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Commit | Line | Data |
---|---|---|
ba9703b0 | 1 | use rustc_data_structures::frozen::Frozen; |
8faf50e0 | 2 | use rustc_data_structures::transitive_relation::TransitiveRelation; |
74b04a01 | 3 | use rustc_infer::infer::canonical::QueryRegionConstraints; |
ba9703b0 | 4 | use rustc_infer::infer::outlives; |
064997fb | 5 | use rustc_infer::infer::outlives::env::RegionBoundPairs; |
74b04a01 XL |
6 | use rustc_infer::infer::region_constraints::GenericKind; |
7 | use rustc_infer::infer::InferCtxt; | |
ba9703b0 XL |
8 | use rustc_middle::mir::ConstraintCategory; |
9 | use rustc_middle::traits::query::OutlivesBound; | |
3c0e092e | 10 | use rustc_middle::ty::{self, RegionVid, Ty}; |
dfeec247 | 11 | use rustc_span::DUMMY_SP; |
ba9703b0 | 12 | use rustc_trait_selection::traits::query::type_op::{self, TypeOp}; |
8faf50e0 | 13 | use std::rc::Rc; |
94222f64 | 14 | use type_op::TypeOpOutput; |
8faf50e0 | 15 | |
c295e0f8 | 16 | use crate::{ |
60c5eb7d XL |
17 | type_check::constraint_conversion, |
18 | type_check::{Locations, MirTypeckRegionConstraints}, | |
19 | universal_regions::UniversalRegions, | |
60c5eb7d XL |
20 | }; |
21 | ||
8faf50e0 | 22 | #[derive(Debug)] |
923072b8 | 23 | pub(crate) struct UniversalRegionRelations<'tcx> { |
8faf50e0 XL |
24 | universal_regions: Rc<UniversalRegions<'tcx>>, |
25 | ||
26 | /// Stores the outlives relations that are known to hold from the | |
9fa01778 | 27 | /// implied bounds, in-scope where-clauses, and that sort of |
8faf50e0 XL |
28 | /// thing. |
29 | outlives: TransitiveRelation<RegionVid>, | |
30 | ||
31 | /// This is the `<=` relation; that is, if `a: b`, then `b <= a`, | |
32 | /// and we store that here. This is useful when figuring out how | |
33 | /// to express some local region in terms of external regions our | |
34 | /// caller will understand. | |
35 | inverse_outlives: TransitiveRelation<RegionVid>, | |
36 | } | |
37 | ||
8faf50e0 XL |
38 | /// As part of computing the free region relations, we also have to |
39 | /// normalize the input-output types, which we then need later. So we | |
9fa01778 | 40 | /// return those. This vector consists of first the input types and |
8faf50e0 XL |
41 | /// then the output type as the last element. |
42 | type NormalizedInputsAndOutput<'tcx> = Vec<Ty<'tcx>>; | |
43 | ||
923072b8 FG |
44 | pub(crate) struct CreateResult<'tcx> { |
45 | pub(crate) universal_region_relations: Frozen<UniversalRegionRelations<'tcx>>, | |
46 | pub(crate) region_bound_pairs: RegionBoundPairs<'tcx>, | |
47 | pub(crate) normalized_inputs_and_output: NormalizedInputsAndOutput<'tcx>, | |
8faf50e0 XL |
48 | } |
49 | ||
923072b8 | 50 | pub(crate) fn create<'tcx>( |
dc9dc135 | 51 | infcx: &InferCtxt<'_, 'tcx>, |
8faf50e0 | 52 | param_env: ty::ParamEnv<'tcx>, |
064997fb | 53 | implicit_region_bound: ty::Region<'tcx>, |
8faf50e0 XL |
54 | universal_regions: &Rc<UniversalRegions<'tcx>>, |
55 | constraints: &mut MirTypeckRegionConstraints<'tcx>, | |
8faf50e0 | 56 | ) -> CreateResult<'tcx> { |
8faf50e0 XL |
57 | UniversalRegionRelationsBuilder { |
58 | infcx, | |
8faf50e0 XL |
59 | param_env, |
60 | implicit_region_bound, | |
61 | constraints, | |
8faf50e0 | 62 | universal_regions: universal_regions.clone(), |
064997fb | 63 | region_bound_pairs: Default::default(), |
8faf50e0 XL |
64 | relations: UniversalRegionRelations { |
65 | universal_regions: universal_regions.clone(), | |
0bf4aa26 XL |
66 | outlives: Default::default(), |
67 | inverse_outlives: Default::default(), | |
