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1 // Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
4 //
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
10
11 //! Generalized type folding mechanism. The setup is a bit convoluted
12 //! but allows for convenient usage. Let T be an instance of some
13 //! "foldable type" (one which implements `TypeFoldable`) and F be an
14 //! instance of a "folder" (a type which implements `TypeFolder`). Then
15 //! the setup is intended to be:
16 //!
17 //! T.fold_with(F) --calls--> F.fold_T(T) --calls--> T.super_fold_with(F)
18 //!
19 //! This way, when you define a new folder F, you can override
20 //! `fold_T()` to customize the behavior, and invoke `T.super_fold_with()`
21 //! to get the original behavior. Meanwhile, to actually fold
22 //! something, you can just write `T.fold_with(F)`, which is
23 //! convenient. (Note that `fold_with` will also transparently handle
24 //! things like a `Vec<T>` where T is foldable and so on.)
25 //!
26 //! In this ideal setup, the only function that actually *does*
27 //! anything is `T.super_fold_with()`, which traverses the type `T`.
28 //! Moreover, `T.super_fold_with()` should only ever call `T.fold_with()`.
29 //!
30 //! In some cases, we follow a degenerate pattern where we do not have
31 //! a `fold_T` method. Instead, `T.fold_with` traverses the structure directly.
32 //! This is suboptimal because the behavior cannot be overridden, but it's
33 //! much less work to implement. If you ever *do* need an override that
34 //! doesn't exist, it's not hard to convert the degenerate pattern into the
35 //! proper thing.
36 //!
37 //! A `TypeFoldable` T can also be visited by a `TypeVisitor` V using similar setup:
38 //! T.visit_with(V) --calls--> V.visit_T(T) --calls--> T.super_visit_with(V).
39 //! These methods return true to indicate that the visitor has found what it is looking for
40 //! and does not need to visit anything else.
41
42 use middle::region;
43 use ty::subst;
44 use ty::adjustment;
45 use ty::{self, Binder, Ty, TyCtxt, TypeFlags};
46
47 use std::fmt;
48 use util::nodemap::{FnvHashMap, FnvHashSet};
49
50 /// The TypeFoldable trait is implemented for every type that can be folded.
51 /// Basically, every type that has a corresponding method in TypeFolder.
52 pub trait TypeFoldable<'tcx>: fmt::Debug + Clone {
53 fn super_fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self;
54 fn fold_with<F: TypeFolder<'tcx>>(&self, folder: &mut F) -> Self {
55 self.super_fold_with(folder)
56 }
57
58 fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool;
59 fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
60 self.super_visit_with(visitor)
61 }
62
63 fn has_regions_escaping_depth(&self, depth: u32) -> bool {
64 self.visit_with(&mut HasEscapingRegionsVisitor { depth: depth })
65 }
66 fn has_escaping_regions(&self) -> bool {
67 self.has_regions_escaping_depth(0)
68 }
69
70 fn has_type_flags(&self, flags: TypeFlags) -> bool {
71 self.visit_with(&mut HasTypeFlagsVisitor { flags: flags })
72 }
73 fn has_projection_types(&self) -> bool {
74 self.has_type_flags(TypeFlags::HAS_PROJECTION)
75 }
76 fn references_error(&self) -> bool {
77 self.has_type_flags(TypeFlags::HAS_TY_ERR)
78 }
79 fn has_param_types(&self) -> bool {
80 self.has_type_flags(TypeFlags::HAS_PARAMS)
81 }
82 fn has_self_ty(&self) -> bool {
83 self.has_type_flags(TypeFlags::HAS_SELF)
84 }
85 fn has_infer_types(&self) -> bool {
86 self.has_type_flags(TypeFlags::HAS_TY_INFER)
87 }
88 fn needs_infer(&self) -> bool {
89 self.has_type_flags(TypeFlags::HAS_TY_INFER | TypeFlags::HAS_RE_INFER)
90 }
91 fn needs_subst(&self) -> bool {
92 self.has_type_flags(TypeFlags::NEEDS_SUBST)
93 }
94 fn has_closure_types(&self) -> bool {
95 self.has_type_flags(TypeFlags::HAS_TY_CLOSURE)
96 }
97 fn has_erasable_regions(&self) -> bool {
98 self.has_type_flags(TypeFlags::HAS_RE_EARLY_BOUND |
99 TypeFlags::HAS_RE_INFER |
100 TypeFlags::HAS_FREE_REGIONS)
101 }
102 /// Indicates whether this value references only 'global'
103 /// types/lifetimes that are the same regardless of what fn we are
104 /// in. This is used for caching. Errs on the side of returning
105 /// false.
