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1 | use crate::ty::{self, Binder, BoundTy, Ty, TyCtxt, TypeVisitableExt}; | |
2 | use rustc_data_structures::fx::FxIndexMap; | |
3 | use rustc_hir::def_id::DefId; | |
4 | ||
5 | use std::collections::BTreeMap; | |
6 | ||
7 | pub use rustc_type_ir::fold::{FallibleTypeFolder, TypeFoldable, TypeFolder, TypeSuperFoldable}; | |
8 | ||
9 | /////////////////////////////////////////////////////////////////////////// | |
10 | // Some sample folders | |
11 | ||
12 | pub struct BottomUpFolder<'tcx, F, G, H> | |
13 | where | |
14 | F: FnMut(Ty<'tcx>) -> Ty<'tcx>, | |
15 | G: FnMut(ty::Region<'tcx>) -> ty::Region<'tcx>, | |
16 | H: FnMut(ty::Const<'tcx>) -> ty::Const<'tcx>, | |
17 | { | |
18 | pub tcx: TyCtxt<'tcx>, | |
19 | pub ty_op: F, | |
20 | pub lt_op: G, | |
21 | pub ct_op: H, | |
22 | } | |
23 | ||
24 | impl<'tcx, F, G, H> TypeFolder<TyCtxt<'tcx>> for BottomUpFolder<'tcx, F, G, H> | |
25 | where | |
26 | F: FnMut(Ty<'tcx>) -> Ty<'tcx>, | |
27 | G: FnMut(ty::Region<'tcx>) -> ty::Region<'tcx>, | |
28 | H: FnMut(ty::Const<'tcx>) -> ty::Const<'tcx>, | |
29 | { | |
30 | fn interner(&self) -> TyCtxt<'tcx> { | |
31 | self.tcx | |
32 | } | |
33 | ||
34 | fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> { | |
35 | let t = ty.super_fold_with(self); | |
36 | (self.ty_op)(t) | |
37 | } | |
38 | ||
39 | fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> { | |
40 | let r = r.super_fold_with(self); | |
41 | (self.lt_op)(r) | |
42 | } | |
43 | ||
44 | fn fold_const(&mut self, ct: ty::Const<'tcx>) -> ty::Const<'tcx> { | |
45 | let ct = ct.super_fold_with(self); | |
46 | (self.ct_op)(ct) | |
47 | } | |
48 | } | |
49 | ||
50 | /////////////////////////////////////////////////////////////////////////// | |
51 | // Region folder | |
52 | ||
53 | impl<'tcx> TyCtxt<'tcx> { | |
54 | /// Folds the escaping and free regions in `value` using `f`. | |
55 | pub fn fold_regions<T>( | |
56 | self, | |
57 | value: T, | |
58 | mut f: impl FnMut(ty::Region<'tcx>, ty::DebruijnIndex) -> ty::Region<'tcx>, | |
59 | ) -> T | |
60 | where | |
61 | T: TypeFoldable<TyCtxt<'tcx>>, | |
62 | { | |
63 | value.fold_with(&mut RegionFolder::new(self, &mut f)) | |
64 | } | |
65 | } | |
66 | ||
67 | /// Folds over the substructure of a type, visiting its component | |
68 | /// types and all regions that occur *free* within it. | |
69 | /// | |
70 | /// That is, `Ty` can contain function or method types that bind | |
71 | /// regions at the call site (`ReLateBound`), and occurrences of | |
72 | /// regions (aka "lifetimes") that are bound within a type are not | |
73 | /// visited by this folder; only regions that occur free will be | |
74 | /// visited by `fld_r`. | |
75 | ||
76 | pub struct RegionFolder<'a, 'tcx> { | |
77 | tcx: TyCtxt<'tcx>, | |
78 | ||
79 | /// Stores the index of a binder *just outside* the stuff we have | |
80 | /// visited. So this begins as INNERMOST; when we pass through a | |
81 | /// binder, it is incremented (via `shift_in`). | |
82 | current_index: ty::DebruijnIndex, | |
83 | ||
84 | /// Callback invokes for each free region. The `DebruijnIndex` | |
85 | /// points to the binder *just outside* the ones we have passed | |
86 | /// through. | |
87 | fold_region_fn: | |
88 | &'a mut (dyn FnMut(ty::Region<'tcx>, ty::DebruijnIndex) -> ty::Region<'tcx> + 'a), | |