8faf50e0 | 68 | }, |
dfeec247 XL |
69 | } |
70 | .create() | |
8faf50e0 XL |
71 | } |
72 | ||
a2a8927a | 73 | impl UniversalRegionRelations<'_> { |
8faf50e0 XL |
74 | /// Records in the `outlives_relation` (and |
75 | /// `inverse_outlives_relation`) that `fr_a: fr_b`. Invoked by the | |
76 | /// builder below. | |
77 | fn relate_universal_regions(&mut self, fr_a: RegionVid, fr_b: RegionVid) { | |
dfeec247 | 78 | debug!("relate_universal_regions: fr_a={:?} outlives fr_b={:?}", fr_a, fr_b); |
8faf50e0 XL |
79 | self.outlives.add(fr_a, fr_b); |
80 | self.inverse_outlives.add(fr_b, fr_a); | |
81 | } | |
82 | ||
83 | /// Given two universal regions, returns the postdominating | |
84 | /// upper-bound (effectively the least upper bound). | |
85 | /// | |
86 | /// (See `TransitiveRelation::postdom_upper_bound` for details on | |
87 | /// the postdominating upper bound in general.) | |
923072b8 | 88 | pub(crate) fn postdom_upper_bound(&self, fr1: RegionVid, fr2: RegionVid) -> RegionVid { |
8faf50e0 XL |
89 | assert!(self.universal_regions.is_universal_region(fr1)); |
90 | assert!(self.universal_regions.is_universal_region(fr2)); | |
5e7ed085 FG |
91 | self.inverse_outlives |
92 | .postdom_upper_bound(fr1, fr2) | |
93 | .unwrap_or(self.universal_regions.fr_static) | |
8faf50e0 XL |
94 | } |
95 | ||
96 | /// Finds an "upper bound" for `fr` that is not local. In other | |
97 | /// words, returns the smallest (*) known region `fr1` that (a) | |
9fa01778 | 98 | /// outlives `fr` and (b) is not local. |
8faf50e0 | 99 | /// |
9fa01778 | 100 | /// (*) If there are multiple competing choices, we return all of them. |
923072b8 | 101 | pub(crate) fn non_local_upper_bounds<'a>(&'a self, fr: RegionVid) -> Vec<RegionVid> { |
8faf50e0 | 102 | debug!("non_local_upper_bound(fr={:?})", fr); |
9fa01778 XL |
103 | let res = self.non_local_bounds(&self.inverse_outlives, fr); |
104 | assert!(!res.is_empty(), "can't find an upper bound!?"); | |
105 | res | |
106 | } | |
107 | ||
108 | /// Returns the "postdominating" bound of the set of | |
109 | /// `non_local_upper_bounds` for the given region. | |
923072b8 | 110 | pub(crate) fn non_local_upper_bound(&self, fr: RegionVid) -> RegionVid { |
5e7ed085 | 111 | let upper_bounds = self.non_local_upper_bounds(fr); |
9fa01778 XL |
112 | |
113 | // In case we find more than one, reduce to one for | |
114 | // convenience. This is to prevent us from generating more | |
115 | // complex constraints, but it will cause spurious errors. | |
dfeec247 | 116 | let post_dom = self.inverse_outlives.mutual_immediate_postdominator(upper_bounds); |
9fa01778 XL |
117 | |
118 | debug!("non_local_bound: post_dom={:?}", post_dom); | |
119 | ||
120 | post_dom | |
5e7ed085 | 121 | .and_then(|post_dom| { |
9fa01778 XL |
122 | // If the mutual immediate postdom is not local, then |
123 | // there is no non-local result we can return. | |
124 | if !self.universal_regions.is_local_free_region(post_dom) { | |
125 | Some(post_dom) | |
126 | } else { | |
127 | None | |
128 | } | |
129 | }) | |
8faf50e0 XL |
130 | .unwrap_or(self.universal_regions.fr_static) |
131 | } | |
132 | ||
133 | /// Finds a "lower bound" for `fr` that is not local. In other | |
134 | /// words, returns the largest (*) known region `fr1` that (a) is | |
9fa01778 | 135 | /// outlived by `fr` and (b) is not local. |
8faf50e0 XL |
136 | /// |
137 | /// (*) If there are multiple competing choices, we pick the "postdominating" | |
138 | /// one. See `TransitiveRelation::postdom_upper_bound` for details. | |