106 fn is_global(&self) -> bool {
107 !self.has_type_flags(TypeFlags::HAS_LOCAL_NAMES)
108 }
109 }
110
111 /// The TypeFolder trait defines the actual *folding*. There is a
112 /// method defined for every foldable type. Each of these has a
113 /// default implementation that does an "identity" fold. Within each
114 /// identity fold, it should invoke `foo.fold_with(self)` to fold each
115 /// sub-item.
116 pub trait TypeFolder<'tcx> : Sized {
117 fn tcx<'a>(&'a self) -> &'a TyCtxt<'tcx>;
118
119 fn fold_binder<T>(&mut self, t: &Binder<T>) -> Binder<T>
120 where T : TypeFoldable<'tcx>
121 {
122 t.super_fold_with(self)
123 }
124
125 fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
126 t.super_fold_with(self)
127 }
128
129 fn fold_mt(&mut self, t: &ty::TypeAndMut<'tcx>) -> ty::TypeAndMut<'tcx> {
130 t.super_fold_with(self)
131 }
132
133 fn fold_trait_ref(&mut self, t: &ty::TraitRef<'tcx>) -> ty::TraitRef<'tcx> {
134 t.super_fold_with(self)
135 }
136
137 fn fold_impl_header(&mut self, imp: &ty::ImplHeader<'tcx>) -> ty::ImplHeader<'tcx> {
138 imp.super_fold_with(self)
139 }
140
141 fn fold_substs(&mut self,
142 substs: &subst::Substs<'tcx>)
143 -> subst::Substs<'tcx> {
144 substs.super_fold_with(self)
145 }
146
147 fn fold_fn_sig(&mut self,
148 sig: &ty::FnSig<'tcx>)
149 -> ty::FnSig<'tcx> {
150 sig.super_fold_with(self)
151 }
152
153 fn fold_output(&mut self,
154 output: &ty::FnOutput<'tcx>)
155 -> ty::FnOutput<'tcx> {
156 output.super_fold_with(self)
157 }
158
159 fn fold_bare_fn_ty(&mut self,
160 fty: &ty::BareFnTy<'tcx>)
161 -> ty::BareFnTy<'tcx>
162 {
163 fty.super_fold_with(self)
164 }
165
166 fn fold_closure_ty(&mut self,
167 fty: &ty::ClosureTy<'tcx>)
168 -> ty::ClosureTy<'tcx> {
169 fty.super_fold_with(self)
170 }
171
172 fn fold_region(&mut self, r: ty::Region) -> ty::Region {
173 r.super_fold_with(self)
174 }
175
176 fn fold_existential_bounds(&mut self, s: &ty::ExistentialBounds<'tcx>)
177 -> ty::ExistentialBounds<'tcx> {
178 s.super_fold_with(self)
179 }
180
181 fn fold_autoref(&mut self, ar: &adjustment::AutoRef<'tcx>)
182 -> adjustment::AutoRef<'tcx> {
183 ar.super_fold_with(self)
184 }
185 }
186
187 pub trait TypeVisitor<'tcx> : Sized {
188 fn visit_binder<T: TypeFoldable<'tcx>>(&mut self, t: &Binder<T>) -> bool {
189 t.super_visit_with(self)
190 }
191
192 fn visit_ty(&mut self, t: Ty<'tcx>) -> bool {
193 t.super_visit_with(self)
194 }
195
196 fn visit_region(&mut self, r: ty::Region) -> bool {
197 r.super_visit_with(self)
198 }
199 }
200
201 ///////////////////////////////////////////////////////////////////////////
202 // Some sample folders
203
204 pub struct BottomUpFolder<'a, 'tcx: 'a, F> where F: FnMut(Ty<'tcx>) -> Ty<'tcx> {
205 pub tcx: &'a TyCtxt<'tcx>,
206 pub fldop: F,
207 }
208
209 impl<'a, 'tcx, F> TypeFolder<'tcx> for BottomUpFolder<'a, 'tcx, F> where
210 F: FnMut(Ty<'tcx>) -> Ty<'tcx>,
211 {
212 fn tcx(&self) -> &TyCtxt<'tcx> { self.tcx }
213
214 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
215 let t1 = ty.super_fold_with(self);
216 (self.fldop)(t1)
217 }
218 }