89 | } | |
90 | ||
91 | impl<'a, 'tcx> RegionFolder<'a, 'tcx> { | |
92 | #[inline] | |
93 | pub fn new( | |
94 | tcx: TyCtxt<'tcx>, | |
95 | fold_region_fn: &'a mut dyn FnMut(ty::Region<'tcx>, ty::DebruijnIndex) -> ty::Region<'tcx>, | |
96 | ) -> RegionFolder<'a, 'tcx> { | |
97 | RegionFolder { tcx, current_index: ty::INNERMOST, fold_region_fn } | |
98 | } | |
99 | } | |
100 | ||
101 | impl<'a, 'tcx> TypeFolder<TyCtxt<'tcx>> for RegionFolder<'a, 'tcx> { | |
102 | fn interner(&self) -> TyCtxt<'tcx> { | |
103 | self.tcx | |
104 | } | |
105 | ||
106 | fn fold_binder<T: TypeFoldable<TyCtxt<'tcx>>>( | |
107 | &mut self, | |
108 | t: ty::Binder<'tcx, T>, | |
109 | ) -> ty::Binder<'tcx, T> { | |
110 | self.current_index.shift_in(1); | |
111 | let t = t.super_fold_with(self); | |
112 | self.current_index.shift_out(1); | |
113 | t | |
114 | } | |
115 | ||
116 | #[instrument(skip(self), level = "debug", ret)] | |
117 | fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> { | |
118 | match *r { | |
119 | ty::ReLateBound(debruijn, _) if debruijn < self.current_index => { | |
120 | debug!(?self.current_index, "skipped bound region"); | |
121 | r | |
122 | } | |
123 | _ => { | |
124 | debug!(?self.current_index, "folding free region"); | |
125 | (self.fold_region_fn)(r, self.current_index) | |
126 | } | |
127 | } | |
128 | } | |
129 | } | |
130 | ||
131 | /////////////////////////////////////////////////////////////////////////// | |
132 | // Bound vars replacer | |
133 | ||
134 | pub trait BoundVarReplacerDelegate<'tcx> { | |
135 | fn replace_region(&mut self, br: ty::BoundRegion) -> ty::Region<'tcx>; | |
136 | fn replace_ty(&mut self, bt: ty::BoundTy) -> Ty<'tcx>; | |
137 | fn replace_const(&mut self, bv: ty::BoundVar, ty: Ty<'tcx>) -> ty::Const<'tcx>; | |
138 | } | |
139 | ||
140 | pub struct FnMutDelegate<'a, 'tcx> { | |
141 | pub regions: &'a mut (dyn FnMut(ty::BoundRegion) -> ty::Region<'tcx> + 'a), | |
142 | pub types: &'a mut (dyn FnMut(ty::BoundTy) -> Ty<'tcx> + 'a), | |
143 | pub consts: &'a mut (dyn FnMut(ty::BoundVar, Ty<'tcx>) -> ty::Const<'tcx> + 'a), | |
144 | } | |
145 | ||
146 | impl<'a, 'tcx> BoundVarReplacerDelegate<'tcx> for FnMutDelegate<'a, 'tcx> { | |
147 | fn replace_region(&mut self, br: ty::BoundRegion) -> ty::Region<'tcx> { | |
148 | (self.regions)(br) | |
149 | } | |
150 | fn replace_ty(&mut self, bt: ty::BoundTy) -> Ty<'tcx> { | |
151 | (self.types)(bt) | |
152 | } | |
153 | fn replace_const(&mut self, bv: ty::BoundVar, ty: Ty<'tcx>) -> ty::Const<'tcx> { | |
154 | (self.consts)(bv, ty) | |
155 | } | |
156 | } | |
157 | ||
158 | /// Replaces the escaping bound vars (late bound regions or bound types) in a type. | |
159 | struct BoundVarReplacer<'tcx, D> { | |
160 | tcx: TyCtxt<'tcx>, | |
161 | ||
162 | /// As with `RegionFolder`, represents the index of a binder *just outside* | |
163 | /// the ones we have visited. | |
164 | current_index: ty::DebruijnIndex, | |
165 | ||
166 | delegate: D, | |
167 | } | |
168 | ||
169 | impl<'tcx, D: BoundVarReplacerDelegate<'tcx>> BoundVarReplacer<'tcx, D> { | |
170 | fn new(tcx: TyCtxt<'tcx>, delegate: D) -> Self { | |
171 | BoundVarReplacer { tcx, current_index: ty::INNERMOST, delegate } | |
172 | } | |
173 | } | |
174 | ||
175 | impl<'tcx, D> TypeFolder<TyCtxt<'tcx>> for BoundVarReplacer<'tcx, D> | |