923072b8 | 139 | pub(crate) fn non_local_lower_bound(&self, fr: RegionVid) -> Option<RegionVid> { |
8faf50e0 | 140 | debug!("non_local_lower_bound(fr={:?})", fr); |
5e7ed085 | 141 | let lower_bounds = self.non_local_bounds(&self.outlives, fr); |
9fa01778 XL |
142 | |
143 | // In case we find more than one, reduce to one for | |
144 | // convenience. This is to prevent us from generating more | |
145 | // complex constraints, but it will cause spurious errors. | |
dfeec247 | 146 | let post_dom = self.outlives.mutual_immediate_postdominator(lower_bounds); |
9fa01778 XL |
147 | |
148 | debug!("non_local_bound: post_dom={:?}", post_dom); | |
149 | ||
5e7ed085 | 150 | post_dom.and_then(|post_dom| { |
dfeec247 XL |
151 | // If the mutual immediate postdom is not local, then |
152 | // there is no non-local result we can return. | |
153 | if !self.universal_regions.is_local_free_region(post_dom) { | |
154 | Some(post_dom) | |
155 | } else { | |
156 | None | |
157 | } | |
158 | }) | |
8faf50e0 XL |
159 | } |
160 | ||
9fa01778 XL |
161 | /// Helper for `non_local_upper_bounds` and `non_local_lower_bounds`. |
162 | /// Repeatedly invokes `postdom_parent` until we find something that is not | |
163 | /// local. Returns `None` if we never do so. | |
164 | fn non_local_bounds<'a>( | |
8faf50e0 | 165 | &self, |
9fa01778 | 166 | relation: &'a TransitiveRelation<RegionVid>, |
5e7ed085 FG |
167 | fr0: RegionVid, |
168 | ) -> Vec<RegionVid> { | |
8faf50e0 XL |
169 | // This method assumes that `fr0` is one of the universally |
170 | // quantified region variables. | |
5e7ed085 | 171 | assert!(self.universal_regions.is_universal_region(fr0)); |
8faf50e0 XL |
172 | |
173 | let mut external_parents = vec![]; | |
9fa01778 | 174 | let mut queue = vec![fr0]; |
8faf50e0 XL |
175 | |
176 | // Keep expanding `fr` into its parents until we reach | |
177 | // non-local regions. | |
178 | while let Some(fr) = queue.pop() { | |
5e7ed085 | 179 | if !self.universal_regions.is_local_free_region(fr) { |
8faf50e0 XL |
180 | external_parents.push(fr); |
181 | continue; | |
182 | } | |
183 | ||
184 | queue.extend(relation.parents(fr)); | |
185 | } | |
186 | ||
187 | debug!("non_local_bound: external_parents={:?}", external_parents); | |
188 | ||
9fa01778 | 189 | external_parents |
8faf50e0 XL |
190 | } |
191 | ||
9fa01778 | 192 | /// Returns `true` if fr1 is known to outlive fr2. |
8faf50e0 XL |
193 | /// |
194 | /// This will only ever be true for universally quantified regions. | |
923072b8 | 195 | pub(crate) fn outlives(&self, fr1: RegionVid, fr2: RegionVid) -> bool { |
5e7ed085 | 196 | self.outlives.contains(fr1, fr2) |
8faf50e0 XL |
197 | } |
198 | ||
199 | /// Returns a vector of free regions `x` such that `fr1: x` is | |
200 | /// known to hold. | |
923072b8 | 201 | pub(crate) fn regions_outlived_by(&self, fr1: RegionVid) -> Vec<RegionVid> { |
5e7ed085 | 202 | self.outlives.reachable_from(fr1) |
8faf50e0 | 203 | } |
60c5eb7d XL |
204 | |
205 | /// Returns the _non-transitive_ set of known `outlives` constraints between free regions. | |
923072b8 | 206 | pub(crate) fn known_outlives(&self) -> impl Iterator<Item = (RegionVid, RegionVid)> + '_ { |
60c5eb7d XL |
207 | self.outlives.base_edges() |
208 | } | |
8faf50e0 XL |
209 | } |
210 | ||
dc9dc135 XL |
211 | struct UniversalRegionRelationsBuilder<'this, 'tcx> { |
212 | infcx: &'this InferCtxt<'this, 'tcx>, | |
8faf50e0 | 213 | param_env: ty::ParamEnv<'tcx>, |
8faf50e0 | 214 | universal_regions: Rc<UniversalRegions<'tcx>>, |