219
220 ///////////////////////////////////////////////////////////////////////////
221 // Region folder
222
223 impl<'tcx> TyCtxt<'tcx> {
224 /// Collects the free and escaping regions in `value` into `region_set`. Returns
225 /// whether any late-bound regions were skipped
226 pub fn collect_regions<T>(&self,
227 value: &T,
228 region_set: &mut FnvHashSet<ty::Region>)
229 -> bool
230 where T : TypeFoldable<'tcx>
231 {
232 let mut have_bound_regions = false;
233 self.fold_regions(value, &mut have_bound_regions,
234 |r, d| { region_set.insert(r.from_depth(d)); r });
235 have_bound_regions
236 }
237
238 /// Folds the escaping and free regions in `value` using `f`, and
239 /// sets `skipped_regions` to true if any late-bound region was found
240 /// and skipped.
241 pub fn fold_regions<T,F>(&self,
242 value: &T,
243 skipped_regions: &mut bool,
244 mut f: F)
245 -> T
246 where F : FnMut(ty::Region, u32) -> ty::Region,
247 T : TypeFoldable<'tcx>,
248 {
249 value.fold_with(&mut RegionFolder::new(self, skipped_regions, &mut f))
250 }
251 }
252
253 /// Folds over the substructure of a type, visiting its component
254 /// types and all regions that occur *free* within it.
255 ///
256 /// That is, `Ty` can contain function or method types that bind
257 /// regions at the call site (`ReLateBound`), and occurrences of
258 /// regions (aka "lifetimes") that are bound within a type are not
259 /// visited by this folder; only regions that occur free will be
260 /// visited by `fld_r`.
261
262 pub struct RegionFolder<'a, 'tcx: 'a> {
263 tcx: &'a TyCtxt<'tcx>,
264 skipped_regions: &'a mut bool,
265 current_depth: u32,
266 fld_r: &'a mut (FnMut(ty::Region, u32) -> ty::Region + 'a),
267 }
268
269 impl<'a, 'tcx> RegionFolder<'a, 'tcx> {
270 pub fn new<F>(tcx: &'a TyCtxt<'tcx>,
271 skipped_regions: &'a mut bool,
272 fld_r: &'a mut F) -> RegionFolder<'a, 'tcx>
273 where F : FnMut(ty::Region, u32) -> ty::Region
274 {
275 RegionFolder {
276 tcx: tcx,
277 skipped_regions: skipped_regions,
278 current_depth: 1,
279 fld_r: fld_r,
280 }
281 }
282 }
283
284 impl<'a, 'tcx> TypeFolder<'tcx> for RegionFolder<'a, 'tcx>
285 {
286 fn tcx(&self) -> &TyCtxt<'tcx> { self.tcx }
287
288 fn fold_binder<T: TypeFoldable<'tcx>>(&mut self, t: &ty::Binder<T>) -> ty::Binder<T> {
289 self.current_depth += 1;
290 let t = t.super_fold_with(self);
291 self.current_depth -= 1;
292 t
293 }
294
295 fn fold_region(&mut self, r: ty::Region) -> ty::Region {
296 match r {
297 ty::ReLateBound(debruijn, _) if debruijn.depth < self.current_depth => {
298 debug!("RegionFolder.fold_region({:?}) skipped bound region (current depth={})",
299 r, self.current_depth);
300 *self.skipped_regions = true;
301 r
302 }
303 _ => {
304 debug!("RegionFolder.fold_region({:?}) folding free region (current_depth={})",
305 r, self.current_depth);
306 (self.fld_r)(r, self.current_depth)
307 }
308 }
309 }
310 }
311
312 ///////////////////////////////////////////////////////////////////////////
313 // Late-bound region replacer
314
315 // Replaces the escaping regions in a type.