176 | where | |
177 | D: BoundVarReplacerDelegate<'tcx>, | |
178 | { | |
179 | fn interner(&self) -> TyCtxt<'tcx> { | |
180 | self.tcx | |
181 | } | |
182 | ||
183 | fn fold_binder<T: TypeFoldable<TyCtxt<'tcx>>>( | |
184 | &mut self, | |
185 | t: ty::Binder<'tcx, T>, | |
186 | ) -> ty::Binder<'tcx, T> { | |
187 | self.current_index.shift_in(1); | |
188 | let t = t.super_fold_with(self); | |
189 | self.current_index.shift_out(1); | |
190 | t | |
191 | } | |
192 | ||
193 | fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> { | |
194 | match *t.kind() { | |
195 | ty::Bound(debruijn, bound_ty) if debruijn == self.current_index => { | |
196 | let ty = self.delegate.replace_ty(bound_ty); | |
197 | debug_assert!(!ty.has_vars_bound_above(ty::INNERMOST)); | |
198 | ty::fold::shift_vars(self.tcx, ty, self.current_index.as_u32()) | |
199 | } | |
200 | _ if t.has_vars_bound_at_or_above(self.current_index) => t.super_fold_with(self), | |
201 | _ => t, | |
202 | } | |
203 | } | |
204 | ||
205 | fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> { | |
206 | match *r { | |
207 | ty::ReLateBound(debruijn, br) if debruijn == self.current_index => { | |
208 | let region = self.delegate.replace_region(br); | |
209 | if let ty::ReLateBound(debruijn1, br) = *region { | |
210 | // If the callback returns a late-bound region, | |
211 | // that region should always use the INNERMOST | |
212 | // debruijn index. Then we adjust it to the | |
213 | // correct depth. | |
214 | assert_eq!(debruijn1, ty::INNERMOST); | |
215 | self.tcx.mk_re_late_bound(debruijn, br) | |
216 | } else { | |
217 | region | |
218 | } | |
219 | } | |
220 | _ => r, | |
221 | } | |
222 | } | |
223 | ||
224 | fn fold_const(&mut self, ct: ty::Const<'tcx>) -> ty::Const<'tcx> { | |
225 | match ct.kind() { | |
226 | ty::ConstKind::Bound(debruijn, bound_const) if debruijn == self.current_index => { | |
227 | let ct = self.delegate.replace_const(bound_const, ct.ty()); | |
228 | debug_assert!(!ct.has_vars_bound_above(ty::INNERMOST)); | |
229 | ty::fold::shift_vars(self.tcx, ct, self.current_index.as_u32()) | |
230 | } | |
231 | _ => ct.super_fold_with(self), | |
232 | } | |
233 | } | |
234 | ||
235 | fn fold_predicate(&mut self, p: ty::Predicate<'tcx>) -> ty::Predicate<'tcx> { | |
236 | if p.has_vars_bound_at_or_above(self.current_index) { p.super_fold_with(self) } else { p } | |
237 | } | |
238 | } | |
239 | ||
240 | impl<'tcx> TyCtxt<'tcx> { | |
241 | /// Replaces all regions bound by the given `Binder` with the | |
242 | /// results returned by the closure; the closure is expected to | |
243 | /// return a free region (relative to this binder), and hence the | |
244 | /// binder is removed in the return type. The closure is invoked | |
245 | /// once for each unique `BoundRegionKind`; multiple references to the | |
246 | /// same `BoundRegionKind` will reuse the previous result. A map is | |
247 | /// returned at the end with each bound region and the free region | |
248 | /// that replaced it. | |
249 | /// | |
250 | /// # Panics | |
251 | /// | |
252 | /// This method only replaces late bound regions. Any types or | |
253 | /// constants bound by `value` will cause an ICE. | |
254 | pub fn replace_late_bound_regions<T, F>( | |
255 | self, | |
256 | value: Binder<'tcx, T>, | |
257 | mut fld_r: F, | |