064997fb | 215 | implicit_region_bound: ty::Region<'tcx>, |
8faf50e0 | 216 | constraints: &'this mut MirTypeckRegionConstraints<'tcx>, |
8faf50e0 XL |
217 | |
218 | // outputs: | |
219 | relations: UniversalRegionRelations<'tcx>, | |
220 | region_bound_pairs: RegionBoundPairs<'tcx>, | |
221 | } | |
222 | ||
a2a8927a | 223 | impl<'tcx> UniversalRegionRelationsBuilder<'_, 'tcx> { |
923072b8 | 224 | pub(crate) fn create(mut self) -> CreateResult<'tcx> { |
8faf50e0 XL |
225 | let unnormalized_input_output_tys = self |
226 | .universal_regions | |
227 | .unnormalized_input_tys | |
228 | .iter() | |
229 | .cloned() | |
230 | .chain(Some(self.universal_regions.unnormalized_output_ty)); | |
231 | ||
232 | // For each of the input/output types: | |
233 | // - Normalize the type. This will create some region | |
234 | // constraints, which we buffer up because we are | |
235 | // not ready to process them yet. | |
236 | // - Then compute the implied bounds. This will adjust | |
237 | // the `region_bound_pairs` and so forth. | |
238 | // - After this is done, we'll process the constraints, once | |
239 | // the `relations` is built. | |
240 | let mut normalized_inputs_and_output = | |
241 | Vec::with_capacity(self.universal_regions.unnormalized_input_tys.len() + 1); | |
242 | let constraint_sets: Vec<_> = unnormalized_input_output_tys | |
243 | .flat_map(|ty| { | |
244 | debug!("build: input_or_output={:?}", ty); | |
5e7ed085 FG |
245 | // We only add implied bounds for the normalized type as the unnormalized |
246 | // type may not actually get checked by the caller. | |
247 | // | |
248 | // Can otherwise be unsound, see #91068. | |
c295e0f8 | 249 | let TypeOpOutput { output: norm_ty, constraints: constraints1, .. } = self |
8faf50e0 XL |
250 | .param_env |
251 | .and(type_op::normalize::Normalize::new(ty)) | |
252 | .fully_perform(self.infcx) | |
f035d41b XL |
253 | .unwrap_or_else(|_| { |
254 | self.infcx | |
255 | .tcx | |
256 | .sess | |
257 | .delay_span_bug(DUMMY_SP, &format!("failed to normalize {:?}", ty)); | |
94222f64 XL |
258 | TypeOpOutput { |
259 | output: self.infcx.tcx.ty_error(), | |
260 | constraints: None, | |
5e7ed085 | 261 | error_info: None, |
94222f64 | 262 | } |
f035d41b | 263 | }); |
94222f64 XL |
264 | // Note: we need this in examples like |
265 | // ``` | |
266 | // trait Foo { | |
267 | // type Bar; | |
268 | // fn foo(&self) -> &Self::Bar; | |
269 | // } | |
270 | // impl Foo for () { | |
271 | // type Bar = (); | |
272 | // fn foo(&self) ->&() {} | |
273 | // } | |
274 | // ``` | |
275 | // Both &Self::Bar and &() are WF | |
c295e0f8 XL |
276 | let constraints_implied = self.add_implied_bounds(norm_ty); |
277 | normalized_inputs_and_output.push(norm_ty); | |
278 | constraints1.into_iter().chain(constraints_implied) | |
8faf50e0 XL |
279 | }) |
280 | .collect(); | |
281 | ||
282 | // Insert the facts we know from the predicates. Why? Why not. | |
283 | let param_env = self.param_env; | |
ba9703b0 | 284 | self.add_outlives_bounds(outlives::explicit_outlives_bounds(param_env)); |
8faf50e0 XL |
285 | |
286 | // Finally: | |
287 | // - outlives is reflexive, so `'r: 'r` for every region `'r` | |
288 | // - `'static: 'r` for every region `'r` | |
289 | // - `'r: 'fn_body` for every (other) universally quantified | |
290 | // region `'r`, all of which are provided by our caller | |
291 | let fr_static = self.universal_regions.fr_static; | |
292 | let fr_fn_body = self.universal_regions.fr_fn_body; | |
293 | for fr in self.universal_regions.universal_regions() { | |