316
317 struct RegionReplacer<'a, 'tcx: 'a> {
318 tcx: &'a TyCtxt<'tcx>,
319 current_depth: u32,
320 fld_r: &'a mut (FnMut(ty::BoundRegion) -> ty::Region + 'a),
321 map: FnvHashMap<ty::BoundRegion, ty::Region>
322 }
323
324 impl<'tcx> TyCtxt<'tcx> {
325 pub fn replace_late_bound_regions<T,F>(&self,
326 value: &Binder<T>,
327 mut f: F)
328 -> (T, FnvHashMap<ty::BoundRegion, ty::Region>)
329 where F : FnMut(ty::BoundRegion) -> ty::Region,
330 T : TypeFoldable<'tcx>,
331 {
332 debug!("replace_late_bound_regions({:?})", value);
333 let mut replacer = RegionReplacer::new(self, &mut f);
334 let result = value.skip_binder().fold_with(&mut replacer);
335 (result, replacer.map)
336 }
337
338
339 /// Replace any late-bound regions bound in `value` with free variants attached to scope-id
340 /// `scope_id`.
341 pub fn liberate_late_bound_regions<T>(&self,
342 all_outlive_scope: region::CodeExtent,
343 value: &Binder<T>)
344 -> T
345 where T : TypeFoldable<'tcx>
346 {
347 self.replace_late_bound_regions(value, |br| {
348 ty::ReFree(ty::FreeRegion{scope: all_outlive_scope, bound_region: br})
349 }).0
350 }
351
352 /// Flattens two binding levels into one. So `for<'a> for<'b> Foo`
353 /// becomes `for<'a,'b> Foo`.
354 pub fn flatten_late_bound_regions<T>(&self, bound2_value: &Binder<Binder<T>>)
355 -> Binder<T>
356 where T: TypeFoldable<'tcx>
357 {
358 let bound0_value = bound2_value.skip_binder().skip_binder();
359 let value = self.fold_regions(bound0_value, &mut false,
360 |region, current_depth| {
361 match region {
362 ty::ReLateBound(debruijn, br) if debruijn.depth >= current_depth => {
363 // should be true if no escaping regions from bound2_value
364 assert!(debruijn.depth - current_depth <= 1);
365 ty::ReLateBound(ty::DebruijnIndex::new(current_depth), br)
366 }
367 _ => {
368 region
369 }
370 }
371 });
372 Binder(value)
373 }
374
375 pub fn no_late_bound_regions<T>(&self, value: &Binder<T>) -> Option<T>
376 where T : TypeFoldable<'tcx>
377 {
378 if value.0.has_escaping_regions() {
379 None
380 } else {
381 Some(value.0.clone())
382 }
383 }
384
385 /// Replace any late-bound regions bound in `value` with `'static`. Useful in trans but also
386 /// method lookup and a few other places where precise region relationships are not required.
387 pub fn erase_late_bound_regions<T>(&self, value: &Binder<T>) -> T
388 where T : TypeFoldable<'tcx>
389 {
390 self.replace_late_bound_regions(value, |_| ty::ReStatic).0
391 }
392
393 /// Rewrite any late-bound regions so that they are anonymous. Region numbers are
394 /// assigned starting at 1 and increasing monotonically in the order traversed
395 /// by the fold operation.
396 ///
397 /// The chief purpose of this function is to canonicalize regions so that two
398 /// `FnSig`s or `TraitRef`s which are equivalent up to region naming will become
399 /// structurally identical. For example, `for<'a, 'b> fn(&'a isize, &'b isize)` and
400 /// `for<'a, 'b> fn(&'b isize, &'a isize)` will become identical after anonymization.