258 | ) -> (T, BTreeMap<ty::BoundRegion, ty::Region<'tcx>>) | |
259 | where | |
260 | F: FnMut(ty::BoundRegion) -> ty::Region<'tcx>, | |
261 | T: TypeFoldable<TyCtxt<'tcx>>, | |
262 | { | |
263 | let mut region_map = BTreeMap::new(); | |
264 | let real_fld_r = |br: ty::BoundRegion| *region_map.entry(br).or_insert_with(|| fld_r(br)); | |
265 | let value = self.replace_late_bound_regions_uncached(value, real_fld_r); | |
266 | (value, region_map) | |
267 | } | |
268 | ||
269 | pub fn replace_late_bound_regions_uncached<T, F>( | |
270 | self, | |
271 | value: Binder<'tcx, T>, | |
272 | mut replace_regions: F, | |
273 | ) -> T | |
274 | where | |
275 | F: FnMut(ty::BoundRegion) -> ty::Region<'tcx>, | |
276 | T: TypeFoldable<TyCtxt<'tcx>>, | |
277 | { | |
278 | let value = value.skip_binder(); | |
279 | if !value.has_escaping_bound_vars() { | |
280 | value | |
281 | } else { | |
282 | let delegate = FnMutDelegate { | |
283 | regions: &mut replace_regions, | |
284 | types: &mut |b| bug!("unexpected bound ty in binder: {b:?}"), | |
285 | consts: &mut |b, ty| bug!("unexpected bound ct in binder: {b:?} {ty}"), | |
286 | }; | |
287 | let mut replacer = BoundVarReplacer::new(self, delegate); | |
288 | value.fold_with(&mut replacer) | |
289 | } | |
290 | } | |
291 | ||
292 | /// Replaces all escaping bound vars. The `fld_r` closure replaces escaping | |
293 | /// bound regions; the `fld_t` closure replaces escaping bound types and the `fld_c` | |
294 | /// closure replaces escaping bound consts. | |
295 | pub fn replace_escaping_bound_vars_uncached<T: TypeFoldable<TyCtxt<'tcx>>>( | |
296 | self, | |
297 | value: T, | |
298 | delegate: impl BoundVarReplacerDelegate<'tcx>, | |
299 | ) -> T { | |
300 | if !value.has_escaping_bound_vars() { | |
301 | value | |
302 | } else { | |
303 | let mut replacer = BoundVarReplacer::new(self, delegate); | |
304 | value.fold_with(&mut replacer) | |
305 | } | |
306 | } | |
307 | ||
308 | /// Replaces all types or regions bound by the given `Binder`. The `fld_r` | |
309 | /// closure replaces bound regions, the `fld_t` closure replaces bound | |
310 | /// types, and `fld_c` replaces bound constants. | |
311 | pub fn replace_bound_vars_uncached<T: TypeFoldable<TyCtxt<'tcx>>>( | |
312 | self, | |
313 | value: Binder<'tcx, T>, | |
314 | delegate: impl BoundVarReplacerDelegate<'tcx>, | |
315 | ) -> T { | |
316 | self.replace_escaping_bound_vars_uncached(value.skip_binder(), delegate) | |
317 | } | |
318 | ||
319 | /// Replaces any late-bound regions bound in `value` with | |
320 | /// free variants attached to `all_outlive_scope`. | |
321 | pub fn liberate_late_bound_regions<T>( | |
322 | self, | |
323 | all_outlive_scope: DefId, | |
324 | value: ty::Binder<'tcx, T>, | |
325 | ) -> T | |
326 | where | |
327 | T: TypeFoldable<TyCtxt<'tcx>>, | |
328 | { | |
329 | self.replace_late_bound_regions_uncached(value, |br| { | |
330 | self.mk_re_free(all_outlive_scope, br.kind) | |
331 | }) | |
332 | } | |
333 | ||
334 | pub fn shift_bound_var_indices<T>(self, bound_vars: usize, value: T) -> T | |
335 | where | |
336 | T: TypeFoldable<TyCtxt<'tcx>>, | |
337 | { | |
338 | let shift_bv = |bv: ty::BoundVar| ty::BoundVar::from_usize(bv.as_usize() + bound_vars); | |
339 | self.replace_escaping_bound_vars_uncached( | |
340 | value, | |
341 | FnMutDelegate { | |
