= br.var.as_usize() {
421 bug!("Not enough bound vars: {:?} not found in {:?}", br, self.bound_vars);
423 let list_var = self.bound_vars[br.var.as_usize()];
425 ty::BoundVariableKind::Region(kind) => {
428 "Mismatched region kinds: {:?} doesn't match var ({:?}) in list ({:?})",
436 "Mismatched bound variable kinds! Expected region, found {:?}",
445 r.super_visit_with(self)
449 #[derive(Debug, PartialEq, Eq, Copy, Clone)]
450 struct FoundEscapingVars;
452 /// An "escaping var" is a bound var whose binder is not part of `t`. A bound var can be a
453 /// bound region or a bound type.
455 /// So, for example, consider a type like the following, which has two binders:
457 /// for<'a> fn(x: for<'b> fn(&'a isize, &'b isize))
458 /// ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ outer scope
459 /// ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ inner scope
461 /// This type has *bound regions* (`'a`, `'b`), but it does not have escaping regions, because the
462 /// binders of both `'a` and `'b` are part of the type itself. However, if we consider the *inner
463 /// fn type*, that type has an escaping region: `'a`.
465 /// Note that what I'm calling an "escaping var" is often just called a "free var". However,
466 /// we already use the term "free var". It refers to the regions or types that we use to represent
467 /// bound regions or type params on a fn definition while we are type checking its body.
469 /// To clarify, conceptually there is no particular difference between
470 /// an "escaping" var and a "free" var. However, there is a big
471 /// difference in practice. Basically, when "entering" a binding
472 /// level, one is generally required to do some sort of processing to
473 /// a bound var, such as replacing it with a fresh/placeholder
474 /// var, or making an entry in the environment to represent the
475 /// scope to which it is attached, etc. An escaping var represents
476 /// a bound var for which this processing has not yet been done.
477 struct HasEscapingVarsVisitor {
478 /// Anything bound by `outer_index` or "above" is escaping.
479 outer_index: ty::DebruijnIndex,
482 impl<'tcx> TypeVisitor<'tcx> for HasEscapingVarsVisitor {
483 type BreakTy = FoundEscapingVars;
485 fn visit_binder<T: TypeVisitable<'tcx>>(
488 ) -> ControlFlow<Self::BreakTy> {
489 self.outer_index.shift_in(1);
490 let result = t.super_visit_with(self);
491 self.outer_index.shift_out(1);
496 fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
497 // If the outer-exclusive-binder is *strictly greater* than
498 // `outer_index`, that means that `t` contains some content
499 // bound at `outer_index` or above (because
500 // `outer_exclusive_binder` is always 1 higher than the
501 // content in `t`). Therefore, `t` has some escaping vars.
502 if t.outer_exclusive_binder() > self.outer_index {
503 ControlFlow::Break(FoundEscapingVars)
505 ControlFlow::CONTINUE
510 fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
511 // If the region is bound by `outer_index` or anything outside
512 // of outer index, then it escapes the binders we have
514 if r.bound_at_or_above_binder(self.outer_index) {
515 ControlFlow::Break(FoundEscapingVars)
517 ControlFlow::CONTINUE
521 fn visit_const(&mut self, ct: ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> {
522 // we don't have a `visit_infer_const` callback, so we have to
523 // hook in here to catch this case (annoying...), but
524 // otherwise we do want to remember to visit the rest of the
525 // const, as it has types/regions embedded in a lot of other
528 ty::ConstKind::Bound(debruijn, _) if debruijn >= self.outer_index => {
529 ControlFlow::Break(FoundEscapingVars)
531 _ => ct.super_visit_with(self),
536 fn visit_predicate(&mut self, predicate: ty::Predicate<'tcx>) -> ControlFlow<Self::BreakTy> {
537 if predicate.outer_exclusive_binder() > self.outer_index {
538 ControlFlow::Break(FoundEscapingVars)
540 ControlFlow::CONTINUE
545 #[derive(Debug, PartialEq, Eq, Copy, Clone)]
548 // FIXME: Optimize for checking for infer flags
549 struct HasTypeFlagsVisitor {
550 flags: ty::TypeFlags,
553 impl std::fmt::Debug for HasTypeFlagsVisitor {
554 fn fmt(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
559 impl<'tcx> TypeVisitor<'tcx> for HasTypeFlagsVisitor {
560 type BreakTy = FoundFlags;
563 #[instrument(skip(self), level = "trace")]
564 fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
565 let flags = t.flags();
566 trace!(t.flags=?t.flags());
567 if flags.intersects(self.flags) {