401 pub fn anonymize_late_bound_regions<T>(&self, sig: &Binder<T>) -> Binder<T>
402 where T : TypeFoldable<'tcx>,
403 {
404 let mut counter = 0;
405 Binder(self.replace_late_bound_regions(sig, |_| {
406 counter += 1;
407 ty::ReLateBound(ty::DebruijnIndex::new(1), ty::BrAnon(counter))
408 }).0)
409 }
410 }
411
412 impl<'a, 'tcx> RegionReplacer<'a, 'tcx> {
413 fn new<F>(tcx: &'a TyCtxt<'tcx>, fld_r: &'a mut F) -> RegionReplacer<'a, 'tcx>
414 where F : FnMut(ty::BoundRegion) -> ty::Region
415 {
416 RegionReplacer {
417 tcx: tcx,
418 current_depth: 1,
419 fld_r: fld_r,
420 map: FnvHashMap()
421 }
422 }
423 }
424
425 impl<'a, 'tcx> TypeFolder<'tcx> for RegionReplacer<'a, 'tcx>
426 {
427 fn tcx(&self) -> &TyCtxt<'tcx> { self.tcx }
428
429 fn fold_binder<T: TypeFoldable<'tcx>>(&mut self, t: &ty::Binder<T>) -> ty::Binder<T> {
430 self.current_depth += 1;
431 let t = t.super_fold_with(self);
432 self.current_depth -= 1;
433 t
434 }
435
436 fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
437 if !t.has_regions_escaping_depth(self.current_depth-1) {
438 return t;
439 }
440
441 t.super_fold_with(self)
442 }
443
444 fn fold_region(&mut self, r: ty::Region) -> ty::Region {
445 match r {
446 ty::ReLateBound(debruijn, br) if debruijn.depth == self.current_depth => {
447 debug!("RegionReplacer.fold_region({:?}) folding region (current_depth={})",
448 r, self.current_depth);
449 let fld_r = &mut self.fld_r;
450 let region = *self.map.entry(br).or_insert_with(|| fld_r(br));
451 if let ty::ReLateBound(debruijn1, br) = region {
452 // If the callback returns a late-bound region,
453 // that region should always use depth 1. Then we
454 // adjust it to the correct depth.
455 assert_eq!(debruijn1.depth, 1);
456 ty::ReLateBound(debruijn, br)
457 } else {
458 region
459 }
460 }
461 r => r
462 }
463 }
464 }
465
466 ///////////////////////////////////////////////////////////////////////////
467 // Region eraser
468
469 impl<'tcx> TyCtxt<'tcx> {
470 /// Returns an equivalent value with all free regions removed (note
471 /// that late-bound regions remain, because they are important for
472 /// subtyping, but they are anonymized and normalized as well)..
473 pub fn erase_regions<T>(&self, value: &T) -> T
474 where T : TypeFoldable<'tcx>
475 {
476 let value1 = value.fold_with(&mut RegionEraser(self));
477 debug!("erase_regions({:?}) = {:?}",
478 value, value1);
479 return value1;
480
481 struct RegionEraser<'a, 'tcx: 'a>(&'a TyCtxt<'tcx>);
482
483 impl<'a, 'tcx> TypeFolder<'tcx> for RegionEraser<'a, 'tcx> {
484 fn tcx(&self) -> &TyCtxt<'tcx> { self.0 }
485
486 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
487 match self.tcx().normalized_cache.borrow().get(&ty).cloned() {
488 None => {}
489 Some(u) => return u
490 }
491
492 let t_norm = ty.super_fold_with(self);
493 self.tcx().normalized_cache.borrow_mut().insert(ty, t_norm);
494 return t_norm;
495 }
496
497 fn fold_binder<T>(&mut self, t: &ty::Binder<T>) -> ty::Binder<T>
498 where T : TypeFoldable<'tcx>
499 {
500 let u = self.tcx().anonymize_late_bound_regions(t);
501 u.super_fold_with(self)
502 }
503
504 fn fold_region(&mut self, r: ty::Region) -> ty::Region {
505 // because late-bound regions affect subtyping, we can't
506 // erase the bound/free distinction, but we can replace
507 // all free regions with 'static.
508 //
509 // Note that we *CAN* replace early-bound regions -- the
510 // type system never "sees" those, they get substituted
511 // away. In trans, they will always be erased to 'static
512 // whenever a substitution occurs.