342 | regions: &mut |r: ty::BoundRegion| { | |
343 | self.mk_re_late_bound( | |
344 | ty::INNERMOST, | |
345 | ty::BoundRegion { var: shift_bv(r.var), kind: r.kind }, | |
346 | ) | |
347 | }, | |
348 | types: &mut |t: ty::BoundTy| { | |
349 | self.mk_bound(ty::INNERMOST, ty::BoundTy { var: shift_bv(t.var), kind: t.kind }) | |
350 | }, | |
351 | consts: &mut |c, ty: Ty<'tcx>| { | |
352 | self.mk_const(ty::ConstKind::Bound(ty::INNERMOST, shift_bv(c)), ty) | |
353 | }, | |
354 | }, | |
355 | ) | |
356 | } | |
357 | ||
358 | /// Replaces any late-bound regions bound in `value` with `'erased`. Useful in codegen but also | |
359 | /// method lookup and a few other places where precise region relationships are not required. | |
360 | pub fn erase_late_bound_regions<T>(self, value: Binder<'tcx, T>) -> T | |
361 | where | |
362 | T: TypeFoldable<TyCtxt<'tcx>>, | |
363 | { | |
364 | self.replace_late_bound_regions(value, |_| self.lifetimes.re_erased).0 | |
365 | } | |
366 | ||
367 | /// Anonymize all bound variables in `value`, this is mostly used to improve caching. | |
368 | pub fn anonymize_bound_vars<T>(self, value: Binder<'tcx, T>) -> Binder<'tcx, T> | |
369 | where | |
370 | T: TypeFoldable<TyCtxt<'tcx>>, | |
371 | { | |
372 | struct Anonymize<'a, 'tcx> { | |
373 | tcx: TyCtxt<'tcx>, | |
374 | map: &'a mut FxIndexMap<ty::BoundVar, ty::BoundVariableKind>, | |
375 | } | |
376 | impl<'tcx> BoundVarReplacerDelegate<'tcx> for Anonymize<'_, 'tcx> { | |
377 | fn replace_region(&mut self, br: ty::BoundRegion) -> ty::Region<'tcx> { | |
378 | let entry = self.map.entry(br.var); | |
379 | let index = entry.index(); | |
380 | let var = ty::BoundVar::from_usize(index); | |
381 | let kind = entry | |
382 | .or_insert_with(|| ty::BoundVariableKind::Region(ty::BrAnon(None))) | |
383 | .expect_region(); | |
384 | let br = ty::BoundRegion { var, kind }; | |
385 | self.tcx.mk_re_late_bound(ty::INNERMOST, br) | |
386 | } | |
387 | fn replace_ty(&mut self, bt: ty::BoundTy) -> Ty<'tcx> { | |
388 | let entry = self.map.entry(bt.var); | |
389 | let index = entry.index(); | |
390 | let var = ty::BoundVar::from_usize(index); | |
391 | let kind = entry | |
392 | .or_insert_with(|| ty::BoundVariableKind::Ty(ty::BoundTyKind::Anon)) | |
393 | .expect_ty(); | |
394 | self.tcx.mk_bound(ty::INNERMOST, BoundTy { var, kind }) | |
395 | } | |
396 | fn replace_const(&mut self, bv: ty::BoundVar, ty: Ty<'tcx>) -> ty::Const<'tcx> { | |
397 | let entry = self.map.entry(bv); | |
398 | let index = entry.index(); | |
399 | let var = ty::BoundVar::from_usize(index); | |
400 | let () = entry.or_insert_with(|| ty::BoundVariableKind::Const).expect_const(); | |
401 | self.tcx.mk_const(ty::ConstKind::Bound(ty::INNERMOST, var), ty) | |
402 | } | |
403 | } | |
404 | ||
405 | let mut map = Default::default(); | |
406 | let delegate = Anonymize { tcx: self, map: &mut map }; | |
407 | let inner = self.replace_escaping_bound_vars_uncached(value.skip_binder(), delegate); | |
408 | let bound_vars = self.mk_bound_variable_kinds_from_iter(map.into_values()); | |
409 | Binder::bind_with_vars(inner, bound_vars) | |
410 | } | |
411 | } | |
412 | ||
413 | /////////////////////////////////////////////////////////////////////////// | |
414 | // Shifter | |
415 | // | |
416 | // Shifts the De Bruijn indices on all escaping bound vars by a | |