dfeec247 | 294 | debug!("build: relating free region {:?} to itself and to 'static", fr); |
8faf50e0 XL |
295 | self.relations.relate_universal_regions(fr, fr); |
296 | self.relations.relate_universal_regions(fr_static, fr); | |
297 | self.relations.relate_universal_regions(fr, fr_fn_body); | |
298 | } | |
299 | ||
dc9dc135 | 300 | for data in &constraint_sets { |
8faf50e0 | 301 | constraint_conversion::ConstraintConversion::new( |
a1dfa0c6 | 302 | self.infcx, |
8faf50e0 | 303 | &self.universal_regions, |
8faf50e0 XL |
304 | &self.region_bound_pairs, |
305 | self.implicit_region_bound, | |
306 | self.param_env, | |
0bf4aa26 | 307 | Locations::All(DUMMY_SP), |
04454e1e | 308 | DUMMY_SP, |
0bf4aa26 | 309 | ConstraintCategory::Internal, |
a1dfa0c6 | 310 | &mut self.constraints, |
dfeec247 XL |
311 | ) |
312 | .convert_all(data); | |
8faf50e0 XL |
313 | } |
314 | ||
315 | CreateResult { | |
ba9703b0 | 316 | universal_region_relations: Frozen::freeze(self.relations), |
8faf50e0 XL |
317 | region_bound_pairs: self.region_bound_pairs, |
318 | normalized_inputs_and_output, | |
319 | } | |
320 | } | |
321 | ||
322 | /// Update the type of a single local, which should represent | |
323 | /// either the return type of the MIR or one of its arguments. At | |
324 | /// the same time, compute and add any implied bounds that come | |
325 | /// from this local. | |
923072b8 | 326 | #[instrument(level = "debug", skip(self))] |
064997fb | 327 | fn add_implied_bounds(&mut self, ty: Ty<'tcx>) -> Option<&'tcx QueryRegionConstraints<'tcx>> { |
94222f64 | 328 | let TypeOpOutput { output: bounds, constraints, .. } = self |
dfeec247 | 329 | .param_env |
b7449926 XL |
330 | .and(type_op::implied_outlives_bounds::ImpliedOutlivesBounds { ty }) |
331 | .fully_perform(self.infcx) | |
332 | .unwrap_or_else(|_| bug!("failed to compute implied bounds {:?}", ty)); | |
8faf50e0 | 333 | self.add_outlives_bounds(bounds); |
b7449926 | 334 | constraints |
8faf50e0 XL |
335 | } |
336 | ||
337 | /// Registers the `OutlivesBound` items from `outlives_bounds` in | |
338 | /// the outlives relation as well as the region-bound pairs | |
339 | /// listing. | |
340 | fn add_outlives_bounds<I>(&mut self, outlives_bounds: I) | |
341 | where | |
342 | I: IntoIterator<Item = OutlivesBound<'tcx>>, | |
343 | { | |
344 | for outlives_bound in outlives_bounds { | |
345 | debug!("add_outlives_bounds(bound={:?})", outlives_bound); | |
346 | ||
347 | match outlives_bound { | |
348 | OutlivesBound::RegionSubRegion(r1, r2) => { | |
dc9dc135 XL |
349 | // `where Type:` is lowered to `where Type: 'empty` so that |
350 | // we check `Type` is well formed, but there's no use for | |
351 | // this bound here. | |
5099ac24 | 352 | if r1.is_empty() { |
dc9dc135 XL |
353 | return; |
354 | } | |
355 | ||
8faf50e0 XL |
356 | // The bound says that `r1 <= r2`; we store `r2: r1`. |
357 | let r1 = self.universal_regions.to_region_vid(r1); | |
358 | let r2 = self.universal_regions.to_region_vid(r2); | |
359 | self.relations.relate_universal_regions(r2, r1); | |
360 | } | |
361 | ||
362 | OutlivesBound::RegionSubParam(r_a, param_b) => { | |
064997fb FG |
363 | self.region_bound_pairs |
364 | .insert(ty::OutlivesPredicate(GenericKind::Param(param_b), r_a)); | |
8faf50e0 XL |
365 | } |
366 | ||
367 | OutlivesBound::RegionSubProjection(r_a, projection_b) => { | |
064997fb FG |
368 | self.region_bound_pairs |
369 | .insert(ty::OutlivesPredicate(GenericKind::Projection(projection_b), r_a)); | |
8faf50e0 XL |
370 | } |
371 | } | |
372 | } | |
373 | } | |
374 | } |