568 ControlFlow::Break(FoundFlags)
570 ControlFlow::CONTINUE
575 #[instrument(skip(self), level = "trace")]
576 fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
577 let flags = r.type_flags();
578 trace!(r.flags=?flags);
579 if flags.intersects(self.flags) {
580 ControlFlow::Break(FoundFlags)
582 ControlFlow::CONTINUE
587 #[instrument(level = "trace")]
588 fn visit_const(&mut self, c: ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> {
589 let flags = FlagComputation::for_const(c);
590 trace!(r.flags=?flags);
591 if flags.intersects(self.flags) {
592 ControlFlow::Break(FoundFlags)
594 ControlFlow::CONTINUE
599 #[instrument(level = "trace")]
600 fn visit_unevaluated(&mut self, uv: ty::Unevaluated<'tcx>) -> ControlFlow<Self::BreakTy> {
601 let flags = FlagComputation::for_unevaluated_const(uv);
602 trace!(r.flags=?flags);
603 if flags.intersects(self.flags) {
604 ControlFlow::Break(FoundFlags)
606 ControlFlow::CONTINUE
611 #[instrument(level = "trace")]
612 fn visit_predicate(&mut self, predicate: ty::Predicate<'tcx>) -> ControlFlow<Self::BreakTy> {
614 "HasTypeFlagsVisitor: predicate={:?} predicate.flags={:?} self.flags={:?}",
619 if predicate.flags().intersects(self.flags) {
620 ControlFlow::Break(FoundFlags)
622 ControlFlow::CONTINUE
627 /// Collects all the late-bound regions at the innermost binding level
629 struct LateBoundRegionsCollector {
630 current_index: ty::DebruijnIndex,
631 regions: FxHashSet<ty::BoundRegionKind>,
633 /// `true` if we only want regions that are known to be
634 /// "constrained" when you equate this type with another type. In
635 /// particular, if you have e.g., `&'a u32` and `&'b u32`, equating
636 /// them constraints `'a == 'b`. But if you have `<&'a u32 as
637 /// Trait>::Foo` and `<&'b u32 as Trait>::Foo`, normalizing those
638 /// types may mean that `'a` and `'b` don't appear in the results,
639 /// so they are not considered *constrained*.
640 just_constrained: bool,
643 impl LateBoundRegionsCollector {
644 fn new(just_constrained: bool) -> Self {
645 LateBoundRegionsCollector {
646 current_index: ty::INNERMOST,
647 regions: Default::default(),
653 impl<'tcx> TypeVisitor<'tcx> for LateBoundRegionsCollector {
654 fn visit_binder<T: TypeVisitable<'tcx>>(
657 ) -> ControlFlow<Self::BreakTy> {
658 self.current_index.shift_in(1);
659 let result = t.super_visit_with(self);
660 self.current_index.shift_out(1);
664 fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
665 // if we are only looking for "constrained" region, we have to
666 // ignore the inputs to a projection, as they may not appear
667 // in the normalized form
668 if self.just_constrained {
669 if let ty::Projection(..) = t.kind() {
670 return ControlFlow::CONTINUE;
674 t.super_visit_with(self)
677 fn visit_const(&mut self, c: ty::Const<'tcx>) -> ControlFlow<Self::BreakTy> {
678 // if we are only looking for "constrained" region, we have to
679 // ignore the inputs of an unevaluated const, as they may not appear
680 // in the normalized form
681 if self.just_constrained {
682 if let ty::ConstKind::Unevaluated(..) = c.kind() {
683 return ControlFlow::CONTINUE;
687 c.super_visit_with(self)
690 fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
691 if let ty::ReLateBound(debruijn, br) = *r {
692 if debruijn == self.current_index {
693 self.regions.insert(br.kind);
696 ControlFlow::CONTINUE
700 /// Finds the max universe present
701 pub struct MaxUniverse {
702 max_universe: ty::UniverseIndex,
706 pub fn new() -> Self {
707 MaxUniverse { max_universe: ty::UniverseIndex::ROOT }
710 pub fn max_universe(self) -> ty::UniverseIndex {
715 impl<'tcx> TypeVisitor<'tcx> for MaxUniverse {
716 fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
717 if let ty::Placeholder(placeholder) = t.kind() {
718 self.max_universe = ty::UniverseIndex::from_u32(
719 self.max_universe.as_u32().max(placeholder.universe.as_u32()),
723 t.super_visit_with(self)
726 fn visit_const(&mut self, c: ty::consts::Const<'tcx>) -> ControlFlow<Self::BreakTy> {
727 if let ty::ConstKind::Placeholder(placeholder) = c.kind() {
728 self.max_universe = ty::UniverseIndex::from_u32(
729 self.max_universe.as_u32().max(placeholder.universe.as_u32()),
733 c.super_visit_with(self)
736 fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
737 if let ty::RePlaceholder(placeholder) = *r {
738 self.max_universe = ty::UniverseIndex::from_u32(
739 self.max_universe.as_u32().max(placeholder.universe.as_u32()),
743 ControlFlow::CONTINUE