417 | // fixed amount. Useful in substitution or when otherwise introducing | |
418 | // a binding level that is not intended to capture the existing bound | |
419 | // vars. See comment on `shift_vars_through_binders` method in | |
420 | // `subst.rs` for more details. | |
421 | ||
422 | struct Shifter<'tcx> { | |
423 | tcx: TyCtxt<'tcx>, | |
424 | current_index: ty::DebruijnIndex, | |
425 | amount: u32, | |
426 | } | |
427 | ||
428 | impl<'tcx> Shifter<'tcx> { | |
429 | pub fn new(tcx: TyCtxt<'tcx>, amount: u32) -> Self { | |
430 | Shifter { tcx, current_index: ty::INNERMOST, amount } | |
431 | } | |
432 | } | |
433 | ||
434 | impl<'tcx> TypeFolder<TyCtxt<'tcx>> for Shifter<'tcx> { | |
435 | fn interner(&self) -> TyCtxt<'tcx> { | |
436 | self.tcx | |
437 | } | |
438 | ||
439 | fn fold_binder<T: TypeFoldable<TyCtxt<'tcx>>>( | |
440 | &mut self, | |
441 | t: ty::Binder<'tcx, T>, | |
442 | ) -> ty::Binder<'tcx, T> { | |
443 | self.current_index.shift_in(1); | |
444 | let t = t.super_fold_with(self); | |
445 | self.current_index.shift_out(1); | |
446 | t | |
447 | } | |
448 | ||
449 | fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> { | |
450 | match *r { | |
451 | ty::ReLateBound(debruijn, br) if debruijn >= self.current_index => { | |
452 | let debruijn = debruijn.shifted_in(self.amount); | |
453 | self.tcx.mk_re_late_bound(debruijn, br) | |
454 | } | |
455 | _ => r, | |
456 | } | |
457 | } | |
458 | ||
459 | fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> { | |
460 | match *ty.kind() { | |
461 | ty::Bound(debruijn, bound_ty) if debruijn >= self.current_index => { | |
462 | let debruijn = debruijn.shifted_in(self.amount); | |
463 | self.tcx.mk_bound(debruijn, bound_ty) | |
464 | } | |
465 | ||
466 | _ if ty.has_vars_bound_at_or_above(self.current_index) => ty.super_fold_with(self), | |
467 | _ => ty, | |
468 | } | |
469 | } | |
470 | ||
471 | fn fold_const(&mut self, ct: ty::Const<'tcx>) -> ty::Const<'tcx> { | |
472 | if let ty::ConstKind::Bound(debruijn, bound_ct) = ct.kind() | |
473 | && debruijn >= self.current_index | |
474 | { | |
475 | let debruijn = debruijn.shifted_in(self.amount); | |
476 | self.tcx.mk_const(ty::ConstKind::Bound(debruijn, bound_ct), ct.ty()) | |
477 | } else { | |
478 | ct.super_fold_with(self) | |
479 | } | |
480 | } | |
481 | ||
482 | fn fold_predicate(&mut self, p: ty::Predicate<'tcx>) -> ty::Predicate<'tcx> { | |
483 | if p.has_vars_bound_at_or_above(self.current_index) { p.super_fold_with(self) } else { p } | |
484 | } | |
485 | } | |
486 | ||
487 | pub fn shift_region<'tcx>( | |
488 | tcx: TyCtxt<'tcx>, | |
489 | region: ty::Region<'tcx>, | |
490 | amount: u32, | |
491 | ) -> ty::Region<'tcx> { | |
492 | match *region { | |
493 | ty::ReLateBound(debruijn, br) if amount > 0 => { | |
494 | tcx.mk_re_late_bound(debruijn.shifted_in(amount), br) | |
495 | } | |
496 | _ => region, | |
497 | } | |
498 | } | |
499 | ||
500 | pub fn shift_vars<'tcx, T>(tcx: TyCtxt<'tcx>, value: T, amount: u32) -> T | |
501 | where | |
502 | T: TypeFoldable<TyCtxt<'tcx>>, | |
503 | { | |
504 | debug!("shift_vars(value={:?}, amount={})", value, amount); | |
505 | ||
506 | if amount == 0 || !value.has_escaping_bound_vars() { | |
507 | return value; | |
508 | } | |
509 | ||
510 | value.fold_with(&mut Shifter::new(tcx, amount)) | |
511 | } |