513 match r {
514 ty::ReLateBound(..) => r,
515 _ => ty::ReStatic
516 }
517 }
518
519 fn fold_substs(&mut self,
520 substs: &subst::Substs<'tcx>)
521 -> subst::Substs<'tcx> {
522 subst::Substs { regions: substs.regions.fold_with(self),
523 types: substs.types.fold_with(self) }
524 }
525 }
526 }
527 }
528
529 ///////////////////////////////////////////////////////////////////////////
530 // Region shifter
531 //
532 // Shifts the De Bruijn indices on all escaping bound regions by a
533 // fixed amount. Useful in substitution or when otherwise introducing
534 // a binding level that is not intended to capture the existing bound
535 // regions. See comment on `shift_regions_through_binders` method in
536 // `subst.rs` for more details.
537
538 pub fn shift_region(region: ty::Region, amount: u32) -> ty::Region {
539 match region {
540 ty::ReLateBound(debruijn, br) => {
541 ty::ReLateBound(debruijn.shifted(amount), br)
542 }
543 _ => {
544 region
545 }
546 }
547 }
548
549 pub fn shift_regions<'tcx, T:TypeFoldable<'tcx>>(tcx: &TyCtxt<'tcx>,
550 amount: u32, value: &T) -> T {
551 debug!("shift_regions(value={:?}, amount={})",
552 value, amount);
553
554 value.fold_with(&mut RegionFolder::new(tcx, &mut false, &mut |region, _current_depth| {
555 shift_region(region, amount)
556 }))
557 }
558
559 /// An "escaping region" is a bound region whose binder is not part of `t`.
560 ///
561 /// So, for example, consider a type like the following, which has two binders:
562 ///
563 /// for<'a> fn(x: for<'b> fn(&'a isize, &'b isize))
564 /// ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ outer scope
565 /// ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ inner scope
566 ///
567 /// This type has *bound regions* (`'a`, `'b`), but it does not have escaping regions, because the
568 /// binders of both `'a` and `'b` are part of the type itself. However, if we consider the *inner
569 /// fn type*, that type has an escaping region: `'a`.
570 ///
571 /// Note that what I'm calling an "escaping region" is often just called a "free region". However,
572 /// we already use the term "free region". It refers to the regions that we use to represent bound
573 /// regions on a fn definition while we are typechecking its body.
574 ///
575 /// To clarify, conceptually there is no particular difference between an "escaping" region and a
576 /// "free" region. However, there is a big difference in practice. Basically, when "entering" a
577 /// binding level, one is generally required to do some sort of processing to a bound region, such
578 /// as replacing it with a fresh/skolemized region, or making an entry in the environment to
579 /// represent the scope to which it is attached, etc. An escaping region represents a bound region
580 /// for which this processing has not yet been done.
581 struct HasEscapingRegionsVisitor {
582 depth: u32,
583 }
584
585 impl<'tcx> TypeVisitor<'tcx> for HasEscapingRegionsVisitor {
586 fn visit_binder<T: TypeFoldable<'tcx>>(&mut self, t: &Binder<T>) -> bool {
587 self.depth += 1;
588 let result = t.super_visit_with(self);
589 self.depth -= 1;
590 result
591 }
592
593 fn visit_ty(&mut self, t: Ty<'tcx>) -> bool {
594 t.region_depth > self.depth
595 }
596
597 fn visit_region(&mut self, r: ty::Region) -> bool {
598 r.escapes_depth(self.depth)
599 }
600 }
601
602 struct HasTypeFlagsVisitor {
603 flags: ty::TypeFlags,
604 }
605
606 impl<'tcx> TypeVisitor<'tcx> for HasTypeFlagsVisitor {
607 fn visit_ty(&mut self, t: Ty) -> bool {
608 t.flags.get().intersects(self.flags)
609 }
610
611 fn visit_region(&mut self, r: ty::Region) -> bool {
612 if self.flags.intersects(ty::TypeFlags::HAS_LOCAL_NAMES) {
613 // does this represent a region that cannot be named
614 // in a global way? used in fulfillment caching.
615 match r {
616 ty::ReStatic | ty::ReEmpty => {}
617 _ => return true,
618 }
619 }
620 if self.flags.intersects(ty::TypeFlags::HAS_RE_INFER) {
621 match r {
622 ty::ReVar(_) | ty::ReSkolemized(..) => { return true }
623 _ => {}
624 }
625 }
626 false
627 }
628 }